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Traditional methods of synthesizing nanomaterials via physical or chemical methods are typically expensive and result in toxic byproducts that adversely affect the environment. In this study, we propose synthesis, characterization, optical and sensing properties of hybrid nanocomposites consisting of Fe-1,4-benzene-dicarboxylates (Fe-BDC) as a porous metal-organic framework (MOF) doped with 10 wt. % of Biochar (BC) derived from food waste (Fe-BDC@BC). The bio-based MOF was characterized by using SEM, TGA, FTIR, and XRD. The structural investigation showed that BC improved the porosity, thermal stability, and crystallinity of Fe-BDC, resulting in a particle size of around 50 nm. Optical investigation showed that the energy gap of the bio-doped MOF decreased by about 6%. A sensitive layer of Fe-BDC@BCs was created on an ITO substrate using the spin coating method to study humidity sensing. The dynamic response of the FE-BDC@BC nanocomposite sensor to the change in humidity from 10% to 95% RH. Fe-BDC@BC demonstrated a sensitive response to humidity of about 96% and quick reaction and recovery times of 10 s and 50 s, respectively, Due to their ease of synthesis, and excellent optical and humidity-sensing response, these bio-based MOFs could be used for the fabrication of optoelectronic and sensing devices. [ABSTRACT FROM AUTHOR]

Biomass derived from agricultural waste in Indonesia is abundant and has potential as a source of renewable energy feedstock. However, analysis is needed to determine the appropriate technology to convert potential biomass into consumable energy forms. This review summarises various data on Indonesia's potential biomass that can be used as a renewable energy feedstock. Biomass and biochar characteristics are systematically discussed, including proximate and ultimate analysis. We then summarise various biochar production technologies based on the biomass used and their yields. The characteristics of biochar produced in both proximate and ultimate analysis and the conversion of biochar into slurry fuel as one of the consumable forms of renewable energy were discussed. Slurry fuel is a potential use of biochar as a liquid fuel. The challenges of developing potential biomass-based bio-slurry production in Indonesia and the future work that needs to be done are presented. [ABSTRACT FROM AUTHOR]

In Ghana, firewood and charcoal are converted to heat energy traditionally by devices that are inefficient and unsustainable. The use of these devices have devastating consequences on the climate and human health. This study designed, produced and evaluated a multifeed biomass gasifier stove (MFGS) which relies on multiple types of biomass such as agricultural, industrial and forest waste as feedstock. The prototype of the MFGS was evaluated in the laboratory and the field to establish its level of efficiency and cleanliness. The MFGS recorded a maximum thermal efficiency and minimum CO emission of 35.8% and 0.23 g/min as compared to 30.0% and 2.32 g/min, respectively, recorded by the best Ghanaian traditional biomass stove (Gyapa). The total global warming impact recorded by the MFGS represent up to reduction of 99% of that of Gyapa making it a tool for fighting global warming and reducing the health risk of users of wood fuel in Ghana. [ABSTRACT FROM AUTHOR]

Improving soil management to enhance soil carbon sequestration (SCS)—a cost-efficient carbon dioxide (CO2) removal approach—can result in co-benefits or trade-offs. Here we address this issue by setting up a modeling framework for Switzerland that combines soil carbon (C) storage, food production and agricultural greenhouse gas (GHG) emissions. The link to food production is crucial because crop types and livestock numbers influence soil organic C (SOC) stocks, through soil C inputs from plants and manure. We estimated SCS rates for the years 2020–2050 for three scenarios, each with two variants for biochar: cover cropping (0.30 t CO2 equivalents [CO2-eq] ha−1 yr−1), biochar addition (0.36–1.8 t CO2-eq ha−1 yr−1) and agroforestry-biochar addition (2.2–2.3 t CO2-eq ha−1 yr−1). Different limiting factors (land and biomass availability, population growth) affected SCS rates and indicated that they cannot be sustained until 2100 under all scenarios (cover cropping: 0.10 t CO2-eq ha−1 yr−1 [2051–2100]; biochar addition: 0.35–1.8 t CO2-eq ha−1 yr−1; agroforestry-biochar addition: 1.0–1.7 t CO2-eq ha−1 yr−1). This information together with the associated GHG emissions is critical for planning net zero strategies and highlights the importance of integrated assessments that capture links between SCS and the food system. [ABSTRACT FROM AUTHOR]

Water hyacinth is classified as a high-risk invasive species but is a source of biomass to obtain bio-oil and biochar by pyrolysis reaction. The Kissinger- Akahira-Sunose model (KAS), Ozawa-Flynn Wall (OFW), and Friedman model, determined the pyrolysis activation energy to be 213.19 kJ mol−1, 222.55 kJ mol−1, and 248.09 kJ mol−1, respectively. Bio-oil was obtained with a 2.2% yield, and a maximum calorific value of 21,641 kJ kg−1. The composition was 44% hydrocarbons, 27% aromatic hydrocarbons, 6% alcohols and phenols, 4% acids, and 19% aldehydes, ketones, ethers, nitriles, and others. A 48.84 wt% biochar was also obtained, gaining energy and active carbon. Bio-oil could be a candidate for the production of refined chemical products. [ABSTRACT FROM AUTHOR]

Sorption treatment of wastewater from chromium compounds is a current and actively developing area of research. However, there is a lack of sorbents combining high efficiency and economic affordability with the possibility of application in industrial conditions. In this work, the sorption properties of biochar material "EcoChar," obtained as a result of fast pyrolysis of agricultural poultry waste, were studied in relation to the removal of trivalent chromium ions, and the basic thermodynamic parameters of the process, which is the type of strong chemisorption, were determined. Based on the IR spectra of the sorbent material, the formation of chelate complexes by hydrolyzed chromium ions with the involvement of carboxylic groups and simple ether bonds is suggested. Using the Langmuir model, the values of sorption capacity of sorbent were found as, 68.8 ± 0,2 mg Cr(III)/g and 87.5 ± 0,3 mg Cr(III)/g at 298 and 318 K, respectively. These values, which are much higher than those of their corresponding waste material counterparts, make the use of this biochar as an adsorbent advantageous for the removal of Cr(III) containing compounds from acidic wastewater. [ABSTRACT FROM AUTHOR]

