Impact of biochar on greenhouse gas emissions and soil carbon sequestration in corn grown under drip irrigation with mulching

Biochar as ammonia exchange biofilm carrier for enhanced aerobic nitrification in activated sludge

The effects of biochar on aerobic nitrification in activated sludge were investigated in sequencing batch reactors. Biochar amended reactors exhibited 87-94 % lower ammonia in effluent and 16-71 % greater removal of total Kjeldahl nitrogen compared to control reactors. Quantitative qPCR analyses revealed that the relative abundance of ammonia oxidizing bacteria (AOB, amoA/16S rRNA genes) was greater in biochar than in control reactors. AOB were enriched on biochar surfaces, with biochar particles having up to 12.1 times greater relative abundance of AOB compared to suspended biomass. Biochar's maximum ammonia sorption capacity of 4.4 mg N/g at pH 7 decreased with decreasing pH, however a pH-sensitive fluorescent probe was used to show that biofilms growing on biochar surfaces maintain a median pH of > 6.7 despite reactor acidification by nitrification. Microbial colonization of biochar in activated sludge creates a pH-sheltered environment that sustains biochar's ammonia sorption capacity, resulting in enrichment of AOB on biochar particles and improved nitrification.

Comparing the effect of applying different types of amendments on carbon emissions and kinetics of degrading total petroleum hydrocarbons in artificial petroleum-contaminated soil

Contamination by spent engine oil represents a significant global environmental challenge as it poses a major hazard to human health, animals, plants, microorganisms, the soil ecosystem, and aquatic ecosystems. This study assumes that some amendments differ significantly in their ability to degrade petroleum hydrocarbons. Therefore, this incubation study was conducted to investigate the effect of different types of inorganic and organic amendments (zeolite, bone char, banana leaves biochar, and wood chips biochar) on carbon emissions (CO2-C) and the kinetics of total petroleum hydrocarbons (TPHC) degradation in artificial petroleum-contaminated soil. These amendments were added to the soil under study at a dose of 3% (w/w). At the end of the incubation period, applying zeolite, bone char, banana leaves biochar, and wood chips biochar to artificial petroleum-contaminated soil significantly reduced cumulative CO2-C emissions compared to the control. The banana leaves biochar significantly decreased TPHC concentrations in artificial petroleum-contaminated soil compared to the control treatment. At the end of the incubation period, adding banana leaves biochar to the soil showed high degradation efficiencies of TPHC which was 36% higher than soil before incubation. The effectiveness of applying amendments used in this experiment on the degradation of TPHC increase was in the order of banana leaves biochar > bone char > wood chips biochar > control > zeolite. The second-order model described the kinetics of total petroleum hydrocarbons better than the first-order model. Banana leaves biochar added to the soil resulted in a significant increase in the degradation rate constant of total petroleum hydrocarbons (k2) compared with the control. A higher k2 value indicates that TPHC degrades more rapidly. The half-life of TPHC degradation in the soil was decreased significantly by adding banana leaves biochar. According to the second-order equation, the half-lives of control, zeolite, bone char, banana leaves biochar, and wood chips biochar were 4.0, 5.3, 2.7, 1.0, and 3.6 years, respectively. The banana leaves biochar amendment might be cheaper and more environmentally friendly than other organic amendments because it has the high potential for carbon sequestration and remediate petroleum-contaminated soil, which would increase the sustainable use of petroleum-contaminated soil leading to preserving the environment.

Using the Conditional Process Analysis Model to Characterize the Evolution of Carbon Structure in Taxodium ascendens Biochar with Varied Pyrolysis Temperature and Holding Time

Temperature determines biochar structure during pyrolysis. However, differences in holding time and feedstock types may affect this relationship. The conditional process analysis model was used in this paper to investigate the potential to affect this mechanism. The branch and leaf parts of Taxodium ascendens were separately pyrolyzed at 350, 450, 650, and 750 °C, and kept for 0.5, 1, and 2 h at each target temperature. We measured the fixed carbon and ash contents and the elemental composition (C, H, O and N) of the raw materials and their char samples. After plotting a Van Krevelen (VK) diagram to determine the aromatization of chars, the changes in the functional groups were analyzed using Fourier transform infrared (FTIR), Raman, and X-ray photoelectron spectroscopy (XPS). The results revealed that pyrolysis at temperatures between 450 and 750 °C accounted for the aromatization of biochar because the atomic H/C ratio of branch-based chars (BC) decreased from 0.53-0.59 to 0.15-0.18, and the ratio of leaf-based chars (LC) decreased from 0.56-0.68 to 0.20-0.22; the atomic O/C ratio of BC decreased from 0.22-0.27 to 0.08-0.11, while that of LC decreased from 0.26-0.28 to 0.18-0.21. Moreover, the average contents of N (1.89%) and ash (13%) in LC were evidently greater than that in BC (N:0.62%; Ash: 4%). Therefore, BC was superior to LC in terms of the stability of biochar. In addition, the increasing ID/IG and ID/I(DR+GL) ratios in BC and LC indicated an increasing amount of the amorphous aromatic carbon structure with medium-sized (2~6 rings) fused benzene rings. According to the CPA analysis, an extension of the holding time significantly enhanced the increase in aromatic structures of LC with temperature. But this extension slightly reduced the growth in aromatic structures of BC. All indicate that holding time and feedstock types (branch or leaf feedstock) could significantly affect the variation in biochar aromatic structure with respect to temperature.

