Final Report Summary - EUROCHAR (Biochar for Carbon sequestration and large-scale removal of greenhouse gases (GHG) from the atmosphere)
Executive Summary:
In the context of climate change mitigation, technologies for removing the CO2 from the atmosphere are key challenges. Transferring biomass to carbon-rich materials with potential mega-scale application is an option to sequester carbon from plant material, taking it out of the short-term carbon cycle and therefore binding CO2 efficiently and even in a useful, productive, way into longer term non-atmospheric carbon pools. The EuroChar project fully met its objective and achieved substantial advancements in new strategies and options to sustainably sequester carbonin soils by means of the use of biochar. The research carefully followed project's the initial workplan with only minor deviations. The results are novel and have been and will continue to be properly disseminated to the scientific community and to the large public via a number of papers (21 in total) and a suite of reports and other materials that finally reached a wide audience, not only in Europe. The science papers are among the most cited in the literature. Vaccari et al. (2012) has been already cited more than 80 times in approximately two and half years, being one of the highly-cited papers in biochar science, so far. Other more recent papers, such as Viger et al. (2014), Criscuoli et al. (2014) and Ventura et al. (2014) are likely to generate new studies and stimulate a large and fruitful debate within the biochar community and beyond. EuroChar focused on two different technological processes for making biochar: gasification (thermal carbonisation – TC) (the SME partner AGT patented a new system) and hydrothermal carbonization (HTC). Biochar was produced from different agricultural products for subsequent detailed analyses and a set of coordinated field studies made at different latitudes in Europe. But the project also addressed specific questions related to the long-term stability of Biochar in soils, its potential toxicity (including genotoxic effects). Large scale application scenarios were also considered, both form Life Cycle Analysis (LCA) and the climatic feedback perspectives.
The main project's results may be summarised as follows:
• Specific analyses made at and in the proximity of the production plants and that were based on SPME (Solid Phase MicroExtraction) showed that the concentration of the 16 semi-volatile Policyclic Aromatic Hydrocarbons (PAH), aldehydes, ketones and phenols, results extremely below the national limit value
• Large differences were observed in the elemental as well as chemical composition of biochar obtained by pyrolysis, pyrogassification and hydrochars. The final carbon content, in particular, varied significantly depending on the feedstock considered while PAH as well as dioxin concentrations were below the limits given by the international and European biochar standard definitions
• The laboratory experiments indicated that biochar is more stable than hydrochar and has a higher C sequestration potential taking into account weathering effects and priming effects on soil organic matter
• Long-term biochar stability in the soil and its long term capacity to sequester carbon was assessed in a series of alpine charcoal hearths that were used more than 150 years ago and then left undisturbed. This enabled to finally estimate the fraction of recalcitrant carbon that underwent major degradation and C-loss over centennial time scales, thus enabling the calculation of the mean residence time (MRT) of biochar in soils
• Biochar effects on model plants were evaluated using model plants and novel tranceiptional approaches to clearly demonstrated the need of developing risk assessment strategies with bioindicators. The results also highlighted that the effects of biochar on plants may operate via hormonal mechanisms and that defense tenes may be affected, too
• the most extensive network for biochar field experimentation was created by Eurochar within the EU. This consists of three core sites, located in Italy, France and the UK (treated with biochar produced by AGT Biochar, Italy), accompanied by four satellite sites. The results of field studies have confirmed that biochar produced by a commercial method (AGT) is sufficiently stable in the soil environment for it to have potential use in carbon sequestration. Biochar application was shown to result in a significant shift in microbial communities present in 2 of the 3 core sites. Understanding these shifts may help in future to elucidate the mechanisms through which biochar contributes to soil fertility
• Scenario Analysis allowed to calculate the potential annual scale of carbon sequestration as being equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties
• Climatic feedback studies demonstrated the occurrence of direct biochar effects on surface albedo, which is likely to affect the surface energy balance and eventually reduce the mitigation potential of C-sequestration
EuroChar involved a number of stakeholders in the EuroChar Stakeholder Committee that examined and reviewed project’s activities. Dissemination activities were implemented to make project’s results available to a wider audience and the media
Project Context and Objectives:
In the context of climate change mitigation, technologies for removing the CO2 from the atmosphere are key challenges.
The search for meaningful ways to transfer carbon from the atmosphere via biomass into useful carbon deposits is currently a key challenge. Transferring biomass to carbon-rich materials with potential mega-scale application is a material option to sequester carbon from plant material, taking it out of the short-term carbon cycle and therefore binding CO2 efficiently and even in a useful, productive, way into longer term non-atmospheric carbon pools.
There are several ongoing efforts aimed at reducing greenhouse gas emissions through sequestration of carbon. Many different strategies have been proposed, ranging from wide-spread afforestation and reforestation to expensive geo-engineering programmes involving the burial of CO2 in deep oceans or in exhausted oil wells (Royal Society, 2009). One promising but simple option is to obtain C-sequestration by increasing the amount of carbon in agricultural soils (Scholes and Noble, 2001). But recent analyses urge caution, highlighting that very often the efforts aimed to achieve C sequestration in soils are offset by other greenhouse gas emissions (Schlesinger, 1999) and that soils generally show low potential to accumulate C (Schlesinger and Lichter, 2001). In addition, soil organic matter remains vulnerable as it can be decomposed rapidly if management practices that favours C-accumulation in the soils are not maintained in the long-term (Rasmussen et al., 1998).
The most obvious alternative for long-term C-sequestration in soils is to transform biomass, and in particular crop residues, into a stable product that can neither be decomposed by soil microorganisms nor be oxidised and then returned to the atmosphere in the form of CO2. One emerging option, in this regard, is to transform biomass into charcoal (or biochar) and add that to agricultural soils biochar, that can be produced through thermochemical or hydrothermal processes and as by-product of energy production, is normally made of 60-80% of Carbon; both carbonization processes are exothermic as they produce rather than consume energy and the black-carbon of biochar is a very stable product and the addition of large amounts of biochar to agricultural soils potentially enhances their fertility and is compatible with sustainable agriculture. Several studies consider that biochar, the carbon-rich product that remains when biomass is heated to high temperature in reduced oxygen conditions provides a stable form of Carbon that cannot be decomposed on centennial or even millennial time-scales. There is increasing evidence that black carbon created after forest fires can be more than 10,000 years old (Preston and Schmidt, 2006) and in the “Terra Preta” soils of the Amazon region biochar has been dated from 500 up to 7000 years (Neves et al., 2003). Those soils, whose prolonged fertility is likely associated to their large C-content, are still used today to produce food for the local populations. However, there are significant unknowns in transferring this ancient technology into modern agricultural systems within Europe and this proposal aims to address some of those unknown issues.
A continuously and rapidly growing literature is supporting biochar as a realistic potential mitigation option. Despite such a growing body of knowledge, carbon sequestration potentials of biochar have been overlooked in national and international frameworks because there are in fact very large uncertainties associated with the large-scale use of biochar for carbon sequestration. These include competition for land-use for food, competition for use of feedstock and agricultural wastes for biofuels. There is also a possibility that toxicological effects exist and that deployment of biochar could have an unknown impact on the delivery of other ecosystem services such as biodiversity of the soil and overall water consumption. Although there is a diversity of opinion among different experts on estimates of the potential future global supply of biomass for bioenergy, gasification or hydrothermal carbonification processes, the general consensus is that the global potential of biomass for these purposes is extremely large compared with biomass currently being used for food, fuel and fibre. For example, a recent report of the International Energy Agency (IEA, 2009) has highlighted a global technical potential of energy from biomass at 1,500 EJ in 2050, whilst total energy demand is estimated to be 1,000 EJ in 2050. With many potential raw materials (called source feedstock) and multiple positive attributes, biochar remains of significant but unrealised global potential, but many issues remain unresolved
The EuroChar Project aims to develop and demonstrate technologies that will contribute effectively and on a large-scale to remove greenhouse gases (GHG) from the atmosphere in a long-term perspective (over 100 years). The project is designed to quantify in a detailed and rigorous way if the biochar option is in fact a realistic strategy to sequester atmospheric carbon, within a European context.
EuroChar is built to reduce those uncertainties and eventually assess C-sequestration potentials for Europe and beyond. All this will be made associating critical demonstration activities, monitoring and testing actions and fundamental science into a coherent framework. With the ambition to go beyond the current state-of-the-art in biochar science the project’s deliverables will provide new data and knowledge required to:
• compare and evaluate the performance of thermochemical and hydrothermal technologies to produce biochar in prototype plants, also in a consistent LCA framework
• understand the physical-chemical properties of biochar produced from different feedstock and different technologies
• assess the short and long-term decomposability of different biochar types and their net potential for C-sequestration
• provide complete and standardised Life Cycle Analysis of biochar production / application
• assess potential toxic effects of different biochar types on plants, soil microbes and earthworms
• understand the net C-sequestration potentials achievable in realistic field situations
• understand implications of modified surface albedo following large-scale biochar application
• provide European-scale scenarios of the implementation of dedicated EU-policies
• propose regulatory frameworks for real-case applications of biochar to land, including mandatory or voluntary trading schemes for C-sequestration
• suggest relevant standards that should be defined for real-case applications
Project Results:
Work package (WP) 1. Demonstration of Industrial biochar production
The objectives of this WP were production of biochar at the pilot scale at two industrial plants in Germany and Italy. The activities of this Work Package were focused on the production of biochar with TC-Thermochemical Carbonization (Participant AGT) and HTC-Hydrothermal Carbonization (Participant CS) technologies from different feedstock, with the aim to provide the materials required under WP4 (chemical and physical characterization), 5 (stability assessment) and 6 (field applications).
TC – Gasification:Gasification is a thermo chemical conversion process in which a carbonaceous material is partially oxidized by heating at high temperatures (1 200°C) in gas (syngas) and charcoal. Syngas is a low calorific power mix of carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen, and is used to power endothermic engines in order to produce electricity and heat. Partner 7 (AGT Advanced Gasification Technology Srl) has developed a fixed-bed, down-draft, open core, compact gasifier which has 500 kW nominal electric capability (micro-generation) using feedstock deriving from agricultural products and by-products. The plant is composed of two principle sections: 1) reactor, where pyrolysis and gasification take place; 2) syngas cleaning system, where cooling, dust and tar removal occur. The gasification reactor consists of a fixed bed of biomass through which the oxidizing agent (air) flows in co-current. Inside the reactor, the partial combustion of the biomass, guaranties the heat necessary for the gasification reaction. The composition of the syngas varies in function of the type of biomass. The charcoal is extracted from reactor by a screw conveyor system and is then conveyed through a transportation system to a storage tank.
HTC – Hydrothermal carbonization: A commercial scale, fully continuous and energy efficient HTC production system from partner 5 (CS carbonSolutions Deutschland GmbH) with a nominal feed mass flow of 1.000 kg/h was used for the production of maize silage samples 1 and 2. The system was fully approved as a waste treatment plant according to German environmental legislation and is operated since October 2010. The system consists of two reaction stages with a temperature of 230°C in stage 1 and a temperature of 180°C in stage 2 respectively. The residence time in reaction stage 1 was at least 15 min and in reaction stage 2 at least 75 min respectively. This process is the standard CS carbonSolutions Deutschland GmbH CS-HTC process. A process scheme showing all main stages is attached. TC process flow chart (Figure_1); HTC process flow chart (Figure_2).
The choice to consider in the EuroChar project activities different materials obtained from innovative advanced biochar technologies rather than from traditional charcoal-making systems was motivated by environmental, technical and economic reasons. It is known that, unlike traditional pyrolysers that are often energy inefficient and highly polluting, some specific goals for modern biochar production are:
1. Value and recovery of co-products to improve process economics and reduce pollution emissions
2. Total control of operating conditions
3. Feedstock flexibility allowing both woody and herbaceous biomass, organic by-product and waste
4. Continuous feed technologies to increase efficiency and reduce pollution emissions associated with batch kilns
5. Exothermic operation (no air infiltration) to improve energy efficiency and charcoal yields
Summary of results and conclusions on gasification (TC):
Gasification is one of the most promising technologies for renewable energy production as it maximize syngas production (at the expense of charcoal) starting from a wide range of dry feedstock. Charcoal obtained in a gasifier is not a by-product but a high quality stable material that can be used in agriculture as soil amendment to increase productivity and to stock carbon in the soil
Gasification must and can rapidly fill competition gaps with other renewable energy technologies primarily anaerobic digestion (biogas). The market is the same but gasification requires lower investment costs which may favout its future massive spread.
Summary of results and conclusions on hydrothermal carbonization (HTC):
The market for HTC hydrochar is more complicated than expected because CO2 certificate prices went down and preparation of feedstock is sometimes expensive (biowaste from municipalities) and complicated and feedstock has sometimes to be purchased or there are no gate fees left (maize silage). All these reasons lead to higher market prices and a not economic HTC process for hydrochar from most of the feedstock used.
Hydrochar is not a by-product of the HTC process but the product and is to valuable to be spread on fields or will be to costly for farmers.
The only economically feasible feedstock at the moment is sewage sludge; maybe legislative and economic conditions will be more favorable for HTC in the future
WP1 clarifies that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste. The knowledge and technology implementation about the two processes were constantly increasing during the progress of the EuroChar project. Regarding gasification, the effort aimed to finalize the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. Concerning HTC, one major finding was that HTC might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage.
Moreover, WP 1 was focused on the production of biochar with TC and HTC technologies from different feedstock, with the aim to provide the materials required under WP4 (chemical and physical characterization), 5 (stability assessment) and 6 (field applications).
Concerning TC, the partner 7 (AGT) produced different biochar from six different agricultural products and by-products. Each feedstock was processed in the test-plant of Cremona (I) for a minimum of one week, converting at least 10 tons (on a dry matter basis) in syngas and charcoal. Biochar was obtained from poplar wood chips, conifer wood chips, sorghum stalks pellets, wheat straw pellets, olive residues and maize silage pellets. All the materials were free of contaminants such as stones, metal, rubber, plastic, pollutant compounds and other foreign bodies, being direct products or by-products of agriculture.
1. Poplar (Populus spp. L.) wood chips were obtained from dedicated short rotation forestry in the Po Valley (Gadesco Pieve Delmona, Lombardy - 45°10I13II N, 10°06I01II E). The age of the forestry at when it was cut down was five years.
2. Conifer wood chips were the result of mountain forestry management in the North Italian Apennines (Valle Staffora, Lombardy Region - 44°45I15II N, 9°13I49II E). The species that compose the final feedstock were: Larch (Larix decidua), Scots pine (Pinus sylvestris L.), Black pine (Pinus nigra A.), Silver fir (Abies alba M.) and Spruce (Picea excelsa L.).
3. Sorghum (Sorghum bicolor L.) was produced in the Po Valley, close to poplar and wheat (Gadesco Pieve Delmona, Lombardy Region - 45°09I10II N, 10°08I33II E). After harvesting, stalks were dried, chopped and pelletted
4. Wheat (Triticum spp. L.) was produced in the Po Valley, close to poplar and sorghum (Gadesco Pieve Delmona, Lombardy Region - 45°08I59II N, 10°08I28II E). After harvesting, straw was chopped and pelleted.
5. Solid olive residues are by-products of the olive milling process. They were produced in Tuscany (San Giovanni Valdarno, Tuscany Region) by means of continuous oil extraction process with two-phase decanters and it also includes the stones.
6. Maize (Zea mais L.) was produced in the Po Valley (close to Forlì, Emilia Romagna Region). After harvesting, chopped stalks were ensiled, then dried and pelletted.
Concerning HTC, the partner 5 (CS) produced different biochar from five different agricultural products and by-products: maize silage, grass, food leftovers, sewage sludge and biogas digestate.
1. Maize silage was obtained from a local farmer in the region near Kleinmachnow (DE) and is usually used as a feeding material for cattle.
2. Grass from public parks in Kleinmachnow (DE) was purified from impurities (e.g. stones, plastic parts) by mechanical means prior to feeding to the HTC mixing and treatment system.
3. Food leftovers were obtained from a local waste management company in Ludwigsfelde (DE).
4. Sewage sludge was obtained from municipal wastewater treatment plant Frankfurt/Oder (DE).
5. Biogas digestate was obtained by a local biogas plant in Klein-Schulzendorf (DE).
Work package (WP) 2. Monitoring of performance of Biochar production
The objectives of this WP were process monitoring and acquisition of plant performance data
Assessment of potential environmental pollution associated to Biochar production
The aim was to study of industrial processes, including the potential risks associated to environmental pollution. Detailed data that has been acquired in great detail, will then enable the activity planned under WP-3, where LCA has been performed.
System performance data, including energy use/production, operating temperatures, gaseous emissions and maintenance activities have been carefully monitored and archived for a prolonged period of time for subsequent. The main task of WP 2 was to deliver conversion process data for Life Cycle Analysis (LCA) done by project partner Imperial College London (IC) in Workpackage 3 and to collect data on possible harmful gaseous substances arising from the two biochar production processes namely thermochemical (TC) processing and Hydrothermal Carbonization (HTC). During the progress of the EUROCHAR project it became clear that more data are needed for a more detailed LCA. Also data on the impact on the environment from construction of the plant were delivered to the project partner IC. Additional data on economics of the process were provided afterwards. A brief summary of data needed for both processes e.g. for the HTC process can be derived from the following list:
SCENARIO HTC ON A WASTEWATER TREATMENT PLANT
1. Feedstock characterisation of digested sewage sludge
2. General
3. Feedstock characterisation
4. Cultivation/Production of Feedstock
5. Storage of Feedstock
6. Transport of Feedstock to processing facility
7. HTC system parameters
8. Inputs and outputs for HTC / TC process
9. Materials of the HTC plant
10. Hydrochar characterisation digested sludge
11. Treatment of hydrochar
12. Storage of Hydrochar
13. Transport of hydrochar for field application
14. Application of hydrochar from digested sewage sludge
For the TC process 6 Scenarios were defined which have been modeled with the help of the SimaPro software used by project partner Imperial College. The differences in the scenarios were the different feedstock used, namely conifer forest residues, srf poplar, wheat straw, sorghum stems, olive residues, maize silage.In the case of HTC 3 scenarios were defined which are based on two different feedstock namely sewage sludge and grass/greenery and two different uses of the process water in the case of grass/greenery. The process water was treated by the patented technology carbonPure(TM), which was also invented during the EUROCHAR project leading to a more ecofriendly overall process. Also additional material data was provided by both companies for the TC and HTC system to include the impact of the construction process of both technologies in the LCA software. No harm to the environment was observed concerning gaseous emissions of TC and HTC systems. The watery phase of the HTC product was not analyzed during the project but is supposed to be harmful to the atmosphere and must be treated. A patented solution is available for the process water in the HTC hydrochar. An example for the conversion process data collected and provided can be derived from figure 1 for the HTC system. An example for the impact on land occupation and construction materials for the TC system can be found in Figure_3.
The potential risks associated to the production of Biochar, have been examined by analysing flue gases using Solid Phase Micro Extraction (SPME) probes, with specific attention to the production of volatile potentially carcinogenic compounds like PAH (Polycyclic Aromatic Hydrocarbons) during gasification and subsequent gas combustion in electric generators. In the case of HTC, the analysis have been made in aqueous solution following the production of carbonaceous slurries. The sampling during the production of Biochar it was necessary to identify substances as VOCs, PAHs and aldehydes. Sampling done with SPME (7µm PDMS) fibre exposed for 1 hour in the two sampling points. The concentration of the 16 PAHs semi volatiles results extremely below the national limit value of 100 ng/mc. In details the concentration detected in the sampling point on the roof resulted lower than the one in the other sampling point, but we can gather that is due to a dilution made by the external air. So the more significant sampling point is the one inside the plant. In the VOCs compound are included both the volatile PAHs, aldehydes, ketones and phenols. The sampling has been made with a exposed SPME PDMS/DVB fibre and Carboxen fiber for 15 minutes. The results shows the presence of aldehyde, ketones and phenol also if in concentration below the national limit value of 5 mg/mc. Even if the concentration of aldehydes and ketones resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. On top of that some ketones and aldehydes are classified as experimental carcinogenic substances (Classification ACGIH class A3). For the liquid Biochar was made a SPME headspace analysis in GC/MS which reveals a significant presence of acetic acid.