The effect of coconut shell biochar on pH, cation exchange capacity (CEC), sesquioxides and residual total petroleum hydrocarbon (TPH) of a crude oil contaminated soil was investigated. Raw coconut shells were carbonized in a muffle furnace at 400°C for 2 hours and chemically activated in sulphuric acid solution for 18 hours to produce coconut shell activated carbon (CSAC). The CSAC and crude oil-contaminated soil from Kaduna Refining and Petrochemical Company had their physicochemical properties determined. Six sets of CSAC- soil mixtures containing 1%, 1.5%, 2%, 2.5%, 3% and 3.5% CSAC content to undergo remediation for 36 days. The pH, cation exchange capacity (CEC) and total petroleum hydrocarbon (TPH) degradation increase with higher CSAC content while sesquioxides composition slightly decreases with CSAC addition. A significant reduction in TPH from (2045 to 447) mg/kg was achieved with peak TPH degradation of 78.14% at 3.5% CSAC content. Therefore, CSAC significantly enhances the adsorption and degradation of petroleum hydrocarbons in the contaminated soil. [ABSTRACT FROM AUTHOR]

The quest for energy efficiency systems is gaining momentum in the present-day context due to prevailing environmental and eco nomic compulsions. One of the alternatives available to meet this requirement is to modify the fuel to make it greener and more reasonable. In the present study, an attempt has been made to assess the performance and emissions of a compression ignition (CI) engine fuelled with B20 biodiesel and nano additives. Experiments have been carried out on a ssingle-cylinder CI engine using waste cooking oil-derived biodiesel, B20 and nano-sized biochar and multi-walled carbon nano tubes (MWCNTs). The nano additives were used in concentrations of 20 and 40 ppm to form four fuel variants, and the results relating to performance and emissions were compared. B20 fuel with MWCNT nanoparticles showed better brake thermal efficiency (BTE), brake-specific fuel consumption and reduced HC and carbon monoxide emissions. On the contrary, increased exhaust temperature and a subsequent increase in NOx emissions were recorded. The activated biochar nanoparticles improved the BTE of the engine with a comparatively better removal of NOx. This intricate behaviour of both the carbon nanoparticles reported in this work requires comprehensive optimization studies in the future. [ABSTRACT FROM AUTHOR]

A study of biochar/polypropylene composites has been conducted to describe the influence of biochars on the supermolecular structure of PP. The first stage of the work described the influence of carbonization on the properties of carbon fillers (tomato and miscanthus). The biochar was added to the polymer matrix, and the composite samples were manufactured by extrusion and injection molding. The influence of the fillers was investigated using WAXS, hot-stage optical microscopy, PLM microscopy, FTIR and ASTM designation. There were showed the strong influence of the biochar fillers on the properties of polypropylene matrix in composite materials. Obtained composites were characterized by the satisfying properties. [ABSTRACT FROM AUTHOR]

Since cement manufacturing contributes significantly to CO2 pollution worldwide, biochar provides a novel opportunity to integrate it into the construction materials and eventually substitute a portion of cement usage. Consequently, this investigation aims to explore the response surface methodology (RSM) to predict compressive strength and identify optimal values for each parameter that affects the preparation of bio-mortars cement with biochar produced from Washingtonia filifera waste pyrolysis (WFWB). The status of the 7-days and 28-days samples compressive strength, porosity, as well as thermal conductivity of the bio-mortars produced by partially substituting cement at different rates (0%, 1%, 2%, 3%, 4%, and 5%) with pyrolyzed WFWB biochar at varying temperatures (300°C, 400°C, and 500°C) were examined experimentally and statistically. Moreover, the parameter effect on the experimental data performance was identified through analysis of variance (ANOVA). Results indicated an increase in the compressive strength at 28 days of almost 12%, 3%, and 2% at an optimum biochar content of 1% for the WFWB500, WFWB400 and WFWB300 samples respectively. In addition, the findings confer the feasibility of producing bio-mortars with a compressive strength of 63.81 MPa at 28 days with a 1% replacement rate of WFWB500 and coefficient of thermal conductivity of 0.52 W/m.K. [ABSTRACT FROM AUTHOR]

In the current study, new prediction models were suggested to predict the compressive strength, porosity, and thermal conductivity of bio-mortar samples by replacing cement by weight with pyrolysis of Washingtonia filifera waste biochar (WFWB). Bio-mortars containing different biochar contents were prepared with the addition of 1%, 2%, 3%, 4%, and 5% pyrolyzed biochar at different temperatures 300°C, 400°C, and 500°C. The mortar samples produced were evaluated for compressive strength at 7 and 28 days. Relation between compressive strength porosity and thermal conductivity values (dependent values), and biochar replacement ratios and pyrolysis temperatures (independent values) was predicted by artificial neural network (ANN) machine learning techniques based on the Levenberg Marquardt algorithm. The results revealed compressive strength increase at 28 days of nearly 12%, 3%, and 2% at 1% optimal biochar replacement content for WFWB500, WFWB400, and WFWB300 specimens, respectively. Moreover, these results provide confidence in the manufacturability of bio-mortars with a compressive strength of 63.81 MPa at 28 days using only 1% substitution of WFWB500 and a thermal conductivity coefficient of 0.52 W/m.K. The importance measure of the variables shows that the most influential variables are the percentage of biochar. The statistical and experimental results also revealed satisfactory agreement. [ABSTRACT FROM AUTHOR]

Biochar (BC) is a soil fertility enhancer, regarded as a potential carbon sequester and nutrient leaching preventer. Various studies have shown better phosphorus (P) availability with adding biochar. However, limited reporting is available on absorption–desorption behaviour of added P and dose optimisation of biochar. Rice straw biochar (RSB) and acacia biochar (ACB), prepared by slow pyrolysis at optimised temperature and pyrolysis time, were incubated at different rates (0, 5, and 10 g kg−1) in loamy sand and clay loam soils to study P sorption compared to the unamended control. The data was observed to be best fitted into Langmuir adsorption isotherm for P adsorption. The effects on maximum P adsorption, bonding energy, and adsorption rate constants were lower in loamy sand compared to clay loam soil. The values of maximum P desorption (Dm) and desorption rate constant (Kd) decreased with the application of biochar. A linear regression equation optimised the amount of P addition for soil amendments. For the soil with inherent P content, rice biochar was the best option (5 g kg−1), while for soils lacking in P, ACB is optimised at 5 g kg−1 with external P input of 1 mg P kg−1 of test soil. This data can be recommended to the farmers as a best practice for the P addition, along with managing farm wastes as biochars to enhance nutrient availability. [ABSTRACT FROM AUTHOR]