Evaluation of net carbon sequestration and ecological benefits from single biochar-incorporated sorghum farmland systems in saline-alkali areas of Inner Mongolia, China

Biochar is widely recognized as a soil amendment to reduce greenhouse gas emissions and enhance soil carbon storage in agroecosystems; however, the systematic focus on carbon balance and ecological benefits in cropping systems remains unclear in saline-alkali areas under water-saving irrigation. Here, a 2-yr field experiment with carbon footprint method was conducted to determine soil carbon budgets, biochar carbon efficiency performance, and the economic and ecological benefits of mulched drip-irrigated sorghum production, in an arid salinized region of Inner Mongolia, China. Corn straw-derived biochar dosages of 0 (CK), 15 (B15), 30 (B30), and 45 (B45) t hm-2 were just applied into the soil in the first crop growing season. A single application of biochar to soil significantly reduced CO2 emissions for the current and subsequent crop-growing seasons, with 13.1%, 16.7%, and 12.5% reductions for B15, B30, and B45, respectively. Compared with the non-biochar control plots, B15, B30, and B45 also increased NPP by 36.7%, 38.4%, and 27.1%, respectively. The actual effects on improving net carbon sequestration for B15, B30, and B45 in the first year were higher than those in the second year, with mean increases of 1.27, 1.47, and 1.36 times, respectively; however, the efficiencies of biochar for fixing carbon per biochar dosage input for B15 were 72.8% and 64.1% higher than those of B30 and B45, respectively. Net profits were significantly improved by 57.2-87.1% by biochar treatments. The environmental benefits of biochar carbon trading revenues for B15, B30, and B45 increased by 105.9%, 162.1%, and 109.6%, respectively. The minimum observation for carbon productivity and the maximum measurements for both the economic and ecological benefits were B15. The B15 also significantly increased sorghum yield and grain number. Results demonstrate that biochar application in the current growing season helps reduce soil carbon emissions, increases net carbon sequestration for current and subsequent sorghum agroecosystems, and enhances net profit and ecological benefits. The optimal positive synergistic effect was observed at a biochar application rate of 15 t hm-2 for reducing soil carbon emissions, increasing crop production, and improving the ecological environment.

A global meta-analysis of yield-scaled N2 O emissions and its mitigation efforts for maize, wheat, and rice

Maintaining or even increasing crop yields while reducing nitrous oxide (N2 O) emissions is necessary to reconcile food security and climate change, while the metric of yield-scaled N2 O emission (i.e., N2 O emissions per unit of crop yield) is at present poorly understood. Here we conducted a global meta-analysis with more than 6000 observations to explore the variation patterns and controlling factors of yield-scaled N2 O emissions for maize, wheat and rice and associated potential mitigation options. Our results showed that the average yield-scaled N2 O emissions across all available data followed the order wheat (322 g N Mg-1 , with the 95% confidence interval [CI]: 301-346) > maize (211 g N Mg-1 , CI: 198-225) > rice (153 g N Mg-1 , CI: 144-163). Yield-scaled N2 O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones, and also showed a trend towards lower intensities from low to high latitudes. This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance. Furthermore, our analysis showed a significant decrease in yield-scaled N2 O emissions with increasing N use efficiency or in N2 O emissions for production systems with cereal yields >10 Mg ha-1 (maize), 6.6 Mg ha-1 (wheat) or 6.8 Mg ha-1 (rice), respectively. This highlights that N use efficiency indicators can be used as valuable proxies for reconciling trade-offs between crop production and N2 O mitigation. For all three major staple crops, reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced-efficiency N fertilizers significantly reduced yield-scaled N2 O emissions at similar or even higher cereal yields. Our data-driven assessment provides some key guidance for developing effective and targeted mitigation and adaptation strategies for the sustainable intensification of cereal production.

