From wastewater treatment to energy devices: A comprehensive review on biochar utilization and reuse pathways.

Variable effects of biochar on soil greenhouse gas emissions: A meta-analysis of climate, soil, and biochar property interactions.

Stage-dependent counteracting effects of biochar on arsenic mobilization and immobilization in paddy soil.

Biochar is an environmentally friendly soil amendment and is widely used for improving soil properties. Especially the Cation Exchange Capacity (CEC) of soil, which is the main criterion for assessing soil nutrients. Therefore, this study proposes a method for predicting the cation exchange capacity of soil, which is of great significance for the precise application of biochar and improving soil amendment efficiency. This study collects and organizes experimental data from published literature on biochar-amended soils to construct a dataset that includes biochar properties (feedstock type, pyrolysis temperature, specific surface area, cation exchange capacity) and soil properties. The dataset is divided into seven groups based on the properties of biochar to investigate the impact of biochar properties on the model's prediction results. Using four machine learning algorithms-Light Gradient Boosting Machine (LightGBM), Deep Neural Network (DNN), Categorical gradient Boosting (CatBoost), and Random Forest (RF)-a predictive model for soil CEC after biochar was established. The results show that the CatBoost model performed best, with a coefficient of determination (R2) of 0.963, a Mean Absolute Error (MAE) of 1.346, and a Root Mean Square Error (RMSE) of 2.238, indicating that it is effective in predicting soil CEC after the addition of biochar. Shapley Additive Explanations (SHAP) analysis and Partial Dependence Plot (PDP) results indicate that the pyrolysis temperature of biochar promotes the predicted values of soil CEC, while biochar with high CEC reduces the predicted values of soil CEC. The reason for this counterintuitive result may be that biochar with a high CEC competes for cations in the soil solution. Choosing biochar produced at high pyrolysis temperatures and with a specific surface area (SSA) below 50 m2/g can achieve a good improvement effect within the studied conditions. This study develops a promising model for predicting soil CEC, which can better optimize actual soil improvement, and provides valuable insights into the mechanism of the impact of biochar on soil CEC.

Improving soil chemical quality while enhancing maize yield is critical for sustainable crop production in acidic soils. We conducted a two-year field experiment on acidic Nitisols in the Burie district, Ethiopia, to evaluate the combined effects of maize cob biochar (BC), vermicompost (VC), and inorganic N/P₂O₅ rates on soil chemical properties and maize productivity. The experiment used a randomized complete block design with a 3 × 3 × 3 factorial arrangement, testing three levels of inorganic N/P₂O₅ (0/0, 120/69, 240/138kg ha-1), BC (0, 4, 8 t ha-1), and VC (0, 5.02, 10.04 t ha-1). Grain yield was recorded annually, and soil samples were collected before and after the experiment to assess changes in chemical properties. Data were analyzed using factorial ANOVA, and treatment means were separated using Tukey's HSD at 5% significance. Economic feasibility was evaluated via partial budget analysis. Under the conditions of this experiment, integrated application of BC, VC, and reduced N/P₂O₅, alongside lime, significantly improved soil pH (4.87 to 5.82), soil organic carbon, total nitrogen, and available phosphorus, while reducing exchangeable acidity, hydrogen, and aluminum. Maize grain yield increased markedly, with the highest yield (12.13 t ha-1) observed under 120/69kg N/P₂O₅ + 8 t BC + 10.04 t VC, a 175.77% increase over the control (4.40 t ha-1). The combination 120/69kg N/P₂O₅ ha-1 + 4 t BC ha-1 + 5 t VC ha-1 achieved consistently high yields (12.09 t ha-1) and the greatest net benefit (1,861 USD ha-1; 289,124 Ethiopian Birr ha-1) with a marginal rate of return of 149.1%. Yield was strongly positively correlated with improved soil chemical properties. Among predictive models, Linear Support Vector Machine (LSVM) provided the highest accuracy (R2 = 0.923) for estimating maize yield under integrated nutrient management. These results indicate that integrating BC and VC with reduced inorganic N/P₂O₅, in combination with lime, can enhance soil chemical quality and maize productivity in acidic Nitisols. These findings suggest potential for sustainable intensification in the study area and similar agro-ecologies, although multi-location and longer-term validation is needed to confirm broader applicability. Further research is needed across diverse environments and longer timeframes.

