Agricultural soils are a significant source of nitrous oxide (N₂O) emissions. The application of biochar to soil offers a synergistic approach to establishing stable organic carbon (C) storage while reducing greenhouse gas (GHG) emissions, particularly through effective reductions in N₂O emissions. However, current biochar application strategies often lack consideration of locally tailored application rates and biochar properties, limiting its N₂O mitigation potential. Here, we conduct a spatially explicit analysis to investigate the N₂O mitigation potential of straw-derived biochar in China’s croplands, exploring optimal application strategies under both ideal and realistic conditions. The key drivers that influence the spatial patterns of straw-derived biochar’s mitigation potential and application strategies are also revealed. We find that applying biochar with optimal strategies could avoid approximately 50% and 36% of nationwide cropland N₂O emissions under ideal and realistic conditions, respectively. The optimal biochar application rate and properties required to achieve the maximum N₂O reduction potential exhibit significant spatial variability, differing among biochar types. Key factors determining the optimal biochar application rate in various regions include N fertilizer application rates and soil organic carbon (SOC) content, while water input—including precipitation and irrigation water input—is the primary factor determining the optimal biochar properties. These findings may inform the development of site-specific biochar application strategies aimed at enhancing the N₂O mitigation efficacy in croplands across China.

Secretion and long-term accumulation of phenolic acid allelopathic substances are critical factors decreasing yield in continuous capsicum cropping systems. However, there are limited effective technologies and methods for removing these substances. In this study, biochar (BC) with ultrahigh specific surface area and pore volume was prepared via K₂CO₃ etching, called carbonate-modified biochar (CBC). Then, it was loaded with horseradish peroxidase (HRP) under glutaraldehyde crosslinking conditions to form HRP–CBC. The maximum loading capacity of HRP reached 311.46 U g⁻¹. Under various factors, the degradation efficiency of allelopathic substances such as ferulic acid followed the order HRP–CBC > HRP–BC > HRP, indicating that the combination of alkaline etching and enzyme immobilization enhances ferulic acid degradation. At a HRP–CBC dose of 2 U mL⁻¹ and pH 7, the degradation of 20 mg L⁻¹ ferulic acid was achieved within 6 h. Furthermore, this method demonstrated excellent degradation performance against multiple phenolic acid compounds responsible for yield reduction in continuous chili pepper cropping systems. HRP–CBC exhibited superior stability, enhanced stress resistance, and broad application potential. The inhibitory effect of ferulic acid on chili seed germination disappeared after degradation by immobilized HRP. Liquid chromatography–mass spectrometry and ecotoxicity analyses confirmed that HRP–CBC degraded ferulic acid into less toxic small organic molecules through a free radical-mediated mechanism. Therefore, a modified biochar immobilized with HRP offers a promising strategy for removing phenolic acid allelopathic substances from continuous cropping systems.

Engineered biochar has emerged as a versatile tool for purpose-specific rhizosphere engineering, offering tailored solutions for enhancing crop production, crop protection, and environmental remediation. Yet, its effectiveness depends on optimizing application for specific functional goals rather than adopting a one-size-fits-all approach. This review explores how engineered biochar shapes rhizosphere processes to support crop production, crop protection, and soil remediation. It examines key mechanisms including enhanced nutrient availability, stimulation of beneficial microbial communities, pathogen suppression, and soil contaminant immobilization, and how different biochar modifications, such as nutrient enrichment, antimicrobial functionalization, and surface engineering, drive these outcomes. The review highlights important trade-offs, such as the competing demands of nutrient availability for crop growth versus contaminant immobilization for remediation, and accounts for the spatial and temporal variability of biochar effects in the rhizosphere. While biochar presents clear synergistic benefits (e.g., improving soil structure, enhancing water retention, reducing greenhouse gas emissions, and enabling carbon sequestration), its practical application faces challenges related to competing objectives, rhizosphere complexity, and economic constraints. Emerging innovations such as nanocomposite biochars, bioprimed biochars, and biochar-microbe synergies offer new avenues for precision agriculture and sustainable land management. Finally, the review emphasizes the importance of long-term field studies to evaluate sustainability, and outlines opportunities for biochar in climate change mitigation, waste valorization, and agroecological resilience. By integrating the latest research on biochar’s mechanisms, challenges, and opportunities, this review provides a comprehensive framework for leveraging engineered biochar to address the pressing challenges of modern agriculture and environmental management.