Response of soil respiration and carbon budget to irrigation quantity/quality and biochar addition in a mulched maize field under drip irrigation

BACKGROUND

Biochar addition strongly alters net carbon (C) balance in agroecosystems. However, the effects of biochar addition on net C balance of maize field under various irrigation water quantities and qualities remains unclear. Thus, a field experiment combining two irrigation levels of full (W1) and deficit irrigation (W2 = 1/2 W1), two water salinity levels of fresh (S0, 0.71 g L-1 ) and brackish water (S1, 4 g L-1 ), and two biochar addition rates of 0 t ha-1 (B0) and 60 t ha-1 (B1) was conducted to investigate soil carbon dioxide (CO2 ) emissions, maize C sequestration and C budget.

RESULTS

Compared with W1, W2 reduced average cumulative CO2 emissions by 6.5% and 19.9% for 2020 and 2021, respectively. The average cumulative CO2 emissions under W1S1 treatments were 5.4% and 22.3% lower than W1S0 for 2020 and 2021, respectively, whereas W2S0 and W2S1 had similar cumulative CO2 emissions in both years. Biochar addition significantly increased cumulative CO2 emissions by 17.8-23.5% for all water and salt treatments in 2020, and reduced average cumulative CO2 emissions by 11.9% for W1 but enhanced it by 8.0% for W2 in 2021. Except for W2S1, biochar addition effectively increased total maize C sequestration by 6.9-14.8% for the other three treatments through ameliorating water and salt stress over the 2 years. Compared with W1S0, W1S1 did not affect net C sequestration, but W2 treatments significantly decreased it. Biochar addition increased net C sequestration by 39.47-43.65 t C ha-1 for four water and salt treatments for the 2 years.

CONCLUSION

These findings demonstrate that biochar addition is an effective strategy to increase both crop C sequestration and soil C storage under suitable water-saving irrigation methods in arid regions with limited freshwater resources. © 2023 Society of Chemical Industry.

Inclusive greenhouse gas budget assessment in turfs: From turf production to disposal of grass clippings

Globally, greenhouse gas (GHG) reduction is a serious concern. To evaluate whether turfs serve as a GHG sink or source, GHG budget assessments for life cycle are required. However, previous studies have only focused on the use of turfs. To bridge these gaps in literature, this study investigated GHG (CO2, N2O, and CH4) emissions from the disposal of grass clippings and soil GHG fluxes in turfs. Additionally, GHG budgets in the turf production phase were assessed. Finally, inclusive GHG budgets from turf production to disposal of grass clippings for four turf uses (soccer stadium, golf course, office, and urban park) were assessed. Grass clippings were disposed in three forms (incineration, leaving as-is, and biochar). We found that GHG emissions from incineration and leaving 1 t-fresh weight (FW) of grass clippings were 0.711 and 0.207 t-CO2e, respectively. Contrastingly, the GHG emissions from the biochar yield from 1 t-FW of grass clippings were -0.200 t-CO2e. Further, annual soil GHG fluxes in newly established Zoysia and Kentucky bluegrass turfs were calculated at 0.067 and 0.040 tCO2e･ha-1･yr-1, respectively. As the turf grass in production fields sequester large amounts of CO2, GHG budgets in turf production phase were estimated at approximately -20 t-CO2e･ha-1･yr-1. Inclusive GHG budget assessment from turf production to disposal of grass clippings showed that turfs only in the urban parks served as a GHG sink and this ability was comparable to CO2 sequestration in forests. To enhance the ability of GHG sinks and to promote changes from a GHG source to GHG sink, our study revealed the importance of reduction of GHG emissions from energy and resource uses (especially fertilizers and gasoline) for turf management.

Carbon offset potential of biochar based straw management under rice- wheat system along Indo-Gangetic Plains of India

