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The use of pyrolyzed carbon, biochar, as a soil amendment is of potential interest for improving phytoremediation of soil that has been contaminated by petroleum hydrocarbons. To examine this question, the research reported here compared the effects of biochar, plants (mesquite tree seedlings), compost and combinations of these treatments on the rate of biodegradation of oil in a contaminated soil and the population size of oil-degrading bacteria. The presence of mesquite plants significantly enhanced oil degradation in all treatments except when biochar was used as the sole amendment without compost. The greatest extent of oil degradation was achieved in soil planted with mesquite and amended with compost (44% of the light hydrocarbon fraction). Most probable number assays showed that biochar generally reduced the population size of the oil-degrading community. The results of this study suggest that biochar addition to petroleum-contaminated soils does not improve the rate of bioremediation. In contrast, the use of plants and compost additions to soil are confirmed as important bioremediation technologies.

An understanding of the influence of biochar on soil organic carbon (SOC) formed from different carbon (C) sources, other than biochar, at field scale is required to accurately assess and predict the C sequestration potential of biochar. For this study, we set up a field experiment in 2009, including four treatments (i.e. B0, B30, B60, and B90, where the biochar application rates were 0, 30, 60, and 90 t ha−1, respectively). We then assessed the impact of biochar after five years (i.e. in 2014) on native SOC derived from C3 (wheat) and C4 (maize) crop residues, and also changes in relatively labile and stable SOC fractions. After five years, the content of native SOC derived from crop residues increased by 81% (from 4.32 to 7.84 g kg−1) in the B0 treatment, while the increases of native SOC were relatively lower in the B30 (61%), B60 (43%), and B90 (26%) treatments. Thus biochar decreased the content of native SOC compared to the B0. Additionally, biochar decreased “labile pool I” (first-step, weak acid hydrolysable) of native SOC by 11.2–47.7%, compared to the B0, but did not influence “labile pool II” (second-step, strong acid hydolysable) and “recalcitrant pool” (acid non-hydolysable). Using the natural abundance 13C, our results showed that 62–74% of the native SOC was derived from wheat across all the treatments. Biochar application decreased the contribution of wheat-derived C to native SOC by 14.7, 29.0, and 41.5% in the B30, B60, and B90 treatments, respectively, while the content of maize-derived native SOC did not change, relative to the B0. In conclusion, although wheat-derived native SOC was higher than maize-derived native SOC, biochar application decreased the contribution of wheat residue to native SOC, possibly by enhancing its degradation, thus decreasing wheat-derived native SOC storage in an agricultural system.

This study investigated economic returns and energy use of alternative rice production systems in North Vietnam with various residue management options. The traditional practice of open burning of rice residues (System A) was compared with the alternative of converting residues to biochar, which was returned to the paddy fields (System B). It was assumed that households used improved cook-stoves and drum ovens to produce biochar, and that the agronomic impacts of biochar compound with increasing biochar applications until reaching maximum benefit at 18 Mg ha−1. This amount of biochar would take eight years to be produced in pyrolytic cook-stoves and drum ovens using the rice residues produced on-site. The net present value (NPV) of producing rice in the two systems was calculated based on their expected streams of costs and benefits. Biochar addition enhanced the NPV of rice by 12% and reduced the non-renewable energy intensity by 27%, relative to System A, after eight years of application. The difference in NPV values between production systems significantly increased to 23% and 71% by crediting GHG emissions abatement in low and high carbon price scenarios, respectively. These findings demonstrate the potential economic benefits of converting rice residues to biochar for soil application.

Low and declining soil organic matter contents pose a significant threat to soil fertility, crop productivity and economic returns in arid and semi-arid agroecosystems. Holistic approaches are required to build and sustain soil organic matter in such soils to enhance nutrient use efficiencies and meet food security. Biochar is emerging as an attractive option for multiple benefits to soil-plant systems and carbon sequestration, especially in low fertility soils. We conducted a two-year maize-wheat rotation field experiments during 2015 and 2016 to test the effects of biochar on crop productivity, soil properties and phosphorous use efficiency (PUE) when applied with organic P sources as either farmyard manure (FYM) or poultry manure (PM) and diammonium phosphate (DAP) chemical fertilizer. Biochar was applied at two rates (0 and 10 t ha −1 ) whereas percentage of organic-inorganic P sources were 0, 25, 50 and 100% respectively. Biochar and manures were incorporated only once at the start of the field experiments whereas chemical fertilizers were applied during each crop cycle. Analysis of the two-year data revealed that biochar and P sources significantly and positively changed crop and soil quality attributes. Application of biochar significantly increased biological and grain yields of maize and wheat, soil organic carbon (SOC), and available nitrogen (N) and P contents without any negative effects on soil pH and electrical conductivity (EC). Addition of 50% P each from organic (FYM or PM) and chemical fertilizer increased biological and grain yields of maize, however, wheat biological and grain yields were higher with 100% PM or FYM in the presence of biochar. SOC and P contents were the highest when biochar was integrated with 100% P from FYM under maize crop. Biochar enhanced PUE from organic P sources more than the chemical fertilizer for both crops. Grain and biological yields of both crops correlated positively with SOC, soil N and soil P contents. We also found strong correlations between SOC, PUE and harvest index (HI) suggesting the benefits of increasing SOC contents under biochar-related integrated nutrient management practices. Overall results from these field experiments indicate potential of biochar to enhance plant nutrition, crop productivity and soil quality in nutrient poor alkaline calcareous soil under maize-wheat cropping system. Long-term farmers’ participatory field experiments, however, are required to extrapolate the potential of biochar integrations into current cereal-based cropping systems of Pakistan.

This review summarizes the influences of pyrolysis conditions and feedstock types on biochar properties, and how biochar properties in turn affect soil properties. Mechanistic evidence of biochar's potential for enhancing crop productivity, carbon sequestration, and nutrient use efficiency are also discussed. The review identifies the knowledge gaps, limitations, and future research directions for large-scale use of biochar. Both pyrolytic parameters and feedstock types are considered to be the main factors controlling biochar properties such as nutrient content, recalcitrance and pH. Biochar produced at low temperatures may improve nutrient availability and crop yield in acidic and alkaline soils, whereas high-temperature biochar may enhance long-term soil carbon sequestration. Biochar can also improve the efficiency of inorganic and organic fertilizers by enhancing microbial functions and reducing nutrient loss, thereby making nutrients more available to plants. Integration of biochar and chemical or organic fertilizers generally provides for better nutrient management and crop yield in most types of soils. Although biochar can improve degraded soils, it is not a panacea; as such, soil- and crop-specific biochar are needed in order to ensure optimum crop yield and agricultural sustainability.

