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Abstract Carbonaceous adsorbents were synthesized from palm kernel shell and palm mesocarp fiber for the adsorption of phenanthrene (PHE) and the highly carcinogenic-benzo(a)pyrene (BaP). The structure and properties of the activated biochar were characterized using standardized analytical tools. The microscopic examinations carried out with SEM and BET results revealed mesoporous structures and interstitial spaces in the activated samples (AB-PKS and AB-PMS). Powder X-ray diffraction (PXRD) results showed that prepared sorbents are amorphous and that activation affected the amorphous cellulose on the surface of the microfibrils which led to a decrease in the intensity of some peaks. Fourier-transform infrared spectroscopy (FTIR) affirms the availability of surface moieties that may promote polycyclic aromatic hydrocarbon (PAH) removal or decontamination of aqueous media. The sorption isotherm and effect of pH on the adsorption of PHE and BaP onto the activated palm kernel shell (AB-PKS) and activated palm mesocarp fiber (AB-PMF) were investigated. The isotherm studies and error analysis (SSE and R 2 ) confirm that the Freundlich model best fits experimental results for AB-PMF; while, the Langmuir model best describes AB-PKS sorption of BaP and PHE, respectively. The optimal removal efficiency for PHE was between 84 and 100% while that of BaP was between 68 and 87% with maximum adsorption capacity (q max) of 19.38–21.98 mg/g and 1.24–13.26 mg/g, respectively. The optimum pH condition for removing PHE is less than 7 and above 7 for BaP. Therefore, the conversion of waste materials to useful sorbents, as well as preliminary adsorption test results obtained suggests a cleaner and cost-effective pathway for waste management and water treatment.

Iron ore tailings (IOT) are industrial solid wastes that pose environmental threats. This study prepared IOT-biochar composite materials as multifunctional soil conditioners through an in-situ growth method. Biochar served as a carrier to improve the dispersity and reactivity of IOT in soil. The IOT-biochar composite (FeOT-BC) showed balanced impacts on soil properties, increasing pH, organic matter and available nutrients compared to IOT alone. This was due to the buffering effects of biochar. In pot experiments, FeOT-BC significantly promoted rice plant growth compared to IOT alone. The improvements were attributed to the improved soil fertility and increased microbial activities induced by biochar. The results suggest that integrating IOT with biochar can mitigate the negative effects of tailings and convert them into a value-added product. The biochar component can optimize the performance of IOT by moderating soil acidification, enhancing nutrient release from iron minerals, and stimulating microbial activities. The IOT-biochar composite materials integrate the functionalities of both components for optimized soil conditioning effects, providing a promising strategy for comprehensive tailings utilization.

Biochar (BC) was used to remove trichloroethylene (TCE) from soil and water phases, and BC modification changed the sorption behavior of pollutants. Microplastics are emerging pollutants in the soil and water phases. Whether microplastics can affect the sorption of TCE by modified BC is not clear. Thus, batch sorption kinetics and isotherm experiments were conducted to elucidate the sorption of TCE on BC, and BC combined with polyethylene (PE) or polystyrene (PS). The results showed that HCl and NaOH modification increased TCE sorption on BC, while HNO3 modification inhibited TCE sorption on BC. When PE/PS and BC coexisted, the TCE sorption capacity decreased significantly on BC-CK + PE, BC-HCl + PE, BC-HNO3 + PE, BC-NaOH + PE, and BC-NaOH + PS, which was likely due to the preferential sorption of PE/PS on BC samples. We concluded that microplastics can change TCE sorption behavior and inhibit TCE sorption on BC samples. Thus, the interaction of BC and microplastics should be considered when BC is used for TCE removal in soil and water remediation. HIGHLIGHTS HCl and NaOH modification increased trichloroethylene (TCE) sorption on biochar.; HNO3 modification inhibited TCE sorption on biochar.; Microplastics could change TCE sorption behavior.; Polyethylene/polystyrene could preferentially adsorb onto biochar and inhibit TCE sorption by biochar samples.;

Leucaena leucocephala, an invasive toxic tree species, has threatened the survival of native plants in the Hengchun Peninsula, southern Taiwan. Due to the small-to-medium diameter, the utilization and processing of L. leucocephala is highly restricted, while its discarding accelerates carbon dioxide emission to the atmosphere. Biochar, produced from the pyrolysis of biomass under an inert atmosphere, is considered an effective carbon sequestration technique with high stability, which is important for long-term carbon storage and soil improvement. L. leucocephala biomass and montmorillonite were co-pyrolyzed under inert conditions, aiming to investigate the effects of different pyrolysis temperatures and montmorillonite blending ratios on biochar yield and carbon retention. Results showed improved biochar yield and carbon retention with increasing montmorillonite addition. Thermogravimetric analysis, nuclear magnetic resonance spectroscopy, and Fourier-transform infrared spectroscopy demonstrated enhanced stability of the modified biochars. The production of modified L. leucocephala biochar represents a promising technique for carbon dioxide sequestration and biochar stabilization, enabling the development of L. leucocephala utilization approaches.