Intensive potato production may reduce the soil organic matter content (SOM), which may impact several soil functions and increase the incidence of potato diseases. We examined if cover crop and addition of organic materials may counteract these effects. Organic materials were one application of biochar mixed with liquid digestate (BLD); solid digestate (SD); or farmyard manure (FYM); with or without winter rye as cover crop, in a field with regular potato growing. Organic amendment increased SOM, especially for FYM and BLD, while cover crop did not affect SOM. Yet, cover crop increased tuber yields in the second year, and reduced the severity of potato diseases by 10% in post-harvest potatoes in both years. In the second year, the number of marketable potatoes after storage increased by 37% with cover crop. Organic amendments did not affect potato yield or quality, but the proportion of marketable potatoes tended to be higher in the amended soil. By lab incubation, BLD showed the largest potential for SOM storage, up to 32 years, followed by FYM and SD. Cover crops and organic amendments is recommended in potato production, especially for early potatoes where there is sufficient time after harvest to establish a good cover crop. [ABSTRACT FROM AUTHOR]

Heavy metals from dental wastewater raised serious environmental health concerns. To address this, an environmental waste-based biochar by eggshell and fly ash was synthesized and characterized. The adsorption characteristics of lead and chromium by biochar were explored and a novel alternative stepwise adsorption process was proposed to improve the removal efficiency. Results indicated that the specific surface area was determined to be 537.6 m2/g. The maximum adsorption capacity for lead and chromium were 149.3 mg/g and 119.0 mg/g, respectively. A theoretical calculation model was developed to predict the concentration of the effluent, followed by experimental validation. The findings indicated that the concentrations of lead and chromium in the effluent remained stable, while the average removal efficiency of lead and chromium increased by 5.56% and 7.02%, respectively, compared to the conventional adsorption method. The calculated values aligned well with the experimental results, demonstrating the success of this innovative adsorption process. [ABSTRACT FROM AUTHOR]

A novel strategy for reclamation and reuse of phosphate from aqueous solution was developed using Mg-enriched biochar prepared from anaerobically digested sludge (ADBC). The ADBC pyrolyzed at 600°C (ADBC-600) exhibited the maximum phosphate removal capacity of 23.2 mg/g, which was much higher than that of raw sludge biocha (10.1 mg/g). Adsorption kinetic and isotherm experiments showed that the adsorption of phosphate on ADBC-600 could be well described by the pseudo-second-order model and Langmuir model, indicating that the adsorption was mainly dominated by chemisorption process. The postsorption characterization results suggested that Mg-induced precipitation was likely the main P adsorption mechanism by ADBC. Moreover, the spent biochar was re-utilized as an efficient phosphate fertilizer for improving wheat seed germination and growth. Provided a sustainable and eco-friendly strategy for sludge treatment and phosphate recovery in wastewater treatment plants (WWTPs) and potential agronomic application. [ABSTRACT FROM AUTHOR]

Meadow soils are one of the important agricultural soil types, biochar is a good soil amendment, whereas the studies on the effects of biochar additions on carbon and nitrogen contents, as well as bacterial communities of meadow soils, were seldom carried out. The effects of one nitrogen addition rates (no addition, 0.2% addition) and two biochar addition patterns (no addition, 1% addition, 3% addition) on the carbon and nitrogen contents, as well as bacterial communities of meadow soils, were investigated by conducting a one-year indoor incubation experiment. Biochar addition increased the relative abundance of Proteobacteria, Chloroflexi and Bacteroidota. The combination of biochar and nitrogen source significantly increased the total organic carbon, ammonium nitrogen, nitrate nitrogen and total nitrogen content of the meadow soil. Therefore, the addition of moderate amounts of biochar to meadow soils can contribute to sustainable ecological agriculture as a form of soil improvement. [ABSTRACT FROM AUTHOR]

Discrimination of the catalytic ability of heterogeneous biochar components is often challenging. Herein, a sewage sludge-derived biochar (SDBC) was prepared to activate peroxydisulfate (PDS) for tetracycline (TC) degradation. To verify the contribution of different carbon components, SDBC was bleached with NaClO2 and CH3COOH to remove noncondensed aromatic carbon (NAC) contained in biochar, which was confirmed by 13C Nuclear Magnetic Resonance. The batch degradation experiment revealed that NAC removal decreased TC degradation by SDBC from 84.1% to 33.2% within 2 h, indicating its significant role in PDS activation. The quenching and electron paramagnetic resonance experiments suggested a very minor contribution of radical pathway in TC degradation. Instead, the electron transfer pathway predominated TC degradation mechanism as inferred by electrochemical tests. This is likely ascribed to formation of a biochar-PDS metastable complex, facilitating electron transfer from tetracycline-like compounds. An X-ray photoelectron spectroscopy confirmed that the percent of graphitic N in SDBC decreased after the degradation reaction, which suggested graphitic N is an important active site in biochar. Besides, acid-washed SDBC did not change TC degradation behavior excluding significant contribution of minerals in SDBC to PDS activation. Thus, the roles of biochar components in catalyzing PDS were quantified for the first time, proving insight for selection and manipulation of biochar in catalyzing PDS in environmental application. [ABSTRACT FROM AUTHOR]

The annual cumin and perennial fennel are economically important medicinal crops of cold dry regions of Pakistan. We hypothesized that the cumin, which produces 2-3 times less biomass, will respond to lower rates of mixture of biochar with synthetic NPK fertilizer or manure, compared to fennel. The NPK, poultry manure and their mixture with wood-derived or cow manure-derived biochars were applied for three consecutive years. No positive relation between application rate of biochar-mixed fertilizers and yield of both crops was observed over three years of study, except that manure-derived biochar-NPK mixture had a positive relation (R² = 0.99, P = 0.01) with the yield of fennel only during the third year. Significant positive influences of biochar-based fertilizers compared to control were observed for cumin and fennel of third year cropping. The co-amendment of NPK (0.14 kg ha-1) with manurederived biochar (6.6 t ha-1) consistently increased the yield of cumin during the first two years of cropping, as opposed to NPK fertilizer. Cumin had a greater seed:stover biomass ratio when it received the co-amendment of wood-derived biochar with NPK or poultry manure. Our findings indicate that there is some potential for biochar-fertilizer amendments to improve the growth of these high-value medicinal crops. [ABSTRACT FROM AUTHOR]

Biosolid-borne heavy metals are the main concern in soils. Therefore, the effects of biosolid biochar application in soils were evaluated in our study through a rice-wheat rotation in fields. The results showed that after the application of biosolid biochar, soil organic matter (SOM), soil pH, and soil total heavy metal concentrations (Cd, Zn, Cu, and Pb) were significantly increased. But the CaCl2 extracted metals concentrations were decreased, and no significant differences in metal concentrations of soil deeper layers (20-100 cm) were found among different treatments. The Cd, Zn, Cu, and Pb concentrations in rice decreased by 13.2%, 37.0%, 9.92%, and 63.0%, respectively, and the concentrations of Cd, Zn, Cu, and Pb in wheat decreased by 20.85%, 19.7%, 48.6%, and 23.6%, respectively, compared with the control treatment. Biosolid biochar can decrease metal availability in soils and increase crop production in fields, thus is suggested to use in fields. [ABSTRACT FROM AUTHOR]

