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Direct air capture (DAC) of CO 2 is considered one of the most promising carbon capture methods to reduce ambient CO 2 concentration for climate change mitigation. Biochar represents an attractive adsorbent for DAC because it is environmentally friendly and cost-effective. In this work, KOH-activated bamboo biochar shows the CO 2 capture capacity of 3.49 mmol g−1 (25 °C, 1 bar), and it is used as an adsorbent to perform direct air capture using a fixed-bed reactor with an ambient CO 2 capture capacity of up to 51.74 μmol g−1. Furthermore, the effect of relative humidity on CO 2 adsorption by biochar was investigated and exhibited promising stability under 2.7% relative humidity. However, the biochar activity for CO 2 capture is reduced to 63.88% under 67.1% humidity after 50 cycles. [Display omitted] • KOH was used to activate bamboo-derived biochar. • Bamboo biochar was investigated in direct air capture of CO 2. • Gas selectivity of biochar during direct air capture. • Effect of relative humidity on direct air capture efficiency. [ABSTRACT FROM AUTHOR]

The continuous rise in global temperatures is an evidence of climate change. CO 2 emissions have caused major problems owing to its contribution to climate change. In particular, the construction industry has a considerable carbon footprint. Therefore, investigations into climate change mitigation are indeed a priority. All steps in the construction process, from raw materials preparation to cement production, contribute to CO 2 emissions. This can be mitigated to a certain extent by incorporating bio-based constituents into construction materials. However, bio-based materials may negatively affect cement reaction and structural performance, despite their positive environmental impacts. Biochar, a carbon-rich product of biomass pyrolysis, is considered a potential substitute for cement replacement that can enhance structural properties if used in appropriate amounts. Although biochar has conventionally been used as a soil amendment in the agricultural industry, researchers have recently investigated its applicability in concrete. Importantly, the results thus far have reported its contribution to the enhancement of the mechanical, thermal, and physical properties of cement. This review provides a comprehensive overview of the physicochemical properties of biochar added cementitious materials, including the fresh and hardened properties of biochar-cement mixtures considering both environmental and economic aspects. • The structure of biochar exhibits excellent compatibility with the cement matrix. • Biochar addition can modify the physical and mechanical properties. • Biochar improves concrete durability, sequesters carbon, and mitigates climate change. • Biochar can be used for carbon sequestration in cement applications. • Economic benefits of biochar-cement composites are not well elaborated in the literature. [ABSTRACT FROM AUTHOR]

Rapid climate change mitigation requires carbon sequestration in addition to greenhouse gas emission reductions. Agriculture may have a high potential for carbon sequestration due to improved practices. However, it is not known how the global warming impacts of crop production could be mitigated especially within an agricultural system. The aim of this study is to evaluate possibilities to neutralize global warming impacts in crop production using biochar produced from side flows and buffer zone biomass. A life cycle assessment methodology is utilized in this research for oat production in the boreal climate zone. Global warming impact reductions are compared for three different side flow utilization options. Traditionally, side flows have been utilized in energy or fodder production, and these options are compared to biochar production at a system level. The potential to use buffer zone biomass for biochar production is also studied. Willow has been selected as a biomass source in buffer zones. Oat production leads to greenhouse gas emissions especially due to the use of fossil and mineral fertilizers in cultivation and heat energy, electricity and fuels in various process phases. The production of one metric ton of oat flakes from cradle to gate generates 700 kg of CO 2 eq emissions. Biochar and energy production from side flows enables a greater reduction in global warming impacts than the feed use of side flows. Buffer zones in willow biomass and biochar production may enable the full neutralization of the global warming potential of oat production within an agricultural system. Further research with actual measurements is required especially on biochar impacts on soil emissions such as N 2 O. This research shows that it could be possible to neutralize global warming impacts from crop production using available technologies and available biomass in agricultural systems. A framework is created for carbon neutral crop production using side flows and buffer zone biomass through biochar. • Global warming potential of oat production is studied using LCA methodology. • Oat flakes production generates emissions of 700 kgCO 2eq t−1. • Side flow use for biochar production leads to the lowest overall GWP impacts. • Buffer zone biomass use for biochar production could mitigate the GWP impacts of oat production. [ABSTRACT FROM AUTHOR]