Work package (WP) 3. Life Cycle Assessment
The objectives of this WP were:
Life Cycle Analysis (LCA) of Biochar Production
a. LCA of Biochar use 'field-to-field' (circular supply chain)
b. Life cycle inventory of feedstock production and supply
c. Life cycle inventory of biomass to biochar conversion processes
d. Life cycle inventory of biochar application pathways
Work Package (WP) 3 of the EuroChar project analysed the potential environmental impacts of the production and application of char by applying the Life Cycle Assessment (LCA) methodology to the project-specific supply chains. The supply chains were modelled according to the two conversion technologies, gasification and Hydrothermal Carbonization (HTC), and the respective feedstocks utilised in the project; conifer forest residues, poplar Short Rotation Forestry (SRF), wheat straw, sorghum stems, olive residues and maize silage for gasification, and sewage sludge and green waste (greenery) for HTC: eight supply chains total. The feedstocks selected provide a representative range of the types of biomass feedstocks suitable for char production; dedicated energy crops (poplar and sorghum stems), woody feedstocks (conifer forest residues), agricultural by-products (wheat straw), waste residues resulting from food processing (olive residues), as well as other waste streams (sewage sludge and greenery). Maize silage was only selected due to its isotopic signature, which assisted with the characterisation of the soil emission measurements in the field trials. The feedstocks are also diverse in terms of product classification (main product vs by-product vs waste), cultivation systems, moisture and carbon contents, and the pre-treatment processing required. The full supply chains were analysed in the attributional LCA (aLCA), which considers only the direct impacts of the life cycle. Therefore the system boundary generally included all processes/products from feedstock cultivation through to the application of char to arable land, with the exception of any ‘storage’ of feedstock or char; this was not modelled as the project partners indicated it to be minimal. The allocation methods applied were based on economic value and energy content. With regards to the consequential LCA (cLCA), which includes certain indirect impacts of the life cycle, the system boundary was expanded for the gasification supply chains to include the production of energy as well as increased crop productivity. The Functional Unit (FU) for the LCA study, to which all inputs, outputs and results were scaled, was equal to the amount of char required to sequester 1 tonne of CO2 (0.273 tonnes of carbon) in the soil (at least 100 years), considering only the char carbon. The Life Cycle Impact Assessment methodology applied in the SimaPro LCA software to determine the potential environmental impacts was ReCiPe. The main focus of the LCA study was the Climate Change impact category, or the Global Warming Potential (GWP) of the char supply chains, as this reflects the carbon sequestration potential. Overall, the GWP of all supply chains was negative (except for maize silage), i.e. a carbon sink in which more CO2 was removed from the atmosphere than was produced or released along the supply chain. The GWP (t CO2 eq.) for the various supply chains according to the FU, and using economic allocation for the gasification supply chains, was: -0.58 (wheat straw), -0.76 (sorghum stems), -0.90 (poplar SRF), -0.89 (olive residues), 0.34 (maize silage), -0.63 (conifer forest residues), -0.26 (sewage sludge), and a range of -0.4 - -0.65 depending on the scenario (greenery). The carbon sequestration potential significantly increases when potential indirect impacts are considered in the cLCA, such as the offsetting of energy and the increased productivity of crops; the GWP (t CO2 eq.) was reduced by 0.74 to -1.32 for the wheat straw supply chain and by 1.86 to -2.62 for sorghum stem. Though the net negative GWP results confirm char production and application as a potential carbon sequestration technology, the results are sensitive to the char carbon oxidation rate. Two different oxidation rates, considering a 100 year timescale, were used in the modelling, one based on the H/C value and the other determined by lab experiments. The oxidation rates for gasification chars were 30% and 61% respectively and for HTC chars 70% and 100.7% respectively. The lab oxidation rate for HTC chars results in net positive GWP, in which case the char production and land application system would not be a viable carbon sequestration technology.
The main focus of the EuroChar project was the carbon sequestration potential of char. However, in addition to the GWP category, it is important to analyse a more complete environmental impact profile. The gasification supply chain with the highest potential environmental impacts profile is maize silage, followed by wheat straw, conifer forest residues, sorghum stem, poplar SRF and olive residues. While for HTC, the supply chain with the highest potential environmental impacts is the sewage sludge scenario, followed by the greenery scenarios. When analysing the complete environmental impacts profiles and normalising the LCA results, the GWP was not the most significant impact (except for the poplar SRF and olive residues supply chain). The other impact categories require further investigation to ensure that the benefits of the char system, in terms of carbon sequestration, do not outweigh any other potential negative environmental impacts. Hotspot analysis of the various supply chains was also conducted to determine which stages in the char life cycle produce the highest potential environmental impacts. For the gasification supply chains, the overall main contributor to the potential environmental impact profile is the feedstock cultivation stage; this was the case for wheat straw, sorghum stem, poplar SRF and maize silage. The main potential impacts for the conifer forest and olive residues are linked to the feedstock transportation stage, followed by the gasification stage; as olive residues are a waste product (i.e. no burdens are associated to the cultivation stage) and the production of conifer forest residues requires minimal inputs. The gasification process itself is of relatively low impact as it only utilises a very small amount of fossil energy sources for the start-up electricity. Transportation only becomes a significant contributor when the feedstock cultivation stage is insignificant, e.g. for conifer residues and olive residues. Only transportation of the feedstock has the potential to generate a significant share of the impacts as the feedstock is very heavy compared to the relative amount of char that needs to be transported downstream in the same supply chain mass flow. Sensitivity with regards to transportation distances was limited for the GWP category, but more pronounced in the other environmental impact categories.
Different biomass feedstocks produce significantly different profiles of environmental impact potential. Agricultural crops generally have an intensive cultivation process, in terms of the use of chemicals, machinery and energy, in contrast to woody biomass feedstocks. Poplar, as it originated from a SRF site, also requires quite intensive management and chemical input and therefore resulted in higher impacts. Conifer residues, a result of general forestry management, had very little impact in the overall supply chain hotspot analysis, while olive residues, a waste product, had no impact as no burden is associated with the feedstock cultivation stage. The classification of the feedstock is another key aspect, e.g. main/single product vs by-product or waste-product. For the agricultural crops, a significant amount of the burdens of cultivating the crop is allocated ‘away’ in the SimaPro unit processes to the sorghum and wheat grains, while in the case of maize silage (a main product) it is responsible for all the impacts of its cultivation. Certain characteristics of the feedstock itself also contribute to the LCA results. For example, moisture content and ash content (as the latter relates directly to the gasification conversion efficiency) are main factors in the mass flow calculations. This is highlighted by the high amounts of maize silage (high moisture content) and conifer residues (low amount of char produced via gasification per unit of feedstock input) required to produce the FU in comparison to, for example, wheat straw (low moisture and relatively high ash content and therefore higher conversion efficiency and amount of char produced). The environmental impact profile confirms that dedicated crops (e.g. maize silage) are not a viable feedstock for char production as the supply chain had a high potential environmental impact profile and did not sequester any carbon. For the HTC supply chains, the HTC process is responsible for the largest share of the potential environmental impacts in all categories except GWP; all feedstocks are modelled as ‘waste’ products. As the inputs and outputs for the HTC process were provided on an aggregate basis, it was not possible to conclude which specific process/input/output is responsible for the greatest share of the potential impact, e.g. whether it is the conversion process itself or one of the post-treatment processes. The benefit of the HTC process is that no pre-processing of the feedstocks is required. However post-treatment processing, such as mechanical pressing and potentially also drying, could be a significant contributor within the HTC ‘black box’/unit process. To limit post-treatment processing, it is best to apply the slurry or the filter coal cake directly, if this does not cause any phytotoxic effects. When comparing the gasification and HTC supply chains, even though the HTC chars were given a higher oxidation rate (70% compared to 30% for gasification), the net negative GWP of some of the HTC greenery scenarios was still greater than three of the gasification supply chains (wheat straw, maize silage and conifer forest residues). The main reason for this is the lack of burdens attributed to the HTC feedstocks as all are waste products. However, if the oxidation rate of the HTC chars was based on the lab studies then all HTC GWP would be positive. Overall, it must be noted that no direct comparisons should be made between the technologies as they utilise different feedstock types and produce different chars. As further suggested in the EuroChar Scenario Analysis (WP 7), the technologies are not mutually exclusive and a market mix should be promoted. As one of the key potential benefits of char application, besides carbon sequestration, is its impact on the ecosystem, data relevant to the LCA was collected from the three main EuroChar field trials: the UK, Italy and France field trial sites. The relevant parameters considered ranged from carbon stocks and soil emissions to crop productivity and irrigation and chemical application requirements. Only gasification char produced from maize silage was applied to the field trial sites and the results from one, maximum two, years were collected. The submitted field trial data was not included in the LCA study as most of the requested parameters were either not significant or not measured/available. The only statistically significant results included an increase in above-ground carbon stocks for the biochar plots in the France site and an increase in CO2 soil emissions for the biochar plots in the UK site.
Work package (WP) 4. Chemical and physical properties of biochar
The objectives of this WP were:
1) Creation of a Biochar data repository on chemical (structural), physical and biological properties of biochar from different feedstock and from different carbonization technologies
2) Assessment of correlations between production technology and Biochar properties
3) Database of toxicology impacts of Biochar in mesocosm experiments using a model plant system
4) Carcinogenic effects of biochar
In WP4 we determined chemical and physical characteristics of modern biochars and hydrochars produced from three different feedstocks (wheat straw, popular wood and olive residues) in order to (1) assess the importance of feedstock and production procedure on their properties, (2) evaluate their effects on soil properties and (2) show that biochars and hydrochars have no negative effects on plant growth. The conceptual approach of this WP consisted in the analyses of elemental composition, chemical composition and PAH as well as dioxin content of modern biochars and hydrochars. Moreover, we assessed their effects on the plant genome and plant growth. We used soil sampled from ancient pits (several hundred years old) as a proxy to assess long-term effects of biochar on soil properties and evaluate the use of ancient charcoal to serve as reference material for modern biochar. To fulfill the requirements of this WP, biochar has been produced with a muffle and a pyrolytic stove in the laboratories. The muffle used is an oven that can reach a maximum temperature of 1100°C. It doesn’t have any flux of inert gases, so its inner atmosphere is rich in oxygen. The pyrolytic stove is formed by two cylinders, one inside the other. Biomass is put inside the inner cylinder and ignited. After a few minutes of conventional combustion, thanks to the dynamics of the exhausted gases that flow between the two cylinders, no more oxygen is available inside the inner chamber and so pyrolisis can occur, transforming the biomass into charcoal. The exhausted gases are burnt at the top of the stove where the two cylinders meet. In the muffle it has been pyrolyzed different feedstock at different temperatures (250°C, 400°C, 500°C, 600°C, 800°C, 860°C, 1000°C). During pyrolisis we monitored the temperature inside the stove and in the flame. The variability of the temperature inside the stove is due to the fact that the “pyrolisis front” (the region where pyrolisis occurs) moves down in the stove with time. These measures show that we cannot precisely define at which temperature and for how long biomass has been exposed to pyrolisis. For this reason, we decided not to use this stove to produce biochar at the bench scale.
Evaluation of composition of modern biochars and hydrochars
Our results indicated strong differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. (Figure_4). Production parameters have a much greater effect on biochar and hydrochar properties than feedstocks. Ancient charcoal has a similar chemical composition as modern biochar. However, their elemental composition and chemical reactivity are very different. Therefore, ancient charcoal may not be used as reference material for stability. PAH as well as dioxin concentrations of modern biochars and hydrochars were below the limits given by the international and European biochar initiatives. Therefore, the use of these materials for soil amelioration may be safe.
Evaluation of biochar effects on soil properties
Biochar effects on soil properties were evaluated using soil from ancient pits containing high amounts of charcoal. In these soils, charcoal was present for several hundred years and we hypothesised that these soils could be model systems allowing for the assessment of effects of biochar as unique amendments on soil properties. These systems are very different from those of Terra Preta, where other exogenous organic materials were used as soil amendments in addition to biochar. Our results showed that several hundred years after biochar addition, the microbial functioning of these soils was not altered concerning the capacity of the microbial communities to degrade plant material as well as modern biochar (Naisse et al., 2014, submitted). This was in contrast to our hypothesis that the microbial communities would have adapted to biochar degradation as shown for Terra Preta (Glaser and Birk 2012).
Evaluation of biochar effects on model plants
The main goals of this task was to study the potential toxicity of Biochar (TC and Hydrochar) using model plants. We have done two different experiments in Germany (University of Halle) and in UK (University of Southampton) to evaluate the potential toxicity of biochar and hydrochar on two different model plant: Arabidopsis thaliana growing in soil using biochar from TC and Tradescantia using hydrochar and biochar from TC.
Toxicity test using Arabidopsis thaliana
In order to test the toxicity of biochar on Arabidopsis, we used different rates of biochar equivalent to : 0 t ha-1, 20 t ha-1, 30 t ha-1, 50 t ha-1 and 100 t ha-1, corresponding to 0, 1.7 2.5 4.2 and 8.3% w/w (dry weight) respectively. Fertilizer could also be applied following manufacturer instruction. Global gene expression arrays were used on biochar-treated plants to analyse the changes in metabolic pathways. A leaf chemical analysis was also performed between plants grown in soil mixed with and without biochar. The leaves were sampled for microarrays and snap frozen in liquid nitrogen. RNA was extracted (Chang et al., 1993) of three replicates of control and five of biochar (50 t ha-1) with fertilizer, and were hybridized to GeneChip Arabidopsis Genome Arrays (Affymetrix, Santa Clara, USA) by the European Arabidopsis Stock Centre (NASC, UK). Data were analysed in GeneSpring (Agilent technologies, Santa Clara, USA). Chips were normalised by MAS5. Differentially expressed genes were identified through t-test between samples of control and biochar (p<0.05 2-fold change difference) with a multiple testing correction (Benjamini-Hochberg). Genes were annotated using GeneSpring (Agilent technologies, Santa Clara, USA) and the website Tair (www.arabidopsis.org). Lyophilised leaf samples were extracted and partitioned according to the method of Foito et al. (2013) for the chemical analysis. The microarray analysis revealed a total of 1076 genes differently expressed when comparing control plants with plants grown in biochar at 50 t ha-1, both with fertilizer. We identified 571 genes that were down-regulated and 505 that were up-regulated in response to biochar application. (Figure_5). Metabolic pathway analysis was performed using mapman (Figure 6). Signalling, transport and biosynthesis of two plant hormones central to growth stimulation – auxin and brassinosteroid – were up-regulated for plants grown with biochar. A significant reduction of anthocyanins, flavonols and glucosinolates was observed for the plants growing in biochar (50 t ha-1) compared to the control In addition, genes controlling cell wall loosening, including numerous xyloglucan endotransglucosylases and expansins (Figure_6) were up-regulated in biochar suggesting enhanced growth was underpinned by increased cell expansion. Transporter genes for sugar, nutrients and aquaporins were upregulated (Figure_6) for better water and nutrient uptake and movement of sugars for metabolism in the plant.
Toxicity test using Tradescantia
We tested genotoxic effects of different hydrochars and biochars with the Tradescantia micronucleus test. For this purpose, chromosomal aberrations in pollen cells of Tradescantia in the form of micronuclei were evaluated microscopically after defined exposition to extracts from char materials. Hydrochars from hydrothermal carbonization mostly exhibited significantly negative results (Busch et al., 2013). Additional germination experiments with hydrochar showed total germination inhibition at additions above 5% (v/v) in comparison to biochar (Figure_7). However, biological post-treatment of previously toxic hydrochar was successful and toxic effects were eliminated (Figure_7). Some post-treated hydrochars even showed growth-stimulating effects. Our results clearly demonstrate the necessity of risk assessment with bioindicators. The chosen tests procedures can contribute to biochar and hydrochar characterization for safe environmental application.
Work package (WP) 5. Short- and long-term stability of biochar
The objectives of WP 5 were:
- to assess the stability of modern biochars and hydrochars
- to test chemical methods in order to develop a simple stability indicator.
We assessed the stability of modern biochars and hydrochars through a combination of physical, chemical and biological methods. Physical methods included application of a protocol, with wetting/drying and freezing/thawing cycles in order to mimic weathering processes occurring after field exposure. Weathered and non-weathered samples were subjected to chemical methods (oxidation and hydrolyses) as well as laboratory incubation in soil. Use of stable isotope analyses allowed for the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. We used for these analyses biochar produced from maize silage incubated at an application rate of 30 Mg ha-1 in soil of the French field experiment. The different methods applied allowed for the analyses of biochar and hydrochar stability at different time scales. Here we will present additional information as well as a synthesis of the most important results.
Chemical stability
Concerning the chemical stability of the different chars, our results showed that oxidation with acid dichromate (0.1 M K2Cr2O7 in 2 M H2SO4) for 12 h is a suitable, simple method, allowing for the assessment of char stability based on elemental composition (Naisse et al., 2013). However, the handling of acid dichromate requires special care as the reagent is toxic, mutagen, carcinogen, and can cause serious problems when entering the drinking water supply. As the chemical reactivity of biochar changes with time, our results further indicated that it is only a poor indicator of stability beyond decadal timescales (Naisse et al., 2014, in press). A better alternative is the simple determination of elemental composition (C and H) and calculating H/C ratio, which has a close correlation to biochar stability (Figure_8).
Short term stability
Short-term biological stability was evaluated during 222 days of laboratory incubation. Our results showed that the biological stability of biochar is higher than that of hydrochar. During the early stage of soil incubation, the hydrochar input induced a positive priming effect, indicating a stimulation of soil organic matter (SOM) mineralization by addition of easily degradable carbon. In contrast, the biochar input induced a negative priming effect showing additional protection of soil organic matter. However, priming is a short-term phenomenon in pasture soil, which lasted only for the first few weeks.
C sequestration potential of biochar and hydrochar
Long-term stability of biochar and hydrochar in soil as well as their C sequestration potential was assessed through extrapolation of mineralisation data from laboratory experiments of weathered and unweathered chars as well as the study of biochar survival in ancient charcoal deposits. The laboratory experiment indicated that biochar is more stable than hydrochar and has a higher C sequestration potential taking into account weathering effects and priming effects on soil organic matter. Half–lives of fresh and weathered hydrochars were estimated between 8.4±0.9 to 10.4±0.3 years, and between 73.6±5.6 to 145.0±24.0 years for fresh and weathered biochars. Carbon sequestration potential including char mineralization, priming effect and physical weathering assessed for both chars, indicates that at the decadal scale, hydrochars and biochars would lead to similar increase of soil C storage. At centennical scale, only biochars would have the potential to increase soil carbon sequestration (Figure_9). We investigated the long term effects of charcoal addition on C sequestration and soil physico-chemical properties by studying a series of abandoned charcoal hearths in the Eastern Alps of Italy established in the XIX century (Figure_9a). This natural setting can be seen as an analogue of a deliberate experiment with replications. Carbon sequestration was assessed indirectly by comparing the amount of pyrogenic C present in the hearths (23.3±4.7 kg C m−2) with the estimated amount of charcoal that was left on the soil after the carbonization (29.3±5.1 kg C m−2). After taking into account uncertainty associated with parameters’ estimation, we were able to conclude that 80±21% of the C originally added to the soil via charcoal can still be found there and that charcoal has an overall Mean Residence Time of 650±139 years, thus supporting the view that charcoal incorporation is an effective way to sequester atmospheric CO2. We also observed an overall change in the physical properties (hydrophobicity and bulk density) of charcoal hearth soils and an accumulation of nutrients compared to the adjacent soil without charcoal. We caution, however, that our site-specific results should not be generalized without further study.
Field experiment with composted hydrochar and composted biochar
A field experiment with composted hydrochar and composted biochar showed a significant increase in topsoil organic carbon contents three weeks after application of compost and composted chars and also after one year of field incubation (Figure_10). The control groups did not show a significant difference to each other (all t0 variants as well as control t0, t1 and t2). The plots with compost treatment were slightly lower in TOC content but still significantly different in comparison to the control. Only variants with biochar treatment still showed a highly significant increase of TOC one year after application in comparison to controls (Figure_10). There was a significant difference of TOC content between t2 compost and t2 BC-C (Figure_10). Only composted biochar application showed a significant increase of black carbon content compared to composted hydrochar, pure compost and control (Figure_10). The increased black carbon content in the composted biochar treatment indicates a higher stability of organic matter and therefore a higher C sequestration potential compared to pure compost or composted hydrochar. The contribution of BC to TOC was about 10% in the topsoil control and in the subsoil of all treatment (Figure_10). In the control plots, BC to TOC contribution decreased during the experiment (Figure_10), indicating sequestration of labile non-BC C during the experiment. This might be due to the growth of species-rich natural grassland, which was not cut during the experimental period. It is known that grassland vegetation sequesters C through rhizo-deposition. After compost application, BC to TOC contribution decreased to about 5% (Figure_10) due to the application of C-rich but BC-poor organic matter. After one year of field incubation, the BC to TOC contribution increased again, indicating that a portion of the applied compost was mineralized while the soil-inherent BC remained more or less constant, although the mineralization effect was not significant (Figure_10). The same trend as for pure compost was observed also for composted hydrochar but mineralization during field incubation was lower than for pure compost (Figure_10). Black carbon to TOC contribution of composted biochar-amended soil increased to 80 – 90% after application and remained more or less constant throughout the experiment (Figure_10). In this treatment, both BC and TOC increased during the experiment, indicating a C sequestration potential of composted biochar beyond biochar alone.