As environmental pollution becomes an increasingly severe issue, the technology of enzyme immobilization on biochar has emerged as a promising solution for water and soil pollution remediation due to its efficiency, cost-effectiveness, and environmental friendliness. This review systematically examines the preparation methods, adaptation mechanisms, and applications of biochar-immobilized enzymes for pollutant removal. It focuses on the interaction between enzymes and biochar carriers, the selection of immobilization techniques, and the stability of immobilized enzymes. Biochar, as a carrier, offers advantages such as low cost, high specific surface area, and a variety of surface functional groups, which can be further enhanced through modification techniques to optimize its compatibility with enzymes. The review also discusses the strengths and weaknesses of various immobilization strategies, highlighting the high stability of covalent binding and the cost-effectiveness of adsorption methods. In the field of environmental remediation, biochar-enzyme composites have demonstrated synergistic effects in efficiently degrading organic pollutants, decoloring dyes, and remediating soil contaminants. While significant progress has been made in laboratory studies, the large-scale application of biochar-immobilized enzymes still faces numerous challenges, including raw material heterogeneity, enzyme deactivation, and ecological safety concerns. Future research should focus on developing intelligent design platforms, optimizing biochar-enzyme compatibility, overcoming the limitations of multifunctional synergistic remediation, and evaluating the long-term ecological impact. By integrating multiple technologies, biochar-immobilized enzymes hold great potential for widespread application in environmental remediation, advancing green and low-carbon technologies.

Soil organic carbon (SOC) decomposition is influenced by fluctuations in moisture levels, which play a crucial role in regulating global soil carbon balance. Biochar is widely used as an amendment to enhance carbon sequestration and soil health. However, the effects of biochar addition and moisture variability on SOC decomposition remain debated. Therefore, we conducted a microcosm incubation experiment to examine how moisture variability intensity and biochar addition affect SOC decomposition in an Alfisol topsoil from Northeast China. Our results show that increased soil moisture variability accelerates SOC decomposition by 0.5–17.2%, enhances total phospholipid fatty acid (PLFA) content by 29.9–39.6%, and raises the Gram-positive to Gram-negative (GP: GN) bacterial ratio by 2.1–11.0%. Additionally, moisture variability intensifies soil residual clay fraction particle content by 0.4–27.5%, contributing further to SOC decomposition. Biochar addition mitigates the impact of moisture fluctuations on SOC decomposition by stabilizing soil aggregates. These findings highlight the key roles of soil microbial communities and aggregate structure in governing SOC decomposition.

The design of phase-change renewable energy-harvesting materials has garnered increasing attention for achieving sustainable energy infrastructure and advanced applications. However, energy storage density that relies on the shape and crystallization of pristine phase-change materials (PCMs) usually lacks charge/discharge efficiency, and the inherent lattice defects in individual supporting scaffolds, further constrain their overall performance. In this study, lignocellulose-based biochar (obtained from spruce thermolysis at 600 °C) was assembled with an organically intercalated montmorillonite (MT) via modification and ultrasonication-assisted vacuum drying to produce engineered biomineral-based composite PCMs that simultaneously improve the latent heat and crystallinity of paraffin PCM. The biomineral hybrid was prepared using two preparation techniques: a conventional method of integrating biochar with clay mineral without intercalation, and a structural engineering approach involving the doping of cationic nanoclay into biochar. The engineered hybrid (EMB) achieved a 516.4% increase in surface area (9.9 m² g^–1 for bulk MT) and demonstrated a high PCM adsorption rate for hexadecane (C₁₆) with 223.3% enhancement in latent heat (15.7 to 121.3 J g^–1). The composite (EMB@C₁₆) also exhibited a 78% enhancement of thermal conductivity and charging/discharging efficiency. Moreover, EMB@C₁₆ retained over 95.9% of latent heat after 1000 cycles of heating (50 °C) and cooling (23 °C), with only a 4.1% reduction, providing continuous thermal energy supply during real-time temperature variation evaluations with thermal infrared imaging under both short and long cycle durations. This fabrication technique provides a rational approach for integrating naturally sourced and thermophysically reinforced biochar-based hybrids for advanced thermal regulation systems.