The Paris Agreement goal of a net-zero equation will require decarbonization technologies in agriculture. Agri-waste biochar offers huge potential for carbon abatement in agricultural soils. The present experiment was carried out to compare the effects of residue management, viz., no residue (NR), residue incorporation (RI), and biochar (BC), as well as nitrogen options for emission reduction and carbon capture under the rice-wheat cropping sequence (RWCS) of the Indo-Gangetic Plains (IGP), India. After two cycles of cropping pattern, the analysis revealed that the biochar application (BC) reduces the RWCS's annual CO2 emissions by 18.1 % over residue incorporation (RI), while CH4 and N2O emissions were reduced by 23 % and 20.6 % over RI and 11 % and 29.3 % over no residue (NR), respectively. The application of biochar-based nutrient composites with rice straw biourea (RSBU) at 100 % and 75 % significantly reduced greenhouse gases (CH4 and N2O) compared to commercial urea at 100 %. The global warming potential of cropping systems recorded with BC was 7 % and 19.3 % lower than NR and RI, respectively, while 6-15 % under RSBU over urea 100 %. The annual carbon footprint (CF) under BC and NR decreased by 37.2 % and 30.8 % over RI, respectively. The net CF under residue burning was estimated to be the highest (132.5 Tg CO2-Ce), followed by RI (55.3 Tg CO2-Ce), showing net positive emissions; however, net negative emissions were found under a biochar-based system. The estimated annual carbon offset potential of a complete biochar system over residue burning, incorporation, and partial biochar as calculated was 189, 112, and 92 Tg CO2-Ce yr-1, respectively. A biochar-based approach to managing rice straw had great carbon offset potential through a large drop in greenhouse gas emissions and an improved soil carbon pool under the rice wheat system along the IGP, India.

Low-density polyethylene microplastics and biochar interactively affect greenhouse gas emissions and microbial community structure and function in paddy soil

Paddy soils are susceptible to microplastics (MPs) contamination. As a common soil amendment, biochar (BC) has been extensively applied in paddy fields. The co-occurrence of MPs and BC may cause interactive effects on soil biogeochemical processes, which has yet been well studied. In this study, a 41-days of microcosm experiment was conducted using paddy soil added with 0.5-1.5 wt% of low-density polyethylene (LDPE) and 5 wt% of BC individually or jointly. Application of BC, LDPE, or their mixture into soil significantly increased the emission of methane (CH4), but suppressed the emission of carbon dioxide (CO2). LDPE addition lowered soil nitrous oxide (N2O) emissions, while BC exerted an opposite effect. Proteobacteria was the most dominant phylum with a relative abundance range of 35.1-51.0%, followed by Actinobacteria (19.3-30.9%) and Acidobacteria (7.5-23.5%). The abundances of the mcrA gene and pH values were increased in soils added with BC or/and LDPE, which were the possible reasons for the higher CH4 emissions in these treatments. The emission of N2O was positively related to the abundances of norB and narG genes, suggesting denitrification was a major pathway to produce N2O. Results of structural equation modeling demonstrated that addition of BC or/and LDPE MPs could affect greenhouse gas emissions from paddy soil by altering soil chemical properties, microbial community structure, and functional gene abundances.

Drip fertigation sustains crop productivity while mitigating reactive nitrogen losses in Chinese agricultural systems: Evidence from a meta-analysis

Drip fertigation can synchronize the supply of nutrients and water for crop demand, offering the potential for minimizing negative environmental impacts and sustaining crop productivity. However, there are no comprehensive evaluations on performances of drip fertigation on environmental nitrogen (N) losses and crop productivity, nationwide. Here, a meta-analysis was performed to quantify overall effects of drip fertigation on N losses and crop productivity in Chinese agricultural systems based on 443 observations from 42 field studies. The results showed that drip fertigation significantly increased crop yields by 9.8 % and slightly increased soil NO emission by 13.9 % compared to the traditional irrigation and fertilization practices (e.g. flooding/furrow irrigation and N broadcasting), while significantly decreasing NH3 volatilization by 14.2 %, soil N2O emission by 28.1 % and NO3--N leaching loss by 71.2 %. There were significant mitigation potentials of environmental N losses by drip fertigation for cereal cropping systems, not for horticultural crops in terms of soil NO emission and not for cotton in terms of NH3 volatilization. Non significant promotion effect on NO emission and significant reduction effects on the other all kinds of environmental N losses by drip fertigation were observed for alkaline soils (pH > 7.3) and coarse-textured soils. In addition, the use of different fertilizer sources and/or soil amendments have shown in popularity as strategies to offset the negative feedback associated with agricultural N losses, no direct synthetic result was shown in drip-fertigated soils. We synthesized 19 studies so as to assess the potential mitigation options for further minimizing N losses in drip fertigation systems, which suggested that deleterious environmental pollution could be further reduced while still achieving high crop yields with a combination of enhanced-efficiency fertilizers (e.g. nitrification or urease inhibitors) or soil amendments (e.g. biochar or straw) to drip fertigation systems.

Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions

Biochar is one of the few nature-based technologies with potential to help achieve net-zero emissions agriculture. Such an outcome would involve the mitigation of greenhouse gas (GHG) emission from agroecosystems and optimization of soil organic carbon sequestration. Interest in biochar application is heightened by its several co-benefits. Several reviews summarized past investigations on biochar, but these reviews mostly included laboratory, greenhouse, and mesocosm experiments. A synthesis of field studies is lacking, especially from a climate change mitigation standpoint. Our objectives are to (1) synthesize advances in field-based studies that have examined the GHG mitigation capacity of soil application of biochar and (2) identify limitations of the technology and research priorities. Field studies, published before 2022, were reviewed. Biochar has variable effects on GHG emissions, ranging from decrease, increase, to no change. Across studies, biochar reduced emissions of nitrous oxide (N2 O) by 18% and methane (CH4 ) by 3% but increased carbon dioxide (CO2 ) by 1.9%. When biochar was combined with N-fertilizer, it reduced CO2 , CH4 , and N2 O emissions in 61%, 64%, and 84% of the observations, and biochar plus other amendments reduced emissions in 78%, 92%, and 85% of the observations, respectively. Biochar has shown potential to reduce GHG emissions from soils, but long-term studies are needed to address discrepancies in emissions and identify best practices (rate, depth, and frequency) of biochar application to agricultural soils.

Successive addition of rice straw biochar enhances carbon accumulation in soil irrigated with saline or non-saline water

Biochar has been evaluated globally to improve soil fertility and mitigate climate change. However, the long-term effects of successive biochar application on carbon (C) accumulation in soil irrigated with saline versus non-saline water (canal water) has not been investigated. A field experiment was conducted to study the effects of rice straw biochar addition rates (0, 2, 4, 8 Mg ha^-1) on C storage in soil irrigated with water of different electrical conductivity [EC, dS m^-1]; 0.3 (non-saline canal irrigation water; CIW), 5 (saline irrigation water; SIW₅), 10 (SIW₁₀), and 15 (SIW₁₅) in a cotton-wheat system. Long-term irrigation with saline water of variable EC levels adversely affected soil functions, reducing above-ground biomass in cotton (12-48%) and wheat (5-27%). In contrast, plots irrigated with saline water but amended with rice straw biochar showed significant improvement in aboveground biomass (both in cotton and wheat), possibly due to its beneficial effects on soil properties such as soil EC, organic carbon, microbial population, water and nutrient availability, bulk density, soil aggregation, and proliferation of roots. Interestingly, the change in total organic C (TOC) stocks (8.5, 17, and 27.5 Mg C ha^-1) after 5 years were found to be almost double the amount of biochar C added (4.3, 8.6, 17.2 Mg ha^-1), indicating stabilization of belowground C inputs from the root biomass by the applied biochar and also possibly through its physical interaction with aggregates and minerals. Even though biochar application to saline water irrigated plots increased the contribution of plant-derived C to overall soil TOC stocks, it was still lower compared with canal water irrigated plots. The study conclusively established that the long-term stabilization of biogenic C through biochar has essential implications for mitigating climate change by accumulating additional C beyond the recalcitrant C contained in biochar.

Effects of dairy processing sludge and derived biochar on greenhouse gas emissions from Danish and Irish soils

Globally, to ensure food security bio-based fertilizers must replace a percentage of chemical fertilizers. Such replacement must be deemed sustainable from agronomic and greenhouse gas (GHG) emission perspectives. For agronomic performance several controlled protocols are in place but not for testing GHG emissions. Herein, a pre-screening tool is presented to examine GHG emissions from bio-waste as fertilizers. The various treatments examined are as follows: soil with added mineral nitrogen (N, 140 kg N ha^-1) fertilizer (MF), the same amount of MF combined with dairy processing sludge (DS), sludge-derived biochar produced at 450 °C (BC450) and 700 °C (BC700) and untreated control (CK). These treatments were combined with Danish (sandy loam) or Irish (clay loam) soils, with carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) emissions and soil inorganic-N contents measured on selected days. During the incubation, biochar mitigated N₂O emissions by regulating denitrification. BC450 reduced N₂O emissions from Danish soil by 95.5% and BC700 by 97.7% compared to emissions with the sludge application, and for Irish soil, the N₂O reductions were 93.6% and 32.3%, respectively. For both soils, biochar reduced CO₂ emissions by 50% as compared to the sludge. The lower N₂O reduction potential of BC700 for Irish soil could be due to the high soil organic carbon and clay content and pyrolysis temperature. For the same reasons emissions of N₂O and CO₂ from Irish soil were significantly higher than from Danish soil. The temporal variation in N₂O emissions was correlated with soil inorganic-N contents. The CH₄ emissions across treatments were not significantly different. This study developed a simple and cost-effective pre-screening method to evaluate the GHG emission potential of new bio-waste before its field application and guide the development of national emission inventories, towards achieving the goals of circular economy and the European Green Deal.