Work package (WP) 6. Biochar stability in Field Applications
The objectives of WP6 were:
1. To assess/demonstrate the potential for Biochar application in short-rotation forestry (SRF) in the EU
2. To quantify the net C-sequestration achievable in SRF
3. To follow the fate of the Biochar in the soil and to quantify changes in the emission of non-CO2 GHG gases
4. To quantify additional potential effects of Biochar on soil fertility, soil biodiversity and SRF productivity
WP6 aimed to demonstrate the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. In addition, the fate of applied biochar, its impact upon greenhouse gas exchange and variations in soil biodiversity and fertility were measured. WP 6 utilised the biochar and hydrochar (HTC) produced by WP1, in collaboration with Carbon Solutions (Germany) and AGT (Italy). In order to understand the impacts of biochar amendment, EUROCHAR set up the most extensive network for biochar research within the EU. This consists of three core sites, located in Italy, France and the UK (treated with biochar produced by AGT Biochar, Italy), plus four satellite sites located in Italy and one in Germany. Impacts of both biochar and hydrothermal char (HTC) were to be assessed, but due to the possibility of elevated PAH’s present within HTC, it was decided to assess these only within pot experiments. Later, evaluation of HTC produced by CarbonSolutions (Deutschland GmbH) found that PAH’s and other potentially harmful components were at levels far below the recommended safety levels, and so they were applied at field scale in the German satellite site at Halle. The core sites consist of two biofuel crop sites, located in Italy (Prato Sesia, comprising of SRF Poplar) and in the UK (West Sussex, comprising of short rotation coppice Willow). A third core site of grassland was located in France (Lusignan) with the aim of assessing biochar application in agricultural pasture (Figure_11). At each site, eight plots were set up. At SRF and SRC sites, plots contained either five (Prato Sesia) or six (WestSussex) experimental trees, surrounded by a row of guard trees in order to limit edge effects. Four replicate treatments were established for yield and biomass results, whilst three replicates were installed to measure soil respiration. Soil respiration was assessed through use of two automated soil respiration chambers per plot, one measuring total soil respiration (Rtot) and another quantifying root excluded soil respiration (Rh). This was achieved through installation of a root exclusion cylinder around the respiration chamber to prevent root invasion into the measurement area. Results from soil respiration analysis at Prato Sesia indicate increased soil respiration during summer in both biochar and control plots, probably as a result of increased soil temperature (Cheng, Lehmann and Engelhard, 2008). Addition of biochar caused no significant difference in flux from root excluded versus non-root excluded plots. Furthermore, there was no significant difference between cumulative flux from biochar or control plots. However, isotopic analysis of CO2 efflux indicated that between 7% and 36% of soil respiration was attributed to biochar amendment, although this varied depending on the date of sampling. A seasonal component was noted, which was further accentuated in root excluded plots. The total respiration attributable to biochar was greater within Rtot samples versus Rh, indicating increased respiration of biochar within the soil when roots were present (Figure_12). During the measurement period (245 days) approximately 7% of total biochar was respired from Rh plots, whilst the total increased to approximately 9% in the presence of roots (Rtot). Soil respiration results at West Sussex indicate an increase in CO2 flux associated with biochar amendment(Ventura et al., 2014). Again, soil respiration increased in both treatment and control plots during the summer as a result of increased soil temperature. Diverging from the results from Prato Sesia, Rtot was significantly increased after biochar application at West Sussex, whilst there was no significant change in Rh. Isotopic analysis elucidated between 12% and 32% of soil respiration was attributable to biochar treatment, again with a seasonal summer component. In agreement with the results from Prato Sesia, Rtot was greater than Rh in biochar treated plots, indicating increased soil respiration as a result of the presence of roots. During the measurement period (164 days) total biochar derived CO2 was between 3% of total Rh, and 8% of Rtot, again indicating the effect of the presence of roots on biochar associated CO2 flux. Overall, whilst the rate of degradation was elevated, the treatment resulted in a protective effect on existing soil organic matter, preventing the loss of 0.5-0.7 t/ha in Italy and the UK respectively. Stem base diameter and height measurements were undertaken at Prato Sesia, combined with destructive dry biomass assessments. No significant difference was determined during either the first or second growth season at the site. Leaf litter biomass showed no effect of biochar application, nor did total C or N concentration within the litter. Furthermore, annual net primary productivity showed no significant difference between treatments. Assessment of N and P leaching within biochar plots showed no significant differences at Prato Sesia at any time point when comparing between biochar and control plots. Assessment of biomass was undertaken through stem diameter and height measurements at three time points, March and December 2012, and again during November 2013. Plant volume indicated no significant effect of treatment, or interaction between treatment and time on total plant volume. Similarly, leaf litter biomass was not significantly affected at approximately 4.5t/ha irrespective of biochar or control treatment. Extraction of resin lysimeters indicated a difference in results when compared to Prato Sesia, with an increase in P-PO4 and N-NH4 leachate in biochar amended plots when compared with controls. At both SRF and SRC sites, a similar negative priming effect was noted. After negating biochar derived C, soil respiration measurements indicated savings of 0.5 t/ha of C in Italy, and 0.7t/ha of C in the UK. In addition, biochar degradation within the soil was significantly higher in the presence of roots when compared to root excluded plots. This is at a higher rate than that measured in lab studies which often do not consider the role of plants in biochar decomposition studies, validating the usefulness of field trials of biochar. When dividing the priming effect by year, it was noted that it is decreased during the second year after amendment. Due to difficulties in equipment maintenance, data from Lusignan 2012-2013 was not sufficient for analysis. Difficulties with data collection were such that there is inadequate data for gap filling during this time period. However, isotopic analysis was undertaken, and this analysis currently undertaken. Furthermore, data is being collected from Lusignan for the 2014 season, so it is hoped that subsequent analysis of these results will be possible to determine whether a similar effect of negative priming can be detected. Soil C content was carried out at Lusignan, indicating that C content within biochar amended plots were considerably higher than those found in control. In addition to the three core sites, a range of additional satellite sites were established. In Pistoia a raised box experiment investigating the effect of HTC on poplar was produced. A raised box experiment was carried out to assess the impacts of HTC on SRC poplar at Pistoia-CESPEVI (PT). This method was chosen as it would prevent HTC treated soil from contaminating the soil environment. This was carried out at a stage in the project when it was thought there may have been potentially toxic effects of HTC’s due to high PAH’s. This was later found to be incorrect, and that HTC’s contain PAH’s below the legal limits in the EU.
After 2 years of measurements of both soil respiration and poplar biomass, it was determined that HTC increased poplar biomass only during the first year after application. Subsequent HTC applications caused no significant increase when compared with the initial HTC application, although all HTC trees had a greater biomass than control trees. Soil respiration was also analysed, and indicated significantly higher respiration in the presence of HTC. Results from Montepulciano site on ecophysiological measurements were published in (Baronti et al., 2014). Briefly, biochar addition significantly increased plant water availability with the consequence of increasing leaf water potential and plant photosynthetic activity in dry periods; and no significant effect on soil hydrophobicity was detected after biochar application. A paper describing the effect on grape yield and grape ripening parameters is in preparation, briefly, grape productivity was significantly increased in biochar treated plots (up to 66% in 2012) with no significant effect on grape maturity parameters. For further details see (Baronti et al., 2014). . Grape productivity was significantly elevated, with no negative impact upon fruit quality (Genesio et al., submitted). Results from Castell’apertole site on LCA analysis were published in (Lugato et al., 2013). The local climate is sub-humid, with annual rainfall of about 990 mm and average annual temperature of 11.6 °C (maximum and minimum average monthly temperatures in July and January are 28 and -3 °C, respectively). The soil has a sandy-loam texture (3.8 27.5 and 68.7% of clay, silt, and sand, respectively), pH (in H2O) of 5.6 and absence of carbonates along the profile. The application of biochar from gasification increased rice grain production by 12%, but such effect was only significantly different at P = 0.16. This was lower than the effect of addition from biochar from pyrolisis (36%, P=0.05) but this is probably due to increased macronutrients present within the slow pyrolisis biochar. LCA analysis calculations utilising the BEAT v2.1 model was utilised. This showed that the stage of the process contributing most to GHG emissions is gasification (more so than supply chains, biochar storage or transport). Drying had a lower GHG impact due to the use of waste heat from the AGT gasifier being used to further dry the feedstock. However, as the biochar is a waste product of the electricity generation of the system, the net GHG emissions are negative when assuming a 76.1% carbon content of biochar, and either of the two mineralization rates (32% and 7.3%) studied. For further details see (Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Results from the final two sites (Halle, Germany and San Michele all’Adige, Italy) are in the process of being analysed. The German site is assessing the stability and potential yield effects of HTC biochar in a field experiment, and was established after it was determined that there were no potentially toxic effects of HTC. It is comparing the impact of HTC, HTC combined with compost, slow pyrolysis biochar combined with compost and no treatment. The Italian site consists of a pot experiment using both AGT and HTC biochars with the aim of assessing their impact upon poplar growth when combined with mycorrhizal inoculation. The implication of biochar application was also studied in relation to soil bacterial and fungal diversity. Soil samples collected from each of the three core sites had DNA extracted from them and the 16S rRNA gene sequenced, allowing for identification of bacteria present within the communities. This amplicon has highly preserved regions, allowing for primer design and amplification, but also contain hypervariable regions permitting differentiation and identification of sequences from difference species. Utilising these methods it was noted that application of biochar caused a significant shift in the weighted UNIFRAC distances in both West Sussex and Prato Sesia (Figure_13). This indicates that the change in diversity is as a result of fluctuating abundance in the core species present. Furthermore, unweighted UNIFRAC analysis demonstrates a small but significant change in the species present between the treatments at all three core sites (Figure_14). Treatment explains between 5-8% of the variation noted in unweighted samples. It is likely that this small shift is in rare species with low abundance, as weighted results indicate a considerably greater portion of the variation (19-34%). Furthermore, when taken with the lack of a significant difference in the phylogenetic diversity scores (measuring alpha diversity) between control and treatment, it is expected that any shifts in the species present are to other similar species. Additionally, assessment of time series samples collected in West Sussex shows a significant effect of time interacting with treatment. Samples collected before biochar was added exhibit no significant difference in either weighted or unweighted UNIFRAC distances. At one month after biochar application, there were still no significant difference between treatments when assessed with weighted UNIFRAC, but a significant difference was present when unweighted UNIFRAC distance was assessed. This implies a minor shift in species under biochar treatment. Samples collected 1 year after biochar application are significantly different from all of those collected within year 1, regardless of treatment, and show greater clustering by treatment when assessed by both weighted and unweighted UNIFRAC. Therefore it seems likely that application of biochar causes a greater shift in community structure with time. This may be due to the increased surface area, nutrient availability and gradually shifting pH as a result of biochar application. In addition, SOM, SOC and electron donation may also result in further selection pressures, leading to rebalancing of microbial population in response to newly available environmental niches.
Work package (WP) 7 Scenario Analysis
The objectives of WP7 were:
1) Evaluate scenarios of large-scale application for C-sequestration
a. Current and future land use and potential for biochar application rates
b. Assessment of C-sequestration potential, based on inventory data
c. Estimation of Net Primary Production (NPP) and Net Ecosystem Production (NEP) for European agriculture
d. Assessment of C-sequestration potential, based on field study data
2) Understand the impact of large scale biochar agricultural application on the climate system on the basis of a sensitivity experiment on the forcing the albedo parameters in a RCM- modelling scheme
3) Understand potential “warming effects” by considering the reduction of net C-emission due to Biochar use at European scale to establish potential “cooling effects” due to changes in atmospheric CO2 concentration.
Work Package (WP7) of the EuroChar project established and analysed various scenarios in terms of feedstock available for the production of char, the subsequent potential scale of char production and land application, as well as the impact of the latter on albedo. The 28 countries of the European Union (EU-28) were considered as the geographical scope and 2010-2050 as the timeline. To determine a potential scale of feedstock available for the production of char, a number of categories were selected in accordance with the European Biochar Certificate: agricultural crop residues, forestry residues and the organic fraction of Municipal Solid Waste (MSW). Only waste and residues were considered to be viable feedstocks for char supply chains and only a certain share (20%) of these residues/wastes were assumed to be available for the production of char. The 20% share assumed to be ‘available’ signifies the many competing uses that exist for biomass feedstocks, however it must be noted that certain uses are not mutually exclusive and a prior use could eventually contribute to the production of char e.g. through recycling or, various renewable energy production pathways that also produce a certain amount of char as a co-product. The calculated technical, annual available feedstock potential for EU-28 was 116 Mt/yr dry feedstock (maximum moisture content of 15%), or 138 Mt/yr ‘wet’ feedstock (original/harvested moisture content). The potential scale is based on the assumption that the average amount of feedstock from 2005-2010 remains static for 2010-2050. Another range of feedstock potentials was calculated considering the average change in feedstock amounts from 2000-2010 and extrapolating this average annual change to 2050. The latter, ‘dynamic’ approach results in dry annual feedstock potentials of 115 Mt in 2010 to 124 Mt in 2020, 137 Mt in 2030, 157 Mt in 2040 and 188 Mt in 2050. As biomass feedstock potentials are volatile, the initial ‘static’ approach was applied as a basis for the further scenarios modelled in the EuroChar project. The estimated feedstock potentials were linked to char production scenarios, which considered three conversion technologies: gasification, Hydrothermal Carbonization (HTC) and slow-pyrolysis. Two production systems were established; one where a single technology is utilised and another system that represents a market mix of technologies. As the technologies are not mutually exclusive, due to their optimisation to different feedstock categories and the production of varying product types with differing characteristics, the ‘market mix’ production system is considered to provide a more realistic scenario and was therefore applied as the basis for the modelling. The potential scale of char production for 2010-2050 was calculated at 14-38 Mt/yr depending on the scenario of technology mix, conversion efficiency, etc. Considering the ‘dynamic’ scale of feedstock availability, annual char production potentials ranged from 13-37 Mt for 2010, 14-40 Mt for 2020, 16-44 Mt for 2030, 18-51 Mt for 2040 and 22-61 Mt for 2050 depending on the scenario. For single technology production systems the annual scale of char production for 2010-2050 ranged from 1-26 Mt for gasification, 25-41 Mt for HTC, and 35-47 Mt for slow-pyrolysis. From the scale of char production, potential arable land coverage was estimated considering three different application scenarios at a single application rate of either 10, 35 or 120 t/ha. The char production scale, considering a technology mix, was calculated to cover 0.1-3.5% of the EU-28 arable land annually from 2010-2050 depending on the scenario. An annual 2% coverage would result in 100% coverage in 50 years, however this only considers a single application per unit land area over the 50 years; char could also be applied to other land types and multiple application frequencies for the low and medium application rates are possible and potentially even required to achieve positive yield impacts. The scenario modelling work in the EuroChar project indicates that a potentially limiting factor in the large-scale production and application of char is the availability of feedstock. The main conversion technologies are well developed and are expected to see an increase in uptake and deployment, promoted by, for example, increased funding for projects in developing countries (pyrolysis cook-stoves), green energy subsidies (gasification), more sustainable routes for waste treatment (HTC), carbon credits, etc. With regards to land application, many types of lands could have char applied and multiple applications are possible either annually or multi-annually. Also, any legislative restrictions in terms of char application to land are expected to decrease over time. The impact of char on the carbon cycle through its production and land application was considered in order to calculate its carbon sequestration potential. The application of char can impact the carbon cycle through changing the Net Primary Productivity (NPP) and/or the soil carbon stock. Char’s impact on biomass productivity is highly uncertain and therefore a single increase of 5% in NPP was considered in the scenario analysis. Considering the calculated scale of char production and land application, this results in an increase of NPP/vegetation carbon stock of 0.037-1.28 Mt of CO2, which is equivalent to 0.0064-0.22% of the total UK emissions in 2012. As the vegetation and soil carbon stocks of croplands are minimal compared to other land area types, such as forests (especially boreal forests), the potential beneficial impact of char on NPP would be significantly greater if char was applied to these other land types. More work is needed to understand if the productivity impacts of char are robust across different soil and vegetation types. The impact of char on the soil carbon stocks was calculated considering initially only the carbon in the char and subsequently also including the supply chain emissions calculated in the Life Cycle Assessment (LCA) (WP 3). Based on the calculated potential scale of char production in the EU-28 from 2010-2050, and considering only the char carbon, the annual sequestration potential was calculated at a level of 16-50 Mt CO2/yr, which is equivalent to 1.79-5.6% of total EU-28 transport emissions in the year 2012. When including the direct, attributional supply chain emissions, the sequestration potential is reduced to 14-40 Mt CO2/yr, similar to a level of 1.57-4.48% of total EU-28 transport emissions in 2012. If the indirect, consequential supply chain emissions are also considered, the carbon sequestration potential would significantly increase. The advantageous consequential impacts are mainly due to the offsetting of fossil energy sources, however the extent of this benefit will depend on the composition of the energy mix, which is expected to become ‘cleaner’ in the future. The combined annual sequestration potential of char production and application in the EU-28 for 2010-2050 considering both NPP and soil impacts, including the supply chain emissions, ranges from 14-41 Mt CO2. Potential closed-loop scenarios, in terms of the carbon cycle as well as considering the mass flows of the project-specific char production and application supply chains, were also established and analysed. Application of the closed-loop methodology to the char carbon cycle is problematic because of the basic carbon neutrality (closed-loop) of cropping (vegetation) systems. Overall, char application is expected to increase the portion of carbon diverted into the longer-term soil carbon stock. The counterfactual assumption in this case is that the carbon in the biomass residues would have returned to the atmosphere via the short-term/fast carbon cycles of decay and heterotrophic respiration. On a mass basis, simple ‘payback’ periods were calculated to determine the number of years needed to obtain the amount of biomass required to produce a certain amount of char. Payback periods were significant and ranged from 4-87 years depending on the crop, the crop yield considered (in this case assuming all yield is utilised), and the amount of char required. When considering that only a 20% share of the yield is available for char production the simple ‘payback’ period increased significantly to 18-434 years depending on the scenario. However, two issues substantively complicated the concept of ‘closed loop systems’ and ‘payback periods. Firstly, the char application rate was chosen to represent the amount of char that is assumed to be required to produce beneficial impacts on crop production. This is considered as a one-off application with the impacts lasting decades. Secondly, as only the gasification technology was considered in the closed-loop scenarios, the main purpose of gasification is to produce a fuel for electricity production as the main product with only a relatively small amount of char as a by-product, about 10% of the feedstock input on a mass basis. We therefore advise caution when interpreting the ‘payback’ periods calculated, as the carbon/biomass ‘lost’ to the atmosphere should be proportionately allocated to the associated electricity production and not exclusively to the char.
Biochar is a promising strategy to safely sequester relevant amounts of carbon into agricultural soils while simultaneously increasing crop yields and soil ecosystem services. Nevertheless, looking toward a possible large-scale application of this technology, a fundamental aspect that needs to be treated, is the assessment of the consequences of implementing this strategy on the surface radiative energy balance. In fact, being a carbon-based substance, biochar has a very low reflectivity, and its addition to agricultural soils is demonstrated to change the background colour of the treated cropland altering (decreasing) the ratio of reflected and incoming shortwave radiation (albedo), potentially affecting the energy fluxes partitioning. EuroChar tackled this topic with a multi scale approach (local-landscape-regional) enabling to improve our knowledge on the impact of biochar on the radiative balance and providing inputs for an improved representation of surface schemes for modelling purposes. The plot scale experiment on wheat showed a surface albedo increase up to 80% in plots treated with biochar in respect to their control. Furthermore it enabled to highlight that biochar application increases soil surface temperature during winter promoting a faster crop growth during the first crop phases (Sensible heat flux was increased by 17% during winter). Moreover an increased evapotranspiration during the crop cycle was observed (+4%), related to the increased biomass and to the higher plant water availability. In the landscape scale experiment, large scale biochar application were simulated by comparing 6 target sites having different soil colour over a 12 years time series by means of satellite datasets of NDVI and Albedo. The objective of the work was to estimate the influence of a change in soil background colour induced by biochar incorporation on the surface shortwave albedo of a complex agricultural system in the Mediterranean environment, as well as its impact on Radiative Forcing. This experiment has been essential to disentangle the existing uncertainties related to the representation of albedo seasonal mode in function of canopy development in complex agricultural Mediterranean environments. In particular the main findings that have been transferred to the modelling section are that i) in complex agricultural systems soil darkening can induce an overall net increase in cumulated absorbed solar radiation in dark soil sites as high as 2%, ii) the magnitude of such effect is modulated by the fractional vegetation cover and by specific canopy reflectivity parameters, but iii) also in high canopy cover conditions (vegetation peak = high LAI) soil background colour has an impact on surface radiation balance. The experiment also highlighted that agricultural policies and the related crop choices do have a relevant impact on the overall Absorbed Solar Energy Balance; this was particularly evident in the case of one of the selected test sites (NE) where, as a consequence of agricultural subsidies to sunflower during the years 2000’s, this crop was implemented on the same dark soil site for almost a decade inducing a significant negative radiative forcing able to offset the expected difference in radiation balance caused by the low soil reflectivity.
The Regional scale modelling experiment, performed perturbing the arable land albedo scheme in WRF model, showed that a small but significant impact on surface temperature is expected as a consequence of a European-scale biochar application and in particular a local temperature increase of about 0.1°K has been detected in Eastern Europe.
Potential impact (including the socio-economic impact and the wider societal implications of the project so far) and the main dissemination activities and the exploitation of results. The length of this part cannot exceed 10 pages.
The potential impact of Eurochar project are numerous.
The results of WP1 clarified that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste.
The knowledge and technology implementation achieved on the two processes will impact on the finalization of the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. New knowledge on HTC revealed that this subproduct might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage. This new information will have an impact on the technological chain and the implementation of new synergies between the two processes.