Abstract Biochar-based carbon management networks (CMNs) offer a means of achieving negative net greenhouse gas (GHG) emissions. Such systems rely on relatively mature technologies for biochar production, distribution and application by tillage; thus, the prospects for near-term scale-up, especially in developing countries with agriculture-intensive economies, are promising. The main technological gap lies in the capability to predict, optimize and monitor the actual climate change mitigation benefits. Computer-aided planning of biochar-based CMNs will be needed to maximize GHG reductions while minimizing any potential adverse environmental impacts. Such models can help decision-makers to understand and optimize the cost/benefit aspects of such systems to accelerate their commercial deployment. This paper gives a brief review of the available scientific literature, and discusses prospective areas for further research to facilitate the large-scale use of biochar as a negative emissions technology (NET). Highlights • Biochar application to soil is a potentially scalable negative emissions technology. • Biochar-based carbon management networks can be operated based on this concept. • Computer-aided planning, optimization and monitoring are required. • An integrated modelling framework should be developed for effective decision support. [ABSTRACT FROM AUTHOR]

Biochar production for soil amendment was recently proposed as a tool to mitigate climate change, reducing soil greenhouse gas (GHG) emissions and sequestrating carbon (C) in soil. The aim of this research project was to test the hypothesis that only biochars with specific requirements (low H/C org and O/C org ratios, high C/N ratio) can reduce soil N 2 O emissions without increasing CO 2 emissions in the short term. A 45-days incubation study was carried out, in which six engineered biochars made from the pyrolysis of wood, switchgrass and the solid fraction of pig manure (SFPM), were amended to two agricultural soils (loamy sand and silt loam) at a dose of 2% (w/w) in 1-liter jars. Soil moisture content was adjusted at 80% of water-filled pore space with a solution of ammonium nitrate that corresponds to 170 kg of nitrogen per hectare. N 2 O and CO 2 emissions were analysed on days 2, 3, and then weekly. Soil chemical properties and bacterial richness, composition and taxonomy were analysed after the incubation period. When compared to the control soils without biochar, N 2 O emissions were decreased by 42 to 90%, but only in the silt loam amended with biochars made from wood and switchgrass, these biochars having a high C/N ratio (>30). Lower N-NH 4 + and N-NO 3 − concentrations were observed in these biochar treatments than in control soil. Moreover, two bacterial classes ( Deltaproteobacteria and Thermoleophilia ) were correlated with a decrease in N 2 O emissions. For each type of biochar, those produced at the highest temperature with low O/C org and H/C org ratios resulted in the lowest increase in CO 2 emissions, which could indicate a higher biochar carbon stability. Overall, results of this study demonstrated that biochar can either increase or decrease soil GHG emissions depending on its properties, and that the effect can differ according to soil properties. Future long-term studies in the field in the presence of crop should be carried out in order to validate the conclusions of this study. [ABSTRACT FROM AUTHOR]

Besides being an opportunity to valorize biomass residues, biochar (i.e., the solid product of biomass pyrolysis) has many potential environmental benefits, such as climate change mitigation and reduced nutrient leaching. Even though the academic interest in biochar has increased, it is not being used at a large scale yet, mainly because of its economic infeasibility compared to fertilizers and because farmers are either unaware of or skeptical about its effects. In this paper, the economics of biochar are examined by performing a systematic review, following the guidelines of the Collaboration for Environmental Evidence. Specifically, it has been examined to which extent the production and application of biochar are yet profitable from an investor's perspective and desirable from a societal perspective. For the first time, this review investigates the extent to which previous studies have included external costs and benefits. We find that profitability and desirability of biochar production and use are highly uncertain and case-specific, depending on factors like location, feedstock, scale, pyrolysis conditions, biochar price, cultivated crop, and the potential internalization of externalities, which hampers private investment. To advance biochar development and deployment, those factors must be considered carefully for each case. Although externalities are included in the literature to some extent, the focus is mostly on external benefits rather than external costs, often focusing on its carbon sequestration potential. The inclusion of externalities in economic assessments is necessary to provide solid arguments to develop policies for the acceleration of market uptake of biochar technology. [ABSTRACT FROM AUTHOR]