Lead (Pb) is a biologically non-essential element in the soil that brutally affects plants and other living organisms in soil; hence, its removal has become a worldwide concern. In this work, a multifunctional nanoscale zerovalent-iron assisted biochar (nFe°/BC) was used to minimize the Pb bioavailability in soil with aim of alleviating the Pb-induced toxicity in sunflower. Results revealed that nFe°/BC treatment had significantly improved plant growth (58%), chlorophyll contents (66%), intracellular permeability (60%), and ratio factor (93%), while decreasing the Pb uptake (78%) in plants. The Pb-immobilization and transformation mechanisms were proposed, suggesting that the presence of organic functional groups over the nFe°/BC surface might induce the complex formation with Pb by the ions exchange process in soil solution. The XPS analysis confirmed that surface-active components (Fe+, O2−, O*, C═O) were the key factor for high Pb-immobilization within soil matrix. In addition, 87% of stable Pb species, including PbCO3, PbO, Pb (OH)2, and Pb-O-Fe were found in the soil surface. Current findings have exposed the diverse functions of nFe°/BC on plant health and established a phenomenon that nFe°/BC application could improve the plant agronomic attributes by regulating the homeostasis of antioxidants and Pb uptake. [ABSTRACT FROM AUTHOR]

As the first version of synthetic hydrogel, poly(2-hydroxyethyl methacrylate) hydrogels have found broad applications. However, their poor mechanical performances have been long-standing hurdles for practical deployments. Herein, we report on strengthening the poly(2-hydroxyethyl methacrylate) hydrogels with biochar nanoparticles and hydrophobic aggregations, which are induced by solvent exchange and reinforced by freeze-thaw. Both the vast anchoring points on the multifunctional surfaces of the biochar nanoparticles and the aggregates formed between poly(2-hydroxyethyl methacrylate) chains engender strong and dissipative physical crosslinks. The resulting hydrogels exhibit marked mechanical properties, encompassing high stretchability ~7, high fracture toughness ~1360 J m−2, high elastic modulus ~180 kPa, low friction coefficient ~0.2, self-recovery, and non-swellability. Furthermore, we demonstrate the versatility of the proposed strategy by using water/ionic liquid binary solvent as the solvent system, Laponite as the nano-reinforcement, and dry-anneal as the hydrophobic aggregation enhancer to synthesize mechanically robust hydrogels. Poly(2-hydroxyethyl methacrylate) hydrogels of superior mechanical properties are expected to enable previously inaccessible applications in biomedicine and engineering. [ABSTRACT FROM AUTHOR]

Straw had huge annual production, burning it in the air will cause serious air pollution. Burning straw into biochar and returning biochar to the field will not only make effective use of straw resources, but also improve soil quality. Different preparation conditions and addition levels of biochar were used to investigate the ammonia nitrogen, nitrate nitrogen, and total nitrogen contents in the soil leaching solution. The results showed that biochar had a favorable adsorption effect on ammonia nitrogen, the cumulative leaching of ammonia nitrogen reduced by 80.16% in the 2% and 400°C biochar addition treatment compared to that without adding biochar. The final leaching solution electrical conductivity value of the experimental group of biochar prepared at 500°C with 1% addition was the highest at 445 μS/cm. Sequencing of microorganisms revealed that biochar altered the structure and abundance of the soil microbial community, particularly increased the relative abundance of nitrifying bacteria. [ABSTRACT FROM AUTHOR]

The physicochemical properties and heavy metals adsorption capacities of biochars derived from cattle manure (CM) and cherry wood (CW) were systematically investigated and compared. The results showed that the yields, pH and the ash content of cattle manure biochars (CMB) were higher due to high levels of mineral constituents in CM. CMB6 and CWB6 showed higher aromaticity and polarity, whereas CMB4 and CWB4 carried higher oxygen-containing functional groups. CMB6 exhibited the maximum adsorption capacities for Pb2+ (40.8 mg·g−1), Cd2+ (24.2 mg·g−1), and Ni2+ (25.1 mg·g−1), with relatively higher adsorption capacities for Pb2+. The adsorption isotherms fitted Langmuir model, indicating that the heavy metal adsorptionoccurred via a combination of physical and chemical adsorption mechanisms. The quantitative analysis showed that the interaction with minerals was the dominant mechanism, especially accounting for about 70% in CMB6. This study provides important information for comprehensive recycling utilization of biomass for sustainable development. [ABSTRACT FROM AUTHOR]

The application of magnetic biochar (MBC) has attracted significant attention due to its recyclability and adsorption capacity for Hg from aqueous solutions. However, its applicability is still inadequate, relying on poor selectivity. Some chemical substances could improve the sorption capacity of MBC. This review offers an advanced technological route to modify-MBC composition with significant adsorption volume toward Hg. Non-polluting humic acid-sodium salts (Ha-Na) were proposed to optimize Fe3O4-modified biochar (FBC), while the pyrolyzed substrate for the initial biochar (BC) production originated from any agricultural biomass material. The non-polluting Ha-Na can improve the FBC-specific surface area, the number and structure of pores, moderate the pH and adsorb Hg(II) from aqueous solutions. Further, the interaction of three simple projected equation mechanisms is proposed for BC, FBC, and Ha-Na. BC modified with the support of Fe3O4 and optimized by Ha-Na can be applied to improve Hg(II) adsorption, while insights and future investigations are suggested. [ABSTRACT FROM AUTHOR]

Although biochar has been investigated extensively to stabilize soil heavy metals, there were limited investigation on the stabilization of soil heavy metals by using biochar under the natural ageing processes of alternate-cooling/heating. In this study, wheat-straw-biochar-treated soil samples contaminated with Pb(II) ions/PbO were subjected to 12 h-freeze/12 h-thaw cycles simulating the natural alternate-cooling/heating process. After the freeze-thaw process, the mobile fractions of leadreduced by 30.0% (500 mg·kg−1 Pb(II) spiked soil) and 19.5% (PbO spiked soil) due to biochar's addition evaluating via 0.01 M HCl batch extraction. Compared with the control, the mobile Pb in treated groups decreased in column leaching. Exchangeable lead decreased by 6.4% – 80.9% due to biochar addition. Freeze-thaw ageing had no significant effects on lower lead leaching and lower exchangeable lead resulted from biochar's addition. Therefore, wheat-straw-biochar treatment is helpful for stabilization of both dissolved Pb and particulate Pb in soil under the alternate-cooling/heating ageing process. [ABSTRACT FROM AUTHOR]