EuroChar will also contribute to the development of industrial process by providing evidence that the production of gaseous pollutants during gasification and Hydrothermal treatments are very low. But it will also generate some caution, as even if the concentration of aldehydes and ketons resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. The observation of a presence of ketons and aldehydes which are classified as experimental carcinogenic substances (Classification ACGIH class A3) will generate some specific attention on the regulations and controls of industrial processes.
The fact that the TC biochar and HTC chars were used not only within the project Eurochar, but also in trials by other external entities will have an impact. The list of organizations that directly benefit from the avaiability of chars is large: CRA-RPS, Research Centre for Soil-Plant System studies of Agricultural Research Council of Italy, Rome (I),CRA-ORT, Research Centre for Horticulture of Agricultural Research Council of Italy, Battipaglia (I),ENR-CCR, Rice Research Centre of Italian National Agency for Rice, Castello d’Agogna (I), Trees and Timber Institute of CNR (National Research Council of Italy), Florence (I), Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Rome (I), Minoprio Foundation, Vertemate con Minoprio (I), University of Bologna, Bologna (I), University of Milan, Milan (I), University of Palermo, Palermo (I), University of Parma, Parma (I), University of Pisa, Pisa (I), University of Udine, Udine (I), UKBRC, UK Biochar Research Centre, University of Edinburgh, Edinburgh (UK), Institut Sylva, Le Bec Hellouin (F), Agronomia Group, Bergamo (I) (Production of ready-to-eat salad vegetables), Plozner, Spilimbergo (I) (Wine farm), TerrAgricola, Varese (I) (Production of soil improvers and growing media), Vivai Pacini, Pescia (I) (Olive nursery), Max-Planck-Institut für Biogeochemie, Jena (DE), Hochschule für nachhaltige Entwicklung Eberswalde, Eberswalde (DE).
Life Cycle assessment (WP3) results will have a potential impact on C-sequestration policies and initiatives. The production and application of char could therefore contribute to climate change mitigation, and new regulations may profit of the information which hass been collected and analysed through LCA. The results will however further discourage the use of dedicated crops for the production of char. The observation that char oxidation rates are important in LCA will impact substantially on future research plans in biochar science. Carbon credits policies will also benefit from the results achieved, to eventually provide a financial incentive for carbon sequestered through the production and land application of biochar. There are a number of other social and economic benefits from the production and application of char. The co-production of energy, e.g. in gasification systems, could offset ‘dirty’ fossil energy sources, which would have a significant impact on climate change. The land application of char could improve ecosystems by increasing nutrient and water retention capabilities. These beneficial impacts on agricultural lands could increase productivity and reduce fertiliser and irrigation requirements, providing significant economic benefits to the farmer and society as a whole. However, the application of char could potentially also have some phytotoxic effects depending on the conversion technology and feedstock used. Safety regulations therefore have to be stringent and post-treatment processing might be required to eliminate such potential detrimental impacts on the ecosystem. Another important conclusion from the LCA results indicates that feedstock transport could cause a significant share of the potential environmental impacts. It is therefore recommended that the char production is either done on-site at the feedstock plantation/origin or located nearby. On-site production could provide an additional revenue stream to the farmer or site manager if the char were to be sold or the co-produced energy exported to the grid. Finally, the lack of LCA-relevant parameters obtained from the field trials indicate that future field studies should consider these parameters in their data collection inventory. Impacts of char application in terms of potentially reducing fertiliser and irrigation requirements or increasing crop productivity could provide significant environmental ‘benefits’. Field trials are required, in combination with controlled lab studies, to provide a more accurate representation of the real impacts/fate of the char applied, and this should therefore be another key continued and future focus within the char research field.
Results obtained in WP4 which determined chemical and physical characteristics of modern biochars and hydrochars produced from different feedstocks pointed to the existence of large differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. This, together with the observation of phytotoxic effects that can be eliminated by chemical (e. g. oxidation) or biological treatment (e. g. composting) will have a direct strong impact on the production of biochar with sufficient environmental safety. And it will stimulate further research which is urgently needed to identify the unknown phytotoxic and genotoxic compounds in the hydrochar since the unknown substances may also impact human health.
Results obtained in WP5 that assessed the stability of modern biochars and hydrochars and developed stability indicator will have a direct impact on the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. The observed differences between biochar and hydrochar and composts will be directly used to estimate the relative effective C-sequestration potential, thus contributing to the development and implementation of new regulations. On the other hands, the same results will stimulate the utilization of co-composted hydrochar as suitable as soil amendment because it may increase the content of organic carbon in compost substrates, even if the low amount of polymerized carbon structures makes this material not resistant enough against microbial degradation.
The results of WP6 demonstrated the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. A key impact of the activity made, is in the creation of major infrastructure in Europe and the establishment of network of biochar field sites that can become a long-term facility, opened to international access. This would provide for some of the first assessments of long term biochar stability at highly instrumented sites, further developing knowledge of the viability of biochar as a method of carbon sequestration. The multi-site experimental data that have been collected are of primary importance for the development of EU standard and policies on C-sequestration as these provide practical evidence that biochar application in soils can be made in a safe and effective way, with limited costs and a net environmental benefit. Results from the Castel all’Apertole and Montepulciano satellite sites demonstrate the viability of biochar as a soil amendment, augmenting crop yield whilst having no negative impact on crop quality (Baronti et al., 2014; Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Furthermore, the elevated water holding capacity of soils treated with biochar may have the potential for utilisation to reduce drought effects and total irrigation required by the crops. This has potential implications for increasing the uptake of biochar soil amelioration within the agricultural community.
Shifts in microbial communities present in 2 of the 3 core sites call for a better understanding of the mechanisms involved, something that may help in future to elucidate how biochar actually contributes to soil fertility.
The results of WP7 that consider scenario analysis in the case of large scale applications of biochar has a number of potential relevant impacts. In terms of feedstock availability, limited impact is expected as only residues and waste are considered a feasible feedstock and only a 20% share of this feedstock category was considered to be available. We consider it unlikely that dedicated cropping solely for the production of char could be regarded as socially acceptable as the scale of cropping required could garner negative attention, similar to that of the food versus fuel debate surrounding bioenergy, as well as divert biomass feedstocks away from other relatively more important uses. As a result, the availability of feedstock is expected to be the limiting factor in the large-scale production and application of char in the EU. The availability of the currently considered feedstock categories is expected to decrease over time as technological advancements aim to reduce any resulting waste and residues from processes and as increasing uses arise for biomass feedstocks. It is therefore important that other types of feedstocks, particularly waste streams, are included as suitable input materials for the char supply chains. The results of the EuroChar scenario modelling could therefore inform and direct the current char standards and certification schemes to investigate and potentially include such categories in their ‘positive list of char feedstocks’. EU policy should also consider reviewing any current legislative barriers preventing the land application of char produced from ‘waste’. The potential annual scale of carbon sequestration calculated in the scenario modelling indicated levels equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties. Climate change is a key challenge faced by modern-day and future societies and any technologies capable of reducing atmospheric CO2 levels should be considered. Besides its benefits in terms of carbon sequestration, char production and application could also potentially provide a more sustainable waste treatment route, and contribute to the production of renewable energy through the main/co-products produced by the conversion technology. Additionally, the application of char could not only increase the productivity of agricultural lands but also assist with the remediation of degraded or contaminated lands. Whilst it was not within the scope of this work to derive a clear conclusion about the best/optimal use of biomass, with regard to renewable energy versus land application of char, we recommend that future research aims to understand the consequential impacts of char application on crop yields as the key determinant of relative benefit of char compared to energy. Concerning the impact of biochar application on albedo and on surface radiative balance the experiments performed enabled to draw a number of recommendations for operational purposes and to highlight research priorities on this topic. Recommendations for optimal biochar application strategy: considering that no significant differences in surface albedo were observed over the application rate of 30tha-1, it would be better to recommend high application rates in order to maximize the carbon sequestration potential without additive impact on the radiation balance. These findings also stress the need to delineate the integration of biochar with other geoengineering strategies based on the change of reflective properties of agricultural surfaces (e.g. the adoption of varieties selected for their reflectivity; white plants). Furthermore, soil incorporation is the biochar application strategy to be recommended to minimize the reduction of the mitigation potential of biochar, together with the adoption of high rates in one single application. Finally, the landscape experiment provided a consistent representation of surface albedo in complex agricultural systems in the Mediterranean environment that can be operationally adopted in RCMs. It also pointed out the need for improving the representation of surface schemes in RCMs with particular reference to the representation complex land-surface feedbacks, which are a consequence of biochar application, by means of biosphere models.
Dissemination activities and the exploitation of results.
At the start of the project the Eurochar website www.eurochar.eu was launched. This website has been used to provide information to anyone interested in the topic as well as a platform to exchange knowledge and data among the participating partners. During the Eurochar project all materials done (deliverables done, report of meeting done) were given to all partners. Dissemination of the knowledge and experiences from Eurochar is essential to ensure the public benefit of such research projects. In addition to scientific journal articles, presentations and posters project partners have also conducted dissemination activities focusing more on end users, stakeholders and policy makers.
In 2011 was organized by University of Halle (Germany), Partner 3 (leader Prof. Bruno Glaser) of Eurochar Project, the European Biochar Symposium. The Symposium was held at the University of Halle in Gemany from 26.to 27 September 2011. The Symposium has been used by Eurochar projects to disseminate the knowledge gained during the projects. In the 2013 was organized by CNR_IBIMET a special session “Stakeholders Committee of Eurochar Project” within the 1th Mediterranean Biochar Symposium.
In general the First Mediterranean Symposium has been used by Eurochar partner to disseminate the knowledge gained. In fact, were a total of 8 oral presentation (such as a keynotes of Franco Miglietta- Eurochar coordinator) and many poster. A large number of students at different levels have been involved in the project for their theses work and internships, a total of 4 PhDs. Eurochar did not organise any specific courses during the project period, but Eurochar results have been presented as part of the regular teaching programmes at the different Universities.
In total 12 contributions (peer reviewed), 37 oral presentation and 14 poster presentation at international conferences have been produced so far. The large number of journals and thematic areas associated demonstrated the high multidisciplary character of EUROCHAR. Results are described and displayed in a general and understandable way. Dissemination of the knowledge and experiences from Eurochar is essential to ensure the public benefit of such research projects. In addition to scientific journal articles, presentations and posters project partners have also conducted dissemination activities focusing more on end users, stakeholders and policy makers. Permanent and bi-directional line of communication with stakeholders through the users group. Formal and informal meetings with stakeholders were celebrated in several regions of Italy, German, UK, France. In addition, the biochar utilization protocol and decision support system was presented to stakeholders in several countries. Stakeholders feedback is an essential component of interaction between the Scientific community (higher education, Research), Industry, Civil Society, Policy makers and Media. Therefore, Eurochar Project considered several activities involving stakeholders, both for transferring scientific and technical results and for capturing and make use of local experiences and perception. The main objective was to promote feedbacks between Eurochar scientists and relevant stakeholders involving private companies, associations and interest groups became involved in EuroChar Project. A cohort of stakeholders, the EuroChar Stakeholder Committee (ESC), was established to give guidance and feedback on the project’s work from an external perspective. It comprised experts from relevant research and application fields. The consolidation of ESC was finalized at the time of the EuroChar kick-off meeting and the specific meeting with ESC was planned at the second project’s years. ESC contributed by reviewing the activities of the project.
Moreover, the Eurochar project will participate to Expo 2015, in the pavilion in the National Research Council. The coordinator of Eurochar Project has invited Lehmann to give a talk about biochar at EXPO in Milan in Summer 2015. Possibility of TeD talks or other biochar related talks. The coordinator would also like to organise a biochar event (Biochar 2015) with outreach to industry, with the possibility of EuroChar being represented there. The type of output from Deliverables of Eurochar project could be shown (for example). Visualisation of albedo effects for wider public/shareholders.
Potential Impact:
The results of WP1 clarified that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste.
The knowledge and technology implementation achieved on the two processes will impact on the finalization of the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. New knowledge on HTC revealed that this subproduct might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage. This new information will have an impact on the technological chain and the implementation of new synergies between the two processes.
EuroChar will also contribute to the development of industrial process by providing evidence that the production of gaseous pollutants during gasification and Hydrothermal treatments are very low. But it will also generate some caution, as even if the concentration of aldehydes and ketons resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. The observation of a presence of ketons and aldehydes which are classified as experimental carcinogenic substances (Classification ACGIH class A3) will generate some specific attention on the regulations and controls of industrial processes.
The fact that the TC biochar and HTC chars were used not only within the project Eurochar, but also in trials by other external entities will have an impact. The list of organizations that directly benefit from the avaiability of chars is large: CRA-RPS, Research Centre for Soil-Plant System studies of Agricultural Research Council of Italy, Rome (I),CRA-ORT, Research Centre for Horticulture of Agricultural Research Council of Italy, Battipaglia (I),ENR-CCR, Rice Research Centre of Italian National Agency for Rice, Castello d’Agogna (I), Trees and Timber Institute of CNR (National Research Council of Italy), Florence (I), Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Rome (I), Minoprio Foundation, Vertemate con Minoprio (I), University of Bologna, Bologna (I), University of Milan, Milan (I), University of Palermo, Palermo (I), University of Parma, Parma (I), University of Pisa, Pisa (I), University of Udine, Udine (I), UKBRC, UK Biochar Research Centre, University of Edinburgh, Edinburgh (UK), Institut Sylva, Le Bec Hellouin (F), Agronomia Group, Bergamo (I) (Production of ready-to-eat salad vegetables), Plozner, Spilimbergo (I) (Wine farm), TerrAgricola, Varese (I) (Production of soil improvers and growing media), Vivai Pacini, Pescia (I) (Olive nursery), Max-Planck-Institut für Biogeochemie, Jena (DE), Hochschule für nachhaltige Entwicklung Eberswalde, Eberswalde (DE).
Life Cycle assessment (WP3) results will have a potential impact on C-sequestration policies and initiatives. The production and application of char could therefore contribute to climate change mitigation, and new regulations may profit of the information which hass been collected and analysed through LCA. The results will however further discourage the use of dedicated crops for the production of char. The observation that char oxidation rates are important in LCA will impact substantially on future research plans in biochar science. Carbon credits policies will also benefit from the results achieved, to eventually provide a financial incentive for carbon sequestered through the production and land application of biochar. There are a number of other social and economic benefits from the production and application of char. The co-production of energy, e.g. in gasification systems, could offset ‘dirty’ fossil energy sources, which would have a significant impact on climate change. The land application of char could improve ecosystems by increasing nutrient and water retention capabilities. These beneficial impacts on agricultural lands could increase productivity and reduce fertiliser and irrigation requirements, providing significant economic benefits to the farmer and society as a whole. However, the application of char could potentially also have some phytotoxic effects depending on the conversion technology and feedstock used. Safety regulations therefore have to be stringent and post-treatment processing might be required to eliminate such potential detrimental impacts on the ecosystem. Another important conclusion from the LCA results indicates that feedstock transport could cause a significant share of the potential environmental impacts. It is therefore recommended that the char production is either done on-site at the feedstock plantation/origin or located nearby. On-site production could provide an additional revenue stream to the farmer or site manager if the char were to be sold or the co-produced energy exported to the grid. Finally, the lack of LCA-relevant parameters obtained from the field trials indicate that future field studies should consider these parameters in their data collection inventory. Impacts of char application in terms of potentially reducing fertiliser and irrigation requirements or increasing crop productivity could provide significant environmental ‘benefits’. Field trials are required, in combination with controlled lab studies, to provide a more accurate representation of the real impacts/fate of the char applied, and this should therefore be another key continued and future focus within the char research field.
Results obtained in WP4 which determined chemical and physical characteristics of modern biochars and hydrochars produced from different feedstocks pointed to the existence of large differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. This, together with the observation of phytotoxic effects that can be eliminated by chemical (e. g. oxidation) or biological treatment (e. g. composting) will have a direct strong impact on the production of biochar with sufficient environmental safety. And it will stimulate further research which is urgently needed to identify the unknown phytotoxic and genotoxic compounds in the hydrochar since the unknown substances may also impact human health.
Results obtained in WP5 that assessed the stability of modern biochars and hydrochars and developed stability indicator will have a direct impact on the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. The observed differences between biochar and hydrochar and composts will be directly used to estimate the relative effective C-sequestration potential, thus contributing to the development and implementation of new regulations. On the other hands, the same results will stimulate the utilization of co-composted hydrochar as suitable as soil amendment because it may increase the content of organic carbon in compost substrates, even if the low amount of polymerized carbon structures makes this material not resistant enough against microbial degradation.
The results of WP6 demonstrated the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. A key impact of the activity made, is in the creation of major infrastructure in Europe and the establishment of network of biochar field sites that can become a long-term facility, opened to international access. This would provide for some of the first assessments of long term biochar stability at highly instrumented sites, further developing knowledge of the viability of biochar as a method of carbon sequestration. The multi-site experimental data that have been collected are of primary importance for the development of EU standard and policies on C-sequestration as these provide practical evidence that biochar application in soils can be made in a safe and effective way, with limited costs and a net environmental benefit. Results from the Castel all’Apertole and Montepulciano satellite sites demonstrate the viability of biochar as a soil amendment, augmenting crop yield whilst having no negative impact on crop quality (Baronti et al., 2014; Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Furthermore, the elevated water holding capacity of soils treated with biochar may have the potential for utilisation to reduce drought effects and total irrigation required by the crops. This has potential implications for increasing the uptake of biochar soil amelioration within the agricultural community.
Shifts in microbial communities present in 2 of the 3 core sites call for a better understanding of the mechanisms involved, something that may help in future to elucidate how biochar actually contributes to soil fertility.
The results of WP7 that consider scenario analysis in the case of large scale applications of biochar has a number of potential relevant impacts. In terms of feedstock availability, limited impact is expected as only residues and waste are considered a feasible feedstock and only a 20% share of this feedstock category was considered to be available. We consider it unlikely that dedicated cropping solely for the production of char could be regarded as socially acceptable as the scale of cropping required could garner negative attention, similar to that of the food versus fuel debate surrounding bioenergy, as well as divert biomass feedstocks away from other relatively more important uses. As a result, the availability of feedstock is expected to be the limiting factor in the large-scale production and application of char in the EU. The availability of the currently considered feedstock categories is expected to decrease over time as technological advancements aim to reduce any resulting waste and residues from processes and as increasing uses arise for biomass feedstocks. It is therefore important that other types of feedstocks, particularly waste streams, are included as suitable input materials for the char supply chains. The results of the EuroChar scenario modelling could therefore inform and direct the current char standards and certification schemes to investigate and potentially include such categories in their ‘positive list of char feedstocks’. EU policy should also consider reviewing any current legislative barriers preventing the land application of char produced from ‘waste’. The potential annual scale of carbon sequestration calculated in the scenario modelling indicated levels equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties. Climate change is a key challenge faced by modern-day and future societies and any technologies capable of reducing atmospheric CO2 levels should be considered. Besides its benefits in terms of carbon sequestration, char production and application could also potentially provide a more sustainable waste treatment route, and contribute to the production of renewable energy through the main/co-products produced by the conversion technology. Additionally, the application of char could not only increase the productivity of agricultural lands but also assist with the remediation of degraded or contaminated lands. Whilst it was not within the scope of this work to derive a clear conclusion about the best/optimal use of biomass, with regard to renewable energy versus land application of char, we recommend that future research aims to understand the consequential impacts of char application on crop yields as the key determinant of relative benefit of char compared to energy. Concerning the impact of biochar application on albedo and on surface radiative balance the experiments performed enabled to draw a number of recommendations for operational purposes and to highlight research priorities on this topic. Recommendations for optimal biochar application strategy: considering that no significant differences in surface albedo were observed over the application rate of 30tha-1, it would be better to recommend high application rates in order to maximize the carbon sequestration potential without additive impact on the radiation balance. These findings also stress the need to delineate the integration of biochar with other geoengineering strategies based on the change of reflective properties of agricultural surfaces (e.g. the adoption of varieties selected for their reflectivity; white plants). Furthermore, soil incorporation is the biochar application strategy to be recommended to minimize the reduction of the mitigation potential of biochar, together with the adoption of high rates in one single application. Finally, the landscape experiment provided a consistent representation of surface albedo in complex agricultural systems in the Mediterranean environment that can be operationally adopted in RCMs. It also pointed out the need for improving the representation of surface schemes in RCMs with particular reference to the representation complex land-surface feedbacks, which are a consequence of biochar application, by means of biosphere models.