As a climate change mitigation strategy, biochar application to soil has been demonstrated to increase soil carbon (C) sequestration and reduce greenhouse gas (GHG) emission. Although numerous manipulative studies have been conducted, it is still not fully understood how biochar application affects soil respiration ( Rs ) and its components (i.e., autotrophic [ Ra ] and heterotrophic respiration [ Rh ]) in forest ecosystems, especially in subtropical forests. In this study, we performed a meta-analysis of forest ecosystems and a field experiment with biochar amendments of 0, 10, and 30 t ha −1 in a subtropical forest in Zhejiang, China to examine the effects of biochar application on Rs and its components. Our results showed that biochar application significantly increased Rs by 20.92% at the global scale with an increase of 20.25% in temperate forests and a nonsignificant effect in subtropical forests. Responses of Rs to biochar application varied with experimental methods and soil textures. Similarly, our field experiment showed that biochar amendment did not significantly affect Ra, Rh , and Rs in a subtropical forest in Eastern China. Specifically, the average Rs under biochar amendments of 0, 10, and 30 t ha −1 were 2.37, 2.06 and 2.15 μmol m −2 s −1 , respectively ( P > 0.05). Both Rs and Rh were positively correlated with microbial biomass C (MBC) and negatively with dissolved organic C (DOC). Both apparent temperature sensitivity ( Q 10 ) of Rh and Rs were significantly higher under biochar treatments than in the control. Our findings indicate the importance of the differential effects of biochar application on Rs in different forest types for C sequestration, which may inform ecosystem and regional models to improve prediction of biochar effects on forest C dynamics and climate-biosphere feedbacks. [ABSTRACT FROM AUTHOR]

Biochar amendment has been proposed as a promising solution to mitigate greenhouse gas (GHG) emissions from agriculture and sustainably enhance crop yield. However, the net GHG mitigation potential of biochar remains uncertain, especially the controversial results from field and laboratory experiments. Using 9970 published observational data derived from 592 peer-reviewed papers, this study highlighted the effects of biochar in field experiments on crop yield, soil organic carbon (SOC) stocks, carbon dioxide (CO 2) and methane (CH 4) fluxes, and soil nitrogen (N) dynamics (i.e., soil inorganic N stocks, nitrous oxide [N 2 O] emissions, ammonia [NH 3 ] volatilization, and inorganic N leaching). Overall, field data indicated that biochar significantly increased gross SOC stocks (26.6%) and crop yield (15.7%), reduced soil CH 4 (−14.8%) and N 2 O (−23.1%) emissions, and ammonium (−24.9%) and total inorganic N leaching (−23.2%) but had no effect on soil CO 2 emissions. Whereas laboratory data generally showed greater effect sizes of biochar on these indictors. Global warming potential was decreased only in field experiments, but both experiments showed similar reductions in GHG intensity. Both experiments suggested that soil and biochar cation exchange capacity, pH, biochar application rate, and nitrogen fertilization interactively regulated biochar effects on crop yield and GHG emissions. The unrealistically high rates of biochar in laboratory experiments may overestimate its benefit on soil C sequestration and/or underestimate its mitigation potential. These findings provide a comprehensive view that biochar amendment may serve as a viable climate-smart agricultural practice that can help in partial achievement of multiple sustainable development goals. • Biochar is an effective strategy for climate-smart agriculture. • Biochar added to field (∼20 Mg ha−1) can increase gross SOC stock by ∼27%. • Biochar can decrease global warming potential and greenhouse gas intensity. • Unrealistically high biochar rates in lab overestimated soil carbon sequestration. [ABSTRACT FROM AUTHOR]

Turning biomass into biochar via pyrolysis followed by its amendment into soil is regarded as a prospective strategy of sequestrating atmospheric carbon and simultaneously aiding both climate change mitigation and adaptation. Biochar's capability of sequestering carbon depends on the solid carbon retention in biochar after pyrolysis and the stability of this carbon. On average, 50% of the carbon in biomass is retained in biochar, of which 5–10% is estimated to be released in the first 100 years after application to soil. This review firstly focuses on roles of minerals in regulating carbon retention and stability, taking both processes of biochar formation and soil carbon sink into consideration. Carbon retention in biochar can be dramatically increased by adding exogenous minerals prior to pyrolysis, especially P, Si, Ca, Mg, and K containing materials, due to the chemical bonding (P-O-C, C-P, C-Si-C, etc.), the physical encapsulation, and the absorption of CO 2 and CH 4 by CaO or MgO. Soil minerals also interact with biochar‑carbon, suppressing physical disintegration, abiotic oxidation, and biotic mineralization, with soil clays, Ca2+ bridging, and poorly crystalline Fe/Al being the dominating factors. Future research should concentrate on systematic evaluation of the roles of minerals in the whole biochar carbon cycle process, i.e., pyrolysis conversion and biochar applications, from the perspective of biomass-energy-climate. [Display omitted] [ABSTRACT FROM AUTHOR]

