Jul 2026· Journal of Plant Nutrition And Soil Science/Zeitschrift für Pflanzenernahrung und Bodenkunde· 0 citations· 50 references
Abstract
Biochar and hydrochar have emerged as promising carbon‐based amendments for enhancing soil carbon sequestration and mitigating greenhouse gas emissions. This review synthesizes and critically compares current knowledge on the production technologies, physicochemical properties, stabilization mechanisms, carbon persistence, and life‐cycle climate performance of biochar and hydrochar, emphasizing their comparative roles as negative emission technologies. Biochar, produced via pyrolysis, is characterized by highly aromatic and condensed carbon structures that confer long‐term stability in soils, frequently yielding mean residence times from centuries to millennia. Hydrochar, generated through hydrothermal carbonization, offers a more efficient path for processing wet feedstocks and waste valorization, yet generally exhibits lower intrinsic stability and greater variability in mineralization rates. The review demonstrates that carbon persistence is governed not only by molecular recalcitrance but also by soil‐mediated mechanisms, including organo‐mineral interactions, aggregate occlusion, and microbial feedbacks. Impacts on CO
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, N
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O, and CH
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fluxes are strongly context‐dependent, reflecting interactions among char properties, soil texture, climate, and management practices. Life‐cycle assessments indicate that biochar systems more consistently deliver net climate benefits, whereas hydrochar performance depends on energy sources and process integration. Beyond climate mitigation, both materials provide agronomic and environmental co‐benefits, including improved soil fertility, water retention, and waste recycling. However, large‐scale deployment remains constrained by methodological heterogeneity, regulatory uncertainty, and economic barriers. The review concludes that biochar and hydrochar are complementary components of climate‐smart land management systems. Future progress depends on standardized methodologies, long‐term field experiment validation, and harmonized carbon accounting frameworks enabling reliable contributions to global net‐zero pathways. Policy alignment will be decisive for responsible and equitable global deployment.
Biochar, a carbon-rich product resulting from the thermochemical transformation of organic biomass under limited oxygen condition, is currently drawing much worldwide attention due to its multiple applications in carbon sequestration, soil improvement, environmental remediation, and biomass waste management. Initially, the focus of research was primarily on the technical possibilities of biochar production, its economic aspects, and its contribution to climate change mitigation through carbon sequestration and the promotion of sustainable agriculture. Nevertheless, recent research indicates the high complexity and dynamics of biochar interactions with the environment, driven by a combination of factors like feedstock type, process conditions, biochar properties, and other factors. While biochar exhibits multiple beneficial effects, including improving soil structure, enhancing nutrient retention, promoting microbial activities, and remediating contaminants, several environmental risks associated with biochar application have also been identified, namely the formation of polycyclic aromatic hydrocarbons (PAHs), heavy metal contamination, creation of persistent free radicals, changes in soil chemistry, and modification of soil microbial community structure. Such risks are greatly related to production process parameters, treatment methods, and biochar application practices. Moreover, differences in feedstock choice, pyrolysis temperature, reactor design, biochar application rate, and analytical methods used make comparative analysis of results difficult.
O. E. Ojewumi, Gang Chen, M. Ojewumi· Green· 0 citations
Sustainable agriculture is increasingly challenged by soil degradation, environmental pollution, and climate change, necessitating the pragmatic and eco-friendly approach. This review systematically synthesizes the role of biochar as multifunctional soil management strategy in enhancing soil health and sustainable environmental management, with particular emphasis on the critical roles of feedstock type and pyrolysis conditions in governing biochar performance. To address existing knowledge gaps, we comprehensively evaluate recent available literature on biochar-based environmental remediation, focusing on key indicators of agricultural sustainability, including nutrients availability, soil biological activity, climate change mitigation, biochar-assisted phytostabilization, and crop productivity. Current evidence indicates that biochar application can achieve a net negative carbon footprint, mitigate greenhouse gas emissions and heavy metal contamination, and improve soil structure, fertility, and overall crop productivity on sustainable-basis. However, these benefits largely depend upon the various important biochar production factors including feedstock source, pyrolysis temperature, biochar stability, residence time, rate of application, and soil pH. Beyond its function as a soil amendment, biochar also serves as a multifunctional resource contributing to bioenergy production, waste reduction, and long-term carbon sequestration. At the same time, this review identifies critical research gaps, including the long-term field performance of biochar, mechanisms underlying the interactions between biochar and agronomic practices, and the environmental and human health risks associated with large-scale agricultural applications. Overall, this work highlights the importance of feedstock selection and pyrolysis parameters in designing biochar for environmental remediation and outlines future research directions to refine biochar engineering, application guidelines, and risk assessment frameworks for its sustainable use.
Ismail Khan, Faming Wang, Abdul Rehman et al.· International journal of phy...· 0 citations
Biochar amendment is a proven strategy for mitigating methane (CH4) emissions and enhancing soil carbon sequestration in rice paddies. However, the depth-dependent dynamics of microbial carbon pump (MCP)-driven recalcitrant organic carbon (ROC) formation and the underlying microbial mechanisms remain poorly characterized, particularly in the purple paddy soils of the central Sichuan Basin, China. To address this gap, we developed a novel quantitative MCP-driven ROC model and conducted a field experiment with four biochar treatments (CK, C2, C4, and C6 t ha-1) to investigate CH4 emissions, methane-cycling microbial community, and soil carbon fractions across a 0-80 cm profile. Biochar amendment significantly reduced CH4 emissions by 57.88-84.51% (peaking at 6 t ha-1) and increased methanogen and methanotroph diversity by 1.30-1.66 times. Although the concentrations of soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), and absolute ROC decreased significantly with depth, the ROC/SOC ratio consistently increased. Crucially, our quantitative model revealed that biochar stimulated both the in vivo turnover and ex vivo modification pathways of the MCP by supplying essential labile substrates, explaining up to 92% of the variance in deep-soil carbon fractions. In conclusion, this study demonstrates that biochar serves as an effective dual-action strategy: mitigating CH4 emissions via microbiome regulation while enhancing long-term carbon sequestration through intensified MCP-driven ROC formation across the entire soil profile.