Biochar may increase soil fertility and crop yield by enhancing soil organic carbon (SOC), nutrient availability and water retention. However, the mechanisms through which biochar effects crop yield at field scale and the time span over which biochar can affect soil properties and crop yield are still little known. The aim of this study was to evaluate the effect of wood biochar as soil amendment, combined with the application of synthetic fertilizer in a zero-tillage system, on soil physical-chemical properties and soybean grain yield in a 5-year field trial settled on a sandy clay loam Haplic Ferralsol of the Brazilian savannah. Immediately after biochar application (year 0), soil pH and plant available water (PAW) increased and Al3+ and bulk density (BD) decreased linearly with biochar application rate. Later, in year 5, biochar had no effect for PAW and BD increased with biochar rates. The SOC was not affected until the third year after application, but increased linearly with biochar rates at 4 and 5 years after its application. Macro-porosity (MAC) was affected in a quadratic manner reaching a maximum at 8 Mg ha−1 biochar rate in years 0 and 2, however in year 5 it decreased with increasing biochar rates. Soybean grain yield increased with biochar rates until the third year after its application. There was almost no interaction effect of biochar and synthetic fertilizer; except for potassium (K+) availability and grain yield in year 3. Possible control mechanisms of biochar effect on soybean grain yield through its effect on soil fertility and physical-hydraulic properties are discussed. The effect of biochar on soybean yield depended on multiple independent factors that included soil and environmental variables. Because of this its effect on yield was variable through the years, which makes it rather unpredictable. Biochar, however, may have an important contribution to sustainable production through enhancing the effect of conservation soil management, like the use of green manure or mulching, on SOC accumulation.

Pyrolysis is one of the most promising technologies for the conversion of biomass into high-value products such as bio-oil, syngas, and biochar in the absence of oxygen. High yield biochar can be produced through torrefaction or slow pyrolysis. The efficiency of biochar production from biomass is highly dependent on the pyrolysis temperature, heating rate, type and composition of feedstock, particle size, and reactor conditions. Application of biochar to agriculture may have a significant effect on reducing global warming through the reduction of greenhouse gas (GHG) emissions and the sequestering of atmospheric carbon into soil. At the same time, biochar can help improve soil health and fertility, and enhance agricultural production. Livestock manure, along with waste-feed residues and bedding materials, is a potential source of biochar. This waste emits significant amounts of GHGs adding to global warming and threatening the environment in other ways. The environmental challenges caused by agricultural and animal-waste disposal can be reduced by recycling the waste using pyrolysis, into biochar, energy, and value-added products. Biochar can act as a sorbent for organic and inorganic contaminants and can efficiently remove these materials from affected waters. Contaminant removal is mainly based on the presence of functional groups and charges on the surface of the biochar. Thus, biochar can help to improve food security by contributing to sustainable production systems and maintaining an eco-friendly environment. This review details the principles and concepts involved in biochar production, the factors that affect biochar quality, as well as the applications of biochar.

Improving plant water use efficiency (WUE) has the potential to lower plant susceptibility to drought. Amending soils with biochar has been suggested as a way to improve WUE, as it has been shown t...

Multiple nutrient deficiencies related to severe soil fertility depletion have emerged as the major constraint to the sustainability of agriculture on a global scale. Use of biochar and biochar-compost mixtures from different alternative organic sources have been proposed as an option for improving soil fertility, restoring degraded land, and mitigating the emissions of greenhouse gasses associated with agriculture. We review the findings of 634 publications in the last decade on biochar and biochar-compost mixtures as soil amendments in order to identify the potential gaps in our understanding of the role of these amendments in agriculture. We found that: i) the majority of published studies have been carried out in developed countries where soils are less impaired in terms of food production capacity than in many developing countries; ii) studies on biochar produced in small kilns are more common than biochars produced at commercial scale in developed countries, whereas biochars produced using traditional techniques are more commonly used than biochars produced in modern pyrolysis units in developing countries; iii) laboratory and greenhouse studies are more common than field studies; and iv) wood and municipal wastes were the major feedstock for the preparation of biochar compared to crop residues and manures. Although, biochar-compost application proved to be more generally effective in improving soil properties and crop yields (field crops and horticulture crops) than biochar alone, along with desired soil properties, could be a feasible alternative to remediate the degraded soils and improve their productivity potential in the long-term. Overall, a lack of long-term, well-designed field studies on the efficacy of biochar and biochar-compost mixtures on different soil types and agro-climatic zones are limiting our current understanding of biochar's potential to enhance crop production and mitigate climate change. We further suggest that greater collaboration between researchers, biochar producers, and policy makers is required to advance the research and uptake of this important technology at a global scale.

Organo-mineral biochar fertiliser has the potential to replace conventional biochar and organic fertiliser to improve soil quality and increase plant photosynthesis. This study explored mechanisms involved in nitrogen (N) cycling in both soil and ginger plants (Zingiber officinale: Zingiberaceae) following different treatments including organic fertiliser, commercial bamboo biochar fertiliser, and organo-mineral biochar fertiliser. Soil received four treatments including (1) commercial organic fertiliser (5 t ha−1) as the control, (2) commercial bamboo biochar fertiliser (5 t ha−1), (3) organo-mineral biochar fertiliser at a low rate (3 t ha−1), and (4) organo-mineral biochar fertiliser at a high rate (7.5 t ha−1). C and N fractions of soil and plant, and gas exchange measurements were analysed. Initially, organo-mineral biochar fertiliser applied at the low rate increased leaf N. Organo-mineral biochar fertiliser applied at the high rate significantly increased N use efficiency (NUE) of the aboveground biomass compared with other treatments and improved photosynthesis compared with the control. There was N fractionation during plant N uptake and assimilation since the 15N enrichment between the root, leaf, and stem were significantly different from zero; however, treatments did not affect this N fractionation. Organo-mineral biochar fertiliser has agronomic advantages over inorganic and raw organic (manure-based) N fertiliser because it allows farmer to put high concentrations of nutrients into soil without restricting N availability, N uptake, and plant photosynthesis. We recommend applying the low rate of organo-mineral biochar fertiliser as a substitute for commercial organic fertiliser.

Global warming will likely enhance greenhouse gas (GHG) emissions from soils. Due to its slow decomposability, biochar is widely recognized as effective in long-term soil carbon (C) sequestration and in mitigation of soil GHG emissions. In a long-term soil warming experiment (+2.5 °C, since July 2008) we studied the effect of applying high-temperature Miscanthus biochar (0, 30 t/ha, since August 2013) on GHG emissions and their global warming potential (GWP) during 2 years in a temperate agroecosystem. Crop growth, physical and chemical soil properties, temperature sensitivity of soil respiration (Rs ), and metabolic quotient (qCO2 ) were investigated to yield further information about single effects of soil warming and biochar as well as on their interactions. Soil warming increased total CO2 emissions by 28% over 2 years. The effect of warming on soil respiration did not level off as has often been observed in less intensively managed ecosystems. However, the temperature sensitivity of soil respiration was not affected by warming. Overall, biochar had no effect on most of the measured parameters, suggesting its high degradation stability and its low influence on microbial C cycling even under elevated soil temperatures. In contrast, biochar × warming interactions led to higher total N2 O emissions, possibly due to accelerated N-cycling at elevated soil temperature and to biochar-induced changes in soil properties and environmental conditions. Methane uptake was not affected by soil warming or biochar. The incorporation of biochar-C into soil was estimated to offset warming-induced elevated GHG emissions for 25 years. Our results highlight the suitability of biochar for C sequestration in cultivated temperate agricultural soil under a future elevated temperature. However, the increased N2 O emissions under warming limit the GHG mitigation potential of biochar.