Biochar has received increasing attention in agricultural and environmental fields as an integrated solution to agricultural waste recycling, soil amendment, carbon sequestration, and greenhouse gas (GHG) reduction. However, obtaining the environmental benefits of biochar is limited by an inadequate number of soil applications. Currently, the willingness to use biochar in soil management is relatively low, which results from the insufficient understanding and promotion of the roles of biochar in soil management and climate change mitigation. This review article presents biochar applications based on carbon-neutral strategies in agricultural soil systems. The primary roles of biochar in soil improvement and remediation are discussed and the main soil application methods are introduced. The focus of this article is on biochar-based soil management strategies for contributing to carbon neutrality. Carbon sequestration using biochar is an application-dependent strategy, as the key to obtaining this ecological benefit is to store biochar products in soil via effective agricultural management. This article offers insights into biochar-based soil management strategies and their contribution to carbon neutrality in agricultural soil systems, with recommendations for appropriate government involvement in promoting biochar-based soil management and for incorporating biochar into the carbon trading market. • The non-CO 2 GHGs account for the majority of carbon emission via agricultural soil. • Incorporating biochar into the global carbon trading market is recommended. • Using biochar to help achieve carbon neutrality is an application-dependent strategy. [ABSTRACT FROM AUTHOR]

Reforestation of landscapes is being used as a method for tackling climate change through carbon sequestration and land restoration, as well as increasing biodiversity and improving the provision of ecosystem services. The success of reforestation activities can be reduced by adverse field conditions, including those that reduce germination and survival of plants. One method for improving success is biochar addition to soil, which is not only known to improve soil carbon sequestration, but is also known to improve growth, health, germination and survival of plants. In this study, biochar was applied to soil at rates of 0, 1, 3 and 6 t ha − 1 along with a direct-seed forest species mix at three sites in western Victoria, Australia. Changes in soil chemistry, including total carbon, and germination and survival of species were measured over an 18 month period. Biochar was found to significantly increase total carbon by up to 15.6% on soils low in carbon, as well as alter electrical conductivity, Colwell phosphorous and nitrate- and ammonium-nitrogen. Biochar also increased the number of species present, and stem counts of Eucalyptus species whilst decreasing stem counts of Acacia species. Biochar has the potential to positively benefit reforestation activities, but site specific and plant–soil–biochar responses require targeted research. [ABSTRACT FROM AUTHOR]

The increasing agro-demands with the burgeoning population lead to the accumulation of lignocellulosic residues. The practice of burning agri-residues has consequences viz. Release of soot and smoke, nutrient depletion, loss of soil microbial diversity, air pollution and hazardous effects on human health. The utilization of agricultural waste as biomass to synthesize biochar and biofuels, is the pertinent approach for attaining sustainable development goals. Biochar contributes in the improvement of soil properties, carbon sequestration, reducing greenhouse gases (GHG) emission, removal of organic and heavy metal pollutants, production of biofuels, synthesis of useful chemicals and building cementitious materials. The biochar characteristics including surface area, porosity and functional groups vary with the type of biomass consumed in pyrolysis and the control of parameters during the process. The major adsorption mechanisms of biochar involve physical-adsorption, ion-exchange interactions, electrostatic attraction, surface complexation and precipitation. The recent trend of engineered biochar can enhance its surface properties, pH buffering capacity and presence of desired functional groups. This review focuses on the contribution of biochar in attaining sustainable development goals. Hence, it provides a thorough understanding of biochar's importance in enhancing soil productivity, bioremediation of environmental pollutants, carbon negative concretes, mitigation of climate change and generation of bioenergy that amplifies circular bioeconomy, and concomitantly facilitates the fulfilment of the United Nation Sustainable Development Goals. The application of biochar as seen is primarily targeting four important SDGs including clean water and sanitation (SGD6), affordable and clean energy (SDG7), responsible consumption and production (SDG12) and climate action (SDG13). [Display omitted] • This review primarily focuses on the potential of biochar in attaining SDGs. • Enhancement of biochar functionality with suitable modification is presented. • Biochar for soil enrichment and mitigation of GHG emissions are elaborated. • Biochar role in removal of pollutants and bioenergy generation has been discussed. [ABSTRACT FROM AUTHOR]