Replacing peat in green roof substrates with sustainable alternatives while maintaining plant performance and ecosystem services remains a critical challenge. We studied biochar-substrate interactions across four commercial green roof formulations (based on the type of organic component) in a greenhouse experiment: pure vermicompost, vermicompost + fen peat, fen peat, and mixed fen/high-moor peat. Substrates were amended with straw biochar, pine bark biochar, or left unamended (5% v/v, n = 4 replicates) and planted with a grass seed mixture mimicking early green roof establishment. Plant growth, nutrient contents (nitrate and phosphate contents), and microbial indicators (microbial biomass carbon (MBC), qCO2, and enzyme activities) were measured 30 days after the experiment began. Straw biochar in vermicompost boosted nitrate (90.8 mg kg−1) and root N (3.1%) compared to the control, while pine bark biochar in mixed peat released phosphate (+375%) and maximized MBC (874 µg g−1). Biochar intensified substrate effects, suppressing CO2 in peat through liming effects (pH from 4.6 to 6.5–7.1) but priming respiration in vermicompost via labile C supply. PCA explained 63% of the variance, with nitrate, plant N, and microbial parameters driving substrate separation. These short-term greenhouse results demonstrate critical biochar-substrate specificity for green roof substrate development, emphasizing formulation-specific matching over universal biochar application.

Shaping Antibiotic Resistance Gene Fate in Soil-Plant Systems: Dual Roles of Biochar Physicochemical Traits Mediated by Pyrolysis Conditions.

Lifecycle environmental impacts of biochar in Belgium: The influence of biochar feedstocks, production temperatures, and applications.

Biochar reshapes soil composition for years, yet most evidence comes from short-term, single-element laboratory incubations, leaving multi-element dynamics in tropical soils poorly resolved. We tracked 11 elements in longan-wood biochar and biochar-amended Ultisols over three years after a single field application, combining micro-XRF with SEM-EDX (one Map Sum Spectrum per group). Soil Fe and Al showed a non-linear response: both peaked at Year 1 (Fe 17.77 ± 3.93; Al 21.33 ± 1.88 wt.%; ~ 3.1- and 1.75-fold above control), fell at Year 2, then rose again at Year 3-a pattern invisible to single time-point studies, consistent with organo-mineral coating formation and reworking. Soil P stayed below detection despite annual fertilisation, indicating persistent Fe-Al phosphate fixation, while soil K peaked at Year 2 (1.82 wt.%). The biochars were Ca-rich (> 60 wt.%), acting as strong liming agents. EM-inoculated biochar showed higher surface carbon (92.7 vs. 77.6 wt.%), consistent with microbial biofilm deposition, though EM did not alter inorganic composition; a high Year-3 N signal (13.52 ± 23.42 wt.%) is a semi-quantitative artefact, not a reliable soil-N value. These findings reveal non-linear multi-element redistribution from a single biochar application and show the value of pairing bulk and surface analysis for long-term biochar-soil studies.

