Vanadium (V) is recognized as an environmental contaminant that adversely affects plant growth and development. The main objective of this study was to investigate the effects of sulfur-modified biochar (SBC) compared to standard biochar (BC) on rice under V suppression (35 mg L−1). Our findings revealed that V stress significantly suppressed rice seedling growth, evidenced by reductions in shoot fresh weight, chlorophyll pigment content, photosynthetic assimilation, and root attributes, with higher V accumulation observed in both shoots and roots of V-stressed plants compared to BC- and SBC-treated plants. SBC application improved rice growth more effectively than BC, exhibiting increases of 61.41% in fresh weight, 63.04% in root length, 66.66% in chlorophyll a, 52.20% in chlorophyll b, and 52.95% in carotenoids, alongside enhanced gas exchange attributes. Notably, SBC reduced V accumulation by 58.33% in shoots and 43.79% in roots compared to V-stressed plants. SBC also induced V stress tolerance in rice by elevating antioxidant enzyme activities in roots and shoots, including superoxide dismutase (SOD, 85.25/89.41%), catalase (CAT, 119.04/100.01%), glutathione peroxidase (GPX, 82.20/79.82%), glutathione S-transferase (GST, 123.74/114.67%), ascorbate peroxidase (APX, 86.56/63.74%), glutathione reductase (GR, 204.87/60.36%), dehydroascorbate reductase (DHAR, 53.60/62.06%), and monodehydroascorbate reductase (MDHAR, 87.09/88.88%), while simultaneously reducing hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels. Furthermore, SBC increased the activities of glyoxalase enzymes (Gly I by 96.15/77.14% and Gly II by 115.78/104.25%), mitigating methylglyoxal (MG) induced toxicity, and enhanced the expression of metal-tolerant (OsFSD1) genes and antioxidant-glyoxalase systems. Overall, SBC application was found to be more effective than raw BC in alleviating V-induced toxic effects and improving rice plant growth. Nonetheless, further studies must be performed to determine exactly driving mechanism involved in the promotion of growth.Graphical

The impact of field aged biochar (FABC) on the adsorption kinetics and transport behavior of weakly hydrophobic antibiotics in soil is scarcely discussed. This study investigated the impact of FABC on weakly hydrophobic antibiotics (sulfadiazine, SD and florfenicol, FF) transport in purple soil by comparing fresh biochar (FBC), one-year aged biochar (ABC1), and five-year aged biochar (ABC5). Through batch adsorption, soil column experiments, and Hydrus 1D modeling, this study examined the evolution of physicochemical properties of biochar, their effects on soil porosity and dispersion, and antibiotic adsorption. Results showed that aging significantly altered biochar characteristics, with carbon (C) content decreasing by 10.40% while oxygen (O) content increased by 40.52%. ABC1 demonstrated optimal performance with a 99.28% increase in specific surface area (SSA) and enhanced oxygen-containing functional groups, leading to maximum antibiotic retention rates of 16.57% for SD and 24.78% for FF. Although ABC5 showed decreased SSA and adsorption capacity, it maintained stable remediation effects through enhanced biochar–soil interactions, as evidenced by increased dispersivity (λ) and hydrodynamic dispersion coefficient (D). The two-site chemical nonequilibrium model (TSM) revealed that the fraction of equilibrium adsorption sites (f) increased from 0.1164 to 0.3514 after aging, indicating improved antibiotic retention. These findings demonstrate that while one-year aging enhanced remediation capacity, five-year aging stabilized environmental effects through modified soil structure.Graphical