In the context of climate change mitigation, technologies for removing the CO2 from the atmosphere are key challenges. Transferring biomass to carbon-rich materials with potential mega-scale application is an option to sequester carbon from plant material, taking it out of the short-term carbon cycle and therefore binding CO2 efficiently and even in a useful, productive, way into longer term non-atmospheric carbon pools. The EuroChar project fully met its objective and achieved substantial advancements in new strategies and options to sustainably sequester carbonin soils by means of the use of biochar. The research carefully followed project's the initial workplan with only minor deviations. The results are novel and have been and will continue to be properly disseminated to the scientific community and to the large public via a number of papers (21 in total) and a suite of reports and other materials that finally reached a wide audience, not only in Europe. The science papers are among the most cited in the literature. Vaccari et al. (2012) has been already cited more than 80 times in approximately two and half years, being one of the highly-cited papers in biochar science, so far. Other more recent papers, such as Viger et al. (2014), Criscuoli et al. (2014) and Ventura et al. (2014) are likely to generate new studies and stimulate a large and fruitful debate within the biochar community and beyond. EuroChar focused on two different technological processes for making biochar: gasification (thermal carbonisation – TC) (the SME partner AGT patented a new system) and hydrothermal carbonization (HTC). Biochar was produced from different agricultural products for subsequent detailed analyses and a set of coordinated field studies made at different latitudes in Europe. But the project also addressed specific questions related to the long-term stability of Biochar in soils, its potential toxicity (including genotoxic effects). Large scale application scenarios were also considered, both form Life Cycle Analysis (LCA) and the climatic feedback perspectives.
The main project's results may be summarised as follows:
• Specific analyses made at and in the proximity of the production plants and that were based on SPME (Solid Phase MicroExtraction) showed that the concentration of the 16 semi-volatile Policyclic Aromatic Hydrocarbons (PAH), aldehydes, ketones and phenols, results extremely below the national limit value
• Large differences were observed in the elemental as well as chemical composition of biochar obtained by pyrolysis, pyrogassification and hydrochars. The final carbon content, in particular, varied significantly depending on the feedstock considered while PAH as well as dioxin concentrations were below the limits given by the international and European biochar standard definitions
• The laboratory experiments indicated that biochar is more stable than hydrochar and has a higher C sequestration potential taking into account weathering effects and priming effects on soil organic matter
• Long-term biochar stability in the soil and its long term capacity to sequester carbon was assessed in a series of alpine charcoal hearths that were used more than 150 years ago and then left undisturbed. This enabled to finally estimate the fraction of recalcitrant carbon that underwent major degradation and C-loss over centennial time scales, thus enabling the calculation of the mean residence time (MRT) of biochar in soils
• Biochar effects on model plants were evaluated using model plants and novel tranceiptional approaches to clearly demonstrated the need of developing risk assessment strategies with bioindicators. The results also highlighted that the effects of biochar on plants may operate via hormonal mechanisms and that defense tenes may be affected, too
• the most extensive network for biochar field experimentation was created by Eurochar within the EU. This consists of three core sites, located in Italy, France and the UK (treated with biochar produced by AGT Biochar, Italy), accompanied by four satellite sites. The results of field studies have confirmed that biochar produced by a commercial method (AGT) is sufficiently stable in the soil environment for it to have potential use in carbon sequestration. Biochar application was shown to result in a significant shift in microbial communities present in 2 of the 3 core sites. Understanding these shifts may help in future to elucidate the mechanisms through which biochar contributes to soil fertility
• Scenario Analysis allowed to calculate the potential annual scale of carbon sequestration as being equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties
• Climatic feedback studies demonstrated the occurrence of direct biochar effects on surface albedo, which is likely to affect the surface energy balance and eventually reduce the mitigation potential of C-sequestration
EuroChar involved a number of stakeholders in the EuroChar Stakeholder Committee that examined and reviewed project’s activities. Dissemination activities were implemented to make project’s results available to a wider audience and the media
Project Context and Objectives:
In the context of climate change mitigation, technologies for removing the CO2 from the atmosphere are key challenges.
The search for meaningful ways to transfer carbon from the atmosphere via biomass into useful carbon deposits is currently a key challenge. Transferring biomass to carbon-rich materials with potential mega-scale application is a material option to sequester carbon from plant material, taking it out of the short-term carbon cycle and therefore binding CO2 efficiently and even in a useful, productive, way into longer term non-atmospheric carbon pools.
There are several ongoing efforts aimed at reducing greenhouse gas emissions through sequestration of carbon. Many different strategies have been proposed, ranging from wide-spread afforestation and reforestation to expensive geo-engineering programmes involving the burial of CO2 in deep oceans or in exhausted oil wells (Royal Society, 2009). One promising but simple option is to obtain C-sequestration by increasing the amount of carbon in agricultural soils (Scholes and Noble, 2001). But recent analyses urge caution, highlighting that very often the efforts aimed to achieve C sequestration in soils are offset by other greenhouse gas emissions (Schlesinger, 1999) and that soils generally show low potential to accumulate C (Schlesinger and Lichter, 2001). In addition, soil organic matter remains vulnerable as it can be decomposed rapidly if management practices that favours C-accumulation in the soils are not maintained in the long-term (Rasmussen et al., 1998).
The most obvious alternative for long-term C-sequestration in soils is to transform biomass, and in particular crop residues, into a stable product that can neither be decomposed by soil microorganisms nor be oxidised and then returned to the atmosphere in the form of CO2. One emerging option, in this regard, is to transform biomass into charcoal (or biochar) and add that to agricultural soils biochar, that can be produced through thermochemical or hydrothermal processes and as by-product of energy production, is normally made of 60-80% of Carbon; both carbonization processes are exothermic as they produce rather than consume energy and the black-carbon of biochar is a very stable product and the addition of large amounts of biochar to agricultural soils potentially enhances their fertility and is compatible with sustainable agriculture. Several studies consider that biochar, the carbon-rich product that remains when biomass is heated to high temperature in reduced oxygen conditions provides a stable form of Carbon that cannot be decomposed on centennial or even millennial time-scales. There is increasing evidence that black carbon created after forest fires can be more than 10,000 years old (Preston and Schmidt, 2006) and in the “Terra Preta” soils of the Amazon region biochar has been dated from 500 up to 7000 years (Neves et al., 2003). Those soils, whose prolonged fertility is likely associated to their large C-content, are still used today to produce food for the local populations. However, there are significant unknowns in transferring this ancient technology into modern agricultural systems within Europe and this proposal aims to address some of those unknown issues.
A continuously and rapidly growing literature is supporting biochar as a realistic potential mitigation option. Despite such a growing body of knowledge, carbon sequestration potentials of biochar have been overlooked in national and international frameworks because there are in fact very large uncertainties associated with the large-scale use of biochar for carbon sequestration. These include competition for land-use for food, competition for use of feedstock and agricultural wastes for biofuels. There is also a possibility that toxicological effects exist and that deployment of biochar could have an unknown impact on the delivery of other ecosystem services such as biodiversity of the soil and overall water consumption. Although there is a diversity of opinion among different experts on estimates of the potential future global supply of biomass for bioenergy, gasification or hydrothermal carbonification processes, the general consensus is that the global potential of biomass for these purposes is extremely large compared with biomass currently being used for food, fuel and fibre. For example, a recent report of the International Energy Agency (IEA, 2009) has highlighted a global technical potential of energy from biomass at 1,500 EJ in 2050, whilst total energy demand is estimated to be 1,000 EJ in 2050. With many potential raw materials (called source feedstock) and multiple positive attributes, biochar remains of significant but unrealised global potential, but many issues remain unresolved
The EuroChar Project aims to develop and demonstrate technologies that will contribute effectively and on a large-scale to remove greenhouse gases (GHG) from the atmosphere in a long-term perspective (over 100 years). The project is designed to quantify in a detailed and rigorous way if the biochar option is in fact a realistic strategy to sequester atmospheric carbon, within a European context.
EuroChar is built to reduce those uncertainties and eventually assess C-sequestration potentials for Europe and beyond. All this will be made associating critical demonstration activities, monitoring and testing actions and fundamental science into a coherent framework. With the ambition to go beyond the current state-of-the-art in biochar science the project’s deliverables will provide new data and knowledge required to:
• compare and evaluate the performance of thermochemical and hydrothermal technologies to produce biochar in prototype plants, also in a consistent LCA framework
• understand the physical-chemical properties of biochar produced from different feedstock and different technologies
• assess the short and long-term decomposability of different biochar types and their net potential for C-sequestration
• provide complete and standardised Life Cycle Analysis of biochar production / application
• assess potential toxic effects of different biochar types on plants, soil microbes and earthworms
• understand the net C-sequestration potentials achievable in realistic field situations
• understand implications of modified surface albedo following large-scale biochar application
• provide European-scale scenarios of the implementation of dedicated EU-policies
• propose regulatory frameworks for real-case applications of biochar to land, including mandatory or voluntary trading schemes for C-sequestration
• suggest relevant standards that should be defined for real-case applications
Project Results:
Work package (WP) 1. Demonstration of Industrial biochar production
The objectives of this WP were production of biochar at the pilot scale at two industrial plants in Germany and Italy. The activities of this Work Package were focused on the production of biochar with TC-Thermochemical Carbonization (Participant AGT) and HTC-Hydrothermal Carbonization (Participant CS) technologies from different feedstock, with the aim to provide the materials required under WP4 (chemical and physical characterization), 5 (stability assessment) and 6 (field applications).
TC – Gasification:Gasification is a thermo chemical conversion process in which a carbonaceous material is partially oxidized by heating at high temperatures (1 200°C) in gas (syngas) and charcoal. Syngas is a low calorific power mix of carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen, and is used to power endothermic engines in order to produce electricity and heat. Partner 7 (AGT Advanced Gasification Technology Srl) has developed a fixed-bed, down-draft, open core, compact gasifier which has 500 kW nominal electric capability (micro-generation) using feedstock deriving from agricultural products and by-products. The plant is composed of two principle sections: 1) reactor, where pyrolysis and gasification take place; 2) syngas cleaning system, where cooling, dust and tar removal occur. The gasification reactor consists of a fixed bed of biomass through which the oxidizing agent (air) flows in co-current. Inside the reactor, the partial combustion of the biomass, guaranties the heat necessary for the gasification reaction. The composition of the syngas varies in function of the type of biomass. The charcoal is extracted from reactor by a screw conveyor system and is then conveyed through a transportation system to a storage tank.
HTC – Hydrothermal carbonization: A commercial scale, fully continuous and energy efficient HTC production system from partner 5 (CS carbonSolutions Deutschland GmbH) with a nominal feed mass flow of 1.000 kg/h was used for the production of maize silage samples 1 and 2. The system was fully approved as a waste treatment plant according to German environmental legislation and is operated since October 2010. The system consists of two reaction stages with a temperature of 230°C in stage 1 and a temperature of 180°C in stage 2 respectively. The residence time in reaction stage 1 was at least 15 min and in reaction stage 2 at least 75 min respectively. This process is the standard CS carbonSolutions Deutschland GmbH CS-HTC process. A process scheme showing all main stages is attached. TC process flow chart (Figure_1); HTC process flow chart (Figure_2).
The choice to consider in the EuroChar project activities different materials obtained from innovative advanced biochar technologies rather than from traditional charcoal-making systems was motivated by environmental, technical and economic reasons. It is known that, unlike traditional pyrolysers that are often energy inefficient and highly polluting, some specific goals for modern biochar production are:
1. Value and recovery of co-products to improve process economics and reduce pollution emissions
2. Total control of operating conditions
3. Feedstock flexibility allowing both woody and herbaceous biomass, organic by-product and waste
4. Continuous feed technologies to increase efficiency and reduce pollution emissions associated with batch kilns
5. Exothermic operation (no air infiltration) to improve energy efficiency and charcoal yields
Summary of results and conclusions on gasification (TC):
Gasification is one of the most promising technologies for renewable energy production as it maximize syngas production (at the expense of charcoal) starting from a wide range of dry feedstock. Charcoal obtained in a gasifier is not a by-product but a high quality stable material that can be used in agriculture as soil amendment to increase productivity and to stock carbon in the soil
Gasification must and can rapidly fill competition gaps with other renewable energy technologies primarily anaerobic digestion (biogas). The market is the same but gasification requires lower investment costs which may favout its future massive spread.
Summary of results and conclusions on hydrothermal carbonization (HTC):
The market for HTC hydrochar is more complicated than expected because CO2 certificate prices went down and preparation of feedstock is sometimes expensive (biowaste from municipalities) and complicated and feedstock has sometimes to be purchased or there are no gate fees left (maize silage). All these reasons lead to higher market prices and a not economic HTC process for hydrochar from most of the feedstock used.
Hydrochar is not a by-product of the HTC process but the product and is to valuable to be spread on fields or will be to costly for farmers.
The only economically feasible feedstock at the moment is sewage sludge; maybe legislative and economic conditions will be more favorable for HTC in the future
WP1 clarifies that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste. The knowledge and technology implementation about the two processes were constantly increasing during the progress of the EuroChar project. Regarding gasification, the effort aimed to finalize the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. Concerning HTC, one major finding was that HTC might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage.
Moreover, WP 1 was focused on the production of biochar with TC and HTC technologies from different feedstock, with the aim to provide the materials required under WP4 (chemical and physical characterization), 5 (stability assessment) and 6 (field applications).
Concerning TC, the partner 7 (AGT) produced different biochar from six different agricultural products and by-products. Each feedstock was processed in the test-plant of Cremona (I) for a minimum of one week, converting at least 10 tons (on a dry matter basis) in syngas and charcoal. Biochar was obtained from poplar wood chips, conifer wood chips, sorghum stalks pellets, wheat straw pellets, olive residues and maize silage pellets. All the materials were free of contaminants such as stones, metal, rubber, plastic, pollutant compounds and other foreign bodies, being direct products or by-products of agriculture.
1. Poplar (Populus spp. L.) wood chips were obtained from dedicated short rotation forestry in the Po Valley (Gadesco Pieve Delmona, Lombardy - 45°10I13II N, 10°06I01II E). The age of the forestry at when it was cut down was five years.
2. Conifer wood chips were the result of mountain forestry management in the North Italian Apennines (Valle Staffora, Lombardy Region - 44°45I15II N, 9°13I49II E). The species that compose the final feedstock were: Larch (Larix decidua), Scots pine (Pinus sylvestris L.), Black pine (Pinus nigra A.), Silver fir (Abies alba M.) and Spruce (Picea excelsa L.).
3. Sorghum (Sorghum bicolor L.) was produced in the Po Valley, close to poplar and wheat (Gadesco Pieve Delmona, Lombardy Region - 45°09I10II N, 10°08I33II E). After harvesting, stalks were dried, chopped and pelletted
4. Wheat (Triticum spp. L.) was produced in the Po Valley, close to poplar and sorghum (Gadesco Pieve Delmona, Lombardy Region - 45°08I59II N, 10°08I28II E). After harvesting, straw was chopped and pelleted.
5. Solid olive residues are by-products of the olive milling process. They were produced in Tuscany (San Giovanni Valdarno, Tuscany Region) by means of continuous oil extraction process with two-phase decanters and it also includes the stones.
6. Maize (Zea mais L.) was produced in the Po Valley (close to Forlì, Emilia Romagna Region). After harvesting, chopped stalks were ensiled, then dried and pelletted.
Concerning HTC, the partner 5 (CS) produced different biochar from five different agricultural products and by-products: maize silage, grass, food leftovers, sewage sludge and biogas digestate.
1. Maize silage was obtained from a local farmer in the region near Kleinmachnow (DE) and is usually used as a feeding material for cattle.
2. Grass from public parks in Kleinmachnow (DE) was purified from impurities (e.g. stones, plastic parts) by mechanical means prior to feeding to the HTC mixing and treatment system.
3. Food leftovers were obtained from a local waste management company in Ludwigsfelde (DE).
4. Sewage sludge was obtained from municipal wastewater treatment plant Frankfurt/Oder (DE).
5. Biogas digestate was obtained by a local biogas plant in Klein-Schulzendorf (DE).
Work package (WP) 2. Monitoring of performance of Biochar production
The objectives of this WP were process monitoring and acquisition of plant performance data
Assessment of potential environmental pollution associated to Biochar production
The aim was to study of industrial processes, including the potential risks associated to environmental pollution. Detailed data that has been acquired in great detail, will then enable the activity planned under WP-3, where LCA has been performed.
System performance data, including energy use/production, operating temperatures, gaseous emissions and maintenance activities have been carefully monitored and archived for a prolonged period of time for subsequent. The main task of WP 2 was to deliver conversion process data for Life Cycle Analysis (LCA) done by project partner Imperial College London (IC) in Workpackage 3 and to collect data on possible harmful gaseous substances arising from the two biochar production processes namely thermochemical (TC) processing and Hydrothermal Carbonization (HTC). During the progress of the EUROCHAR project it became clear that more data are needed for a more detailed LCA. Also data on the impact on the environment from construction of the plant were delivered to the project partner IC. Additional data on economics of the process were provided afterwards. A brief summary of data needed for both processes e.g. for the HTC process can be derived from the following list:
SCENARIO HTC ON A WASTEWATER TREATMENT PLANT
1. Feedstock characterisation of digested sewage sludge
2. General
3. Feedstock characterisation
4. Cultivation/Production of Feedstock
5. Storage of Feedstock
6. Transport of Feedstock to processing facility
7. HTC system parameters
8. Inputs and outputs for HTC / TC process
9. Materials of the HTC plant
10. Hydrochar characterisation digested sludge
11. Treatment of hydrochar
12. Storage of Hydrochar
13. Transport of hydrochar for field application
14. Application of hydrochar from digested sewage sludge
For the TC process 6 Scenarios were defined which have been modeled with the help of the SimaPro software used by project partner Imperial College. The differences in the scenarios were the different feedstock used, namely conifer forest residues, srf poplar, wheat straw, sorghum stems, olive residues, maize silage.In the case of HTC 3 scenarios were defined which are based on two different feedstock namely sewage sludge and grass/greenery and two different uses of the process water in the case of grass/greenery. The process water was treated by the patented technology carbonPure(TM), which was also invented during the EUROCHAR project leading to a more ecofriendly overall process. Also additional material data was provided by both companies for the TC and HTC system to include the impact of the construction process of both technologies in the LCA software. No harm to the environment was observed concerning gaseous emissions of TC and HTC systems. The watery phase of the HTC product was not analyzed during the project but is supposed to be harmful to the atmosphere and must be treated. A patented solution is available for the process water in the HTC hydrochar. An example for the conversion process data collected and provided can be derived from figure 1 for the HTC system. An example for the impact on land occupation and construction materials for the TC system can be found in Figure_3.
The potential risks associated to the production of Biochar, have been examined by analysing flue gases using Solid Phase Micro Extraction (SPME) probes, with specific attention to the production of volatile potentially carcinogenic compounds like PAH (Polycyclic Aromatic Hydrocarbons) during gasification and subsequent gas combustion in electric generators. In the case of HTC, the analysis have been made in aqueous solution following the production of carbonaceous slurries. The sampling during the production of Biochar it was necessary to identify substances as VOCs, PAHs and aldehydes. Sampling done with SPME (7µm PDMS) fibre exposed for 1 hour in the two sampling points. The concentration of the 16 PAHs semi volatiles results extremely below the national limit value of 100 ng/mc. In details the concentration detected in the sampling point on the roof resulted lower than the one in the other sampling point, but we can gather that is due to a dilution made by the external air. So the more significant sampling point is the one inside the plant. In the VOCs compound are included both the volatile PAHs, aldehydes, ketones and phenols. The sampling has been made with a exposed SPME PDMS/DVB fibre and Carboxen fiber for 15 minutes. The results shows the presence of aldehyde, ketones and phenol also if in concentration below the national limit value of 5 mg/mc. Even if the concentration of aldehydes and ketones resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. On top of that some ketones and aldehydes are classified as experimental carcinogenic substances (Classification ACGIH class A3). For the liquid Biochar was made a SPME headspace analysis in GC/MS which reveals a significant presence of acetic acid.