World tomato production is in the increase, generating large amounts of organic agricultural waste, which are currently incinerated or composted, releasing CO2 into the atmosphere. Organic waste is not only produced from conventional but also urban agricultural practices due recently gained popularity. An alternative to current waste management practices and carbon sequestration opportunity is the production of biochar (thermally converted biomass) from tomato plant residues and use as a soil amendment. To address the real contribution of biochar for greenhouse gas mitigation, it is necessary to assess the whole life cycle from the production of the tomato biomass feedstock to the actual distribution and utilisation of the biochar produced in a regional context. This study is the first step to determine the technical and environmental potential of producing biochar from tomato plant (Solanum lycopersicum arawak variety) waste biomass and utilisation as a soil amendment. The study includes the characterisation of tomato plant residue as biochar feedstock (cellulose, hemicellulose, lignin and metal content); feedstock thermal stability; and the carbon footprint of biochar production under urban agriculture at pilot and small-scale plant, and conventional agriculture at large-scale plant. Tomato plant residue is a potentially suitable biochar feedstock under current European Certification based on its lignin content (19.7%) and low metal concentration. Biomass conversion yields of over 40%, 50% carbon stabilization and low pyrolysis temperature conditions (350-400°C) would be required for biochar production to sequester carbon under urban pilot scale conditions; while large-scale biochar production from conventional agricultural practices have not the potential to sequestrate carbon because its logistics, which could be improved. Therefore, the diversion of tomato biomass waste residue from incineration or composting to biochar production for use as a soil amendment would environmentally be beneficial, but only if high biochar yields could be produced.

Biochar has been widely researched as an important technology for climate smart agriculture yet work is still necessary to identify the magnitude of potential greenhouse gas (GHG) mitigation and mechanisms involved. This study measured slow-pyrolysis wood-derived biochar's impact on GHG efflux, mineral N dynamics and soil organic C in a series of two incubations across fertilized and unfertilized agricultural soils and soil moisture regimes. This research explored the magnitude of biochar's full GHG mitigation potential and drivers of such impacts. Results of this incubation indicate slow-pyrolysis wood-derived biochar has potential to provide annual emission reductions of 0.58 to 1.72 Mg CO2-eq ha−1 at a 25 Mg ha−1 biochar application rate. The greatest GHG mitigation potential was from C sequestration and nitrous oxide (N2O) reduction in mineral N fertilized soils, with minimal impacts on N2O emissions in unfertilized soils, carbon dioxide (CO2) emissions and methane (CH4) uptake. Analysis of mineral N dynamics in the bulk soil and on biochar isolates indicated that neither biochar impacts on net mineralization and nitrification nor retention of ammonium (NH4+) on biochar isolates could explain biochar's N2O reduction. Instead, biochar amendments exhibited consistent N2O emission reductions relative to the N2O emission in the control soil regardless of soil type and fertilization. Results across a soil moisture gradient suggest that woody biochar may aerate soils shifting redox conditions and subsequent N2O production. Understanding the magnitude of biochar's GHG reduction potential and the mechanisms driving these effects can help inform biochar modeling efforts, explain field results and identify agricultural applications that maximize biochar's full GHG mitigation potential. This article is protected by copyright. All rights reserved.

A life cycle assessment was conducted to study the environmental effects of a biochar-soil system and to identify the main environmental hotspots. Six scenarios were evaluated, which included the production of biochar from agricultural and forestry residual biomass pyrolyzed at 300, 400, and 500 °C, using a functional unit of 1 t of produced biochar. Modeling of the system and evaluation of impacts were performed using SimaPro selecting impact categories of climate change, human toxicity, freshwater eutrophication, and fossil depletion. According to the results, the climate change impact category presented the greatest relative importance in the life cycle of biochar, with greenhouse gas emission reductions of up to 2.74 t CO 2 eq t −1 biochar when the biochar applied to soil is produced from forestry residual biomass at 500 °C. In relation to hotspots in the life cycle of biochar, transportation was the only stage identified that contributes environmental loads to the system, in contrast, carbon storage, natural gas avoided and urea avoided generate environmental benefits. Carbon storage in biochar is the main hotspot in the system associated to climate change, while the avoided use of natural gas and urea have great influence on fossil depletion, freshwater eutrophication, and human toxicity categories. These categories are highly sensible to allocation methodology options and the assumptions associated to the system boundaries expansion. This finding requires a comprehensive justification and to guarantee the data quality when the system expansion is considered in a LCA study of a biochar-soil system, including energy balance and syngas use, as well as, avoided urea estimation. This study considered one agricultural season, and future works should consider biochar amounts used as soil amendment in each agricultural season for evaluating residual effects of biochar use regarding fertilizers savings.

Soil degradation, characterized by declines in nutrient status and simultaneous accumulation of pesticide residues, is a major problem affecting agricultural ecosystems. Previous studies indicate that biochar application to soil has promise as a practical method to alleviate these pressures: increasing crop yield and enhancing pesticide degradation. Here, we review the roles of biochar in both chemical and biological promotion of pesticide degradation and the potential benefits of biochar relating to the efficiency of fertilizer use, availability of nutrients, and nutrient exchange. Biochar typically has a high surface area featuring many functional groups, a high cation exchange capacity, and high stability. Major factors that impact on the nutrient retention characteristics of biochar (e.g., feedstock, pyrolysis temperature, and application rate) are also discussed herein. Nonetheless, more studies of the long-term impacts on soil properties from biochar addition are still required before it can be possible to accurately quantify the sustainability of this approach to sequester carbon and restore soil function.

Biochar generated from thermochemical conversion of biomass reduces greenhouse gas emissions and is useful for improving ecological systems in agriculture. However, certain biochars function well in improving soil, and other biochars do not. Why? Because it is not clear how to prepare the best biochar for soil. There is a disconnect between biochar preparation and returning the biochar to the soil. To elucidate this relationship, this paper reviews (i) technologies for preparing biochar, (ii) how preparation conditions affect biochar properties, and (iii) the effects on soil physical and chemical properties. In addition to reducing greenhouse gas emissions, biochar improves the physicochemical and microbial properties of soil and absorbs poisonous and pernicious substances. Therefore, as biochar is produced by pyrolysis, optimizing processing conditions to improve its properties for agricultural use is a key issue explored in this article.