The study was conducted to investigate carbon stock, flux, and sequestration potential as well as the response of groundnut (yield) to different fortification approaches. A greenhouse experiment was conducted using four treatment combinations, fortified biochar with T. albuminosus (B + T), biochar (B), T. albuminosus, and control laid in a Complete Randomized Design (CRD). The result showed increased carbon sequestration, stock, and a subsequent decrease in carbon emission in treatment B + T relative to other treatments. Untreated samples recorded the lowest values with 3.69 g kg-1 sequestered carbon 24.97 kg ha- stock 4.92% carbon emission and a net flux of -20.70. The highest groundnut yield was also recorded in the B + T treatment with a value of 1131.10 kg ha-1. However, biochar treatment recorded the highest biomass and stover yield 5.62 t ha-1 and 3.82 t ha-1 respectively. In conclusion, the Fortification of biochar with T. albuminosus proved efficient in improving carbon sequestration, increasing carbon stock, and reducing emission as well as other nutrients in soils under cultivation. Also, using B + T as an amendment under optimal growth conditions is recommended for better groundnut production. The study's constraints lie in its execution within controlled greenhouse settings, potentially limiting its applicability to real-world field conditions. Thus, caution should be exercised when extending these findings to field applications, ensuring the validation of the approach's effectiveness.

Abstract Background Water stress is a major danger to crop yield, hence new approaches to strengthen plant resilience must be developed. To lessen the negative effects of water stress on wheat plants, present study was arranged to investigate the role of synergistic effects of biochar, trans-zeatin riboside (t-ZR), and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat. Results In a three-replication experiment comprising of four treatments (T0: Control, T1: Drought stress (DS), T2: DS + t-ZR with biochar, T3: DS + A. brasilense with biochar), we observed notable improvements in soil quality and enzymatic activities in water-stressed wheat plants with the application of t-ZR and A. brasilense with biochar. In drought stress, Treatment having the application of A. brasilense with biochar performs best as compared to the other and significant increased the enzymatic activities such as peroxidase (7.36%), catalase (8.53%), superoxide dismutase (6.01%), polyphenol oxidase (14.14%), and amylase (16.36%) in wheat plants. Different enzymatic activities showed different trends of results. Soil organic C, dissolved organic C, dissolved organic N also enhanced 29.46%, 8.59%, 22.70% respectively with the application of A. brasilense with biochar under drought stress condition. Conclusions The synergistic action of A. brasilense and biochar creates an effective microbiological environment that supports essential plant physiological processes during drought stress. This enhancement is attributed to improved soil fertility and increased organic matter content, highlighting the potential of these novel strategies in mitigating water stress effects and enhancing crop resilience.

Abstract Biochar is a promising solution to alleviate the negative impacts of salinity stress on agricultural production. Biochar derived from food waste effect was investigated on three plant species, Medicago sativa, Amaranthus caudatus, and Zea mays, under saline environments. The results showed that biochar improved significantly the height by 30%, fresh weight of shoot by 35% and root by 45% of all three species compared to control (saline soil without biochar adding), as well as enhanced their photosynthetic pigments and enzyme activities in soil. This positive effect varied significantly between the 3 plants highlighting the importance of the plant-biochar interactions. Thus, the application of biochar is a promising solution to enhance the growth, root morphology, and physiological characteristics of plants under salt-induced stress.