Biochar is a porous carbonaceous material containing abundant redox functional groups and inorganic minerals, making it a potential electrode material. Nine electrodes were prepared with biochar produced from three different feedstocks at three pyrolysis temperatures, and their oxygen reduction reaction (ORR) activity and electrochemical impedance spectroscopy (EIS) were investigated. The results showed that all biochar electrodes had certain electrocatalytic activity as their current density ranged from 0.26 to 2.17 mA cm−2, half-wave potential at 0.24–0.41 V, electron transfer number at 2.1–3.9, Rct at 9.2–61.2 Ω, and Cdl at 1.1 × 10−6 – 2.2 × 10−4 F. For most biochar electrodes, the current density and half-wave potential increased as the pyrolysis temperature increased from 500°C to 700°C, which was closely related to the increase in aromatization degree (H/C) of biochar. Dairy manure biochar showed much lower current density and half-wave potential than sewage sludge biochar and wood chip biochar, probably due to its relatively smaller surface area. This study indicated that biochars could be converted to carbon electrodes, and both feedstock and pyrolysis temperature could influence the ORR activity of biochar electrodes. [ABSTRACT FROM AUTHOR]

Biochar is a promising material for environmental amendment. However, the adsorption mechanism of nitrogen-based ionic species, particularly the pH dependence, is still under debate because of its high susceptibility to experimental conditions. In this study, the adsorption of ammonium sulfate by rice-husk biochar produced by low-temperature carbonation as an eco-friendly approach was studied using Fourier-transform infrared (FT-IR) spectroscopy, 13C magic-angle spinning (MAS) nuclear magnetic resonance (NMR), and open-space analysis using positrons coupled with molecular simulations. In the aqueous solution with pH of 5.38, graphenes are isolated exposing fresh surfaces, which physisorb N H 4 + via interaction with π electrons rather than surface functional groups. Furthermore, the low-temperature carbonation leads to a lower degree of graphitization with grain boundary defects in graphene, triggering the fracture of graphene during the shaking process in an aqueous solution. S O 4 2 − physisorption occurs as an outer-sphere surface complex on the positive charge caused by a charge transfer of ∼2.5% from the terminal hydrogen at the graphene edge. A decrease in aqueous pH by ∼0.7% significantly changes the above adsorption properties both on the surfaces and at the edges: diminishment of physisorption and transition to chemisorption by the formation of an inner-sphere surface complex. [ABSTRACT FROM AUTHOR]

Adding biochar to soil can alter soil properties and thus affect plant growth; however, the effect of biochar on biological nitrogen fixation, carbon accumulation and water-use efficiency of chickpea in tropical soils is not fully understood. Therefore, this study assessed the efficacy of biochar derived from poultry litter (denoted as PLB) and acacia (denoted as ACB) feedstocks on biological nitrogen fixation, carbon accumulation and water-use efficiency (δ13C) of chickpea grown in three contrasting soils of Fernwood (Arenosol) and Griffin (Helvic Acrisol) and Pinedene (Gleyic Acrisol). The biochars were applied at the rate of 0.5%, 1% and 2% (w/w) with control (0%) and replicated four times. Chickpeas grown in PLB treatments in Griffin and Pinedene soils investigated accumulated more N and C, for greater biomass production, resulting in an average total N-fixed of 77 and 52 mg N/plant, respectively. Nitrogen fixation and carbon accumulation of chickpea increased by the addition of 0.5% PLB and ACB in the Fernwood soil. The findings of this study demonstrate the potential of improving N inputs through biological nitrogen fixation with poultry litter biochar application in soils with varying nutrient status and texture, which is important in arid environments with limited N inputs. [ABSTRACT FROM AUTHOR]

Organic pollution of agricultural land will cause environmental problems and agricultural economic effects. To explore the reliable effect of remediation of organic pollution in agricultural land, wheat straw biochar was prepared in this paper. Moreover, this paper uses experimental research and comparison methods to study the difference in the adsorption performance of biochar at different pyrolysis temperatures on polycyclic aromatic hydrocarbons (PAHs) and the effect of pyrolysis biochar on the availability of phenanthrene and pyrene microorganisms in the soil at the same temperature. Additionally, statistical methods are utilised in this research to do analytics and data processing on test data, and test findings are visually displayed using a combination of graphs and tables. Finally, to understand the experimental research findings, this system employs analytical approaches. The results of the experiment show that wheat straw biochar can effectively reduce soil organic pollution, which can expand the research on the restoration of other crop straw biochar on agricultural land. [ABSTRACT FROM AUTHOR]

Lettuce (Lactuca sativa L.) efficient use of nitrogen (NUE) determines its growth and yield. We assessed the interaction effect of N fertilizer and biochar of different particle sizes and rates on NUE, growth and yield of lettuce. A factorial design arranged in Randomized Complete Block Design with four replications was used to conduct a field experiment at the FRNR farm, Kwame Nkrumah University of Science and Technology, Ghana. The treatment consisted of biochar at 8.33 t and 16.67 t ha-1 with different particle sizes (<2, 5 and 10 mm) and five rates (0, 31.3, 62.5, 93.83 and 125 kg ha-1) of inorganic N fertilizer. Our result showed that integrating 8.33 t ha-1 of <2mm and 5mm biochar with 62.5 and 93.8 kgN ha-1, respectively improved lettuce growth, NUE by 30% and yield. The yield (19.3 t ha-1) obtained with these applications is comparable to the achievable yield (20 t ha-1) of lettuce under the sole N recommended rate (125 kgN ha-1). In conclusion, with 8.33 t ha-1 of <2mmbiochar, farmers can reduce the recommended inorganic N rate of lettuce by half (62.5 kg ha-1) and still attain good yield with improved post-harvest soil fertility. This has implications for farmers' production costs, agriculture waste management and climate change mitigation strategies. [ABSTRACT FROM AUTHOR]