Soil contamination by microplastics (MPs) and heavy metals (HMs), particularly cadmium (Cd), poses an emerging threat to agricultural sustainability, food safety, and human health. Although the individual effects of MPs and Cd on crop performance have been widely investigated, their interactive impacts on rice remain poorly understood. Biochar (BC) and melatonin (MT) have recently attracted attention for their capacity to alleviate HM toxicity and abiotic stress in plants; however, their combined potential to mitigate MP-Cd co-stress has not yet been explored. This study aimed to evaluate the individual and enhanced effects of BC and MT on rice growth, physiological and molecular responses, Cd bioavailability, and soil properties under MP-Cd co-contamination. Exposure to Cd (20mg kg⁻¹) and MPs (1%) significantly inhibited rice growth and productivity by inducing oxidative stress, enhancing Cd uptake and accumulation, suppressing chlorophyll biosynthesis, and impairing water and nutrient acquisition. In contrast, the combined application of BC (2%) and MT (100 µM) markedly alleviated these adverse effects and outperformed individual amendments. Co-application substantially increased chlorophyll content (82%), leaf relative water content (48.47%), antioxidant enzyme activities (57.84-99.42%), proline accumulation (49.21%), and endogenous melatonin (EM) levels (48.35%). At the molecular level, BC + MT treatment upregulated antioxidant-related genes (OsAPx6, OsCAT, OsPOD, and OsSOD), the proline biosynthesis gene OsP5CS, and the MT biosynthesis gene OsCOMT, while significantly downregulating Cd transporter genes (OsNRAMP1 and OsHMA3). Furthermore, this combined treatment reduced soil Cd bioavailability and Cd accumulation in rice tissues, while improving soil fertility by increasing nitrogen (N), phosphorus (P), potassium (K), and soil organic carbon (SOC). This study provides the first evidence that the combined application of BC and MT effectively mitigates the detrimental effects of simultaneous MP and Cd contamination in rice. The enhanced physiological, molecular, and soil-level improvements induced by BC and MT collectively enhance rice growth and productivity under MP-Cd stress. These findings highlight a promising, integrated remediation strategy to manage co-pollution of MPs and HMs in agricultural soils, with important implications for sustainable crop production and food security.

Combined organic amendments reduce Cd accumulation in double-cropping rice by restructuring soil bacterial communities.

This experiment was conducted to evaluate the responses of two barley (Hordeum vulgare L.) cultivars, Ibaa 99 and Ibaa 265, to increasing levels of biochar application (0, 2, 4, and 6 ha-1) and determine subsequent effects on some yield components, total productivity, and harvest index. Most of the studied traits exhibited highly significant positive responses as indicated by the data. The highest overall mean values for grains per spike (48.5), 1000-grain weight (44.5 g), total grain yield (4.47 ha-1), biological yield (11.54 ha-1), and harvest index (38.48%) were recorded at the maximum biochar level (6 ha-1), which translated into a 50.5% increase above the control as far as grain productivity was concerned. On the other hand, spike number {m-2} showed a clear parabolic trend, reaching its maximum at 4 ha-1 with 322.5 spikes m-2 and then reduced sharply to 296 spikes m-2 at 6 ha-1 due to a temporary biological nitrogen immobilization. Because of its better genetic and physiological efficiency in source-tosink partitioning, "Ibaa 99" consistently outperformed "Ibaa 265" in all the parameters studied to give a superior grain output of 3.94 ha-1 and a harvest index of 38.62%. The two-way interaction exhibited strong genotypic sensitivity; "Ibaa 265" suddenly dropped at 6 ha-1,231 m-2, but "Ibaa 99" continued to make an upward linear response for spikes m-2 up to the maximum biochar level (361 spikes m-2). However, "Ibaa 265" exhibited a great biological mechanism for compensating for yield components, maximizing grains per spike to counteract the decrease in spike density (47.0). At 4.82 ha-1 and 12.19 ha-1, respectively, the combination of (Ibaa 99 + 6 ha-1} biochar produced the experiment’s highest grain and biological yields. Thus, it is highly recommended to combine charcoal amendments with high-performing genotypes as a sustainable strategy to maximize barley output.

Contrasting mechanisms of biochar-nitrogen interactions under inorganic and organic fertilizers: Integrated evidence from incubation, volatilization, leaching, and apparent nitrogen partitioning.

Straw biochar modulates manganese/cadmium enrichment in paddy algae under simulated warming: Combined experimental and modeling study.