Only a few have evaluated the mitigation of greenhouse emissions and profit analysis along with soil carbon sequestration for corn cultivation. This experiment was conducted to evaluate the carbon sequestration and mitigation of greenhouse gas emissions as well as their profit analysis with different composts mixed with biochar during corn cultivation. This experimental data provided the second year of corn cultivation. The soil type used was clay loam. The application amounts of synthetic fertilizer and biochar were 220–30–155 kg ha−1 (N–P–K) as the recommended amount after soil analysis and 2600 kg ha−1 based on 1.3% of soil bulk density. For the biannual experimental results, it appeared that carbon sequestration in cow manure cooperated with biochar was highest at 2.3 tons ha−1 and recovered from 67.3 to 78.5% with biochar application. Furthermore, mitigation of CO2-eq. emission as greenhouse gases was estimated to be at 7.3–8.4 MT ha−1, and its profit was evaluated from $7.2 to 8.4 as lowest, from $57.2 to 66.6 as medium and from $139.7 to 162.7 as highest per hectare regardless of organic compost types used. For agricultural practice in Korea, it is evaluated that the market price of CO2 in corn field cooperated with 2600 kg ha−1 of biochar application ranged from $57.2 to 162.7 per hectare in Korean Climate Exchange. For corn biomass, the treatment with biochar application did not significantly decrease compared with the only organic compost application. Based on these experimental results, it might be applied for carbon trading with clean development mechanism for agricultural practices.

Wood represents the single most important source of renewable energy worldwide and depending on the mechanism of energy production can lead to the production of by-products with vastly different properties (i.e. wood ash (WA) from incineration and biochar (BC) from pyrolysis). These are typically applied to land, however, a critical comparison of their impact on soil quality and carbon (C) cycling is lacking. To address this, we generated biochar (450 °C) and wood ash (870 °C) from the same mixed hardwood feedstock and added it to an agricultural grassland at comparable rates under both laboratory and field conditions (10 t ha −1 and 571 kg ha −1 for BC and WA, respectively). We hypothesized that alkaline, nutrient-rich wood ash would stimulate microbial activity, resulting in the loss of soil organic matter (SOM), while biochar which is recalcitrant to microbial attack would promote the stabilization of native SOM. The effects on the soil microbial community and soil C and N cycling were determined over 1 year. Overall, biochar promoted soil quality by enhancing nutrient availability (P and K), moisture retention and increasing soil C content. However, it was also associated with an increase in below-ground CO 2 loss. As plant productivity was unaffected and laboratory incubations of biochar with 14 C-labelled SOM showed no indication of priming, we deduce that this CO 2 originates from the biochar itself. This is supported by the lack of effect of biochar on soil N cycling, microbial biomass and community structure. Wood ash had almost no effect on either soil quality or vegetation quality (yield and foliar nutrient content) under field conditions but did induce negative SOM priming under both laboratory and field conditions. We conclude that when applied at field-relevant rates, neither amendment had a detrimental effect on native SOM cycling. While wood ash promotes the retention of native SOM, biochar may be a better strategy for enhancing SOM levels because of its intrinsic recalcitrant character, however, this needs to be offset against the reduced amount of energy derived from pyrolysis in comparison to incineration.

Biochar application is a widely investigated topic nowadays, and precisely described biochar parameters are key information for the understanding of its behaviour in soil and other media. Pore structure and surface properties determine biochar fate. However, there is lack of complex, investigative studies describing the influence of biomass properties and pyrolysis conditions on the pore structure of biochars. The aim of our study was to evaluate a wide range of gathered agriculture residues and elevated pyrolysis temperature on the biochar surface properties and pore composition, predicting biochar behaviour in the soil. The biomass of herbaceous and wood plants was treated by slow pyrolysis, with the final temperature ranging from 400 to 600 °C. Specific surface ranged from 124 to 511 cm2 g-1 at wood biochar and from 3.19 to 192 cm2 g-1 at herbaceous biochar. The main properties influencing biochar pore composition were increasing pyrolysis temperatures and lignin (logarithmically) and ash contents (linearly) of biomass. Increasing lignin contents and pyrolysis temperatures caused the highest biochar micropore volume. The total biochar pore volume was higher of wood biomass (0.08-0.3 cm-3 g-1). Biochars of wood origin were characterised by skeletal density ranging from 1.479 to 2.015 cm3 g-1 and herbaceous ones 1.506-1.943 cm3 g-1, and the envelope density reached 0.982 cm3 g-1 at biochar of wheat grain origin and was generally higher at biochars of herbaceous origin. Density was not pyrolysis temperature dependent.

Straw incorporation, a common agricultural practice for improving soil quality in paddy soil, leads to the increase of methane (CH4) emission. Application of biochar in soil is an attractive method to sequestrate carbon and reduce the emission of greenhouse gas. This study aimed at exploring the effect of biochar on CH4 emission in the paddy soil with straw incorporation. In this study, the low-temperature biochar (BC300) and high-temperature biochar (BC500 and BC700) were incubated with or without straw in soil. Soil CH4 fluxes were monitored during the whole period of laboratory incubation. Soil properties were measured, including pH, redox potential (Eh) and dissolved organic carbon (DOC). The abundance and composition of methanogenic archaeal and methanotrophic bacterial communities were analyzed by real-time quantitative PCR (qPCR) and high-throughput sequencing, respectively. When no straw was applied, low-temperature biochar decreased soil Eh, increased the abundances of methanogenic archaea, and thus promoted the emission of CH4, while high-temperature biochar had little effect on CH4 emission. When straw was applied, biochar inhibited CH4 emission by decreasing the content of available carbon for methanogenic archaea. The inhibition effect of high-temperature biochar was stronger than that of low-temperature biochar. The results indicated that CH4 emission was affected by both biochar type and straw application. Biochar could significantly decrease CH4 emission when straw was returned to paddy soil, and the decrease induced by high-temperature biochar was stronger than that of low-temperature biochar.

Biochar is produced by pyrolysis of biomass residues under limited oxygen conditions. In recent years, biochar as an amendment has received increasing attention on composting and soil remediation, due to its unique properties such as chemical recalcitrance, high porosity and sorption capacity, and large surface area. This paper provides an overview on the impact of biochar on the chemical characteristics (greenhouse gas emissions, nitrogen loss, decomposition and humification of organic matter) and microbial community structure during composting of organic wastes. This review also discusses the use of biochar for remediation of soils contaminated with organic pollutants and heavy metals as well as related mechanisms. Besides its aging, the effects of biochar on the environment fate and efficacy of pesticides deserve special attention. Moreover, the combined application of biochar and compost affects synergistically on soil remediation and plant growth. Future research needs are identified to ensure a wide application of biochar in composting and soil remediation. Graphical abstract ᅟ.