In this study, a 30-days laboratory experiment was implemented to investigate the impact of additive biochar on the stabilization of heavy metals in chicken manure compost. Results showed that after the addition of rice straw-derived biochar, heavy metals were more stabilized except Cu, of which the residual fractions distinctly decreased due to the interaction with organic functional groups from biochar. Given the bioavailability of heavy metals, the biochar addition at a 10% proportion decreased the concentration of CaCl2-extractable Cr, Zn, Ni, and Cd. Besides, CaCl2-extractable As did not differ significantly between treatments with and without biochar addition. Furthermore, the CaCl2-extractable Cu was higher than the control, in agreement with the observed changes in speciation. Environment pollution assessment by integrating potential ecological risk assessment explicated the chicken manure compost reached avery high-risk pollution level, and decreased with biochar addition. Therein, Cd was the dominant pollutant with very high potential risk. [ABSTRACT FROM AUTHOR]

There is a need to prepare a high-efficient sorbent to remove the recalcitrant tetracycline (TC) in wastewater. Herein, biochar-supported zerovalent iron (BC/ZVI) was fabricated in nitrogen ambience via one-step co-pyrolysis of hematite and pinewood. X-ray diffractometer pattern indicated pinewood catalyzed conversion of hematite to ZVI, which was otherwise transformed to FeO, Fe3O4 and ZVI without biomass. Batch sorption results indicated that TC removal capacities at pH 5 were 8.02, 177.70 and 301.39 mg g−1 by BC, ZVI and BC/ZVI, respectively. Overall, BC/ZVI showed excellent TC removal capacity through the complexation with Fe ions, surface adsorption and degradation. Thus, the agricultural and industrial wastes were converted via a one-step co-pyrolysis to a value-added product for highly efficient removal of TC in wastewater. [ABSTRACT FROM AUTHOR]

Biochar has received continuous attention in recent years due to its high specific surface area, rich micropores, and many types of functional groups. In this study, the migration behavior of modified micro-nano biochar (MMNBC) in heterogeneous media under the influence of ionic strength and flow rate was studied by column experiments. The results showed that the mobility of MMNBC could be increased by increasing the flow rate and decreasing IS. The retention of MMNBC in quartz sand coated with clay minerals was higher than that of pure quartz sand, and the difference existed due to the surface properties. The main reason is that the clay mineral coating adds cations on the surface of quartz sand, which generates electrostatic interaction with MMNBC, which promote the adsorption of MMNBC on the medium. This study provides a theoretical basis for effectively controlling the groundwater environment problems caused by the migration of biochar. [ABSTRACT FROM AUTHOR]

The coprecipitation method was used to produce magnetic cotton straw biochar (MCS). Elemental analysis, FTIR, XRD, SEM, BET and magnetization curves were used to characterize MCS and CS. The results show that the MCS had excellent magnetic separation properties. When the pH value was higher than 5, the pH of the aniline solution had little effect on the adsorption capacity of MCS and CS. However, with increasing temperature, the adsorption capacity increased significantly. The maximum adsorption capacities of MCS and CS for aniline were 38.67 mg/g and 42.57 mg/g, respectively. The adsorption process of aniline was spontaneous, endothermic, and involved monolayer sorption and chemical adsorption. The adsorption capacity was due to the presence in magnetic biochar of phenolic hydroxyls and H-bond donors that adsorbed aniline. Therefore, the application of MCS presents good prospects for the removal of toxic and refractory aniline from water. [ABSTRACT FROM AUTHOR]

To explore the feasibility of biochar for reducing mobility and bioavailability of heavy metals in different contaminated soils, batch incubation experiments including column leaching and pot experiments were conducted to investigate the effects of biochar input on soil pH, the bioavailability of heavy metals (Cd, Zn, and Pb) and their species in three different contaminated soils treated with different swine biochar application rates. The results show that biochar has more potential for pH improvement in acidic soils than neutral and alkaline soil. After 42 d incubation, the pH values of the acidic soils increased from 5.90 to 7.23, while the pH values of neutral/alkaline soils did not change significantly. The available heavy metals showed a decreasing trend as the biochar application rate increases. The order of the immobilization effect is Pb>Zn>Cd. Possible immobilization mechanisms are mainly ion exchange, complexation, π bond action and precipitation on the surface of biochar. [ABSTRACT FROM AUTHOR]

Biochar is a product rich in carbon, which improve the soil attributes and crop yield. In the Brazilian tropical dry region, common bean is cultivated under rainfed, in poor, acidic, and with low water retention soils. This work aims to evaluate the effect of biochar on soil physical and chemical attributes, on evapotranspiration (ET), water use efficiency (WUE), and on bean yield. The field experiment was conducted over four biochar rates (B0: no biochar; B10: biochar at 10 t ha−1; B20: 20 t ha−1 and B40: 40 t ha−1), and three replications. Our analysis revealed that different rates of biochar do not affect the soil physical attributes due to a mismatch between soil texture and the particle size of biochar. Treatments with biochar promoted an increase in soil pH, P content, cation exchange capacity, reduced the Al+H content, which caused an increase in bean yield and consequently WUE. Our findings expand our knowledge about the effect of the biochar applied to the Acrisols on decreasing the soil acidity and to increase the yield and WUE, and add important information that can be suitable for development of strategy to mitigate problems caused by instability of rains and poor fertility soils. [ABSTRACT FROM AUTHOR]

Biochar, a carbon-rich material resulting from pyrolysation, is one of the proposed alternatives as a substrate component to peat. The aim of this study was to investigate the effect of different ratios of peat substitution with a locally available hardwood biochar on the chemical characteristics of growing media, seed germination, plant morphological and nutritional parameters of Tagetes patula. Experimental results show that biochar can be used as a partial peat replacement, showing a complementary liming effect, rising the initial pH of peat (2.8) to values of 4.5 and 7.3 in mixtures with 50% and 75% substitution of peat by biochar, respectively. The mixture with a 50% biochar rate exhibited the strongest change between initial and final pH, rising from 4.5 to 5.7. Increasing content of biochar in the mixtures corresponded to increasing content of total K, Ca, Mg, available K and decreasing level of available Mg. The highest germination percentage was observed in the mixtures with biochar rates from 50% to 100%. Among all substrates, the greatest plant diameter, true leaf area and total root length were measured in the 50% peat substitution mixture, where the highest contents of P, K and Ca in plant shoots were found. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of nitrogen (N) application combined with cotton stalk or its biochar on soil organic carbon (SOC) fractions and enzyme activity. The field experiment was conducted over three cropping seasons with three organic C treatments and three N application rates. Three organic C treatments were set as no organic C amended (CK), cotton stalk (ST), cotton stalk biochar (BC). Three N applied at rates of 0, 300, and 450 kg N ha−1 (N0, N300, and N450, respectively). Results showed that N fertilisation alone reduced dissolved organic C (DOC) and N450 reduced easily oxidisable organic C (EOC) in 2015–2016. Microbial biomass C (MBC) basal soil respiration (BSR), β-glucosidase activity (BG), and N-acetyl-glucosaminidase activity (NAG) activity in N450 were greater than in N0. On average, SOC was 13.4% −36.6% greater in ST and 23.7–59.2% greater in BC than that in CK. ST and BC increased soil organic C fractions, MBC and non-labile organic C (non-LOC) were greater in BC than in ST. BC decreased soil DOC/TOC, EOC/TOC ratios, increased soil non-LOC/TOC ratio and cotton yield, ST increased the ratios of labile C and enzymes activity in soil. Therefore, integrating 300 kg ha−1 N fertilisation with biochar is an optimising management strategy to promote C sequestration and sustain the crop productivity in a drip-irrigated cotton field. [ABSTRACT FROM AUTHOR]