Biochar application is known to improve soil quality, enhance nutrient bioavailability, and increase carbon retention. However, its effects on ecoenzymatic activities and stoichiometric relationships in saline-alkali soils remain poorly understood. This study examines how biochar amendments influence microbial stoichiometry, nutrient limitations, and carbon use efficiency in saline-alkali soils. We compared two types of biochar—acid-modified biochar (pH 2.3) and alkaline biochar (pH 8.8)—at application rates of 1%, 2%, and 5% in soils planted with Medicago sativa L. Our results demonstrated that alkaline biochar increased enzymatic C:N stoichiometry at higher rates, while acid-modified biochar decreased it at lower rates. Both biochar types reduced enzymatic C:P and N:P stoichiometry; alkaline biochar shifted microbial metabolism from nitrogen to phosphorus limitation, while acid-modified biochar alleviated nitrogen limitation at rates of 2% and 5%. Furthermore, alkaline biochar at rates of 2% and 5% reduced microbial carbon limitation and enhanced carbon use efficiency, whereas acid-modified biochar did not. Microbial carbon use efficiency was consistently higher with alkaline biochar than with acid-modified biochar at equivalent application rates. These findings highlight that the impact of biochar on soil microbial processes depends on the biochar feedstock type, with differences in surface adsorption properties, nutrient supply, pH, and liming effects driving changes in soil properties, microbial community dynamics, and plant growth. Our study offers insights into optimizing nutrient cycling and carbon sequestration in saline-alkali soils, demonstrating the potential of biochar in sustainable soil management.Graphical

Dark fermentation is a biological process that converts organic molecules into molecular hydrogen and stands out as one of the most promising methods for extracting bioenergy from wastewater. The accumulation of end-products causes varying inhibitory effects on the process, posing a key challenge. This study explored the efficacy and mechanisms of biochar as a cost-effective solution to mitigating the inhibitory effects of end-products in major types of dark fermentative hydrogen production processes and provided for the first time a quantitative analysis of the relative contribution of each mechanistic pathway. Results showed that biochar was more effective in butyrate-type than ethanol-type fermentations. In butyrate-type fermentation facing endogenous and exogenous volatile acid inhibition, biochar increased hydrogen production by 145.74% and 64.95%, respectively. In ethanol-type fermentation, biochar increased hydrogen production by 10.53% and 18.09% under endogenous and exogenous inhibitions from ethanol, respectively. Mechanistic analyses revealed three primary pathways through which biochar mitigated product inhibition: pH buffering, cell colonization, and inhibitor adsorption. The relative contribution of each pathway varied by fermentation type. In butyrate-type fermentation, pH buffering was critical, accounting for 42.9% of the mitigation effect, while cell colonization was primary in ethanol-type fermentation, contributing 32.4%. This study demonstrated the different roles of biochar in mitigating production inhibition in diverse fermentation types, highlighting its potential to enhance hydrogen energy recovery in dark fermentation.Graphic

Biochar can enhance soil health and plant productivity, but the underlying mechanisms remain elusive. Here we tackled this question through the lens of the rhizosphere using wheat as a model plant. We examined the impact of four feedstocks (corn stover, cattle manure, pine sawdust, or wheat straw) and two application rates. Biochar modulated root metabolism, where amino acid metabolism was the most common, leading to cascade effects on a wide range of secondary metabolites, including many plant signaling molecules involved in plant–microbe interactions. All biochar treatments increased rhizosphere microbial diversity, altered community composition, enhanced microbial interactions, and resulted in potential functional changes. Increased Burkholderiales (denitrifying bacteria) abundance and decreased Thermoplasmata (archaeal methanogens) abundance could explain biochar’s widely reported effects of mitigating nitrous oxide and methane. Biochar enhanced positive correlations among microbes and network modularity, suggesting local adaptation through synergism and the formation of modules of functionally interrelated taxa. A diversity of keystone taxa from dominant and non-dominant phyla emerged, including those known to mediate methane, nitrogen, and sulfur cycling. Treatment-specific alterations also occurred, and biochar feedstock choice exerted greater influence than application rate. Wheat biochar at 0.25% showed the strongest and distinct modulating effects, resulting in orchestrated changes in root metabolome and rhizosphere microbiome, especially those relevant to plant–microbe interactions and plant growth promotion. Our work provides new insights into the potential of top-down rhizosphere microbiome engineering through biochar-based reprogramming of root-microbe interactions.Graphical