Nitrogen (N)-containing fertilizers, such as slurry and ammonium nitrate (NH4NO3), can significantly increase soil nitrous oxide (N2O) emissions following addition to agricultural soil. Biochar amendment to soil has been observed to suppress N2O emissions in a number of studies. However, the effect varies depending on many factors, including when biochar is added to soil concurrently with organic or mineral fertilizers. An incubation was conducted in which bamboo biochar (created at 800°C) was added to an ex-rice paddy soil (1% rate) concurrently with dairy cattle slurry or NH4NO3 (100 mg N kg−1). At three time points, following biochar amendment, 15N-labelled NH4NO3 (50 mg N kg−1) was added to the soil to determine the N2O emissions derived from nitrification and denitrification in the 24 h that followed (at 70% water filled pore space; days 0, 7, and 28). Nitrous oxide emissions from slurry-amended soils were much greater than those from NH4NO3-amended soils, as well as the proportion of soil N2O emissions derived from denitrification. Biochar amendment did not significantly affect soil N2O emissions or consistently affect the percentage of soil N2O emissions derived from nitrification in slurry or NH4NO3-amended treatments. The lack of N2O-emission suppression with biochar amendment may have been due to the relatively-low addition rate of a biochar that had a low content of volatile organic carbons and redox-reactive organic/inorganic compounds, and did not greatly increase the pH of the acidic soil (pH 5). These results suggest that bamboo biochar produced at such a high temperature may not be suitable for mitigation of soil N2O emissions.

Addition of organic amendment with inorganic fertilizers is a suitable strategy to achieve sustainable agricultural production. But this practice is associated with increased carbon mineralization leading to release of carbon dioxide, a potential greenhouse gas for global warming. In this perspective, the present experiment was conducted in acidic sandy loam soils of north-east India to characterize the carbon mineralization, soil enzyme activities and okra (Abelmoschus esculentus L.) productivity under three (farmyard manure, vermicompost and biochar) commonly used organic amendments when added with inorganic fertilizers. Eight treatments were laid in a randomized block design with three replications. Vermicompost application increased the activities of soil enzymes with greater availability of soil nitrogen, phosphorous and potassium while biochar (hardwood) addition decreased the enzyme activities. Addition of biochar recorded the lowest rate of carbon mineralization (9%), the highest half -life of carbon (64%), higher soil organic carbon (12%) and stable organic carbon fractions (F3 fraction-12% and F4 fraction- 9%) with the highest okra yield compared to vermicompost and farmyard manure. Plant morphological attributes (plant height, leaf number, leaf area and photosynthesis of okra) were significantly enhanced due to addition of organics especially vermicompost and biochar with inorganic fertilizers. The addition of biochar recorded lower benefit cost ratio (3.5 and 3.8) but its application with inorganic fertilizers recorded the highest agronomic efficiency signifying potentiality to uphold efficient nitrogen use and environmental sustainability. Thus, addition of biochar in acidic soil would be a sustainable option to reduce carbon mineralization and uphold crop productivity.

Nitrogen (N) fertilization of forests for increasing carbon sequestration and wood volume is expected to influence soil greenhouse gas (GHG) emissions, especially to increase N2O emissions. As biochar application is known to affect soil GHG emissions, we investigated the effect of biochar application, with and without N fertilization, to a forest soil on GHG emissions in a controlled laboratory study. We found that biochar application at high (10%) application rates increased CO2 and N2O emissions when applied without urea-N fertilizer. At both low (1%) and high biochar (10%) application rates CH4 consumption was reduced when applied without urea-N fertilizer. Biochar application with urea-N fertilization did not increase CO2 emissions compared to biochar amended soil without fertilizer. In terms of CO2-eq, the net change in GHG emissions was mainly controlled by CO2 emissions, regardless of treatment, with CH4 and N2O together accounting for less than 1.5% of the total emissions.

The additions of straw and biochar have been suggested to increase soil fertility, carbon sequestration, and crop productivity of agricultural lands. To our knowledge, there is little information on the effects of straw and biochar addition on soil nitrogen form, carbon storage, and super rice yield in cold waterlogged paddy soils. We performed field trials with four treatments including conventional fertilization system (CK), straw amendment 6 t ha−1 (S), biochar amendment 2 t ha−1 (C1), and biochar amendment 40 t ha−1 (C2). The super japonica rice variety, Shennong 265, was selected as the test crop. The results showed that the straw and biochar amendments improved total nitrogen and organic carbon content of the soil, reduced N2O emissions, and had little influence on nitrogen retention, nitrogen density, and CO2 emissions. The S and C1 increased NH4+-N content, and C2 increased NO3−-N content. Both S and C1 had little influence on soil organic carbon density (SOCD) and C/N ratio. However, C2 greatly increased SOCD and C/N ratio. C1 and C2 significantly improved the soil carbon sequestration (SCS) by 62.9 and 214.0% (P

Biochar has been shown to influence soil CO and NO emissions following application to soil, but the presence of carbonates in biochars has largely confounded efforts to differentiate among labile and recalcitrant C pools in biochar and establish their timeframe of influence. Understanding the mechanism, magnitude, and duration of biochar C pools' influence on C and N dynamics is imperative to successful implementation of biochar for C sequestration. Here we therefore aim to assess biochar organic and inorganic C pool impacts on CO and NO emissions from soil amended with two untreated biochars, inorganic carbon (as NaCO), acid (HCl) and bicarbonate (NaHCO) extracts of the biochars, and acid and bicarbonate/acid-washed biochars during a 140-d soil incubation. We hypothesized that (i) both biochar labile organic carbon (LOC) and inorganic carbon (IC) pools contribute significantly to short-term (

In order to determine the efficacy of vegetable waste and pine cone biochar for immobilization of metal/metalloid (lead and arsenic) and abundance of microbial community in different agricultural soils, we applied the biochar produced at two different temperatures to two contaminated soils. Biochar was produced by vegetable waste, pine cone, and their mixture (1:1 ww −1 ) at 200 °C (torrefied biomass) and 500 °C (biochar). Contaminated soils were incubated with 5% (ww −1 ) torrefied biomass or biochar. Sequential extraction, thermodynamic modeling, and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy were used to evaluate the metal immobilization. Microbial communities were characterized by microbial fatty acid profiles and microbial activity was assessed by dehydrogenase activity. Vegetable waste and the mixture of vegetable waste and pine cone biochar exhibited greater ability for Pb immobilization than pine cone biochar and three torrefied biomass, and vegetable waste biochar was found to be most effective. However, torrefied biomass was most effective in increasing both microbial community and dehydrogenase activity. This study confirms that vegetable waste could be a vital biomass to produce biochar to immobilize Pb, and increase the microbial communities and enzyme activity in soils. Biomass and pyrolytic temperature were not found to be effective in the immobilization of As in this study.

Improved soil carbon sink capability is important for the mitigation of carbon dioxide emissions and the enhancement of soil productivity. Biochar and organic fertilizer (OF) showed a significant improving effect on microalgae in soil carbon sink capacity, and the ultimate soil total organic carbons with microalgae-OF, microalgae-biochar, microalgae-OF-biochar were about 16, 67 and 58% higher than that with microalgae alone, respectively, indicating that carbon fixation efficiency of microalgae applied in soil was improved with biochar and OF whilst the soil carbon capacity was promoted, the mechanism of which is illustrated through simulative experiments. Organic fertilizer could spur algal conversion of carbon into cell molecules by increasing intracellular polysaccharide production of microalgae. Biochar could change carbon metabolism pathway of microalgae through altering the yield of intracellular saccharides, and yield and type of extracellular saccharides. There was a superimposition effect on the soil carbon sink when biochar and OF were both present with microalgae.