Low molecular weight organic acids (LMWOAs) are common and abundant compounds in the environment, responsible for the release of the nutrients from rhizosphere into the soil solution and, therefore, facilitating the availability of these nutrients for plants. Sewage sludge biochar (SSB) is considered to be a potential source of phosphorus (P) in soil. In this context, the efficacy of twelve LMWOAs in releasing SSB-bearing P was tested in a laboratory extraction experiment. Moreover, the potential effects of (i) biochar pyrolysis temperature (varying from 220°C to 620°C) and (ii) other elements in SS, to estimate the P bonds attacked predominantly by the LMWOAs, were also assessed. The results revealed citric acid was the most effective extraction agent enhancing the mobility of the SSB-derived P. P release was strongly affected by biochar pyrolysis temperature (the highest P release was from the 320°C biochar, significant at p < 0.05). Moreover, the results showed that P was released preferably from Fe-P bearing compounds in SS. Citric acid was recorded as less effective at releasing other nutrients, such as Ca, Mg, K, indicating the exceptional performance of citric acid in P release from biochar without substantial effect on the other nutrients. [ABSTRACT FROM AUTHOR]

Production of biochar is accomplished by pyrolysis of corncobs at 350 °C (BC-350) and 450 °C (BC-450) under oxygen-limited conditions. The chemical and physical properties were investigated via XRD, FTIR, BET, SEM and EDX analysis. Batch experiments were conducted for the adsorption of Pb2+ ions from aqueous solution onto biochar with regards to pH, contact time, biochar dose and initial Pb2+ concentration. The adsorption efficiency of Pb2+ was increased as increasing pH and biochar dose up to 1.5 g/L. Kinetic and isothermal studies demonstrated that the experimental data were fitted with the pseudo-second-order model, Langmuir and Freundlich isotherms. The study emphasized the preferable pyrolysis temperature which is 450 °C. According to the Dubinin-Kaganer-Radushkevich (DKR) model, the adsorption process of Pb2+ was a chemical and endothermic reaction. Results showed the applicability of corncob based biochar to be used as an efficient and low cost adsorbent for Pb2+ ions removal. [ABSTRACT FROM AUTHOR]

The focus was to assess the effects of biochar on Cd uptake by various vegetables and its downward movement in saline-alkali soil and carried out in polluted pots experiment. The results showed that the biomass of vegetables increased significantly by 16.9% to 519.9% while the Cd concentration in green pepper and eggplant fruits was decreased by 6.8% to 11.5% and 15.1% to 15.4% with the biochar application. The Cd in contaminated soil profile was transferred from topsoil (0-6 cm) to subsoil (6-12 cm) that was observed as 14.30 ± 4.17 mg kg-1. The concentrations of Cd in soil with different fractions like exchangeable, reducible and oxidizable and the Cd uptake by vegetables were reduced. The release of residual Cd was decreased by 0.3 to 20.1% over time with biochar application (0-12 cm). The biochar was effective in mitigating the soil Cd pollution by preventing the vertical Cd leaching. [ABSTRACT FROM AUTHOR]

The effects of straw input, including three strategies: chopped straw, straw-derived compost and biochar, on bacterial communities and chemical composition in maize rhizosphere were investigated according to a three-year field experiment. Illumina MiSeq sequencing showed that biochar input increased bacterial richness but decreased bacterial diversity in rhizosphere when compared with the results from no straw control. The functional prediction of Kyoto Encyclopedia of Genes and Genome pathways confirmed that soil subjected to straw input changed the abundance of microbiomes involved in carbohydrate metabolism significantly. Metabolomics analysis showed that straw input changed the metabolite profile of the rhizosphere soil of maize, which was most evident in the treatment of chopped-straw input. The match between the global metabolic profiles and bacterial distribution patterns was weak by performing Procrustes analysis (m2 = 0.851, R = 0.386, P < 0.05). However, the associations between the special members of genera, predicted function involved in carbohydrate metabolism, and rhizosphere metabolites, including sugars and organic acid, were significant (P < 0.05). [ABSTRACT FROM AUTHOR]

Although biochar has potential benefits in environmental and agronomic aspects, short-term application of biochar to rice does not increase grain yield. The objective of this study was to identify the crop growth characteristics responsible for why applying biochar over the short-term does not increase grain yield in rice, thus providing information for how to increase grain yield in rice following short-term application of biochar. Field experiments were conducted to investigate the effects of biochar application (20 t ha–1) on yield attributes and crop growth characteristics in rice grown under two N rates in two years. Results showed that biochar application had no significant effects on grain yield or yield components. Biochar application increased radiation use efficiency and biomass production during post-heading and total biomass production by 7–16%. Pre-heading biomass translocation and harvest index were decreased by 4–11% with biochar application. These results indicate that the lack of increased yield in rice following short-term application of biochar is attributable to compensation between increased biomass production resulting from improved post-heading crop growth and decreased harvest index resulting from reduced pre-heading biomass translocation. The finding of this study suggests that establishing a compatible relationship between post-heading crop growth and pre-heading biomass translocation is critical for increasing grain yield in rice following application of biochar over the short-term. [ABSTRACT FROM AUTHOR]

We have investigated the effectiveness of a new soybean fertilization technique, named crack fertilization, which involves the application of nodule bacteria on biochar to soybean roots through cracks formed between planting rows during midterm tillage. In the present study, the factors and timing of crack fertilization were investigated in an upland field converted from a paddy. The variables investigated were: 1) crack formation without the application of any agricultural materials, and 2) the application of biochar or 3) nodule bacteria on biochar into cracks. The treatment periods were: 1) before sowing, 2) during midterm tillage, and 3) during both periods. The combination of crack fertilization and reduced tillage was also tested. The method of crack fertilization that increased yield was the combination of crack formation and the application of biochar, and the most effective period for the treatment was before sowing in the reduced tillage field. Seed yields in conventional and reduced tillage fields were comparable in the upland field converted from the paddy. These results suggest that the application of biochar into cracks after scratching the soil surface to remove weeds before sowing is a practical method of increasing soybean yield in upland fields converted from paddies. [ABSTRACT FROM AUTHOR]

