Biochar and nano biochar: Enhancing salt resilience in plants and soil while mitigating greenhouse gas emissions: A comprehensive review

Salinity stress poses a significant challenge to agriculture, impacting soil health, plant growth and contributing to greenhouse gas (GHG) emissions. In response to these intertwined challenges, the use of biochar and its nanoscale counterpart, nano-biochar, has gained increasing attention. This comprehensive review explores the heterogeneous role of biochar and nano-biochar in enhancing salt resilience in plants and soil while concurrently mitigating GHG emissions. The review discusses the effects of these amendments on soil physicochemical properties, improved water and nutrient uptake, reduced oxidative damage, enhanced growth and the alternation of soil microbial communities, enhance soil fertility and resilience. Furthermore, it examines their impact on plant growth, ion homeostasis, osmotic adjustment and plant stress tolerance, promoting plant development under salinity stress conditions. Emphasis is placed on the potential of biochar and nano-biochar to influence soil microbial activities, leading to altered emissions of GHG emissions, particularly nitrous oxide(N2O) and methane(CH4), contributing to climate change mitigation. The comprehensive synthesis of current research findings in this review provides insights into the multifunctional applications of biochar and nano-biochar, highlighting their potential to address salinity stress in agriculture and their role in sustainable soil and environmental management. Moreover, it identifies areas for further investigation, aiming to enhance our understanding of the intricate interplay between biochar, nano-biochar, soil, plants, and greenhouse gas emissions.

Nano-biochar as a potential amendment for metal(loid) remediation: Implications for soil quality improvement and stress alleviation

Metal(loid) contamination of agricultural soils has become an alarming issue due to its detrimental impacts on soil health and global agricultural production. Therefore, environmentally sustainable and cost-effective solutions are urgently required for soil remediation. Biochar, particularly nano-biochar, exhibits superior and high-performance capabilities in the remediation of metal(loid)-contaminated soil, owing to its unique structure and large surface area. Current researches on nano-biochar mainly focus on safety design and property improvement, with limited information available regarding the impact of nano-biochar on soil ecosystems and crop defense mechanisms in metal(loid)-contaminated soils. In this review, we systematically summarized recent progress in the application of nano-biochar for remediation of metal(loid)-contaminated soil, with a focus on possible factors influencing metal(loid) uptake and translocation in soil-crop systems. Additionally, we conducted the potential/related mechanisms by which nano-biochar can mitigate the toxic impacts of metal(loid) on crop production and security. Furthermore, the application of nano-biochar in field trials and existing challenges were also outlined. Future studies should integrate agricultural sustainability and ecosystem health targets into biochar design/selection. This review highlighted the potential of nano-biochar as a promising soil amendment for enhancing the remediation of metal(loid)-contaminated agricultural soils, thereby promoting the synthesis and development of highly efficient nano-biochar towards achieving environmental sustainability.

Mechanism for combined application of biochar and Bacillus cereus to reduce antibiotic resistance genes in copper contaminated soil and lettuce

The remediation of agricultural soil contaminated by antibiotic resistance genes (ARGs) is of great significance for protecting food safety and human health. Reducing the availability of copper in soil may control coresistance to ARGs. However, the feasibility of applying nano-biochar and Bacillus cereus to mitigate the spread of ARGs in Cu contaminated soil remains unclear. Therefore, this study investigated the use of biochar with different particle sizes (2 % apple branch biochar and 0.5 % nano-biochar) and 3 g m-2B. cereus in a 60-day pot experiment with growing lettuce. The effects of single and combined application on the abundances of ARGs in Cu-contaminated soil (Cu = 200 mg kg-1) were compared, and the related mechanisms were explored. Studies have shown that the addition of biochar alone is detrimental to mitigating ARGs in soil-lettuce systems. The combined application of 3 g m-2B. cereus and 0.5 % nano-biochar effectively inhibited the proliferation of ARGs in Cu-contaminated soil, and 3 g m-2B. cereus effectively inhibited the proliferation of ARGs in lettuce. Partial least squares-path modeling and network analysis showed that bacterial communities and mobile genetic elements were the key factors that affected the abundances of ARGs in rhizosphere soil, and Cu resistance genes and bioavailable copper (acid extractable state Cu (F1) + reducing state Cu (F2)) had less direct impacts. The bacterial community was the key factor that affected the abundances of ARGs in lettuce. Rhodobacter (Proteobacteria), Corynebacterium (Actinobacteria), and Methylobacterium (Proteobacteria) may have been hosts of ARGs in lettuce plants. B. cereus and nano-biochar affected the abundances of ARGs by improving the soil properties and reducing the soil bioavailability of Cu, as well as directly or indirectly changing the bacterial community composition in soil and lettuce, thereby impeding the transport of ARGs to aboveground plant parts.