Biochar application for greenhouse gas mitigation, contaminants immobilization and soil fertility enhancement: A state-of-the-art review

Rising global temperature, pollution load, and energy crises are serious problems, recently facing the world. Scientists around the world are ambitious to find eco-friendly and cost-effective routes for resolving these problems. Biochar has emerged as an agent for environmental remediation and has proven to be the effective sorbent to inorganic and organic pollutants in water and soil. Endowed with unique attributes such as porous structure, larger specific surface area (SSA), abundant surface functional groups, better cation exchange capacity (CEC), strong adsorption capacity, high environmental stability, embedded minerals, and micronutrients, biochar is presented as a promising material for environmental management, reduction in greenhouse gases (GHGs) emissions, soil management, and soil fertility enhancement. Therefore, the current review covers the influence of key factors (pyrolysis temperature, retention time, gas flow rate, and reactor design) on the production yield and property of biochar. Furthermore, this review emphasizes the diverse application of biochar such as waste management, construction material, adsorptive removal of petroleum and oil from aqueous media, immobilization of contaminants, carbon sequestration, and their role in climate change mitigation, soil conditioner, along with opportunities and challenges. Finally, this review discusses the evaluation of biochar standardization by different international agencies and their economic perspective.

Biochar application for remediation of organic toxic pollutants in contaminated soils; An update

Bioremediation of organic contaminants has become a major environmental concern in the last few years, due to its bio-resistance and potential to accumulate in the environment. The use of diverse technologies, involving chemical and physical principles, and passive uptake utilizing sorption using ecofriendly substrates have drawn a lot of interest. Biochar has got attention mainly due to its simplicity of manufacturing, treatment, and disposal, as it is a less expensive and more efficient material, and has a lot of potential for the remediation of organic contaminants. This review highlighted the adverse impact of persistent organic pollutants on the environment and soil biota. The utilization of biochar to remediate soil and contaminated compounds i.e., pesticides, polycyclic aromatic hydrocarbons, antibiotics, and organic dyes has also been discussed. The soil application of biochar has a significant impact on the biodegradation, leaching, and sorption/desorption of organic contaminants. The sorption/desorption of organic contaminants is influenced by chemical composition and structure, porosity, surface area, pH, and elemental ratios, and surface functional groups of biochar. All the above biochar characteristics depend on the type of feedstock and pyrolysis conditions. However, the concentration and nature of organic pollutants significantly alters the sorption capability of biochar. Therefore, the physicochemical properties of biochar and soils/wastewater, and the nature of organic contaminants, should be evaluated before biochar application to soil and wastewater. Future initiatives, however, are needed to develop biochars with better adsorption capacity, and long-term sustainability for use in the xenobiotic/organic contaminant remediation strategy.

Impact of single biochar application on maize growth and water-fertilizer productivity under different irrigation regimes

The improvement of soil water and nutrient availability through soil management practices are crucial in promoting crop growth and obtaining high water-fertilizer productivity under limited irrigation. In this study, a 2×4 fully randomized factorial design with two drip-irrigation regimes and four biochar rates was performed during maize crop growing seasons for a semiarid region of China in 2015 and 2016. Irrigation regimes was applied on the basis of the water lower limit of -15 kPa soil matric potential as W15 and -35 kPa as W35. Maize straw-derived biochar application rate of 0 (B0), 15 (B15), 30 (B30), and 45 (B45) t ha^-1 was once applied to sandy loam soil in the first growing season. Our results showed that the W15 and W35 regimes generally increased soil nutrient availability and organic matter content under all biochar treatment rates for the entire growth period. In comparison, the B45-induced increase in available P and K was higher in the W15 regime than in the W35 regime during the second growing season. Furthermore, biochar treatment improved the comprehensive fertility index (CFI), leaf area index, and yield of maize. Within the same biochar treatment, the CFI value was higher in the W15 regime than in the W35 regime during the first growing season. However, the opposite was observed in the second growing season. The average irrigation water productivity (IWP) increased by 11.6%, 8.8%, and 7.8% in the W35 regime and by 15.2%, 12.9%, and 10.2% in the W15 regime for the B15, B30, and B45 treatments, respectively. Moreover, biochar treatment enhanced maize grain yield and partial fertilizer productivity (PFP) of synthetic N, P, and K fertilizers under both irrigation regimes. The highest PFP values were observed in the B15 treatment under W15. In general, a one-time application of biochar treatment at a rate of 15 t ha^-1 in the first growing season is recommended in terms of increasing the availability of N, P, K, and organic matter in sandy loam and also improve water-fertilizer productivity under irrigation water lower limit of -15 kPa soil matric potential.