This study presents the development of a novel, disposable, and eco-friendly electrochemical device based on biochar-modified screen-printed electrodes (SPE/BC) for the detection of the antibiotic trimethoprim. Biochar, derived from sewage sludge, was applied as a nanomaterial to enhance the sensitivity of the sensor for trimethoprim quantification in environmental, biological, and pharmaceutical samples. Characterization techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy, were used to assess the properties of biochar. Surface area, pore volume, and pore diameter were measured using the Brunauer–Emmett–Teller method. The electrochemical sensor performance was analyzed using impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry, revealing a strong synergistic effect on the trimethoprim oxidation process. The device showed high sensitivity with a detection limit of 71.0 nmol L⁻¹ over a linear range of 1.75–231.43 μmol L⁻¹. Recovery studies in synthetic urine, tap water, and pharmaceutical tablets demonstrated recoveries of 92%–99%, with no sample pretreatment. The sensor exhibited selectivity towards common interferents such as sulfamethoxazole, urea, and ascorbic acid, making it a practical tool for detecting trimethoprim as an emerging pollutant.

Pyrolysis requires extensive experimentation to achieve optimum thermochemical conversion, which can be addressed by integrating machine learning (ML) predictive solutions. The abundant availability of algae with low volume footprint makes it viable green biomass to achieve thermochemical products. For optimum algal biochar (BC) yield production, the relation of ultimate, proximate analysis with process conditions is critical. This study’s objective is twofold: It aims to develop a robust ML model, trained on diverse literature data and optimized using particle swarm optimization and genetic algorithm, that predicts BC yield across various feedstocks and conditions. Secondly, the optimum process parameters are derived to maximize BC yield with the experimental validation for the collected samples at their respective chemical and structural compositions. Limited data points for algal biomass induce a comparative analysis of ML models, including Gaussian process regression, ensembled tree (ET), decision tree and support vector machine. The predictive capability of ET enhanced through optimization performed exceptionally well for BC yield prediction with testing R² = 0.77993 and RMSE = 6.9792. 2D and 3D partial dependence plots imply that BC yield is primarily influenced by pyrolysis temperature, volatile matter, and heating rate with SHAP values of 1.2785, 0.3972, and 0.2949, respectively. Monte Carlo simulation and Sobol sensitivity analysis substantiate statistically the impact of selected features on algal BC yield. Inverse optimization of ET model suggests that the maximum BC yield production is 76.33% at a temperature of 500 °C, a heating rate of 10 °C/min, a residence time of 60 min, a N₂ flow rate of 0.5 L/min, and particle size of 1.5mm.

Addressing the surging global energy demand while mitigating environmental degradation necessitates a paradigm shift from conventional energy systems to sustainable alternatives. However, the inherent intermittency of renewable energy sources mandates efficient harvesting mechanisms and advanced storage technologies to ensure uninterrupted energy availability. Thus, optimizing energy generation and storage systems is imperative for maximizing renewable energy utilization and advancing carbon neutrality. Biochar-based phase change materials (PCMs) emerge as a viable solution, simultaneously enhancing thermal energy storage efficiency and contributing to carbon sequestration. This study synthesizes biochar-based PCM composites using Neem (Azadirachta indica) seed-derived biochar, produced at two distinct pyrolysis temperatures (300 °C and 500 °C), and impregnated with lauric acid (LA). Comprehensive characterization through BET surface area analysis, FT-IR spectroscopy, SEM–EDS, DSC, and TGA evaluated the structural, chemical, and thermal properties of the composites. The biochar pyrolyzed at 500 °C exhibits a significantly higher surface area (668 m²/g), facilitating enhanced PCM loading. FT-IR analysis confirmed the successful impregnation of LA while preserving its molecular structure, while SEM analysis revealed a highly porous biochar network that optimizes PCM accommodation. DSC and TGA results demonstrated an impressive latent heat storage capacity up to 94.92 J/g, stable phase transition behavior, and improved thermal stability. Leakage tests and infrared thermal imaging further validated the composites’ shape-stabilizing efficiency, ensuring controlled heat absorption and dissipation without PCM leakage. By utilizing waste biomass, this study presents a sustainable and cost-effective approach to advanced thermal management, contributing to enhanced energy conservation and a reduced carbon footprint.