Nano-biochar: recent progress, challenges, and opportunities for sustainable environmental remediation

Biochar is a carbonaceous by-product of lignocellulosic biomass developed by various thermochemical processes. Biochar can be transformed into "nano-biochar" by size reduction to nano-meters level. Nano-biochar presents remarkable physico-chemical behavior in comparison to macro-biochar including; higher stability, unique nanostructure, higher catalytic ability, larger specific surface area, higher porosity, improved surface functionality, and surface active sites. Nano-biochar efficiently regulates the transport and absorption of vital micro-and macro-nutrients, in addition to toxic contaminants (heavy metals, pesticides, antibiotics). However an extensive understanding of the recent nano-biochar studies is essential for large scale implementations, including development, physico-chemical properties and targeted use. Nano-biochar toxicity on different organisms and its in-direct effect on humans is an important issue of concern and needs to be extensively evaluated for large scale applications. This review provides a detailed insight on nanobiochar research for (1) development methodologies, (2) compositions and properties, (3) characterization methods, (4) potentiality as emerging sorbent, photocatalyst, enzyme carrier for environmental application, and (5) environmental concerns.

Effect of different aging treatments on the transport of nano-biochar in saturated porous media

Widely used for soil amendment, carbon sequestration, and remediation of contaminated soils, biochars (BCs) inevitably produce a large number of nanoparticles with relatively high mobility. Geochemical aging alters chemical structure of these nanoparticles and thus affect their colloidal aggregation and transport behavior. In this study, the transport of ramie derived nano-BCs (after ball-milling) was investigated by different aging treatments (i.e., photo (PBC) and chemical aging (NBC)) as well as the managing BC under different physicochemical factors (i.e., flow rates, ionic strengths (IS), pH, and coexisting cations). Consequences of the column experiments indicated aging promoted the mobility of the nano-BCs. Compared to the nonaging BC, consequences of spectroscopic analysis demonstrated the aging BCs exhibited a number of tiny corrosion pores. Both of these aging treatments contribute to a more negative zeta potential and a higher dispersion stability of the nano-BCs, which is caused by the abundance of O-functional groups. Also the specific surface area and mesoporous volume of both aging BCs increased significantly, with the increase being more pronounced for NBC. The breakthrough curves (BTCs) obtained for the three nano-BCs were modelled by the advection-dispersion equation (ADE), which included first-order deposition and release terms. The ADE revealed high mobility of aging BCs, which meant their retention in saturated porous media was reduced. This work contributes to a comprehensive understanding of the transport of aging nano-BCs in the environment.

A performance evaluation study of nano-biochar as a potential slow-release nano-fertilizer from wheat straw residue for sustainable agriculture

Agro-Wastes are identified as to manufacture potential valuable organic biochar fertilizer product economically while also managing the waste. Biochar (BC) produced from agriculture waste is helps to improve the soil because of its neutral pH, addition of organic carbon to the soil and lower salt index values. This study focused on the development of nano-biochar into a more enhanced biochar product where it was checked whether the biochar derived from wheat straw can absorb nutrients and then act as support matter for releasing micro-nutrients and macro-nutrients for the plants on slow liberation basis. Wheat biochar (WBC) and wheat nano-biochar (WBNC) were synthesized by pyrolysis at two different temperatures and nutrients were fused into the WBC via impregnation technique. Physical parameters such as Proximate, Ultimate analysis & other were also studied and inspected by standard control procedures. Studies were also carried out on water retention (WR), water absorbance (WA), swelling ratio (SR) and equilibrium water content (EWC) for all samples; data was collected and compared for the better sample. Slow-release studies performed portrayed the release pattern of nutrients for prolonged periods, which are very important for the plant growth, yield and productivity. Overall, the experimental results displayed that BNC produced at 350 °C showed promising features of (SI:0.05, SR: 3.67, WA:64%, EWC:78.6%, FC:53.05% and pH:7.22), is a good substance however the nano-biochar has improved results; environmental friendly & could be utilized as a potential fertilizer on slow release for sustainable and green agriculture application.