Dissolved organic matter (DOM) is a key factor in soil carbon sequestration and greenhouse gas emissions (GHGs). However, the molecular-level change of soil DOM and the implications of GHGs under different long-term fertilization regimes (LFRs) remain elusive. Therefore, we conducted a long-term field experiment with an unfertilized control (CK) and fertilization regimes (chemical fertilizer (F), straw (ST), and biochar (BC)), We employed the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to explore the molecular-level change of soil DOM. Our findings revealed that LFR, especially BC, increased the quantity, molecular weight, double bond equivalence, aromaticity index and molecular formula complexity of DOM. The F increased the molecular diversity and functional complexity of DOM and decreased the Gibbs free energy (ΔG Cox°), whereas BC and ST decreased the molecular diversity because of greater accumulation of lignin-like compounds and increased the ΔG Cox°. The specific molecular evolution and fractionation analysis indicated that LFR increased the aggregation of specific molecules: BC stimulated high O/C and molecularly stable lignin compounds accumulation, whereas ST promoted lignin and unsaturated hydrocarbon compound accumulation. Simultaneously, the F increased GHGs (CH4 and N2O), whereas the BC significantly decreased the CH4 emissions and the global warming potential. Furthermore, the correlation analysis revealed that the quantity and quality of DOM were closely correlated with GHGs, the quantity of DOM and unstable compounds increased the CH4 and N2O emissions, and the relative abundance of persistent compounds decreased CH4 emissions. These findings elucidate the potential mechanisms by which LFR, especially BC, regulates DOM characteristics and subsequently influences GHGs, which contributes to the development of more effective soil management strategies for mitigating GHGs while maintaining soil health and productivity.Graphical

Peatlands are an important natural store of carbon (C). Drainage of lowland peatlands for agriculture and the subsequent loss of anaerobic conditions had turned these C stores into major emitters of greenhouse gases (GHGs). Practical management strategies are needed to reduce these emissions, and ideally to reverse them to achieve net GHG removal (GGR). Here we show that a combination of enhanced C input as recalcitrant organic matter, CH4 suppression by addition of terminal electron acceptors, and suppression of decomposition by raising water levels has the potential to achieve GGR in agricultural peat. We measured GHG (CO2, N2O, and CH4) fluxes for 1 year with intensive sampling (6 times within the first 56 days) followed by monthly sampling in outdoor mesocosms with high (0 cm) and low (− 40 cm) water table treatments and five contrasting organic amendments (Miscanthus-derived biochar, Miscanthus chip, paper waste, biosolids, and barley straw) were applied to high water table cores, with and without iron sulphate (FeSO4). Biochar produced the strongest net soil C gain, suppressing both peat decomposition and CH4 emissions. No other organic amendment generated similar GGR, due to higher decomposition and CH4 production. FeSO4 application further suppressed CO2 and CH4 release following biochar addition. While we did not account for life-cycle emissions of biochar production, or its longer-term stability, our results suggest that biochar addition to re-wetted peatlands could be an effective climate mitigation strategy.

Converting crop residues into biochar and subsequently incorporating it into soils is a promising strategy to improve carbon sequestration in agroecosystems. However, differences in the potential mechanisms for soil organic carbon (SOC) accumulation between biochar and its feedstock materials remain unclear. This study performed a nine-year field experiment involving four treatments in a Mollisol: mineral fertilizers alone and combined with maize straw or its biochar, and control without fertilizers and amendments. The main objectives of this study were to assess how straw and biochar incorporation influence SOC content, SOC chemical composition, microbial necromass carbon (MNC) content, and microbial community characteristics. Compared with mineral fertilizers alone, straw and biochar significantly (P < 0.05) increased SOC content, while biochar (40.5% increase) had more pronounced effects than straw (23.7% increase). Similarly, both straw and biochar increased MNC content and boosted microbial biomass, but straw had a more pronounced impact than did biochar. Additionally, biochar markedly increased SOC aromaticity by 26.6% (P < 0.05), while straw reduced SOC aromaticity by 2.85% (P > 0.05). Fungi, rather than bacteria, played a more crucial role in increasing SOC content through their necromass inputs under both straw and biochar incorporation. Our results demonstrated that straw enhanced SOC accumulation primarily through entombing effect of microbial necromass, while biochar enhanced SOC accumulation primarily through biochemical protection from recalcitrant aromatic carbon. The present findings provide valuable insight into the potential mechanisms of field practices that lead to maximize soil carbon sequestration.Graphical