Interactive effects of microplastics, biochar, and earthworms on CO2 and N2O emissions and microbial functional genes in vegetable-growing soil

Soil carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions are two main greenhouse gases that play important roles in global warming. Studies have shown that microplastics, biochar, and earthworms can significantly affect soil greenhouse gas emissions. However, few studies have explored how their interactions affect soil CO₂ and N₂O emissions. A mesocosm experiment was conducted to investigate their interactive effects on soil greenhouse gases and soil microbial functional genes in vegetable-growing soil under different incubation times. Biochar alone or combined with microplastics significantly decreased soil CO₂ emissions but had no effect on soil N₂O emissions. Microplastics and biochar inhibited CO₂ emissions and promoted N₂O emissions in the soil with earthworms. The addition of microplastics, biochar, and earthworms had significant effects on soil chemical properties, including dissolved organic carbon, ammonia nitrogen, nitrate nitrogen, total nitrogen, and pH. Microplastics and earthworms selectively influenced microbial abundances and led to a fungi-prevalent soil microbial community, while biochar led to a bacteria-prevalent microbial community. The interactions of microplastics, biochar, and earthworms could alleviate the reduction of the bacteria-to-fungi ratio and the abundance of microbial functional genes caused by microplastics and earthworms alone. Microplastics significantly inhibited microorganisms as well as C and N cycling functional genes in earthworm guts, while biochar obviously stimulated them. The influence of the addition of exogenous material on soil greenhouse gas emissions, soil chemical properties, and functional microbes differed markedly with soil incubation time. Our results indicated that biochar is a promising amendment for soil with microplastics or earthworms to simultaneously mitigate CO₂ emissions and regulate soil microbial community composition and function. These findings contribute to a better understanding of the interaction effects of microplastics, biochar, and earthworms on soil carbon and nitrogen cycles, which could be used to help conduct sustainable environmental management of soil.

Biochar raw material selection and application in the food chain: A review

As one of the largest carbon emitters, China promises to achieve carbon emissions neutrality by 2060. Various industries are developing businesses to reduce carbon emissions. As an important greenhouse gas emissions scenario, the reduction of carbon emissions in the food chain can be achieved by preparing the wastes into biochar. The food chain, as one of the sources of biochar, consists of production, processing and consumption, in which many wastes can be transferred into biochar. However, few studies use the food chain as the system to sort out the raw materials of biochar. A systematic review of the food chain application in serving as raw materials for biochar is helpful for further application of such technique, providing supportive information for the development of biochar preparation and wastes treating. In addition, there are many pollution sources in the food production process, such as agricultural contaminated soil and wastewater from livestock and aquatic, that can be treated on-site to achieve the goal of treating wastes with wastes within the food chain. This study focuses on waste resource utilization and pollution remediation in the food chain, summarizing the sources of biochar in the food chain and analyzing the feasibility of using waste in food chain to treat contaminated sites in the food chain and discussing the impacts of the greenhouse gas emissions. This review provides a reference for the resource utilization of waste and pollution reduction in the food chain.

Production and beneficial impact of biochar for environmental application: A comprehensive review

This review focuses on a holistic view of biochar, production from feedstock's, engineering production strategies, its applications and future prospects. This article reveals a systematic emphasis on the continuation and development of biochar and its production methods such as Physical engineering, chemical and bio-engineering techniques. In addition, biochar alternatives such as nutrient formations and surface area made it a promising cheap source of carbon-based products such as anaerobic digestion, gasification, and pyrolysis, commercially available wastewater treatment, carbons, energy storage, microbial fuel cell electrodes, and super-capacitors repair have been reviewed. This paper also covers the knowledge blanks of strategies and ideas for the future in the field of engineering biochar production techniques and application as well as expand the technology used in the circular bio-economy.