Living wall systems (LWSs) help to alleviate the climate and biodiversity harms associated with buildings and bring benefits to building occupants. Their performance can be variable and existing research points to the planting substrate as a key design factor. This study provides quantitative evidence on the physical, thermal and moisture performance of three planting substrates that vary according to the proportion of biochar added to green waste compost (GWC). Thermal conductivity (Wm⁻¹ K⁻¹), thermal resistivity (mK W⁻¹), volumetric moisture content (%) and mass (g) are measured for each fraction, replicated six times. Controlled drying procedures were employed, measuring these properties at a range of moisture levels. Data analysis finds that volumetric moisture content and biochar fraction have a statistically significant (p ≤ 0.05) effect on thermal conductivity. Added biochar is associated with non-linear reductions in thermal conductivity at low moisture levels. This suggests increasing the biochar fraction while reducing moisture in the substrate of a LWS will reduce its thermal conductivity, with a 100 mm planting substrate with 30% biochar and 30%vol moisture content providing 0.82 m² KW⁻¹ of thermal resistance, compared to 0.46 m² KW⁻¹ without added biochar. The methods build on previous work to assess the properties of different planting substrates for LWSs, providing a practical, lab-based assessment of biochar. The data produced are useful for researchers and professionals seeking to understand how biochar additions impact irrigation and thermal performance when specifying and designing LWSs and underline the potential value of biochar for improving the thermal performance of green infrastructure more widely.

Perfluorooctanoic acid (PFOA) has emerged as a new urgent pollutant in aquatic environments due to its high persistence and ecotoxicity. In photocatalytic degradation systems, challenges such as rapid recombination of electron–hole pairs (e⁻/h⁺), short lifespans of reactive oxygen species (ROS), and insufficient ROS generation hinder the efficient degradation of PFOA. This study presents a novel "scallop cage" architecture, constructed using Ulva biochar to create confined spaces that encapsulate the Fe₃O₄/ZnO heterojunction. This approach not only controls the crystal size of the Fe₃O₄/ZnO heterojunction but also confines the degradation reactions to a specific space, significantly shortening the mass transfer distance for ROS and effectively mitigating their rapid deactivation in aqueous-phase degradation processes. Furthermore, the confinement effect enhances the generation of multiple reactive species (·O₂⁻, ·OH, ¹O₂, and h⁺). The optimized FZS@UBC-2 composite photocatalyst achieved a PFOA removal efficiency of 97.53%. In practical applications, FZS@UBC-2 efficiently decomposes PFOA in complex aqueous matrices and can be easily recovered using an external magnetic field. This work not only expands the application of algae-derived biochar in advanced oxidation processes but also offers a sustainable strategy for addressing persistent organic pollutants in aquatic environments.

Engineered biochar with enhanced photochemical properties holds great potential for environmental remediation. However, natural humic substances, crucial players in environmental redox processes, are structurally complex and slow-forming, hindering mechanistic insights and practical applications. Here, we propose a co-engineering strategy that combines biochar with artificial humic substances synthesized from pine sawdust via controlled hydrothermal humification (180–340 °C). Modulating the hydrothermal temperature can yield artificial humic substances with diverse degradation degrees of lignin, yielding tailored phenolic architectures and electron-donating capacities (EDC). Using Ag⁺ photoreduction as a model reaction, we demonstrate that artificial humic substances produced at 340 °C exhibit optimal phenol content and the strongest reducing capacity (19.2-fold greater than that of substances synthesized at 180 °C). Notably, higher molecular weight fractions (> 5 kDa) of artificial humic substances were found to dominate Ag⁺ photoreduction due to their enriched phenolic content and superior EDC. Mechanistic investigations reveal that photo-excited phenolic groups generate superoxide radical (O₂^•−), initiating Ag⁺ reduction via a ligand-to-metal charge transfer (LMCT) pathway. Moreover, we discovered a previously overlooked phenomenon: hydrochar undergoes photo-induced dissolution, further enhancing photoreduction. This work provides new insights into the temperature-dependent lignin transformation into redox-active artificial humic substances and highlights the dynamic photochemical behavior of engineered biochar (hydrochar) under solar irradiation.