Material selection and production conditions are imperative for determining the functional performances of composite materials. Phase-change composites obtained from phase-change materials (PCMs) and supporting matrices exhibit high thermal energy storage density. They are used to overcome the intermittency issues of wind and solar energy, as well as to reduce waste heat dissipation to the environment. However, the large-scale utilization of composite and pristine materials has severe drawbacks, primarily stemming from the complex fabrication routes of the encapsulating agents, leakage, and inadequate thermal stability. In this study, biochar-based phase-change composites were fabricated using vacuum infiltration techniques, and the effects of biomass feedstock and pyrolysis temperature on the performance of the composite were elucidated using different types of biowastes and temperatures. This approach has several advantages, including facile production techniques, low-cost carbon sources, and environmental friendliness. The PCM adsorption ratio of biochars derived from rice husk (RH) and Miscanthus straw linearly correlated with the pyrolysis temperature (550–700 °C), while RH700 resulted in a composite with a high enthalpy per unit mass of hexadecane (HXD) in RH700/HXD (250.9 J g−1) owing to the high surface area of RH700 (74.66 m2 g−1). The crystalline temperature increased slightly from 10.7 °C in RH550/HXD to 10.9 °C in RH700/HXD, suggesting improved molecular motion and crystal growth of HXD. Wheat straw biomass pyrolyzed at a low temperature (550 °C), displaying a reduced surface area at 700 °C (7.35 m2 g−1) and exhibiting the lowest energy storage density. The latent heat efficiency reached 99.5–100%, where RH700/HXD exhibited 100% efficiency. The composites demonstrated strong leakage resistance at high heating temperatures (60 °C, above the melting temperature of HXD), good chemical compatibility between the biochar and HXD, and high durability after 500 thermal cycles. Therefore, the extent of PCM loading and energy storage density improvements primarily depends on the pyrolysis conditions, feedstock used, and pore size distribution of the biochar samples. This research provides insights into the fabrication of phase-change composites and optimization of the carbonization process of different biomasses used for thermal management applications, such as building energy savings.Graphical

Application of advanced techniques and machine learning (ML) for designing and predicting the properties of engineered hydrochar/biochar is of great agro-environmental concern. Carbon (C) stability and phosphorus (P) availability in hydrochar (HC) are among the key limitations as they cannot be accurately predicted by traditional one-factor tests and might be overcome by engineering the pristine HC. Therefore, the aims of this study were (1) to determine the optimal production conditions of engineered swine manure HC with high C stability and P availability, and (2) to develop the best ML models to predict the properties of HC derived from different feedstocks. Pristine- (HC) and FeCl3 impregnated swine manure-derived HC (HC-Fe) were produced by hydrothermal carbonization under different pH (4, 7, and 10), reaction temperature (180, 220, and 260 ℃), and residence time (60, 120, and 180 min) and characterized using thermo-gravimetric, microscopic, and spectroscopic analyses. Also, different ML algorithms were used to model and predict the hydrochar solid yield, properties, and nutrients content. FeCl3 impregnation increased Fe-phosphate content, while it reduced H/C and O/C ratios and hydroxyapatite P content, and therefore improved C stability and P availability in the HC-Fe as compared to HC, particularly under lower pH (4), temperature of 220 ℃, and at 120 min. The generalized additive ML model outperformed the other models for predicting the HC properties with a correlation coefficient of 0.86. The ML analysis showed that the most influential features on the hydrochar C stability were the H and O contents in the biomass, while P availability in HC was more dependent on the C, N and O contents in biomass. These results provided optimal production conditions for Fe-engineered manure hydrochar and identified the best performing ML model for predicting hydrochar properties. The main implication of this study is that it offers a high potential to improve the utilization of biowastes and produce biowaste-derived engineered hydrochar with high C stability and P availability on a large scale.Graphical