A simple method for the synthesis of biochar nanodots using hydrothermal reactor

Biochar is a stable carbon rich by-product synthesized through pyrolysis of plant and animal based biomass, and nano-biochar material has gained increasing attention due to its unique properties for environmental applications. In the present study, a simple cost-effective method for the synthesis of biochar nanoparticles through hydrothermally using agricultural residuals and by-products was developed. Both soybean straw and cattle manure were selected as the feedstock to produce the bulk-biochar. The synthesis procedure involved the digestion of the bulk-biochar with concentrated nitric acid and sulfuric acid in a high pressure condition using a hydrothermal reactor. The suspension was isolated using vacuum filtration with 0.22-μm membrane followed by drying at 65 °C in an oven. Scanning electron microscopy results revealed that both of the biochars had a well-developed porous structure following pyrolysis. Both transmission electron microscopy and the dynamic light scattering results of the hydrothermally treated biochar indicated that the soybean straw and cattle manure biochar nanodots had an average of 5-nm and 4-nm in size, respectively. Overall two raw materials produced 8.5–10% biochar nanodots. The present method presents a simple, quick and cost-effective method for synthesis of biochar nanodots. The method provided a useful tool discovering the applicability biochar nanodots for environmental applications.

• Nano-biochar formation from bulk-biochar using hydrothermal reactor

• Evaluate nano-biochar's environmental fate and behavior in soil and water

• Synthesize multifunctional adsorbent using nano-biochar as primary material

Spectroscopic studies on the phosphorus adsorption in salt-affected soils with or without nano-biochar additions

Biochar amendment may be an effective solution of maintaining phosphorus (P) and sustaining agricultural production in salt affected soils. However, the behavior of P adsorption in salt-affected soils with nano-biochar (nB) amendment is unclear. Batch adsorption experiments were conducted to investigate the impacts of different levels of soil salinity amended with nB at rates of 0, 0.10%, 0.20%, and 0.50% (w/w) on the P adsorption isotherm and also, mechanisms of P adsorption by using spectroscopic analysis. The results showed that P adsorption increased with increasing soil salinity with or without nB addition. Under level of 120 mg P L^-1, adsorption capacity of P increased from 992.8 mg kg^-1 for high saline soil (S5) to 1144.0 mg kg^-1 after treated with 0.20% nB. The results of P adsorption were agreed with Langmuir and Freundlich isotherm models. Fourier transform infrared analysis (FTIR) of nB showed that the surface of nB decorated with oxygenated functional groups which play an important role in the adsorption of P anions. Analyzes of FTIR and XRD indicated that the main adsorption mechanism for P adsorption on nB in salt affected soils was surface precipitation. Our findings suggest that the nano-biochar amendment in salt affected soils can be a promising enhancer for P adsorption.

Biochar for delivery of agri-inputs: Current status and future perspectives

Biochar, a carbonaceous porous material produced from the pyrolysis of agricultural residues and solid wastes has been widely used as a soil amendment. Recent publications on biochar are primarily focussed with its application in climatic aspects, contaminant immobilization, soil amendment strategies, nutrient recovery, engineered material production and waste-water treatment. Numerous studies have reported the positive attribute of biochar's nutrient value that helps in improving plant growth and fertilizer use efficiency. The renewability, low-cost, high porosity, high surface area and customizable surface chemistry of biochar offers ample prospect in several engineering applications, some of which needs significant attention. This review aims at systematically assessing the uses of biochar as a potential carrier material for delivery of agrochemicals and microbes. The key parameters of biochar that are crucial to assess the potential of any material to be used for delivery purposes are discussed. The parameters such as the physicochemical properties of biochar, the mechanistic aspects of adsorption and release of agrochemicals and microbes from biochar, comparative assessment of biochar over other carrier materials, long-term effects of biochar and the economic and environmental benefits of biochar are discussed in detail. At the end, a brief perspective has also been laid out to discuss how nano-interventions could further be helpful to tailor biochar properties useful for delivery applications.