Work package (WP) 3. Life Cycle Assessment
The objectives of this WP were:
Life Cycle Analysis (LCA) of Biochar Production
a. LCA of Biochar use 'field-to-field' (circular supply chain)
b. Life cycle inventory of feedstock production and supply
c. Life cycle inventory of biomass to biochar conversion processes
d. Life cycle inventory of biochar application pathways
Work Package (WP) 3 of the EuroChar project analysed the potential environmental impacts of the production and application of char by applying the Life Cycle Assessment (LCA) methodology to the project-specific supply chains. The supply chains were modelled according to the two conversion technologies, gasification and Hydrothermal Carbonization (HTC), and the respective feedstocks utilised in the project; conifer forest residues, poplar Short Rotation Forestry (SRF), wheat straw, sorghum stems, olive residues and maize silage for gasification, and sewage sludge and green waste (greenery) for HTC: eight supply chains total. The feedstocks selected provide a representative range of the types of biomass feedstocks suitable for char production; dedicated energy crops (poplar and sorghum stems), woody feedstocks (conifer forest residues), agricultural by-products (wheat straw), waste residues resulting from food processing (olive residues), as well as other waste streams (sewage sludge and greenery). Maize silage was only selected due to its isotopic signature, which assisted with the characterisation of the soil emission measurements in the field trials. The feedstocks are also diverse in terms of product classification (main product vs by-product vs waste), cultivation systems, moisture and carbon contents, and the pre-treatment processing required. The full supply chains were analysed in the attributional LCA (aLCA), which considers only the direct impacts of the life cycle. Therefore the system boundary generally included all processes/products from feedstock cultivation through to the application of char to arable land, with the exception of any ‘storage’ of feedstock or char; this was not modelled as the project partners indicated it to be minimal. The allocation methods applied were based on economic value and energy content. With regards to the consequential LCA (cLCA), which includes certain indirect impacts of the life cycle, the system boundary was expanded for the gasification supply chains to include the production of energy as well as increased crop productivity. The Functional Unit (FU) for the LCA study, to which all inputs, outputs and results were scaled, was equal to the amount of char required to sequester 1 tonne of CO2 (0.273 tonnes of carbon) in the soil (at least 100 years), considering only the char carbon. The Life Cycle Impact Assessment methodology applied in the SimaPro LCA software to determine the potential environmental impacts was ReCiPe. The main focus of the LCA study was the Climate Change impact category, or the Global Warming Potential (GWP) of the char supply chains, as this reflects the carbon sequestration potential. Overall, the GWP of all supply chains was negative (except for maize silage), i.e. a carbon sink in which more CO2 was removed from the atmosphere than was produced or released along the supply chain. The GWP (t CO2 eq.) for the various supply chains according to the FU, and using economic allocation for the gasification supply chains, was: -0.58 (wheat straw), -0.76 (sorghum stems), -0.90 (poplar SRF), -0.89 (olive residues), 0.34 (maize silage), -0.63 (conifer forest residues), -0.26 (sewage sludge), and a range of -0.4 - -0.65 depending on the scenario (greenery). The carbon sequestration potential significantly increases when potential indirect impacts are considered in the cLCA, such as the offsetting of energy and the increased productivity of crops; the GWP (t CO2 eq.) was reduced by 0.74 to -1.32 for the wheat straw supply chain and by 1.86 to -2.62 for sorghum stem. Though the net negative GWP results confirm char production and application as a potential carbon sequestration technology, the results are sensitive to the char carbon oxidation rate. Two different oxidation rates, considering a 100 year timescale, were used in the modelling, one based on the H/C value and the other determined by lab experiments. The oxidation rates for gasification chars were 30% and 61% respectively and for HTC chars 70% and 100.7% respectively. The lab oxidation rate for HTC chars results in net positive GWP, in which case the char production and land application system would not be a viable carbon sequestration technology.
The main focus of the EuroChar project was the carbon sequestration potential of char. However, in addition to the GWP category, it is important to analyse a more complete environmental impact profile. The gasification supply chain with the highest potential environmental impacts profile is maize silage, followed by wheat straw, conifer forest residues, sorghum stem, poplar SRF and olive residues. While for HTC, the supply chain with the highest potential environmental impacts is the sewage sludge scenario, followed by the greenery scenarios. When analysing the complete environmental impacts profiles and normalising the LCA results, the GWP was not the most significant impact (except for the poplar SRF and olive residues supply chain). The other impact categories require further investigation to ensure that the benefits of the char system, in terms of carbon sequestration, do not outweigh any other potential negative environmental impacts. Hotspot analysis of the various supply chains was also conducted to determine which stages in the char life cycle produce the highest potential environmental impacts. For the gasification supply chains, the overall main contributor to the potential environmental impact profile is the feedstock cultivation stage; this was the case for wheat straw, sorghum stem, poplar SRF and maize silage. The main potential impacts for the conifer forest and olive residues are linked to the feedstock transportation stage, followed by the gasification stage; as olive residues are a waste product (i.e. no burdens are associated to the cultivation stage) and the production of conifer forest residues requires minimal inputs. The gasification process itself is of relatively low impact as it only utilises a very small amount of fossil energy sources for the start-up electricity. Transportation only becomes a significant contributor when the feedstock cultivation stage is insignificant, e.g. for conifer residues and olive residues. Only transportation of the feedstock has the potential to generate a significant share of the impacts as the feedstock is very heavy compared to the relative amount of char that needs to be transported downstream in the same supply chain mass flow. Sensitivity with regards to transportation distances was limited for the GWP category, but more pronounced in the other environmental impact categories.
Different biomass feedstocks produce significantly different profiles of environmental impact potential. Agricultural crops generally have an intensive cultivation process, in terms of the use of chemicals, machinery and energy, in contrast to woody biomass feedstocks. Poplar, as it originated from a SRF site, also requires quite intensive management and chemical input and therefore resulted in higher impacts. Conifer residues, a result of general forestry management, had very little impact in the overall supply chain hotspot analysis, while olive residues, a waste product, had no impact as no burden is associated with the feedstock cultivation stage. The classification of the feedstock is another key aspect, e.g. main/single product vs by-product or waste-product. For the agricultural crops, a significant amount of the burdens of cultivating the crop is allocated ‘away’ in the SimaPro unit processes to the sorghum and wheat grains, while in the case of maize silage (a main product) it is responsible for all the impacts of its cultivation. Certain characteristics of the feedstock itself also contribute to the LCA results. For example, moisture content and ash content (as the latter relates directly to the gasification conversion efficiency) are main factors in the mass flow calculations. This is highlighted by the high amounts of maize silage (high moisture content) and conifer residues (low amount of char produced via gasification per unit of feedstock input) required to produce the FU in comparison to, for example, wheat straw (low moisture and relatively high ash content and therefore higher conversion efficiency and amount of char produced). The environmental impact profile confirms that dedicated crops (e.g. maize silage) are not a viable feedstock for char production as the supply chain had a high potential environmental impact profile and did not sequester any carbon. For the HTC supply chains, the HTC process is responsible for the largest share of the potential environmental impacts in all categories except GWP; all feedstocks are modelled as ‘waste’ products. As the inputs and outputs for the HTC process were provided on an aggregate basis, it was not possible to conclude which specific process/input/output is responsible for the greatest share of the potential impact, e.g. whether it is the conversion process itself or one of the post-treatment processes. The benefit of the HTC process is that no pre-processing of the feedstocks is required. However post-treatment processing, such as mechanical pressing and potentially also drying, could be a significant contributor within the HTC ‘black box’/unit process. To limit post-treatment processing, it is best to apply the slurry or the filter coal cake directly, if this does not cause any phytotoxic effects. When comparing the gasification and HTC supply chains, even though the HTC chars were given a higher oxidation rate (70% compared to 30% for gasification), the net negative GWP of some of the HTC greenery scenarios was still greater than three of the gasification supply chains (wheat straw, maize silage and conifer forest residues). The main reason for this is the lack of burdens attributed to the HTC feedstocks as all are waste products. However, if the oxidation rate of the HTC chars was based on the lab studies then all HTC GWP would be positive. Overall, it must be noted that no direct comparisons should be made between the technologies as they utilise different feedstock types and produce different chars. As further suggested in the EuroChar Scenario Analysis (WP 7), the technologies are not mutually exclusive and a market mix should be promoted. As one of the key potential benefits of char application, besides carbon sequestration, is its impact on the ecosystem, data relevant to the LCA was collected from the three main EuroChar field trials: the UK, Italy and France field trial sites. The relevant parameters considered ranged from carbon stocks and soil emissions to crop productivity and irrigation and chemical application requirements. Only gasification char produced from maize silage was applied to the field trial sites and the results from one, maximum two, years were collected. The submitted field trial data was not included in the LCA study as most of the requested parameters were either not significant or not measured/available. The only statistically significant results included an increase in above-ground carbon stocks for the biochar plots in the France site and an increase in CO2 soil emissions for the biochar plots in the UK site.
Work package (WP) 4. Chemical and physical properties of biochar
The objectives of this WP were:
1) Creation of a Biochar data repository on chemical (structural), physical and biological properties of biochar from different feedstock and from different carbonization technologies
2) Assessment of correlations between production technology and Biochar properties
3) Database of toxicology impacts of Biochar in mesocosm experiments using a model plant system
4) Carcinogenic effects of biochar
In WP4 we determined chemical and physical characteristics of modern biochars and hydrochars produced from three different feedstocks (wheat straw, popular wood and olive residues) in order to (1) assess the importance of feedstock and production procedure on their properties, (2) evaluate their effects on soil properties and (2) show that biochars and hydrochars have no negative effects on plant growth. The conceptual approach of this WP consisted in the analyses of elemental composition, chemical composition and PAH as well as dioxin content of modern biochars and hydrochars. Moreover, we assessed their effects on the plant genome and plant growth. We used soil sampled from ancient pits (several hundred years old) as a proxy to assess long-term effects of biochar on soil properties and evaluate the use of ancient charcoal to serve as reference material for modern biochar. To fulfill the requirements of this WP, biochar has been produced with a muffle and a pyrolytic stove in the laboratories. The muffle used is an oven that can reach a maximum temperature of 1100°C. It doesn’t have any flux of inert gases, so its inner atmosphere is rich in oxygen. The pyrolytic stove is formed by two cylinders, one inside the other. Biomass is put inside the inner cylinder and ignited. After a few minutes of conventional combustion, thanks to the dynamics of the exhausted gases that flow between the two cylinders, no more oxygen is available inside the inner chamber and so pyrolisis can occur, transforming the biomass into charcoal. The exhausted gases are burnt at the top of the stove where the two cylinders meet. In the muffle it has been pyrolyzed different feedstock at different temperatures (250°C, 400°C, 500°C, 600°C, 800°C, 860°C, 1000°C). During pyrolisis we monitored the temperature inside the stove and in the flame. The variability of the temperature inside the stove is due to the fact that the “pyrolisis front” (the region where pyrolisis occurs) moves down in the stove with time. These measures show that we cannot precisely define at which temperature and for how long biomass has been exposed to pyrolisis. For this reason, we decided not to use this stove to produce biochar at the bench scale.
Evaluation of composition of modern biochars and hydrochars
Our results indicated strong differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. (Figure_4). Production parameters have a much greater effect on biochar and hydrochar properties than feedstocks. Ancient charcoal has a similar chemical composition as modern biochar. However, their elemental composition and chemical reactivity are very different. Therefore, ancient charcoal may not be used as reference material for stability. PAH as well as dioxin concentrations of modern biochars and hydrochars were below the limits given by the international and European biochar initiatives. Therefore, the use of these materials for soil amelioration may be safe.
Evaluation of biochar effects on soil properties
Biochar effects on soil properties were evaluated using soil from ancient pits containing high amounts of charcoal. In these soils, charcoal was present for several hundred years and we hypothesised that these soils could be model systems allowing for the assessment of effects of biochar as unique amendments on soil properties. These systems are very different from those of Terra Preta, where other exogenous organic materials were used as soil amendments in addition to biochar. Our results showed that several hundred years after biochar addition, the microbial functioning of these soils was not altered concerning the capacity of the microbial communities to degrade plant material as well as modern biochar (Naisse et al., 2014, submitted). This was in contrast to our hypothesis that the microbial communities would have adapted to biochar degradation as shown for Terra Preta (Glaser and Birk 2012).
Evaluation of biochar effects on model plants
The main goals of this task was to study the potential toxicity of Biochar (TC and Hydrochar) using model plants. We have done two different experiments in Germany (University of Halle) and in UK (University of Southampton) to evaluate the potential toxicity of biochar and hydrochar on two different model plant: Arabidopsis thaliana growing in soil using biochar from TC and Tradescantia using hydrochar and biochar from TC.
Toxicity test using Arabidopsis thaliana
In order to test the toxicity of biochar on Arabidopsis, we used different rates of biochar equivalent to : 0 t ha-1, 20 t ha-1, 30 t ha-1, 50 t ha-1 and 100 t ha-1, corresponding to 0, 1.7 2.5 4.2 and 8.3% w/w (dry weight) respectively. Fertilizer could also be applied following manufacturer instruction. Global gene expression arrays were used on biochar-treated plants to analyse the changes in metabolic pathways. A leaf chemical analysis was also performed between plants grown in soil mixed with and without biochar. The leaves were sampled for microarrays and snap frozen in liquid nitrogen. RNA was extracted (Chang et al., 1993) of three replicates of control and five of biochar (50 t ha-1) with fertilizer, and were hybridized to GeneChip Arabidopsis Genome Arrays (Affymetrix, Santa Clara, USA) by the European Arabidopsis Stock Centre (NASC, UK). Data were analysed in GeneSpring (Agilent technologies, Santa Clara, USA). Chips were normalised by MAS5. Differentially expressed genes were identified through t-test between samples of control and biochar (p<0.05 2-fold change difference) with a multiple testing correction (Benjamini-Hochberg). Genes were annotated using GeneSpring (Agilent technologies, Santa Clara, USA) and the website Tair (www.arabidopsis.org). Lyophilised leaf samples were extracted and partitioned according to the method of Foito et al. (2013) for the chemical analysis. The microarray analysis revealed a total of 1076 genes differently expressed when comparing control plants with plants grown in biochar at 50 t ha-1, both with fertilizer. We identified 571 genes that were down-regulated and 505 that were up-regulated in response to biochar application. (Figure_5). Metabolic pathway analysis was performed using mapman (Figure 6). Signalling, transport and biosynthesis of two plant hormones central to growth stimulation – auxin and brassinosteroid – were up-regulated for plants grown with biochar. A significant reduction of anthocyanins, flavonols and glucosinolates was observed for the plants growing in biochar (50 t ha-1) compared to the control In addition, genes controlling cell wall loosening, including numerous xyloglucan endotransglucosylases and expansins (Figure_6) were up-regulated in biochar suggesting enhanced growth was underpinned by increased cell expansion. Transporter genes for sugar, nutrients and aquaporins were upregulated (Figure_6) for better water and nutrient uptake and movement of sugars for metabolism in the plant.
Toxicity test using Tradescantia
We tested genotoxic effects of different hydrochars and biochars with the Tradescantia micronucleus test. For this purpose, chromosomal aberrations in pollen cells of Tradescantia in the form of micronuclei were evaluated microscopically after defined exposition to extracts from char materials. Hydrochars from hydrothermal carbonization mostly exhibited significantly negative results (Busch et al., 2013). Additional germination experiments with hydrochar showed total germination inhibition at additions above 5% (v/v) in comparison to biochar (Figure_7). However, biological post-treatment of previously toxic hydrochar was successful and toxic effects were eliminated (Figure_7). Some post-treated hydrochars even showed growth-stimulating effects. Our results clearly demonstrate the necessity of risk assessment with bioindicators. The chosen tests procedures can contribute to biochar and hydrochar characterization for safe environmental application.
Work package (WP) 5. Short- and long-term stability of biochar
The objectives of WP 5 were:
- to assess the stability of modern biochars and hydrochars
- to test chemical methods in order to develop a simple stability indicator.
We assessed the stability of modern biochars and hydrochars through a combination of physical, chemical and biological methods. Physical methods included application of a protocol, with wetting/drying and freezing/thawing cycles in order to mimic weathering processes occurring after field exposure. Weathered and non-weathered samples were subjected to chemical methods (oxidation and hydrolyses) as well as laboratory incubation in soil. Use of stable isotope analyses allowed for the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. We used for these analyses biochar produced from maize silage incubated at an application rate of 30 Mg ha-1 in soil of the French field experiment. The different methods applied allowed for the analyses of biochar and hydrochar stability at different time scales. Here we will present additional information as well as a synthesis of the most important results.
Chemical stability
Concerning the chemical stability of the different chars, our results showed that oxidation with acid dichromate (0.1 M K2Cr2O7 in 2 M H2SO4) for 12 h is a suitable, simple method, allowing for the assessment of char stability based on elemental composition (Naisse et al., 2013). However, the handling of acid dichromate requires special care as the reagent is toxic, mutagen, carcinogen, and can cause serious problems when entering the drinking water supply. As the chemical reactivity of biochar changes with time, our results further indicated that it is only a poor indicator of stability beyond decadal timescales (Naisse et al., 2014, in press). A better alternative is the simple determination of elemental composition (C and H) and calculating H/C ratio, which has a close correlation to biochar stability (Figure_8).
Short term stability
Short-term biological stability was evaluated during 222 days of laboratory incubation. Our results showed that the biological stability of biochar is higher than that of hydrochar. During the early stage of soil incubation, the hydrochar input induced a positive priming effect, indicating a stimulation of soil organic matter (SOM) mineralization by addition of easily degradable carbon. In contrast, the biochar input induced a negative priming effect showing additional protection of soil organic matter. However, priming is a short-term phenomenon in pasture soil, which lasted only for the first few weeks.
C sequestration potential of biochar and hydrochar
Long-term stability of biochar and hydrochar in soil as well as their C sequestration potential was assessed through extrapolation of mineralisation data from laboratory experiments of weathered and unweathered chars as well as the study of biochar survival in ancient charcoal deposits. The laboratory experiment indicated that biochar is more stable than hydrochar and has a higher C sequestration potential taking into account weathering effects and priming effects on soil organic matter. Half–lives of fresh and weathered hydrochars were estimated between 8.4±0.9 to 10.4±0.3 years, and between 73.6±5.6 to 145.0±24.0 years for fresh and weathered biochars. Carbon sequestration potential including char mineralization, priming effect and physical weathering assessed for both chars, indicates that at the decadal scale, hydrochars and biochars would lead to similar increase of soil C storage. At centennical scale, only biochars would have the potential to increase soil carbon sequestration (Figure_9). We investigated the long term effects of charcoal addition on C sequestration and soil physico-chemical properties by studying a series of abandoned charcoal hearths in the Eastern Alps of Italy established in the XIX century (Figure_9a). This natural setting can be seen as an analogue of a deliberate experiment with replications. Carbon sequestration was assessed indirectly by comparing the amount of pyrogenic C present in the hearths (23.3±4.7 kg C m−2) with the estimated amount of charcoal that was left on the soil after the carbonization (29.3±5.1 kg C m−2). After taking into account uncertainty associated with parameters’ estimation, we were able to conclude that 80±21% of the C originally added to the soil via charcoal can still be found there and that charcoal has an overall Mean Residence Time of 650±139 years, thus supporting the view that charcoal incorporation is an effective way to sequester atmospheric CO2. We also observed an overall change in the physical properties (hydrophobicity and bulk density) of charcoal hearth soils and an accumulation of nutrients compared to the adjacent soil without charcoal. We caution, however, that our site-specific results should not be generalized without further study.
Field experiment with composted hydrochar and composted biochar
A field experiment with composted hydrochar and composted biochar showed a significant increase in topsoil organic carbon contents three weeks after application of compost and composted chars and also after one year of field incubation (Figure_10). The control groups did not show a significant difference to each other (all t0 variants as well as control t0, t1 and t2). The plots with compost treatment were slightly lower in TOC content but still significantly different in comparison to the control. Only variants with biochar treatment still showed a highly significant increase of TOC one year after application in comparison to controls (Figure_10). There was a significant difference of TOC content between t2 compost and t2 BC-C (Figure_10). Only composted biochar application showed a significant increase of black carbon content compared to composted hydrochar, pure compost and control (Figure_10). The increased black carbon content in the composted biochar treatment indicates a higher stability of organic matter and therefore a higher C sequestration potential compared to pure compost or composted hydrochar. The contribution of BC to TOC was about 10% in the topsoil control and in the subsoil of all treatment (Figure_10). In the control plots, BC to TOC contribution decreased during the experiment (Figure_10), indicating sequestration of labile non-BC C during the experiment. This might be due to the growth of species-rich natural grassland, which was not cut during the experimental period. It is known that grassland vegetation sequesters C through rhizo-deposition. After compost application, BC to TOC contribution decreased to about 5% (Figure_10) due to the application of C-rich but BC-poor organic matter. After one year of field incubation, the BC to TOC contribution increased again, indicating that a portion of the applied compost was mineralized while the soil-inherent BC remained more or less constant, although the mineralization effect was not significant (Figure_10). The same trend as for pure compost was observed also for composted hydrochar but mineralization during field incubation was lower than for pure compost (Figure_10). Black carbon to TOC contribution of composted biochar-amended soil increased to 80 – 90% after application and remained more or less constant throughout the experiment (Figure_10). In this treatment, both BC and TOC increased during the experiment, indicating a C sequestration potential of composted biochar beyond biochar alone.