Biochar is a solid material obtained from reductive, oxygen-free processes, i.e. the thermo-chemical conversion of biomass in oxygen-limited environment. The obtained products have high carbon sequestration potential and strong nutrient-water absorption capacities because of the enlarged carbon surfaces. It is not yet clear how carbon stimulates agrochemical parameters in soil and how those characteristics are developing as time goes on a long-term basis. Samples of ancient (25, 35, 80 years old) plant coal-affected soils were collected in a temperate deciduous forest site located in the south part of the Bukk Mountains (in North Eastern Hungary). Physical–chemical soil characteristics, such as soil pH, cation exchange capacity (CEC), the organic and inorganic nitrogen (NH4 +, NH3 −) and the available nutrients (P2O5 and K2O), were estimated beside organic matter (SOM) content, measured by two different methods. Levels of polycyclic aromatic hydrocarbon (PAH) compounds in soil and in various biochar samples were assessed in relation with permissible limit values and potential toxicity. Positive correlation was found between the amount of available nutrients, total organic nitrogen content, cation exchange capacity and the age of plant coal-affected soils. The sample soils were exposed to continuous plant coal biochar effect for 25 years, during which macronutrients absorbed and accumulated in the plant coal surfaces. After this period, the degradation of carbon developed simultaneously with the reduction of the amount of available nutrients, till the end of the studied 80-year-affecting period. Measured CEC level indicated positive correlation with nutrient availability and the age of biochar-affected soils. Our results support the hypothesis that biochar in soil can improve its general agrochemical characteristics in relation with its persistence in a specific soil-plant system. Potential PAH content and toxicity of biochar products are key issues of developing proper application rates in sustainable agricultural practices.

In many developing countries, traditional earth-mound kilns are still the principal technology for biochar production. The present study focused on the production and characterization of two biochars from common agricultural and forestry residues in Cameroon: corncob and eucalyptus tree bark. A pilot-scale retort kiln, made from local material, was constructed for biochar production. Its production efficiency varied between 33 and 68%, compared to the 10–22% obtained with traditional biochar production systems. Both biochars exhibited good agronomic properties and fulfilled key quality criteria for soil carbon sequestration, as described by the European Biochar Certificate (EBC) and the International Biochar Initiative (IBI). Organic carbon (Corg) > 50%, H/Corg

As the commercial production and distribution of biochar continues to grow internationally, and its applications diversifying from its early uses as soil amendment, it is important to study the environmental impacts and economic performance of biochar in comparison to activated carbon in order to assess its value. The goal of the study was to assess, through a meta-analysis, the environmental and economic performance of biochar in comparison to activated carbon under an equivalent functional unit to adsorb heavy metals. More than 80 data points on adsorption capacity of biochar and activated carbon were identified through literature, which were statistically analyzed as part of the study. Biochar was found to have lower energy demand and global warming potential impact than activated carbon, where average energy demands were calculated as 6.1 MJ/kg and 97 MJ/kg and average greenhouse gas emissions calculated as −0.9 kg CO 2 eq/kg and 6.6 kg CO 2 eq/kg for biochar and activated carbon, respectively. When adsorption of heavy metals were used as the functional unit during analysis, results indicate that there is typically an order of magnitude difference between the two materials, where biochar was found to have lower environmental impacts. The environmental impact resulting from long distance transportation of biochar would not overturn this conclusion. The adsorption cost of biochar was lower than activated carbon to remove chromium and zinc with a 95% confidence. Adsorption cost for lead and copper were found to be comparable, and therefore the specific type of biochar and its price could shift results both ways. There is evidence that biochar, if engineered correctly for the task, could be at least as effective as activated carbon and at a lower cost.

Biochar can remediate degraded soils and maintain or improve soil health, but specific and predictable effects on soil properties and crop productivity are unknown because of complex interactions associated with climate patterns, inherent soil characteristics, site-specific crop and soil management practices, and the source, production characteristics, and amount of biochar applied. This multi-location field study was designed and conducted to determine if consistent response patterns could be elucidated by controlling the type and amount of biochar applied, depth of incorporation, and soil/crop management practices as much as possible for six U.S. locations. When averaged for five reporting locations, biochar or biochar plus manure (bio + man) treatments significantly ( P P P = 0.017) at one of the six locations. Overall, we conclude that hardwood biochar produced by fast pyrolysis can be an effective soil amendment for increasing SOC levels within a broad range of temperate soils, but crop yield responses should be anticipated only when specific soil quality problems limit productivity.

The interaction between biochar and soil changes nitrogen (N) dynamics in different ecosystems. Although multiple studies have reported influences of biochar on soil inorganic N (SIN) including ammonium (NH4+-N) and nitrate (NO3−-N), the influences reported are contradictory. We undertook a meta-analysis to investigate how biochar properties and the interaction among biochar, soil and fertilisation affect SIN. This quantitative analysis used 56 studies with 1080 experimental cases from manuscripts published between 2010 and 2015. Overall, we found that biochar reduced SIN regardless of experimental conditions (approximately − 11 ± 2% of NH4+-N and − 10 ± 1.6% of NO3−-N); however, 95% of cases were observed within one year after biochar application. SIN was best explained by residence time of biochar in soil, pyrolysis temperature, application rate, fertiliser type, and soil pH. The effects of biochar were complex due to the interaction of biochar with environmental factors. Most biochar trials used wood as a feedstock, but woody biochar did not decrease SIN as much as other plant-derived biochars. When biochar was used with NH4-based fertilisers, SIN decreased compared to biochar with no fertiliser. In contrast, adding organic fertiliser with biochar increased SIN compared to biochar alone. SIN was clearly reduced after one month of biochar application, suggesting that biochar should be applied at least one month prior to planting so plants are not affected by decreased N. Our results revealed that the interactions between biochar and environmental factors, pyrolysis temperature of biochar and biochar surface properties are the main driving factors affecting SIN. There were limited long-term studies of > 1 year, thus the long-term effects of biochar on SIN still remain unclear.