Crop residue management remains a major problem in the Indian agriculture sector. The in-situ firing of crop residues has been linked to air pollution, global warming, soil fertility decline and others. Biochar conversion through slow pyrolysis could be one of the techniques for the safe disposal of crop residues. 212.04 ± 44.27 MT biochar could be produced from 517.82 MT crop residues in India. Biochar conversion of crop residues can address agriculture production, safe drinking water, livelihood, energy security and environmental protection. Soil amendment with biochar sequestrate about 376.11 ± 78.52 MT CO 2 e carbon and help retain about 1.66 ± 0.46 MT of soil nutrients. Also, crop residues derived biochar has an estimated market value of approximately $500 billion in India. Biochar applications in the cosmetics, pharma and chemical industries offer market and employment opportunities. This review discusses the impact of in-situ crop residue burning and its biochar conversion through slow pyrolysis as part of sustainable crop residue management. Also, biochar applications and socio-economic aspects of crop residues – biochar system has been deliberated to fulfil several sustainable development goals (SDGs). [Display omitted] • Impacts of crop residues in-situ firing in India were quantified and discussed. • Biochar conversion of crop residues for its strategic management was discussed. • Impact of pyrolysis process parameters on biochar yield & properties was reviewed. • Biochar as a conventional & upcoming value-added product was comprehensively analysed. • Crop residues – biochar system for the attainment of SDGs has been mapped. [ABSTRACT FROM AUTHOR]

[Display omitted] • VM/FC and VM/(FC + VM) could be used as a substitute indicator for O/C or H/C. • The standardization of the indicators of biochar stability was linked with O/C. • Pyrolysis temperature was the main factor affecting biochar stability. • Abiotic biochar stability assessment methods were divided into three categories. Biochar produced from thermochemical processing biomass is being developed as an effective way to mitigate climate change. The stability of biochar means the potential capability of fixing biochar carbon in the soil environment. The method for biochar stability assessment is significant to its climate change mitigation potential. However, there is no standard method available to use, and the stability of biochar assessed by the diverse methods has a significant difference. Nevertheless, the comparative study on the diversified stability assessment methods is limited. In the present study, the biochars were pyrolyzed from soybean straw, wood sawdust, and Chlorella Vulgaris at temperatures ranging from 300 to 800 °C. Then, the evaluation methods, such as ultimate analysis, proximate analysis, the Edinburgh stability tool, X-ray photoelectron spectroscopy (XPS), solid state 13C nuclear magnetic resonance (NMR), and thermogravimetric analysis, were compared to assess the stability of biochars. The stability indicators obtained by most methods, excluding aromatic C from NMR and C–C/C = C/ C–H from XPS, were closely related to the pyrolysis temperature (ANOVA analysis, p < 0.05). The volatile matter/(fixed carbon + volatile matter) had high correlations with other indicators (Pearson coefficient, |r|>0.36, p < 0.05) except for C–C/C = C/C–H from XPS. The cluster analysis indicates the studied stability methods could be divided into three categories, according to which the proximate analysis may be developed as an alternative to O/C and H/C. These research findings help provide the reference for the classification and selection of stability assessment method for the accurate and efficient evaluation of biochar stability. [ABSTRACT FROM AUTHOR]

The biochar is a solid carbon-rich, porous material produced by the thermochemical conversion of a diverse range of biomass feedstocks under an inert atmosphere (i.e., in the absence of oxygen). We can produce the biochar at all likely scales, ranging from the industrial to the domestic level and even at individual farms, thus, the biochar industry is leading as a most appropriate at different socioeconomic settings. The possibility of sustainable biochar production practices and multi-functionality features make it a promising candidate to fulfill an increasing demand in the fields of soil amendment, agricultural sustainability, environmental protection, cutting-edge materials, and to achieve circular bioeconomy and mitigation of climate change. An available fraction of waste biomass (agroforestry waste, biomass crops, agricultural residues, mill residues, and animal manure, and many more) can be used efficiently in pyrolysis and converted into desired biochar materials, besides this alternative energy products, such as syngas, bio-oil, electricity generation, and process heat. This report emphasizes the fate of biomass composition, pyrolysis mechanisms, and applications of modern analytical and characterization techniques that are being adopted, applied, and standardized to improve understandings of molecular, structural, and surface properties characteristics of biochar. To achieve precisely designed biochar, there is a need to understand the latest advances in biochar materialization mechanisms and structure-application relationships to speed up their agronomic applications and to achieve a zero-waste dream. This report also summarizes a wide range of literature published on feedstocks, pyrolysis, and biochar and suggests several practical recommendations appropriate to implement and bring together specific details on the thermochemical conversion of biomass, desired biochar properties, organic and inorganic phases, and the significance to the agronomic applications. A schematic illustration of sustainable biochar production, application, and impact on global climate. [Display omitted] • Sustainability is motivating aspect in management of biomass feedstocks supply chain. • Report examines relationships of biomass feedstock composition and pyrolysis products. • Physicochemical properties of biochar influences structure-application relationships. • Current challenges covered to achieve viable biochar production and desired biochar. [ABSTRACT FROM AUTHOR]