Although manganese-modified biochar (MBC) effectively immobilizes Cd and As, the effects of low-molecular-weight organic acids (LA) on the performance and efficiency of Cd and As remediation in agricultural soils when co-applied with MBC in different application sequences remain unclear. This study examined the effects of LA on the MBC-mediated remediation of Cd/As-contaminated soil via the immersion of MBC in LA and LA-MBC to facilitate co-applications on contaminated soil using different application sequences. Results revealed that after LA immersion, the pH of MBC decreased by 0.14-2.10 units, accompanied by increases in electrical conductivity and Mn concentration. LA treatment also induced surface alterations characterized by cracks, depressions, reduced Mn oxide particles, and weakened MnO2 diffraction peaks. These changes promoted soil Cd/As mobilization, increasing the TCLP-Cd by 40.2-110.1% and available As by 22.0-70.0%, thereby reducing MBC immobilization efficiency. Application sequence markedly affected the remediation outcomes, in order of decreasing remediation effectiveness: LA pre-addition > MBC pre-addition > simultaneous application. Simultaneous LA-MBC application led to a 12.4-62.6% decrease in the relative abundance of soil Gemmatimonadota. In contrast, the relative abundance of Firmicutes and Myxococcota increased by 47.0-184.9% and 39.5-273.8%, respectively. This study systematically assessed the effects of LA and MBC application sequences at different time intervals on the bioavailability of Cd/As. A "LA-MBC-microorganism" interaction model is proposed, demonstrating that LA structurally reshapes MBC and alters microbial communities, which may modulate Cd/As speciation. Based on pollutant behavior and amendment dynamics, a spatiotemporally optimized strategy is proposed to improve in situ remediation and reduce environmental risks.

The application of passivators represents a typical remediation strategy for soil heavy metal pollution， a process that not only affects heavy metal bioavailability but also modifies nitrogen transformation processes. However， the influence of passivators on the structure of functional microbial communities governing nitrogen transformation in cadmium （Cd）-contaminated soils remains poorly understood. In this study， typical passivators （lime and biochar） were applied in a pot experiment with rapeseed cultivated in Cd-contaminated soil. High-throughput sequencing and complementary methodologies were employed to investigate shifts in gene abundance and community characteristics of soil nitrogen-fixing bacteria and ammonia-oxidizing microorganisms， along with their driving factors. The results revealed that lime application significantly reduced the Shannon index of nitrogen-fixing bacteria， ammonia-oxidizing archaea （AOA）， and ammonia-oxidizing bacteria （AOB） by 8.62%， 9.11%， and 82.80%， respectively， while increasing their Simpson index by 22.78%， 3.56%， and 55.86%. In contrast， biochar application exclusively reduced the Shannon index of AOB by 80.13% and increased its Simpson index by 71.63%. Lime significantly enhanced AOA amoA gene abundance but reduced AOB amoA gene abundance， whereas biochar induced no significant changes in amoA genes. Lime markedly altered the β-diversity of nitrogen-fixing bacteria， AOA， and AOB， while biochar only significantly affected AOA β-diversity. These findings demonstrate that passivators can restructure soil microbial communities involved in nitrogen transformation， with lime exerting more substantial effects than biochar. Additionally， both passivators significantly modified the relative abundance of dominant microbial groups （e.g.， Proteobacteria and Crenarchaeota） within functional communities. Changes in key nitrogen-transforming microbial communities showed strong correlations with soil physicochemical properties： Nitrogen-fixing bacteria were primarily governed by pH and available Cd （ACd）； AOA by ACd and pH； and AOB by soil organic matter （SOM）， pH， and ACd. Within nitrogen-fixing bacteria， Geobacter exhibited significant positive correlations with ACd， NH4+， and NO3- but a negative correlation with pH， while Azohydromonas displayed inverse responses. Among AOA， Crenarchaeota and Thaumarchaeota positively correlated with pH but negatively with ACd， whereas Nitrososphaera showed negative correlations with pH but positive associations with soil total nitrogen （STN）. For AOB， taxa such as β-Proteobacteria demonstrated positive correlations with ACd， NH4+， and NO3- but negative correlations with pH. By elucidating how passivators （particularly lime） significantly restructure key microbial consortia involved in soil nitrogen transformation， this study provides a theoretical foundation for understanding the mechanisms through which passivators influence nitrogen cycling processes in Cd-contaminated soils.