To address the urgent need to mitigate agricultural greenhouse gas emissions, research is investigating innovative strategies, including the application of biochar in various agricultural practices. Feeding biochar to cattle is an interesting strategy that not only aims to improve animal health and productivity, but can also have a cascading effect on soil improvement and CO₂ sequestration. Analysing the recovery efficiency of digested biochar and its structural integrity can provide insight into the potential of post-digestion biochar application. Here biochar quantification in dung is investigated for the first time using three different methodologies, namely thermal analysis, elemental analysis, and dichromate oxidation. Results indicate that a relative quantification within ± 1% biochar is possible. The majority of biochar (70–90%) fed to dairy cows survived digestion. The analysis further reveals selective preservation of the most stable condensed aromatic fractions of biochar during digestion, similar to short-term ageing in soil. The remaining digested biochar has an H/C ratio of 0.22 and an O/C ratio of 0.05, meeting the criteria for highly stable biochar. Our findings suggest that the digested biochar is highly suitable for long-term carbon sequestration when applied to soil via manure, offering a promising strategy for compensating agricultural greenhouse gas emissions.

Mounting global crisis including environmental degradation, resource depletion, and health threats, necessitates the exploration of various transformative, novel, and multifunctional materials with practical applications. Nanobiochar, a nanoscale biochar produced through pyrolysis and post-pyrolysis modifications, has emerged as a versatile and sustainable carbon-based nanomaterial with numerous applications. Biochar nanocomposites, engineered hybrid materials developed from biochar and nanomaterials, have further amplified the applications of biochar. Although the environmental applications of nanobiochar and biochar nanocomposites have been extensively studied, their potential applications in other critical sectors are less explored and not well understood. This review explores the potential applications of nanobiochar and biochar nanocomposites in the medical, energy, construction, polymer, and agriculture sectors. The unique properties of nanobiochar and biochar nanocomposites make them a promising candidate for healthcare applications, aligned with the One Health approach. In times of resource depletion and climate change, such composite materials show promise as a valuable resource for alternative energy storage solutions, sustainable construction, and climate-smart agriculture. However, further research is needed on the biocompatibility and extended ecotoxicity of these hybrid materials. The integration of nanobiochar and biochar nanocomposites in various domains and broadening their scope of application into underexplored sectors will address knowledge gaps and expand the use of emerging technologies for a sustainable and low-carbon future. This review underscores the need for more interdisciplinary research to fully leverage the potential of these composite resources and facilitate the transition to a more resilient and resource-efficient future.

Biochar is widely recognised as a carbon dioxide removal (CDR) technology, but its stability depends on feedstock, pyrolysis conditions, and the soil environment. Current CDR schemes prioritise highly stable biochars to ensure long-term permanence, requiring high pyrolysis temperatures that reduce carbon yield and intensify competition for biomass. This perspective explores potential synergies between two distinct CDR approaches, biochar application and peatland rewetting, where rewetted peatlands could enhance biochar permanence by suppressing microbial decomposition, offering a means to improve both carbon retention and resource efficiency. Using decomposition rate modifiers from biogeochemical models, we estimate biochar stability in rewetted peat and assess its CDR efficiency relative to a counterfactual of high-stability biochar application to dry soils. This perspective suggests that rewetted peatlands significantly reduce biochar carbon losses, particularly for lower-stability biochars, making them more viable for long-term CDR. By allowing greater flexibility in biochar selection, this approach could improve the scalability of biochar deployment while alleviating biomass supply constraints. While challenges such as land-use transitions and methane emissions must be addressed, integrating biochar with peatland rewetting presents a high-impact strategy to optimise the efficiency of biomass-based CDR.