• i-Tree planting tool was used for a life cycle analysis on current and potential CSS. • The CSS potential of green yards is limited, but the impact increases with upscaling. • Soil with added biochar can significantly contribute to the CSS capacity. • CSS needs more attention in the planning of urban green. Cities have been identified as key actors in climate change mitigation. Nature based carbon sinks have been suggested as a means of mitigating the greenhouse gas emissions of cities. Although there are several studies on the carbon storage and sequestration (CSS) of urban green, the role of residential sites is not fully understood. In addition, the carbon storage of soils is often excluded. Also the implications for planning require more attention. This study estimates the CSS potential of trees and biochar in urban residential yards and identifies effective means to enhance it. Moreover, the study discusses the results at the city scale. The research is based on a case study in Helsinki, Finland, and applies i-Tree planting tool to assess the current and potential life cycle CSS of the case area. The results reveal that trees and the mixing of biochar into growing medium can increase the CSS considerably. The CSS potential of the case area is 520 kg CO 2 per resident during 50 years. The added biochar accounts for 65 % of the capacity and the biomass of trees accounts for 35 %. At the city scale, it would lead to 330 000 t CO 2 being stored during 50 years. The findings suggest that green planning could contribute more strongly to climate change mitigation by encouraging the use of biochar and the planting of trees, in addition to ensuring favourable growing conditions. [ABSTRACT FROM AUTHOR]

In an endeavor to make biochar affordable for small-scale farmers, the flame-curtain based Kon-Tiki kiln technology was used in this study. Oil palm fronds were pyrolyzed in earth and metal Kon-Tiki kilns to produce biochar which has properties suitable for acid soil amelioration and climate change mitigation. • Both metal and earth Kon-Tiki kilns produce OPF biochars of similar quality. • Average OPF biochar yield from both kilns was 16 ± 4 wt. % with a pH of 10.02 ± 0.04. • Apparent carbon sequestration potential of Kon-Tiki OPF biochar is 0.27 ± 0.04 kg CO2 /kg OPF. • Correlation between molar H/C ratio and pyrolysis temperature of Kon-Tiki kiln has been identified. • Earth Kon-Tiki kiln is one of the most cost-effective processes for smallholders to produce OPF biochar (177 USD /t). Kon-Tiki kilns have been recommended as an easy-to-use, affordable yet environment-friendly approach to produce biochar. The flame curtain technology has been tested on a limited range of ligno-cellulosic biomass; therefore, this study explored the operation and performance of earth (EKT) and metal (MKT) Kon-Tiki kilns using abundantly available tropical oil palm frond (OPF). The apparent carbon sequestration potential (CSP) was estimated based on the H/C org ratio method. Our results demonstrated that both kilns reached highest treatment temperatures of 790 ± 100 ℃ (EKT) and 792 ± 44 ℃ (MKT) (p = 0.98) and exhibited a sinus wave-like temperature profile in the case of MKT. The average biochar yield produced from both kilns was 16 ± 4 wt. % with a fixed carbon and ash content of 56 ± 3 wt. % and 27 ± 3 wt. %, respectively. The OPF biochar had a pH of 10.02 ± 0.04 with a liming capacity of 8.91 ± 0.17 % calcium carbonate equivalent. The molar H/C and O/C ratios were 0.45 ± 0.03 and 0.19 ± 0.09, both satisfying IBI and EBC criteria for biochar. OPF biochars were mesoporous (< 50 nm) with a BET (N 2) surface area of 180–190 m2/g. OPF biochar had an average CSP of 0.27 ± 0.04 kgCO 2 /kg OPF. Biochar production cost was estimated to be 177 and 335 USD /t for EKT and MKT respectively. Our study demonstrated that OPF biochar of similar quality, quantity and CSP can be produced by both EKT and MKT. [ABSTRACT FROM AUTHOR]