Work package (WP) 6. Biochar stability in Field Applications
The objectives of WP6 were:
1. To assess/demonstrate the potential for Biochar application in short-rotation forestry (SRF) in the EU
2. To quantify the net C-sequestration achievable in SRF
3. To follow the fate of the Biochar in the soil and to quantify changes in the emission of non-CO2 GHG gases
4. To quantify additional potential effects of Biochar on soil fertility, soil biodiversity and SRF productivity
WP6 aimed to demonstrate the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. In addition, the fate of applied biochar, its impact upon greenhouse gas exchange and variations in soil biodiversity and fertility were measured. WP 6 utilised the biochar and hydrochar (HTC) produced by WP1, in collaboration with Carbon Solutions (Germany) and AGT (Italy). In order to understand the impacts of biochar amendment, EUROCHAR set up the most extensive network for biochar research within the EU. This consists of three core sites, located in Italy, France and the UK (treated with biochar produced by AGT Biochar, Italy), plus four satellite sites located in Italy and one in Germany. Impacts of both biochar and hydrothermal char (HTC) were to be assessed, but due to the possibility of elevated PAH’s present within HTC, it was decided to assess these only within pot experiments. Later, evaluation of HTC produced by CarbonSolutions (Deutschland GmbH) found that PAH’s and other potentially harmful components were at levels far below the recommended safety levels, and so they were applied at field scale in the German satellite site at Halle. The core sites consist of two biofuel crop sites, located in Italy (Prato Sesia, comprising of SRF Poplar) and in the UK (West Sussex, comprising of short rotation coppice Willow). A third core site of grassland was located in France (Lusignan) with the aim of assessing biochar application in agricultural pasture (Figure_11). At each site, eight plots were set up. At SRF and SRC sites, plots contained either five (Prato Sesia) or six (WestSussex) experimental trees, surrounded by a row of guard trees in order to limit edge effects. Four replicate treatments were established for yield and biomass results, whilst three replicates were installed to measure soil respiration. Soil respiration was assessed through use of two automated soil respiration chambers per plot, one measuring total soil respiration (Rtot) and another quantifying root excluded soil respiration (Rh). This was achieved through installation of a root exclusion cylinder around the respiration chamber to prevent root invasion into the measurement area. Results from soil respiration analysis at Prato Sesia indicate increased soil respiration during summer in both biochar and control plots, probably as a result of increased soil temperature (Cheng, Lehmann and Engelhard, 2008). Addition of biochar caused no significant difference in flux from root excluded versus non-root excluded plots. Furthermore, there was no significant difference between cumulative flux from biochar or control plots. However, isotopic analysis of CO2 efflux indicated that between 7% and 36% of soil respiration was attributed to biochar amendment, although this varied depending on the date of sampling. A seasonal component was noted, which was further accentuated in root excluded plots. The total respiration attributable to biochar was greater within Rtot samples versus Rh, indicating increased respiration of biochar within the soil when roots were present (Figure_12). During the measurement period (245 days) approximately 7% of total biochar was respired from Rh plots, whilst the total increased to approximately 9% in the presence of roots (Rtot). Soil respiration results at West Sussex indicate an increase in CO2 flux associated with biochar amendment(Ventura et al., 2014). Again, soil respiration increased in both treatment and control plots during the summer as a result of increased soil temperature. Diverging from the results from Prato Sesia, Rtot was significantly increased after biochar application at West Sussex, whilst there was no significant change in Rh. Isotopic analysis elucidated between 12% and 32% of soil respiration was attributable to biochar treatment, again with a seasonal summer component. In agreement with the results from Prato Sesia, Rtot was greater than Rh in biochar treated plots, indicating increased soil respiration as a result of the presence of roots. During the measurement period (164 days) total biochar derived CO2 was between 3% of total Rh, and 8% of Rtot, again indicating the effect of the presence of roots on biochar associated CO2 flux. Overall, whilst the rate of degradation was elevated, the treatment resulted in a protective effect on existing soil organic matter, preventing the loss of 0.5-0.7 t/ha in Italy and the UK respectively. Stem base diameter and height measurements were undertaken at Prato Sesia, combined with destructive dry biomass assessments. No significant difference was determined during either the first or second growth season at the site. Leaf litter biomass showed no effect of biochar application, nor did total C or N concentration within the litter. Furthermore, annual net primary productivity showed no significant difference between treatments. Assessment of N and P leaching within biochar plots showed no significant differences at Prato Sesia at any time point when comparing between biochar and control plots. Assessment of biomass was undertaken through stem diameter and height measurements at three time points, March and December 2012, and again during November 2013. Plant volume indicated no significant effect of treatment, or interaction between treatment and time on total plant volume. Similarly, leaf litter biomass was not significantly affected at approximately 4.5t/ha irrespective of biochar or control treatment. Extraction of resin lysimeters indicated a difference in results when compared to Prato Sesia, with an increase in P-PO4 and N-NH4 leachate in biochar amended plots when compared with controls. At both SRF and SRC sites, a similar negative priming effect was noted. After negating biochar derived C, soil respiration measurements indicated savings of 0.5 t/ha of C in Italy, and 0.7t/ha of C in the UK. In addition, biochar degradation within the soil was significantly higher in the presence of roots when compared to root excluded plots. This is at a higher rate than that measured in lab studies which often do not consider the role of plants in biochar decomposition studies, validating the usefulness of field trials of biochar. When dividing the priming effect by year, it was noted that it is decreased during the second year after amendment. Due to difficulties in equipment maintenance, data from Lusignan 2012-2013 was not sufficient for analysis. Difficulties with data collection were such that there is inadequate data for gap filling during this time period. However, isotopic analysis was undertaken, and this analysis currently undertaken. Furthermore, data is being collected from Lusignan for the 2014 season, so it is hoped that subsequent analysis of these results will be possible to determine whether a similar effect of negative priming can be detected. Soil C content was carried out at Lusignan, indicating that C content within biochar amended plots were considerably higher than those found in control. In addition to the three core sites, a range of additional satellite sites were established. In Pistoia a raised box experiment investigating the effect of HTC on poplar was produced. A raised box experiment was carried out to assess the impacts of HTC on SRC poplar at Pistoia-CESPEVI (PT). This method was chosen as it would prevent HTC treated soil from contaminating the soil environment. This was carried out at a stage in the project when it was thought there may have been potentially toxic effects of HTC’s due to high PAH’s. This was later found to be incorrect, and that HTC’s contain PAH’s below the legal limits in the EU.
After 2 years of measurements of both soil respiration and poplar biomass, it was determined that HTC increased poplar biomass only during the first year after application. Subsequent HTC applications caused no significant increase when compared with the initial HTC application, although all HTC trees had a greater biomass than control trees. Soil respiration was also analysed, and indicated significantly higher respiration in the presence of HTC. Results from Montepulciano site on ecophysiological measurements were published in (Baronti et al., 2014). Briefly, biochar addition significantly increased plant water availability with the consequence of increasing leaf water potential and plant photosynthetic activity in dry periods; and no significant effect on soil hydrophobicity was detected after biochar application. A paper describing the effect on grape yield and grape ripening parameters is in preparation, briefly, grape productivity was significantly increased in biochar treated plots (up to 66% in 2012) with no significant effect on grape maturity parameters. For further details see (Baronti et al., 2014). . Grape productivity was significantly elevated, with no negative impact upon fruit quality (Genesio et al., submitted). Results from Castell’apertole site on LCA analysis were published in (Lugato et al., 2013). The local climate is sub-humid, with annual rainfall of about 990 mm and average annual temperature of 11.6 °C (maximum and minimum average monthly temperatures in July and January are 28 and -3 °C, respectively). The soil has a sandy-loam texture (3.8 27.5 and 68.7% of clay, silt, and sand, respectively), pH (in H2O) of 5.6 and absence of carbonates along the profile. The application of biochar from gasification increased rice grain production by 12%, but such effect was only significantly different at P = 0.16. This was lower than the effect of addition from biochar from pyrolisis (36%, P=0.05) but this is probably due to increased macronutrients present within the slow pyrolisis biochar. LCA analysis calculations utilising the BEAT v2.1 model was utilised. This showed that the stage of the process contributing most to GHG emissions is gasification (more so than supply chains, biochar storage or transport). Drying had a lower GHG impact due to the use of waste heat from the AGT gasifier being used to further dry the feedstock. However, as the biochar is a waste product of the electricity generation of the system, the net GHG emissions are negative when assuming a 76.1% carbon content of biochar, and either of the two mineralization rates (32% and 7.3%) studied. For further details see (Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Results from the final two sites (Halle, Germany and San Michele all’Adige, Italy) are in the process of being analysed. The German site is assessing the stability and potential yield effects of HTC biochar in a field experiment, and was established after it was determined that there were no potentially toxic effects of HTC. It is comparing the impact of HTC, HTC combined with compost, slow pyrolysis biochar combined with compost and no treatment. The Italian site consists of a pot experiment using both AGT and HTC biochars with the aim of assessing their impact upon poplar growth when combined with mycorrhizal inoculation. The implication of biochar application was also studied in relation to soil bacterial and fungal diversity. Soil samples collected from each of the three core sites had DNA extracted from them and the 16S rRNA gene sequenced, allowing for identification of bacteria present within the communities. This amplicon has highly preserved regions, allowing for primer design and amplification, but also contain hypervariable regions permitting differentiation and identification of sequences from difference species. Utilising these methods it was noted that application of biochar caused a significant shift in the weighted UNIFRAC distances in both West Sussex and Prato Sesia (Figure_13). This indicates that the change in diversity is as a result of fluctuating abundance in the core species present. Furthermore, unweighted UNIFRAC analysis demonstrates a small but significant change in the species present between the treatments at all three core sites (Figure_14). Treatment explains between 5-8% of the variation noted in unweighted samples. It is likely that this small shift is in rare species with low abundance, as weighted results indicate a considerably greater portion of the variation (19-34%). Furthermore, when taken with the lack of a significant difference in the phylogenetic diversity scores (measuring alpha diversity) between control and treatment, it is expected that any shifts in the species present are to other similar species. Additionally, assessment of time series samples collected in West Sussex shows a significant effect of time interacting with treatment. Samples collected before biochar was added exhibit no significant difference in either weighted or unweighted UNIFRAC distances. At one month after biochar application, there were still no significant difference between treatments when assessed with weighted UNIFRAC, but a significant difference was present when unweighted UNIFRAC distance was assessed. This implies a minor shift in species under biochar treatment. Samples collected 1 year after biochar application are significantly different from all of those collected within year 1, regardless of treatment, and show greater clustering by treatment when assessed by both weighted and unweighted UNIFRAC. Therefore it seems likely that application of biochar causes a greater shift in community structure with time. This may be due to the increased surface area, nutrient availability and gradually shifting pH as a result of biochar application. In addition, SOM, SOC and electron donation may also result in further selection pressures, leading to rebalancing of microbial population in response to newly available environmental niches.
Work package (WP) 7 Scenario Analysis
The objectives of WP7 were:
1) Evaluate scenarios of large-scale application for C-sequestration
a. Current and future land use and potential for biochar application rates
b. Assessment of C-sequestration potential, based on inventory data
c. Estimation of Net Primary Production (NPP) and Net Ecosystem Production (NEP) for European agriculture
d. Assessment of C-sequestration potential, based on field study data
2) Understand the impact of large scale biochar agricultural application on the climate system on the basis of a sensitivity experiment on the forcing the albedo parameters in a RCM- modelling scheme
3) Understand potential “warming effects” by considering the reduction of net C-emission due to Biochar use at European scale to establish potential “cooling effects” due to changes in atmospheric CO2 concentration.
Work Package (WP7) of the EuroChar project established and analysed various scenarios in terms of feedstock available for the production of char, the subsequent potential scale of char production and land application, as well as the impact of the latter on albedo. The 28 countries of the European Union (EU-28) were considered as the geographical scope and 2010-2050 as the timeline. To determine a potential scale of feedstock available for the production of char, a number of categories were selected in accordance with the European Biochar Certificate: agricultural crop residues, forestry residues and the organic fraction of Municipal Solid Waste (MSW). Only waste and residues were considered to be viable feedstocks for char supply chains and only a certain share (20%) of these residues/wastes were assumed to be available for the production of char. The 20% share assumed to be ‘available’ signifies the many competing uses that exist for biomass feedstocks, however it must be noted that certain uses are not mutually exclusive and a prior use could eventually contribute to the production of char e.g. through recycling or, various renewable energy production pathways that also produce a certain amount of char as a co-product. The calculated technical, annual available feedstock potential for EU-28 was 116 Mt/yr dry feedstock (maximum moisture content of 15%), or 138 Mt/yr ‘wet’ feedstock (original/harvested moisture content). The potential scale is based on the assumption that the average amount of feedstock from 2005-2010 remains static for 2010-2050. Another range of feedstock potentials was calculated considering the average change in feedstock amounts from 2000-2010 and extrapolating this average annual change to 2050. The latter, ‘dynamic’ approach results in dry annual feedstock potentials of 115 Mt in 2010 to 124 Mt in 2020, 137 Mt in 2030, 157 Mt in 2040 and 188 Mt in 2050. As biomass feedstock potentials are volatile, the initial ‘static’ approach was applied as a basis for the further scenarios modelled in the EuroChar project. The estimated feedstock potentials were linked to char production scenarios, which considered three conversion technologies: gasification, Hydrothermal Carbonization (HTC) and slow-pyrolysis. Two production systems were established; one where a single technology is utilised and another system that represents a market mix of technologies. As the technologies are not mutually exclusive, due to their optimisation to different feedstock categories and the production of varying product types with differing characteristics, the ‘market mix’ production system is considered to provide a more realistic scenario and was therefore applied as the basis for the modelling. The potential scale of char production for 2010-2050 was calculated at 14-38 Mt/yr depending on the scenario of technology mix, conversion efficiency, etc. Considering the ‘dynamic’ scale of feedstock availability, annual char production potentials ranged from 13-37 Mt for 2010, 14-40 Mt for 2020, 16-44 Mt for 2030, 18-51 Mt for 2040 and 22-61 Mt for 2050 depending on the scenario. For single technology production systems the annual scale of char production for 2010-2050 ranged from 1-26 Mt for gasification, 25-41 Mt for HTC, and 35-47 Mt for slow-pyrolysis. From the scale of char production, potential arable land coverage was estimated considering three different application scenarios at a single application rate of either 10, 35 or 120 t/ha. The char production scale, considering a technology mix, was calculated to cover 0.1-3.5% of the EU-28 arable land annually from 2010-2050 depending on the scenario. An annual 2% coverage would result in 100% coverage in 50 years, however this only considers a single application per unit land area over the 50 years; char could also be applied to other land types and multiple application frequencies for the low and medium application rates are possible and potentially even required to achieve positive yield impacts. The scenario modelling work in the EuroChar project indicates that a potentially limiting factor in the large-scale production and application of char is the availability of feedstock. The main conversion technologies are well developed and are expected to see an increase in uptake and deployment, promoted by, for example, increased funding for projects in developing countries (pyrolysis cook-stoves), green energy subsidies (gasification), more sustainable routes for waste treatment (HTC), carbon credits, etc. With regards to land application, many types of lands could have char applied and multiple applications are possible either annually or multi-annually. Also, any legislative restrictions in terms of char application to land are expected to decrease over time. The impact of char on the carbon cycle through its production and land application was considered in order to calculate its carbon sequestration potential. The application of char can impact the carbon cycle through changing the Net Primary Productivity (NPP) and/or the soil carbon stock. Char’s impact on biomass productivity is highly uncertain and therefore a single increase of 5% in NPP was considered in the scenario analysis. Considering the calculated scale of char production and land application, this results in an increase of NPP/vegetation carbon stock of 0.037-1.28 Mt of CO2, which is equivalent to 0.0064-0.22% of the total UK emissions in 2012. As the vegetation and soil carbon stocks of croplands are minimal compared to other land area types, such as forests (especially boreal forests), the potential beneficial impact of char on NPP would be significantly greater if char was applied to these other land types. More work is needed to understand if the productivity impacts of char are robust across different soil and vegetation types. The impact of char on the soil carbon stocks was calculated considering initially only the carbon in the char and subsequently also including the supply chain emissions calculated in the Life Cycle Assessment (LCA) (WP 3). Based on the calculated potential scale of char production in the EU-28 from 2010-2050, and considering only the char carbon, the annual sequestration potential was calculated at a level of 16-50 Mt CO2/yr, which is equivalent to 1.79-5.6% of total EU-28 transport emissions in the year 2012. When including the direct, attributional supply chain emissions, the sequestration potential is reduced to 14-40 Mt CO2/yr, similar to a level of 1.57-4.48% of total EU-28 transport emissions in 2012. If the indirect, consequential supply chain emissions are also considered, the carbon sequestration potential would significantly increase. The advantageous consequential impacts are mainly due to the offsetting of fossil energy sources, however the extent of this benefit will depend on the composition of the energy mix, which is expected to become ‘cleaner’ in the future. The combined annual sequestration potential of char production and application in the EU-28 for 2010-2050 considering both NPP and soil impacts, including the supply chain emissions, ranges from 14-41 Mt CO2. Potential closed-loop scenarios, in terms of the carbon cycle as well as considering the mass flows of the project-specific char production and application supply chains, were also established and analysed. Application of the closed-loop methodology to the char carbon cycle is problematic because of the basic carbon neutrality (closed-loop) of cropping (vegetation) systems. Overall, char application is expected to increase the portion of carbon diverted into the longer-term soil carbon stock. The counterfactual assumption in this case is that the carbon in the biomass residues would have returned to the atmosphere via the short-term/fast carbon cycles of decay and heterotrophic respiration. On a mass basis, simple ‘payback’ periods were calculated to determine the number of years needed to obtain the amount of biomass required to produce a certain amount of char. Payback periods were significant and ranged from 4-87 years depending on the crop, the crop yield considered (in this case assuming all yield is utilised), and the amount of char required. When considering that only a 20% share of the yield is available for char production the simple ‘payback’ period increased significantly to 18-434 years depending on the scenario. However, two issues substantively complicated the concept of ‘closed loop systems’ and ‘payback periods. Firstly, the char application rate was chosen to represent the amount of char that is assumed to be required to produce beneficial impacts on crop production. This is considered as a one-off application with the impacts lasting decades. Secondly, as only the gasification technology was considered in the closed-loop scenarios, the main purpose of gasification is to produce a fuel for electricity production as the main product with only a relatively small amount of char as a by-product, about 10% of the feedstock input on a mass basis. We therefore advise caution when interpreting the ‘payback’ periods calculated, as the carbon/biomass ‘lost’ to the atmosphere should be proportionately allocated to the associated electricity production and not exclusively to the char.
Biochar is a promising strategy to safely sequester relevant amounts of carbon into agricultural soils while simultaneously increasing crop yields and soil ecosystem services. Nevertheless, looking toward a possible large-scale application of this technology, a fundamental aspect that needs to be treated, is the assessment of the consequences of implementing this strategy on the surface radiative energy balance. In fact, being a carbon-based substance, biochar has a very low reflectivity, and its addition to agricultural soils is demonstrated to change the background colour of the treated cropland altering (decreasing) the ratio of reflected and incoming shortwave radiation (albedo), potentially affecting the energy fluxes partitioning. EuroChar tackled this topic with a multi scale approach (local-landscape-regional) enabling to improve our knowledge on the impact of biochar on the radiative balance and providing inputs for an improved representation of surface schemes for modelling purposes. The plot scale experiment on wheat showed a surface albedo increase up to 80% in plots treated with biochar in respect to their control. Furthermore it enabled to highlight that biochar application increases soil surface temperature during winter promoting a faster crop growth during the first crop phases (Sensible heat flux was increased by 17% during winter). Moreover an increased evapotranspiration during the crop cycle was observed (+4%), related to the increased biomass and to the higher plant water availability. In the landscape scale experiment, large scale biochar application were simulated by comparing 6 target sites having different soil colour over a 12 years time series by means of satellite datasets of NDVI and Albedo. The objective of the work was to estimate the influence of a change in soil background colour induced by biochar incorporation on the surface shortwave albedo of a complex agricultural system in the Mediterranean environment, as well as its impact on Radiative Forcing. This experiment has been essential to disentangle the existing uncertainties related to the representation of albedo seasonal mode in function of canopy development in complex agricultural Mediterranean environments. In particular the main findings that have been transferred to the modelling section are that i) in complex agricultural systems soil darkening can induce an overall net increase in cumulated absorbed solar radiation in dark soil sites as high as 2%, ii) the magnitude of such effect is modulated by the fractional vegetation cover and by specific canopy reflectivity parameters, but iii) also in high canopy cover conditions (vegetation peak = high LAI) soil background colour has an impact on surface radiation balance. The experiment also highlighted that agricultural policies and the related crop choices do have a relevant impact on the overall Absorbed Solar Energy Balance; this was particularly evident in the case of one of the selected test sites (NE) where, as a consequence of agricultural subsidies to sunflower during the years 2000’s, this crop was implemented on the same dark soil site for almost a decade inducing a significant negative radiative forcing able to offset the expected difference in radiation balance caused by the low soil reflectivity.
The Regional scale modelling experiment, performed perturbing the arable land albedo scheme in WRF model, showed that a small but significant impact on surface temperature is expected as a consequence of a European-scale biochar application and in particular a local temperature increase of about 0.1°K has been detected in Eastern Europe.
Potential impact (including the socio-economic impact and the wider societal implications of the project so far) and the main dissemination activities and the exploitation of results. The length of this part cannot exceed 10 pages.
The potential impact of Eurochar project are numerous.
The results of WP1 clarified that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste.
The knowledge and technology implementation achieved on the two processes will impact on the finalization of the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. New knowledge on HTC revealed that this subproduct might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage. This new information will have an impact on the technological chain and the implementation of new synergies between the two processes.
EuroChar will also contribute to the development of industrial process by providing evidence that the production of gaseous pollutants during gasification and Hydrothermal treatments are very low. But it will also generate some caution, as even if the concentration of aldehydes and ketons resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. The observation of a presence of ketons and aldehydes which are classified as experimental carcinogenic substances (Classification ACGIH class A3) will generate some specific attention on the regulations and controls of industrial processes.