Industrialization, urbanization and poor waste management have led to environmental pollution which has emerged as a major global concern requiring the development of sustainable and eco-friendly remediation strategies. In this sense, biochar from agricultural residues has been shown to be a promising material for environmental management. The pyrolysis of sugarcane bagasse, an abundant by-product of the sugar industry, provides a promising opportunity for the production of inexpensive and renewable biochar feedstock. This review highlights the production, physicochemical properties and environmental applications of sugarcane bagasse biochar for pollution mitigation and sustainability enhancement. Biochar has high porosity, large surface area, functional groups, mineral content and aromatic carbon structure that are important structural and surface properties making it very efficient for different environmental applications . Its role in carbon sequestration is particularly important, with the stable carbon matrix of biochar helping to store carbon for the long-term and reduce greenhouse gases. Also, the sugarcane bagasse biochar is capable of improving soil fertility by increasing the retention of nutrients, water holding capacity, microbial activity and balancing the soil pH which contributes to sustainable agriculture. The review also discusses the adsorption capacity of sugarcane bagasse biochar in removing organic and inorganic pollutants such as dyes, heavy metals and toxic compounds from water and air. The factors influencing the adsorption performance such as pyrolysis temperature, surface modification, pH and contact time are also discussed. Recent advances of engineered and modified biochars for improved removal of pollutants are also reviewed. Sugarcane bagasse biochar is, in general, an environmentally sustainable, economically viable and multifunctional material with great potential for pollution control, waste valorization and climate change mitigation. Further research is needed to optimize the production processes and expand its large scale environmental applications.

ABSTRACT Heavy reliance on synthetic nitrogen (N) fertilizers has resulted in soil degradation, declining soil productivity, and lower N use efficiency (NUE). Sustainable alternatives such as biochar (BC) and biofertilizers (BFs) offer promising solutions to enhance soil health and support yield improvement. This study investigates the individual and combined effects of BC and microbial BFs on soil properties, corn growth, and yield under controlled greenhouse conditions. A randomized experiment with seven treatments consisting of granular urea, BC, BFs, and their combinations were conducted using clay loam soil. Soil samples collected at four growth stages were analyzed for inorganic N forms, including ammonium-N (NH4 +–N) and nitrate-N (NO3 −–N), as well as organic matter (OM), phosphorus (P), potassium (K), and other physicochemical properties, while plant growth traits, chlorophyll content, biomass, and grain yield were measured. Treatments containing BC and/or BFs significantly increased soil OM and nutrient availability, including N, P, and K. In addition, these treatments improved plant height, leaf number, and chlorophyll concentration, resulting in 14–17% greater biomass and 14–19% higher yield compared to the control. Notably, the integrated application of BC, BFs, and 50% urea treatment increased yield and biomass by 25% and 28%, respectively, values comparable to full urea application, indicating that N fertilizer use can be reduced without compromising productivity. Overall, the results highlight strong synergistic benefits of BC and BFs for sustainable corn production.

The impact of microplastics on soil micro-food webs is regulated by biochar and earthworms.

ABSTRACT The aim of the present study was to evaluate the interactive effects of various biochar sources (sheep manure, rice husk, and municipal solid waste, applied at 3% (w/w)) and Si application rates (200 and 400 mg Si kg−1 soil) on grain yield, nutrient composition of triticale (X Triticosecale Wittmack), and the chemical properties of Pb-contaminated calcareous soil in a greenhouse trial. Among the biochars tested, sheep manure biochar was the most effective at reducing soil available Pb concentration (16.6% reduction), likely because of its high pH, phosphorus, and soluble salt content. The highest Si application rate (400 mg Si kg−1) also significantly reduced soil available Pb concentration by 6.6%. However, the most effective treatment for enhancing triticale grain yield (68% increase) and reducing grain Pb concentration (54% reduction) compared to the control was the combined application of sheep manure biochar and the lower Si level (200 mg Si kg−1). At the higher Si application rate (400 mg Si kg−1), both grain yield and macro- and micronutrient uptake were markedly suppressed, potentially due to nutrient antagonisms associated with sodium metasilicate. These results underscore the synergistic effects of sheep manure biochar and moderate Si application in immobilizing soil Pb, enhancing triticale nutrient uptake, and improving grain yield in Pb-contaminated calcareous soils. The study recommends further investigations into using other silicon compounds, such as calcium and potassium silicates, and biochars produced at varying pyrolysis temperatures, to assess their potential in mitigating the adverse effects of Pb on triticale growth in calcareous soils.