Influence of activated biochar pellet fertilizer application on greenhouse gas emissions and carbon sequestration in rice (Oryza sativa L.) production

Supplemental activated biochar pellet fertilizers (ABPFs) were evaluated as a method to sequester carbon and reduce greenhouse gas (GHG) emissions, and improve rice production. The evaluated treatments were a control (standard cultivation method, no additives applied), activated rice hull biochar pellets with 40% of N (ARHBP-40%), and activated palm biochar pellets with 40% of N (APBP-40%). The N supplied by the ARHBP-40% and APBP-40% treatments reduced the need for supplemental inorganic nitrogen (N) fertilizer by 60 percent. The ARHBP-40% treatment sequestered as much as 1.23 tonne ha^-1 compared to 0.89 tonne ha^-1 in the control during the rice-growing season. In terms of greenhouse gas (GHG) emissions, CH₄ emissions were not significantly different (p > 0.05) between the control and the ARHBP-40%, while the lowest N₂O emissions (0.002 kg ha^-1) were observed in the ARHBP-40% during the crop season. Additionally, GHG (CO₂-equiv.) emissions from the ARHBP-40% application were reduced by 10 kg ha^-1 compared to the control. Plant height in the control was relatively high compared to others, but grain yield was not significantly different among the treatments. The application of the ARHBP-40% can mitigate greenhouse gas emissions and enhance carbon sequestration in crop fields, and ABPFs can increase N use efficiency and contribute to sustainable agriculture.

Influence of Acidified Biochar on CO2–C Efflux and Micronutrient Availability in an Alkaline Sandy Soil

Biochar, an alkaline carbonaceous substance resulting from the thermal pyrolysis of biomass, reportedly enhances the micronutrient availability in acidic soils with little or no effect on alkaline soils. In this study, biochars were produced from poultry manure (PM) at 350 °C and 550 °C (BC350 and BC550 respectively). The acidified biochars (ABC350 and ABC550, respectively) were incorporated into an alkaline sandy soil, and their effects on the soil micronutrients (Cu, Fe, Mn and Zn) availability, and CO2–C efflux were investigated in a 30-day incubation study. The treatments (PM, BC350, BC550, ABC350, and ABC550) were administered in triplicate to 100 g soil at 0%, 1%, and 3% (w/w). Relative to the poultry manure treatment, acidification drastically reduced the pH of BC350 and BC550 by 3.13 and 4.28 units, respectively, and increased the micronutrient availability of the studied soil. Furthermore, the biochars (both non-acidified and acidified) reduced the CO2 emission compared to that of the poultry manure treatment. After 1% treatment with BC550 and ABC550, the CO2 emissions from the soil were 89.6% and 91.4% lower, respectively, than in the 1% poultry manure treatment. In summary, acidified biochar improved the micronutrient availability in alkaline soil, and when produced at higher temperature, can mitigate the CO2 emissions of soil carbon sequestration.

Evaluation of N2O emission from rainfed wheat field in northwest agricultural land in China

The net greenhouse gas (NGHG) emissions and net greenhouse gas intensity (NGHGI) were investigated via the determination of nitrous oxide (N₂O) emission in loess soil under rainfed winter wheat monocropping system during 3 years of field study in Northwest China. Five treatments were carried out: control (N₀), conventional nitrogen (N) application (N_Con), optimized N application with straw (SN_Opt), optimized N application with straw and 5% of dicyanodiamide (SN_Opt + DCD), and optimized N rate of slow release fertilizer with straw (SSRF_Opt). Over a 3-year period, the NGHG emissions were achieved 953, 1322, 564, and 1162 kg CO₂-eq ha^-1, simultaneously, and the NGHGI arrived 158, 223, 86, and 191 kg CO₂-eq t^-1 grain in N_Con, SN_Opt, SN_Opt + DCD, and SSR_Opt grain, respectively. Contrasted with conventional farming system, optimized farming methods reduced 32% of N fertilizer use without significant decrease in grain yield, but brought about 38% increase in N₂O emissions, up to 28% gained in soil CH₄ uptake. Thus, it was observed that the straw incorporation performs noticeable increased in N₂O emissions in the winter wheat cropping season. Among the optimized N fertilizer rates compared with the SN_Opt treatment, the SN_Opt +DCD and SSR_Opt treatments decreased in N₂O emissions by approximately 55% and 13%, respectively. Additionally, the N₂O emission factor across over a 3-year period was 0.41 ± 0.08% derived from N fertilizer, and it was half of IPCC default values for upland corps. It is expected possibly due to low precipitation and soil moisture with the monocropping system. The 25% higher in the amount of rainfall (almost 300 mm in 2013-2014) during a cropping season underwent into 1-2-fold increase in N₂O emissions from N-fertilized plots. As the statistical differences among annual cumulative emissions coincided with that during winter wheat growing season, it can be concluded that crop growing season is a vital important period for the determination of N₂O emissions from under rainfed monocropping system.