The fact that the TC biochar and HTC chars were used not only within the project Eurochar, but also in trials by other external entities will have an impact. The list of organizations that directly benefit from the avaiability of chars is large: CRA-RPS, Research Centre for Soil-Plant System studies of Agricultural Research Council of Italy, Rome (I),CRA-ORT, Research Centre for Horticulture of Agricultural Research Council of Italy, Battipaglia (I),ENR-CCR, Rice Research Centre of Italian National Agency for Rice, Castello d’Agogna (I), Trees and Timber Institute of CNR (National Research Council of Italy), Florence (I), Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Rome (I), Minoprio Foundation, Vertemate con Minoprio (I), University of Bologna, Bologna (I), University of Milan, Milan (I), University of Palermo, Palermo (I), University of Parma, Parma (I), University of Pisa, Pisa (I), University of Udine, Udine (I), UKBRC, UK Biochar Research Centre, University of Edinburgh, Edinburgh (UK), Institut Sylva, Le Bec Hellouin (F), Agronomia Group, Bergamo (I) (Production of ready-to-eat salad vegetables), Plozner, Spilimbergo (I) (Wine farm), TerrAgricola, Varese (I) (Production of soil improvers and growing media), Vivai Pacini, Pescia (I) (Olive nursery), Max-Planck-Institut für Biogeochemie, Jena (DE), Hochschule für nachhaltige Entwicklung Eberswalde, Eberswalde (DE).
Life Cycle assessment (WP3) results will have a potential impact on C-sequestration policies and initiatives. The production and application of char could therefore contribute to climate change mitigation, and new regulations may profit of the information which hass been collected and analysed through LCA. The results will however further discourage the use of dedicated crops for the production of char. The observation that char oxidation rates are important in LCA will impact substantially on future research plans in biochar science. Carbon credits policies will also benefit from the results achieved, to eventually provide a financial incentive for carbon sequestered through the production and land application of biochar. There are a number of other social and economic benefits from the production and application of char. The co-production of energy, e.g. in gasification systems, could offset ‘dirty’ fossil energy sources, which would have a significant impact on climate change. The land application of char could improve ecosystems by increasing nutrient and water retention capabilities. These beneficial impacts on agricultural lands could increase productivity and reduce fertiliser and irrigation requirements, providing significant economic benefits to the farmer and society as a whole. However, the application of char could potentially also have some phytotoxic effects depending on the conversion technology and feedstock used. Safety regulations therefore have to be stringent and post-treatment processing might be required to eliminate such potential detrimental impacts on the ecosystem. Another important conclusion from the LCA results indicates that feedstock transport could cause a significant share of the potential environmental impacts. It is therefore recommended that the char production is either done on-site at the feedstock plantation/origin or located nearby. On-site production could provide an additional revenue stream to the farmer or site manager if the char were to be sold or the co-produced energy exported to the grid. Finally, the lack of LCA-relevant parameters obtained from the field trials indicate that future field studies should consider these parameters in their data collection inventory. Impacts of char application in terms of potentially reducing fertiliser and irrigation requirements or increasing crop productivity could provide significant environmental ‘benefits’. Field trials are required, in combination with controlled lab studies, to provide a more accurate representation of the real impacts/fate of the char applied, and this should therefore be another key continued and future focus within the char research field.
Results obtained in WP4 which determined chemical and physical characteristics of modern biochars and hydrochars produced from different feedstocks pointed to the existence of large differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. This, together with the observation of phytotoxic effects that can be eliminated by chemical (e. g. oxidation) or biological treatment (e. g. composting) will have a direct strong impact on the production of biochar with sufficient environmental safety. And it will stimulate further research which is urgently needed to identify the unknown phytotoxic and genotoxic compounds in the hydrochar since the unknown substances may also impact human health.
Results obtained in WP5 that assessed the stability of modern biochars and hydrochars and developed stability indicator will have a direct impact on the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. The observed differences between biochar and hydrochar and composts will be directly used to estimate the relative effective C-sequestration potential, thus contributing to the development and implementation of new regulations. On the other hands, the same results will stimulate the utilization of co-composted hydrochar as suitable as soil amendment because it may increase the content of organic carbon in compost substrates, even if the low amount of polymerized carbon structures makes this material not resistant enough against microbial degradation.
The results of WP6 demonstrated the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. A key impact of the activity made, is in the creation of major infrastructure in Europe and the establishment of network of biochar field sites that can become a long-term facility, opened to international access. This would provide for some of the first assessments of long term biochar stability at highly instrumented sites, further developing knowledge of the viability of biochar as a method of carbon sequestration. The multi-site experimental data that have been collected are of primary importance for the development of EU standard and policies on C-sequestration as these provide practical evidence that biochar application in soils can be made in a safe and effective way, with limited costs and a net environmental benefit. Results from the Castel all’Apertole and Montepulciano satellite sites demonstrate the viability of biochar as a soil amendment, augmenting crop yield whilst having no negative impact on crop quality (Baronti et al., 2014; Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Furthermore, the elevated water holding capacity of soils treated with biochar may have the potential for utilisation to reduce drought effects and total irrigation required by the crops. This has potential implications for increasing the uptake of biochar soil amelioration within the agricultural community.
Shifts in microbial communities present in 2 of the 3 core sites call for a better understanding of the mechanisms involved, something that may help in future to elucidate how biochar actually contributes to soil fertility.
The results of WP7 that consider scenario analysis in the case of large scale applications of biochar has a number of potential relevant impacts. In terms of feedstock availability, limited impact is expected as only residues and waste are considered a feasible feedstock and only a 20% share of this feedstock category was considered to be available. We consider it unlikely that dedicated cropping solely for the production of char could be regarded as socially acceptable as the scale of cropping required could garner negative attention, similar to that of the food versus fuel debate surrounding bioenergy, as well as divert biomass feedstocks away from other relatively more important uses. As a result, the availability of feedstock is expected to be the limiting factor in the large-scale production and application of char in the EU. The availability of the currently considered feedstock categories is expected to decrease over time as technological advancements aim to reduce any resulting waste and residues from processes and as increasing uses arise for biomass feedstocks. It is therefore important that other types of feedstocks, particularly waste streams, are included as suitable input materials for the char supply chains. The results of the EuroChar scenario modelling could therefore inform and direct the current char standards and certification schemes to investigate and potentially include such categories in their ‘positive list of char feedstocks’. EU policy should also consider reviewing any current legislative barriers preventing the land application of char produced from ‘waste’. The potential annual scale of carbon sequestration calculated in the scenario modelling indicated levels equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties. Climate change is a key challenge faced by modern-day and future societies and any technologies capable of reducing atmospheric CO2 levels should be considered. Besides its benefits in terms of carbon sequestration, char production and application could also potentially provide a more sustainable waste treatment route, and contribute to the production of renewable energy through the main/co-products produced by the conversion technology. Additionally, the application of char could not only increase the productivity of agricultural lands but also assist with the remediation of degraded or contaminated lands. Whilst it was not within the scope of this work to derive a clear conclusion about the best/optimal use of biomass, with regard to renewable energy versus land application of char, we recommend that future research aims to understand the consequential impacts of char application on crop yields as the key determinant of relative benefit of char compared to energy. Concerning the impact of biochar application on albedo and on surface radiative balance the experiments performed enabled to draw a number of recommendations for operational purposes and to highlight research priorities on this topic. Recommendations for optimal biochar application strategy: considering that no significant differences in surface albedo were observed over the application rate of 30tha-1, it would be better to recommend high application rates in order to maximize the carbon sequestration potential without additive impact on the radiation balance. These findings also stress the need to delineate the integration of biochar with other geoengineering strategies based on the change of reflective properties of agricultural surfaces (e.g. the adoption of varieties selected for their reflectivity; white plants). Furthermore, soil incorporation is the biochar application strategy to be recommended to minimize the reduction of the mitigation potential of biochar, together with the adoption of high rates in one single application. Finally, the landscape experiment provided a consistent representation of surface albedo in complex agricultural systems in the Mediterranean environment that can be operationally adopted in RCMs. It also pointed out the need for improving the representation of surface schemes in RCMs with particular reference to the representation complex land-surface feedbacks, which are a consequence of biochar application, by means of biosphere models.
Dissemination activities and the exploitation of results.
At the start of the project the Eurochar website www.eurochar.eu was launched. This website has been used to provide information to anyone interested in the topic as well as a platform to exchange knowledge and data among the participating partners. During the Eurochar project all materials done (deliverables done, report of meeting done) were given to all partners. Dissemination of the knowledge and experiences from Eurochar is essential to ensure the public benefit of such research projects. In addition to scientific journal articles, presentations and posters project partners have also conducted dissemination activities focusing more on end users, stakeholders and policy makers.
In 2011 was organized by University of Halle (Germany), Partner 3 (leader Prof. Bruno Glaser) of Eurochar Project, the European Biochar Symposium. The Symposium was held at the University of Halle in Gemany from 26.to 27 September 2011. The Symposium has been used by Eurochar projects to disseminate the knowledge gained during the projects. In the 2013 was organized by CNR_IBIMET a special session “Stakeholders Committee of Eurochar Project” within the 1th Mediterranean Biochar Symposium.
In general the First Mediterranean Symposium has been used by Eurochar partner to disseminate the knowledge gained. In fact, were a total of 8 oral presentation (such as a keynotes of Franco Miglietta- Eurochar coordinator) and many poster. A large number of students at different levels have been involved in the project for their theses work and internships, a total of 4 PhDs. Eurochar did not organise any specific courses during the project period, but Eurochar results have been presented as part of the regular teaching programmes at the different Universities.
In total 12 contributions (peer reviewed), 37 oral presentation and 14 poster presentation at international conferences have been produced so far. The large number of journals and thematic areas associated demonstrated the high multidisciplary character of EUROCHAR. Results are described and displayed in a general and understandable way. Dissemination of the knowledge and experiences from Eurochar is essential to ensure the public benefit of such research projects. In addition to scientific journal articles, presentations and posters project partners have also conducted dissemination activities focusing more on end users, stakeholders and policy makers. Permanent and bi-directional line of communication with stakeholders through the users group. Formal and informal meetings with stakeholders were celebrated in several regions of Italy, German, UK, France. In addition, the biochar utilization protocol and decision support system was presented to stakeholders in several countries. Stakeholders feedback is an essential component of interaction between the Scientific community (higher education, Research), Industry, Civil Society, Policy makers and Media. Therefore, Eurochar Project considered several activities involving stakeholders, both for transferring scientific and technical results and for capturing and make use of local experiences and perception. The main objective was to promote feedbacks between Eurochar scientists and relevant stakeholders involving private companies, associations and interest groups became involved in EuroChar Project. A cohort of stakeholders, the EuroChar Stakeholder Committee (ESC), was established to give guidance and feedback on the project’s work from an external perspective. It comprised experts from relevant research and application fields. The consolidation of ESC was finalized at the time of the EuroChar kick-off meeting and the specific meeting with ESC was planned at the second project’s years. ESC contributed by reviewing the activities of the project.
Moreover, the Eurochar project will participate to Expo 2015, in the pavilion in the National Research Council. The coordinator of Eurochar Project has invited Lehmann to give a talk about biochar at EXPO in Milan in Summer 2015. Possibility of TeD talks or other biochar related talks. The coordinator would also like to organise a biochar event (Biochar 2015) with outreach to industry, with the possibility of EuroChar being represented there. The type of output from Deliverables of Eurochar project could be shown (for example). Visualisation of albedo effects for wider public/shareholders.
Potential Impact:
The results of WP1 clarified that there is no competition between gasification (thermochemical carbonization - TC) and hydrothermal carbonization (HTC) due to the differences concerning the starting feedstock: dry in the first case (water content always below 15%), mainly product and byproduct of agriculture and forestry, wet in the second one, mainly waste.
The knowledge and technology implementation achieved on the two processes will impact on the finalization of the closed-loop system process for eliminating tar, obtaining a clean tar-free synthesis gas able to run on a variety of engines and turbines producing energy and heat. New knowledge on HTC revealed that this subproduct might serve as a pre-treatment stage before the gasification stage for wet biomass replacing the drying process. The wet biomass will be converted via HTC to form hydrochar with a total solids content of approx. 70% after mechanical dewatering. This could be used as an input feedstock to the gasification stage. This new information will have an impact on the technological chain and the implementation of new synergies between the two processes.
EuroChar will also contribute to the development of industrial process by providing evidence that the production of gaseous pollutants during gasification and Hydrothermal treatments are very low. But it will also generate some caution, as even if the concentration of aldehydes and ketons resulted below the limit value, their presence is noteworthy because of their reaction with some air compounds to create ozone and NOx compound (nitrogen oxides) that are harmful for the environment. The observation of a presence of ketons and aldehydes which are classified as experimental carcinogenic substances (Classification ACGIH class A3) will generate some specific attention on the regulations and controls of industrial processes.
The fact that the TC biochar and HTC chars were used not only within the project Eurochar, but also in trials by other external entities will have an impact. The list of organizations that directly benefit from the avaiability of chars is large: CRA-RPS, Research Centre for Soil-Plant System studies of Agricultural Research Council of Italy, Rome (I),CRA-ORT, Research Centre for Horticulture of Agricultural Research Council of Italy, Battipaglia (I),ENR-CCR, Rice Research Centre of Italian National Agency for Rice, Castello d’Agogna (I), Trees and Timber Institute of CNR (National Research Council of Italy), Florence (I), Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Rome (I), Minoprio Foundation, Vertemate con Minoprio (I), University of Bologna, Bologna (I), University of Milan, Milan (I), University of Palermo, Palermo (I), University of Parma, Parma (I), University of Pisa, Pisa (I), University of Udine, Udine (I), UKBRC, UK Biochar Research Centre, University of Edinburgh, Edinburgh (UK), Institut Sylva, Le Bec Hellouin (F), Agronomia Group, Bergamo (I) (Production of ready-to-eat salad vegetables), Plozner, Spilimbergo (I) (Wine farm), TerrAgricola, Varese (I) (Production of soil improvers and growing media), Vivai Pacini, Pescia (I) (Olive nursery), Max-Planck-Institut für Biogeochemie, Jena (DE), Hochschule für nachhaltige Entwicklung Eberswalde, Eberswalde (DE).
Life Cycle assessment (WP3) results will have a potential impact on C-sequestration policies and initiatives. The production and application of char could therefore contribute to climate change mitigation, and new regulations may profit of the information which hass been collected and analysed through LCA. The results will however further discourage the use of dedicated crops for the production of char. The observation that char oxidation rates are important in LCA will impact substantially on future research plans in biochar science. Carbon credits policies will also benefit from the results achieved, to eventually provide a financial incentive for carbon sequestered through the production and land application of biochar. There are a number of other social and economic benefits from the production and application of char. The co-production of energy, e.g. in gasification systems, could offset ‘dirty’ fossil energy sources, which would have a significant impact on climate change. The land application of char could improve ecosystems by increasing nutrient and water retention capabilities. These beneficial impacts on agricultural lands could increase productivity and reduce fertiliser and irrigation requirements, providing significant economic benefits to the farmer and society as a whole. However, the application of char could potentially also have some phytotoxic effects depending on the conversion technology and feedstock used. Safety regulations therefore have to be stringent and post-treatment processing might be required to eliminate such potential detrimental impacts on the ecosystem. Another important conclusion from the LCA results indicates that feedstock transport could cause a significant share of the potential environmental impacts. It is therefore recommended that the char production is either done on-site at the feedstock plantation/origin or located nearby. On-site production could provide an additional revenue stream to the farmer or site manager if the char were to be sold or the co-produced energy exported to the grid. Finally, the lack of LCA-relevant parameters obtained from the field trials indicate that future field studies should consider these parameters in their data collection inventory. Impacts of char application in terms of potentially reducing fertiliser and irrigation requirements or increasing crop productivity could provide significant environmental ‘benefits’. Field trials are required, in combination with controlled lab studies, to provide a more accurate representation of the real impacts/fate of the char applied, and this should therefore be another key continued and future focus within the char research field.
Results obtained in WP4 which determined chemical and physical characteristics of modern biochars and hydrochars produced from different feedstocks pointed to the existence of large differences in the elemental as well as chemical composition of modern biochars and hydrochars from the three different feedstocks. This, together with the observation of phytotoxic effects that can be eliminated by chemical (e. g. oxidation) or biological treatment (e. g. composting) will have a direct strong impact on the production of biochar with sufficient environmental safety. And it will stimulate further research which is urgently needed to identify the unknown phytotoxic and genotoxic compounds in the hydrochar since the unknown substances may also impact human health.
Results obtained in WP5 that assessed the stability of modern biochars and hydrochars and developed stability indicator will have a direct impact on the assessment of biochar stability and its C sequestration potential in soil taking into account its effect on soil organic matter mineralisation. The observed differences between biochar and hydrochar and composts will be directly used to estimate the relative effective C-sequestration potential, thus contributing to the development and implementation of new regulations. On the other hands, the same results will stimulate the utilization of co-composted hydrochar as suitable as soil amendment because it may increase the content of organic carbon in compost substrates, even if the low amount of polymerized carbon structures makes this material not resistant enough against microbial degradation.
The results of WP6 demonstrated the impact of biochar application to short rotation forestry (SRF) within the EU, whilst assessing the amendments potential for carbon sequestration and SRF productivity. A key impact of the activity made, is in the creation of major infrastructure in Europe and the establishment of network of biochar field sites that can become a long-term facility, opened to international access. This would provide for some of the first assessments of long term biochar stability at highly instrumented sites, further developing knowledge of the viability of biochar as a method of carbon sequestration. The multi-site experimental data that have been collected are of primary importance for the development of EU standard and policies on C-sequestration as these provide practical evidence that biochar application in soils can be made in a safe and effective way, with limited costs and a net environmental benefit. Results from the Castel all’Apertole and Montepulciano satellite sites demonstrate the viability of biochar as a soil amendment, augmenting crop yield whilst having no negative impact on crop quality (Baronti et al., 2014; Lugato et al., 2013). As such, augmented yield coupled with no decline in crop quality may result in an economic bonus from utilising biochar in this manner. It may be possible to utilise biochar instead or traditional fertilisers for some soil types with certain crops, which may result in further economic savings to the farmer. However, this requires further research as only two satellite sites assessed the impact of biochar amendment on crop yield. Furthermore, the elevated water holding capacity of soils treated with biochar may have the potential for utilisation to reduce drought effects and total irrigation required by the crops. This has potential implications for increasing the uptake of biochar soil amelioration within the agricultural community.
Shifts in microbial communities present in 2 of the 3 core sites call for a better understanding of the mechanisms involved, something that may help in future to elucidate how biochar actually contributes to soil fertility.
The results of WP7 that consider scenario analysis in the case of large scale applications of biochar has a number of potential relevant impacts. In terms of feedstock availability, limited impact is expected as only residues and waste are considered a feasible feedstock and only a 20% share of this feedstock category was considered to be available. We consider it unlikely that dedicated cropping solely for the production of char could be regarded as socially acceptable as the scale of cropping required could garner negative attention, similar to that of the food versus fuel debate surrounding bioenergy, as well as divert biomass feedstocks away from other relatively more important uses. As a result, the availability of feedstock is expected to be the limiting factor in the large-scale production and application of char in the EU. The availability of the currently considered feedstock categories is expected to decrease over time as technological advancements aim to reduce any resulting waste and residues from processes and as increasing uses arise for biomass feedstocks. It is therefore important that other types of feedstocks, particularly waste streams, are included as suitable input materials for the char supply chains. The results of the EuroChar scenario modelling could therefore inform and direct the current char standards and certification schemes to investigate and potentially include such categories in their ‘positive list of char feedstocks’. EU policy should also consider reviewing any current legislative barriers preventing the land application of char produced from ‘waste’. The potential annual scale of carbon sequestration calculated in the scenario modelling indicated levels equal to 5-6% of EU-28 transport emissions (reference year 2012). The results therefore indicate that the production and land application of char is a potential carbon sequestration technology and the project could therefore inform EU policy to promote the deployment of char or at least support further research to address any remaining uncertainties. Climate change is a key challenge faced by modern-day and future societies and any technologies capable of reducing atmospheric CO2 levels should be considered. Besides its benefits in terms of carbon sequestration, char production and application could also potentially provide a more sustainable waste treatment route, and contribute to the production of renewable energy through the main/co-products produced by the conversion technology. Additionally, the application of char could not only increase the productivity of agricultural lands but also assist with the remediation of degraded or contaminated lands. Whilst it was not within the scope of this work to derive a clear conclusion about the best/optimal use of biomass, with regard to renewable energy versus land application of char, we recommend that future research aims to understand the consequential impacts of char application on crop yields as the key determinant of relative benefit of char compared to energy. Concerning the impact of biochar application on albedo and on surface radiative balance the experiments performed enabled to draw a number of recommendations for operational purposes and to highlight research priorities on this topic. Recommendations for optimal biochar application strategy: considering that no significant differences in surface albedo were observed over the application rate of 30tha-1, it would be better to recommend high application rates in order to maximize the carbon sequestration potential without additive impact on the radiation balance. These findings also stress the need to delineate the integration of biochar with other geoengineering strategies based on the change of reflective properties of agricultural surfaces (e.g. the adoption of varieties selected for their reflectivity; white plants). Furthermore, soil incorporation is the biochar application strategy to be recommended to minimize the reduction of the mitigation potential of biochar, together with the adoption of high rates in one single application. Finally, the landscape experiment provided a consistent representation of surface albedo in complex agricultural systems in the Mediterranean environment that can be operationally adopted in RCMs. It also pointed out the need for improving the representation of surface schemes in RCMs with particular reference to the representation complex land-surface feedbacks, which are a consequence of biochar application, by means of biosphere models.