Biochar has been increasingly recommended for world agriculture, but the effects on microbial activities in agricultural soils has not yet thoroughly assessed. In this study, using a meta-analysis of experiment data retrieved from literature published up to March 1, 2015, changes were examined in microbial biomass and soil respiration in agricultural soils with biochar addition. Microbial responses to biochar addition were quantified in soil respiration quotient (RQ), microbial quotient (MQ) and metabolic quotient ( q CO 2 ) and their differences were evaluated between with and without biochar addition, and among groups of biochar production conditions and experiment conditions. There was an overall increase by 25% in soil microbial biomass carbon (SMBC) and nitrogen (SMBN) but a decrease by 13% in q CO 2 , under biochar compared to the control. Whereas, microbial biomass carbon was increased by 26% but total soil CO 2 production unchanged, across all short term experiments up to 6 months following a single biochar addition. A significant reduction (by q CO 2 was found under crop residue and manure biochars in term of feedstock, and biochars pyrolyzed at high temperature over 500 °C in term of pyrolysis temperature. Whereas, the reduction was great (by over 30%) both in clay soils and in neutral soils but moderate (by 15%) in soil organic carbon (SOC) depleted soils, respectively in terms of soil texture, reaction and SOC level. Thus, soil conditions exerted great impacts on microbial metabolic quotient changes compared to biochar conditions. Nevertheless, microbial responses to biochar addition to agricultural soils were much uncertain with respect to both biochar and experiment conditions. Long term field experiments are still deserved to monitor soil microbial processes as long as sustainable soil managements are concerned with biochar technology in agriculture.

Biochar and composted manure can impart benefits, such as improved nutrient cycling, increased productivity, and carbon sequestration, when they are applied to agricultural soils. There are limited data, however, on how these additives effect mixed perennial communities. We compare plant and soil community responses by using factorial applications of Royal Oak biochar (0%, 2.6%, and 5.2%) and composted manure (0 and 4.5 kg m −2 ) in a tallgrass prairie restoration in Iowa. We found that biochar contributed to ecosystem function by increasing total carbon in the soil. We also found that biochar increased plant species richness and the 5.2% biochar treatment increased the biomass of plant species in the seed mix. Phosphorus cycling was altered by both the biochar and manure treatments; in soils with manure, biochar addition reduced phosphorus (P) availability compared with the control, but in soils without manure, biochar increased P availability. Belowground, the biochar and manure treatments affected the relative density of gram-negative bacteria, the relative density of actinobacteria, and root colonization by mycorrhizae. Contrary to our hypotheses, however, the biochar and manure treatments did not change total plant cover, total aboveground peak biomass, overall plant community, soil pH, inorganic nitrogen concentrations, extractable soil K, plant tissue N, soil microbial biomass-carbon, nematode density, and overall microbial community composition. Overall, we found several benefits and few externalities associated with biochar and composted manure addition to tallgrass prairie. However, these products can vary considerably and their interactions with soil, plants, and microbes can be situation specific. More study is needed to identify the characteristics of biochar that can affect mixed perennial communities prior to widespread use.

Land-applied biosolids (sludge) can improve food production sustainability through nutrient recycling. Biosolids-derived biochar may enhance soil fertility and overall soil health. However, there is little information on the conversion of biosolids to biochar using traditional kilns, or effects on biochar characteristics and plant growth. Biochar was produced from biosolids using two pyrolysis methods: 1) a traditional retort kiln (Top-lid Updraft-TLUD) intended for use by small farmers and gardeners, and 2) a laboratory muffle furnace, with the aim of evaluating biochar characteristics and its effects on Zea mays L. (corn) seed germination, growth and nutrition. Biochar produced in a muffle furnace contained 70% more ash, 78% more fixed carbon, and 63% less volatile matter than biochar produced by TLUD, which raised concern regarding TLUD-derived biochar toxicity The TLUD-derived biochar inhibited corn seed germination in a petri dish bioassay at biochar application rates from 2.5 to 100 Mg ha −1 . However, germination increased from 29% (control) to approximately 60%, at 60 Mg ha −1 or greater rates, with muffle furnace biochar. A greenhouse experiment was conducted to evaluate the growth and nutrition of corn grown in soil treated with 0, 5, 10, 20 and 60 Mg ha −1 biochar pre-incubated for two weeks in moistened soil. The muffle furnace biochar had no negative effect on plant growth and N nutrition, whereas the TLUD biochar at a 60 Mg ha −1 rate, reduced plant growth and increased plant N concentrations four-fold, compared to the control. Both biochars increased plant P concentrations with increasing application rates. Biosolids biochar produced via TLUD at rates below 20 Mg ha −1 may benefit crop production, although an incubation or weathering period may be necessary to limit potential short-term, phytotoxic effects. Future research needs include optimizing TLUD operational parameters and identifying weathering processes that improve biochar product quality for agronomic use.

While soil freeze-thaw cycles can decrease soil nutrient retention over winter by increasing leaching losses and greenhouse gas emissions, biochar as a soil amendment could mitigate these effects. Nevertheless, there is often variation in the effectiveness of different biochar formulations with respect to soil nutrient retention. We added 15N tracer to soil mesocosms to examine the effects of biochar produced under a series of pyrolysis temperatures (250–600 °C) on soil nitrogen retention in response to variation in soil freeze-thaw cycle intensity (−10 °C vs. 0 °C following spring melt). We also examined the subsequent effects on plant nitrogen uptake, soil nitrous oxide (N2O) emissions and nitrogen leaching losses. As we predicted, increased soil freezing increased inorganic nitrogen losses through leaching and decreased the biomass of the test crop Arugula (Eruca sativa) the following growing season. Biochar amendment increased both soil 15N retention over winter and the subsequent plant 15N uptake, with the biochar generated at the highest temperature exhibiting the strongest effects on plant 15N uptake. Biochar addition also significantly mitigated the negative soil freezing effect on subsequent plant biomass. Nevertheless, biochar addition combined with freezing increased N2O emissions. Overall, our results confirm that biochar application can mitigate soil nitrogen losses over winter, although it may also interact with soil freezing to increase emissions of the greenhouse gas N2O.

An experiment of different application rates of biochar and biochar combined with nitrogen fertiliser was conducted at experimental field on a Haplic Luvisol located in Nitra region of Slovakia during the growing season of spring barley (2014). The aim of this study was to evaluate the effects of biochar and biochar combined with nitrogen fertilisation on the soil organic carbon (SOC). The treatments consisted of 0, 10 and 20 t/ha of biochar application (B0, B10 and B20) combined with 0, 40 and 80 kg/ha N of nitrogen fertiliser applied (N0, N40 and N80). The results showed that SOC content at the beginning and end of the trial was always higher at the plots amended with biochar as compared to control plots (B0N0, B0N40 and B0N80); however, statistically significant effects were observed only at the beginning of the trial as well as at the end of trial in B20N40 treatments. Overall, the highest values of SOC contents were obtained at the beginning as well as at the end of the trial when 10 and 20 t/ha of biochar was applied together with 40 kg/ha N.

Given its high pore volume and adsorption capacity, and when applied as an agricultural soil amendment, its ability to enhance the soil’s nutrient- and water- holding capacities, biochar has become a focus of research interest. In most applications, crop productivity is significantly increased after agricultural soils are amended with biochar. In addition to increasing soil quality, the biochar amendments sequester carbon within the soil. However, the long-term effects of amending agricultural soils with biochar are difficult to predict, because the mechanisms behind the increase in productivity of biochar amended soils are not yet fully understood. Long-term detrimental effects on soil and the environment can occur if biochar is applied haphazardly. Current knowledge and the additional experimental work required to thoroughly understand the influence of biochar amendment on the behavior of agricultural soils processes are reviewed. Further, studies on the post production processing of biochar are discussed in the context of the possible engineering of biochar for particular states of soil degradation.