To determine the sorption potential and mechanisms of tetracycline (TC) on pristine and H2O2-modified biochars, rape stalk biochars were produced and modified by H2O2. The specific surface area and pore volume of biochars increased with improving pyrolysis temperature, while the acidic groups decreased. Moreover, modified by H2O2, much more oxygen-containing functional groups were introduced. The results of sorption dynamics and isothermals tests showed that RB300 had the largest TC sorption capacity of 35.90 mg/g, which was ascribed to a plenty of non-carbonized organic matter and surface functional groups were retained. Modified by H2O2, the sorption of TC on biochars was enhanced which indicated the dominated sorption mechanisms were H-bonding and π–π electron donor acceptor interaction. The pH value would impact on sorption, and the maximum sorption capacity was obtained at pH = 9.0. Both cation concentration and type would affect the TC sorption. [ABSTRACT FROM AUTHOR]

The Cd(II) adsorption of kiwi biochar functionalized with Mg-Fe (3:1) layered double hydroxides (LDH) was studied. And the biochar was got via liquid-phase deposition, by incorporating Mg-Fe layered double hydroxide (Mg-Fe LDH) particles into kiwi biochar (KB/LDH). The batch of sorption experiments were studied, including adsorption kinetics and isotherm and the effects of pH, ion strength (IS) and co-existing ions. The KB/LDH composite showed a strong sorption ability to Cd(II) in aqueous solutions with the adsorption capacity of 25.6 mg g−1, compared with pristine biochar of 1.78 mg g−1. The adsorption of Cd(II) on KB/LDH composite increased with the decreasing of IS, decreased first and then grew larger with the increase of pH and was observed irrespective of the co-existence of K+, Cl− and NO3−. To sum up, the KB/LDH can be potentially used as an alternative adsorbent to amend the water and soil contaminated by Cd(II). [ABSTRACT FROM AUTHOR]

The effect of oxalic acid on phenanthrene sorption was varied from that on pyrene sorption. 1.0 mg L-1 of oxalic acid inhibited phenanthrene sorption, whereas 20, 50 and 100 mg L-1 of oxalic acid enhanced the sorption. However, pyrene sorption onto biochar was all inhibited among different concentrations of oxalic acid. New functional groups and increased polarity were observed in the biochar coexisted with oxalic acid, moreover, a high concentration of oxalic acid led to an increased specific surface area of the biochar. These changed factors contributed to biochar sorption to phenanthrene, which was dominated by surface adsorption. Weakened aromaticity and increased release of dissolved organic carbon from biochar may have been the main reason for inhibited pyrene sorption onto biochar by oxalic acid. Therefore, this study suggested that root exudates could greatly influence the sorption behavior of biochar towards PAHs in soil rhizosphere, which deserves attention in agricultural systems. [ABSTRACT FROM AUTHOR]

The hydrofluoric acid modified biochar (HF-BC) was obtained, aiming to improve its performance for activating persulfate (PS) to make acid orange 7 (AO7) degraded in water solution. Results showed that the surface area, micropore volume, carboxyl and phenolic hydroxyl group content of HF-BC increased by 171%, 172%, 23.8% and 50%, respectively, compared to unmodified biochar (BC). The decolorization of AO7 in HF-BC/PS and BC/PS systemwas much more rapid and efficient than that in HF-BC, BC and PS alone system. For the HF-BC/PS system, the AO7 was removal of 99.8%, much higher than that of BC/PS system, probably because of its better surface characteristics. Moreover, for the HF-BC/PS system, it was the higher PS concentration and HF-BC dosage that caused greater AO7 degradation rates, and lower pH was favorable for the degradation. Our results provided a novel method to design biochar as an activator for persulfate-based remediation of dye wastewater. Abbreviations: HF-BC, hydrofluoric acid modified biochar; BC, unmodified biochar; AO7, Acid orange 7; PS, persulfate [ABSTRACT FROM AUTHOR]

The effect of biochar (BC) addition on NOx gas emissions was investigated from a calcareous soil. Application rates of zero (BC0), 1 (BC1), 2 (BC2), 5 (BC5), and 10 (BC10) percent weight/weight were used. The NOx emission flux was measured in a dynamic flux chamber. The flux was generally higher in BC0 than in the amended plots. The total NOx emission from BC1, BC2, BC5, and BC10 fell by 50.3, 75.3, 80.4, and 79.6%, respectively, relative to BC0. The emission flux from the BC5 showed a minimum average of 21.1 ± 13.5 μg N/(m2•h) for NO, −0.81 ± 1.31 μg N/(m2•h) for NO2, and 20.6 ± 13.8 μg N/(m2•h) for NOx. By comparison, the measured maximum average emission flux from the BC0 was 107.2 ± 30.98 μg N/(m2•h) for NO, −2.31 ± 2.56 μg N/(m2•h) for NO2, and 105.3 ± 45.3 μg N/(m2•h) for NOx. The results indicate that biochar amendment can potentially reduce NOx emissions. [ABSTRACT FROM AUTHOR]

Adding easily decomposable organic materials into flooded nitrate-rich soils can effectively decrease the soil nitrate concentration and repair nitrate-rich soil. However, nitrate reduction is usually accompanied with an increase in N2O emission. This study was conducted to reduce N2O emission in a nitrate-rich vegetable soil flooded for remediation and amended with biochar. Nitrate-rich vegetable soil was placed in five treatment groups: flooding (F); flooding with rice straw (F + RS); flooding with rice straw and 1% biochar (F + RS + 1% biochar); flooding with rice straw and 3% biochar (F + RS + 3% biochar); flooding with rice straw and CaO (F + RS + CaO). Biochar and CaO reduced the N2O emission levels relative to the F + RS group, with the former being more effective than the latter, achieving reduction of 40.70% (3% biochar) and 17.35% (CaO) of cumulative N2O emission. The 3% biochar was more effective than the 1% biochar. Regression analysis showed a positive correlation between the abundance of NO reductase gene (norB) and soil N2O emission flux. In general, biochar and CaO could effectively reduce N2O emissions from a nitrate-rich vegetable soil during flooding remediation, duo to elevating soil pH and altering denitrifying activity. The norB gene was the most important denitrifying gene driving soil N2O emission in the remediation. [ABSTRACT FROM AUTHOR]