Abstract Production of liquid fertilizers containing nitrogenous nutrients and biostimulants from sewage sludge (SS-NB) has been attracting increasing attention due to its excellent fertilization effect and resource recycling attributes. To better understand the functional effects of nutrients and biostimulants in SS-NB on soil, the adsorption capacity and mechanism of straw biochar (SB) and wood chip biochar (WCB) for alkaline and neutral SS-NB components were investigated. The adsorption of total organic carbon (TOC) from alkaline and neutral SS-NB by WCB was 61.14% and 89.73%, respectively, higher than that by SB, which was 56.25% and 83.36%. Moreover, TOC from neutral SS-NB was more readily adsorbed, especially for fulvic and humic acids. SB had a strong adsorption capacity for calcium ions and nitrogen (TKN, nitrate N, protein, amino acid) and released large amounts of P. In addition, WCB and SB showed a strong affinity for macromolecules (proteins) and reducing substances (lignin and lipids) and excellent fixation ability for phytohormones and allelochemicals. However, WCB adsorbed more types of molecular substances than SB while maintaining a high immobilization rate. Analysis of the adsorption mechanism showed that surface amino groups of the biochar were involved in adsorption, while WCB had additionally high adsorption efficiencies through pore adsorption, hydrogen bonding adsorption and pore size-exclusion effects. The study revealed that biochar can be used as an efficient adsorption carrier for SS-NB to improve soil fertility management. Graphical Abstract

Abstract Persistent free radicals (PFRs) are emerging substances with diverse impacts in biochar applications, necessitating accurate prediction of their content and types prior to their optimal use and minimal adverse effects. This prediction task is challenging due to the nonlinearity and intricate variable relationships of biochar. Herein, we employed data-driven techniques to compile a dataset from peer-reviewed publications, aiming to systematically predict the PFRs by developing supervised machine learning models. Notably, extreme gradient boosting (XGBoost) model exhibited the best predictive performance for both regression and classification tasks in predicting the PFRs, achieving a test R2 value of 0.95 for PFR content prediction, along with an Area Under the Receiver Operating Curve (AUROC) of 0.92 for PFR type prediction, respectively. Based on XGBoost model, a graphical user interface (GUI) was developed to access PFRs predictions. Analysis of feature importance revealed that the biochar properties, such as metal/non-metal doping, pyrolysis temperature, carbon content, and specific surface area were identified as the four most significant factors influencing PFRs contents. Regarding the types of PFRs in biochar, specific surface area, pyrolysis temperature, carbon content, and feedstock were top-ranked influencing factors. These findings provide valuable guidance for accurately predicting both the contents and types of PFRs in biochar, and also hold significant potential for highly efficient utilization of biochar across various applications. Graphical Abstract

The addition of biochar and the use of membrane coverings are two methods used in aerobic composting of agricultural waste. The effectiveness of each of these two methods on compost quality and reduction of greenhouse gas emissions was tested in the laboratory. The results showed that both methods increased the maximum composting temperature and extended the thermophilic period. The germination index of biochar-treated compost and membrane-covered compost reached 70% on the 18th day, which was 12 days earlier than the corresponding value in the control group. The products from the biochar-treated compost had higher pH and lower electrical conductivity, compared with the product of the control group, indicating that these products are more suitable for acidic soils. In terms of greenhouse gas reduction, both methods were found to reduce the emissions of CH4 and N2O from composting. The addition of biochar had a better emission reduction effect on N2O, whereas the membrane covering technique yielded a better effect on CH4 emission reduction. The results of this study provide technical support for managed aerobic composting to reduce greenhouse gas emissions.

Abstract Biochar can improve soil health and fix CO2 by altering soil microenvironment, thus impacting the global carbon cycle and the change of soil ecological environment. Recent studies show that cotton byproduct-derived biochar is a potential effective amendment for soil improvement so that it could play an important role in agricultural and environmental conservation. In this work, research topics on cotton byproduct-derived biochar in soil in last decade and so are systematically reviewed for better understanding of the progresses of cotton byproduct-derived biochar in (i) the morphologic and physicochemical characterization, (ii) latest research hotspots and trends, (iii) the roles in soil reclamation, and (iv) relevant carbon sequestration mechanisms. Finally, the future research directions regarding cotton byproduct-derived biochar mingled to soil environment are discussed. Insight derived from this work would provide scientific basis for promoting more applications of cotton byproduct-derived biochar in soil ecological restoration and carbon fixation. Graphical Abstract