The agricultural practices in south western Morocco reserve a majority of the water resources to be used for irrigation. The extent of irrigated agriculture combined with high evaporative rates, lead to the depletion of water resources and degradation of soil quality. To remedy to this problem, biochar, a pyrolysed biomass, is highly considered to improve retaining water and nutrients in soils. For this biochar research, argan shells obtained after extraction of argan oil were used as the biomass source to produce biochar. According to the best of our knowledge, no research to date has been carried out on the production and characterization of biochar produced from argan shells wastes. To produce biochar, we have used a pyrolytic stove fabricated in Morocco from locally available materials. The biochar sample collected was then crushed, sieved (

This study presents a suitable solution for management of the noxious weed Parthenium hysterophorus by using its biomass for biochar formation. The impact of application of Parthenium biochar on soil and the rice wheat cultivation system was observed over a period of one year in field experiments. The treatments applied to the field were biochar (BC) only, recommended commercial fertilizer (CF) only, BC along with 50% of CF (BC + CF), and Control, without any treatment. The growth parameters of the plants were measured in the rice and wheat crops. Commercial fertilizer showed the best agronomic performance in rice and wheat, while similar results were obtained in the BC + CF application. However, the results were not so significant with BC only. It was observed that biochar application can cut down the cost of fertilizer to half although the yield obtained is just as good as with full application of CF. Biochar acted as a conditioner in field soil and improved the C/N ratio. Structure of soil as well as the water and nutrient holding capacity of soil was improved owing to macroporous nature of biochar revealed by SEM. However, applied biochar was not found very stable as the C content applied to the soil in the form of biochar decreased in the soil over a one-year period from 47.39% to 36.54%. This could be due to some original plant residues left in the biochar on account of incomplete pyrolysis in the partial absence of oxygen indicating a high H/C ratio of 0.64. This research suggests application of Parthenium biochar at lower rates annually not only providing fresh C content and charged surfaces to the soil but also a substrate and C source to the microbes inhabiting the macropores and mesopores present in biochar as indicated by SEM. The char formed from Parthenium biomass was environmentally sustainable by utilizing renewable supply of biogas in a fabricated hybrid cooking stove.

This study investigated the carbon footprint of two different biochar production systems for application to paddy fields. The impacts of using rice straw-derived biochar in raw form (System A) were compared with those arising from using rice straw biochar enriched with lime, clay, ash and manure (System B). The GHG abatement of the management of one Mg of rice straw in Systems A and B was estimated at 0.27 and 0.61 Mg CO 2 -eq, respectively, in spring season, and 0.30 and 1.22 Mg CO 2 -eq in summer. The difference is mainly due to greater reduction of soil CH 4 emissions by enriched biochar.

Incorporating crop residues and biochar have received increasing attention as tools to mitigate atmospheric carbon dioxide (CO2) emissions and promote soil carbon (C) sequestration. However, direct comparisons between biochar, torrefied biomass and straw on both labile and recalcitrant soil organic matter (SOM) remains poorly understood. In this study, we explored the impact of biochars produced at different temperatures and torrefied biomass on the simple C substrates (glucose, amino acids), plant residues (Lolium perenne L.) and native SOM breakdown in soil using a 14C labeling approach. Torrefied biomass and biochars produced from wheat straw at four contrasting pyrolysis temperatures (250, 350, 450 and 550 °C) were incorporated into a sandy loam soil and their impact on C turnover compared to an un-amended soil or one amended with unprocessed straw. Biochar, torrefied biomass and straw application induced a shift in the soil microbial community size, activity and structure with the greatest effects in the straw-amended soil. In addition they also resulted in changes in microbial carbon use efficiency (CUE) leading to more substrate-C being partitioned into catabolic processes. While overall the biochar, torrefied biomass and straw addition increased soil respiration, it reduced the turnover rate of the simple C substrates, plant residues and native SOM and had no appreciable effect on the turnover rate of the microbial biomass. The negative SOM priming was positively correlated with biochar production temperature. We therefore ascribe the increase in soil CO2 efflux to biochar-derived C rather than that originating from SOM. In conclusion, the SOM priming magnitude is strongly influenced by both the soil organic C quality and the biochar properties. In comparison to straw, biochar has the greatest potential to promote soil C storage. However, straw and torrefied biomass may have other co-benefits which may make them more suitable as a CO2 abatement strategy. This article is protected by copyright. All rights reserved.

Biochars produced from pelletized grape vine (GV) and sunflower husk (SFH) agricultural residues were studied by pyrolysis in a batch reactor at 400 and 500 °C. Chemical and physical evolution of the biomass under pyrolysis conditions was determined and the products were characterized, including the main gaseous organic components. Results showed a decrease in solid biochar yield with increasing temperature. Biochar is defined as a “porous carbonaceous solid” produced by thermochemical conversion of organic materials in an oxygen depleted atmosphere, which has physiochemical properties suitable for the safe and long-term storage of carbon in the environment and, potentially, soil improvement. The aim of this work is to improve the knowledge and acceptability of alternative use of the biochar gained from agro-forestry biomass residuals, such as grape vine and sunflower husks, by means of modern chemical and physical characterization tools.

Biochar additions to agricultural soil have been shown to result in numerous potential benefits; however, most studies have been conducted in greenhouse or laboratory trials with few being conducted in the field and particularly in association with organic farming systems. Herein, we address this gap by conducting on-farm studies on the efficacy of locally produced biochar as a soil amendment in small-scale organic agriculture on ten farms in San Juan County, WA. Biochar produced from local timber harvest residues in the San Juan Islands was applied in factorial combination with a poultry litter based fertilizer to replicated plots on all ten farms. Dry beans (Phaseolus vulgaris L.) were grown on eight of the farms with green beans and cauliflower being grown on the other two. Soils were examined for nitrogen (N), phosphorus (P), and carbon (C) pools during the growing season. Dry bean samples were evaluated for metal and nutrient uptake. Biochar additions increased soil total C by 32–33%, soil available NH4+ by 45–54% through mid-season, pontentially mineralizable N by 48–110%, and citrate extractable P by 29%; biochar additions enhanced soil NO3−-N, NH4+-N, and P retention in the rooting zone by 33%, 53% and 39% respectively. Increased availability of soil P, Fe, Mg, Zn was reflected in the nutrient concentration of harvested dry beans. Our study demonstrates that locally produced wood biochar has the potential to increase soil nutrient availability and uptake. By producing biochar from timber harvest residues and applying them on neighboring organic farms on the San Juan Islands, WA, this study leveraged the local resources and community readiness to drive forest restoration and sustainable agricultural practices in addition to the demonstrated potential short-term benefits of biochar additions for organic farms on the sandy soils of the San Juan Islands.