Yue-Feng Li, Hongyu Chen, Jie Chen et al.· Journal of Environmental Man...· 0 citations
Sustainable soil fertility management requires amendments that improve nutrient retention while supporting nutrient recycling. This review synthesizes current evidence on how biomass type and pyrolysis conditions determine biochar properties and, consequently, the dynamics of N, P, K, S, Ca, and Mg in soils. The analysis integrates bibliometric screening, comparative data on feedstock groups, and mechanistic evidence on adsorption–desorption, ion exchange, precipitation, microbial transformations, aging, and nutrient release. Feedstocks were grouped into agricultural, woody, animal, urban, and aquatic biomasses, whose mineral composition and structural features produced contrasting nutrient-source potentials. Across the biochars reviewed, pyrolysis temperatures ranged from 200 to 900 °C, generating materials with pH values of 4.7–13.7, surface areas of 0.18–545.66 m2 g−1, and nutrient contents of 0.04–8.22% N, 0.02–5.30% P, and 0.15–7.01% K. Higher pyrolysis temperatures generally increased aromaticity, alkalinity, porosity, and mineral concentration, whereas mineral-rich feedstocks provided greater direct nutrient and base-cation inputs. This review shows that BC functionality is context-dependent and should be matched to soil nutrient limitations, pH, texture, and crop requirements to improve nutrient-use efficiency and support sustainable agriculture.
Karen Bibiana Quiroga-Salinas, M. Martínez-Cordón, Y. Agámez-Pertuz· Sustainability· 0 citations
Biochar has emerged as one of the most promising nature-based strategies for improving soil quality, enhancing crop productivity and supporting climate-smart agriculture. However, the agronomic performance of biochar remains highly variable because its effects are governed by complex interactions among feedstock characteristics, pyrolysis conditions, soil properties and management practices. This review synthesizes recent advances in biochar research (2019–2026), examining how production variables determine biochar physicochemical properties and how these properties subsequently influence soil functioning, plant performance and long-term agricultural sustainability. The review integrates evidence on feedstock selection, pyrolysis technologies, biochar modification strategies and the relationships between biochar properties and soil physical, chemical and biological processes. Particular attention is given to crop productivity, nutrient use efficiency, stress mitigation, contaminant immobilization, greenhouse gas mitigation and long-term soil resilience. Across the literature, the most consistent agronomic benefits were observed when biochar was applied to degraded or resource-limited soils and integrated with complementary management practices, whereas responses were often limited under fertile soils, low application rates or short experimental periods. Rather than identifying a universally superior biochar, the evidence indicates that agronomic performance depends on matching biochar characteristics to specific production objectives and environmental conditions. Based on these findings, this review proposes a transition from generalized biochar application towards optimized deployment strategies supported by standardized characterization, long-term multi-site validation and integrated environmental and economic assessments. This synthesis provides a comprehensive framework for guiding future research and facilitating the effective implementation of biochar within sustainable and regenerative agricultural systems.
Ágata Cristiana Correia, C. Pessoa, P. Legoinha et al.· The Scientist· 0 citations
Biochar, a carbon-rich solid produced through oxygen-limited pyrolysis of biomass, is increasingly considered a soil amendment for sustainable soil fertility management. Indian agriculture faces continuing pressure from soil degradation, declining soil organic carbon, nutrient depletion, crop-residue burning and climate variability, all of which constrain productivity and resource-use efficiency. This review synthesises literature and field-based evidence relevant to the use of biochar in Indian soil-crop systems. It discusses biochar production through slow, fast and flash pyrolysis using crop residues, woody biomass, and livestock or poultry manure at 300–700 °C, and relates these production conditions to key properties, including porosity, specific surface area, alkaline pH, fixed carbon content and nutrient composition. The review also examines the principal mechanisms through which biochar improves soil fertility, including modification of bulk density, water-holding capacity, aggregate stability, cation exchange capacity, soil reaction, nutrient retention and microbial activity. Evidence reviewed here indicates that biochar can reduce nutrient leaching, influence nitrogen and phosphorus dynamics, contribute to soil carbon sequestration, and mitigate selected greenhouse gas emissions, although responses depend on feedstock, pyrolysis conditions, soil type and crop requirement. Field observations from India suggest that applications within the range of 5–20 t ha⁻¹ can improve the productivity of rice, wheat, maize, legumes, oilseeds, plantation crops and vegetables, with stronger responses generally reported in acidic, sandy and degraded soils. The review further identifies practical constraints to adoption, including production cost, inconsistent product quality, limited standardisation, insufficient extension support and variable soil-crop compatibility. Integrating biochar with integrated nutrient management and decentralised residue management may support more sustainable soil fertility strategies in India.
Manoj Kumar, A. Pandey, Ashutosh Singh et al.· International Journal of Env...· 0 citations