Abstract The adaptation of biochar in anaerobic digestion (AD) positively influences the conversion of substrate to biomethane and promotes system stability. This study investigated the influence of biochar (BC) doses (0 to 8 g/L) on the Biochemical Methane Potential (BMP) of glucose during a 60-day AD in a mesophilic batch-type reactor. The first 6.5 weeks of the experimentation were dedicated to the microorganism’s adaptation to the biochar and degradation of organics from the used inoculum (3 phases of the glucose feeding). The last 2 weeks (4th phase of glucose feeding) represented the assumption, that glucose is the sole carbon source in the system. A machine learning model based on the autoregressive integrated moving average (ARIMA) method was used to model the cumulative BMP. The results showed that the BMP increased with the amount of BC added. The highest BMP was obtained at a dose of 8 g/L, with a maximum cumulative BMP of 390.33 mL CH4/g-VS added. Likewise, the system showed stability in the pH (7.17 to 8.17). In contrast, non-amended reactors produced only 135.06 mL CH4/g-VS and became acidic at the end of the operation. Reducing the influence of carbon from inoculum, sharpened the positive effect of BC on the kinetics of biomethane production from glucose.

Abstract Biochar application can alleviate the adverse effects of saline-alkali stress on crops. However, the long-term effects of one-off biochar application on soil physicochemical properties, salt concentration, nutrient availability, soil enzyme activities, and rice yield under highly saline-alkali paddy soils remain unclear. Here, a 6-year paddy field study was conducted in a saline-alkali paddy field using two nitrogen application levels (0 and 225 kg ha−1) and four biochar application rates [0 (T0), 1.5% (T1.5), 3.0% (T3.0), and 4.5% (T4.5) biochar, w/w]. The results showed that compared with T0, the bulk density (BD) under T1.5, T3.0, and T4.5 treatments significantly decreased by 11.21%, 16.33%, and 25.57%, while total porosity (Tp) and saturated hydraulic conductivity (Ks) increased by 19.15–27.34% and 3217.78–5539.83%, respectively. Biochar consistently improved soil macro-aggregates, mean weight diameter (MWD), and the percentage of water-stable aggregates (PWSA) over the years. Additionally, one-off application of biochar continuously reduced the soil Na+ concentration, Na+/K+ ratio, Na+/Ca2+ ratio, saturated paste extract (ECe), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SARe). However, it reduced the pH in 2021 and 2022 only. It enhanced the concentration of K+, Ca2+, Mg2+, and cation exchange capacity (CEC) over the 6-year study, indicating its longer-term positive impact. Furthermore, the one-off biochar application, especially under high application rate treatments (T3.0 and T4.5), significantly and continuously improved nutrient availability and soil enzyme activities. However, alkali-hydrolysable nitrogen (AN) decreased in the initial year of biochar application. The grain yield of T1.5, T3.0, and T4.5 surpassed that of T0 by 116.38%, 141.24%, and 145.20%, respectively. Notably, the rice yield reached its peak with the treatment of 3.0% (w/w) in all 6 years of study period. These findings offered new perspectives on repairing and improving soil quality and production ability of highly saline-alkali paddy soils. Graphical Abstract

Abstract This study involved the production of 20 biochar samples derived from secondary medicinal residues of Snow Lotus Oral Liquid, processed within the temperature range of 200–600 °C. Additionally, four medicinal residues, including dissolved organic matter (DOM), from 24 samples obtained using the shaking method, served as the primary source material. The investigation focused on two key factors: the modifier and preparation temperature. These factors were examined to elucidate the spectral characteristics and chemical properties of the pharmaceutical residues, biochar, and DOM. To analyze the alterations in the spectral attributes of biochar and medicinal residues, we employed near-infrared spectroscopy (NIR) in conjunction with Fourier-infrared one-dimensional and two-dimensional correlation spectroscopy. These findings revealed that modifiers enhanced the aromaticity of biochar, and the influence of preparation temperature on biochar was diminished. This observation indicates the stability of the aromatic functional group structure. Comparative analysis indicated that Na2CO3 had a more pronounced structural effect on biochar, which is consistent with its adsorption properties. Furthermore, we utilized the fluorescence indices from UV–visible spectroscopy and excitation-emission-matrix spectra with the PARAFAC model to elucidate the characteristics of the fluorescence components in the DOM released from the samples. The results demonstrated that the DOM released from biochar primarily originated externally. Aromaticity reduction and increased decay will enhance the ability of the biochar to bind pollutants. Those results confirmed the link between the substantial increase in the adsorption performance of the high-temperature modified charcoal in the previous study and the structural changes in the biochar. We investigated the structural changes of biochar and derivative DOM in the presence of two perturbing factors, modifier and preparation temperature. Suitable modifiers were selected. Preparation for the study of adsorption properties of snow lotus medicinal residues.