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Considerable interest is being shown in using biochar production from waste biomass with a variety of disciplines to address the most pressing environmental challenges. Biochar produced by the thermal decomposition of biomass under oxygen-limited conditions is gaining popularity as a low-cost amendment for agro-ecosystems. The efficiency of biochar formation is affected by temperature, heating rate, feedstock type, particle size and reactor conditions. Properties such as pH, surface area and ash content of produced biochar increases with increasing temperatures. Biochar produced at lower heating rates may have high porosity and be beneficial for morphological changes in the soil. Biochar can help to enhance soil health and fertility as well as improve agricultural yield. As a result, biochar can assist in increasing food security by promoting sustainable agricultural systems and preserving an eco-friendly environment. Biochar is also widely being used as a sorbent for organic and inorganic pollutants, owing to its large surface area, allowing it to be immobilized from soil with ease. The functional groups and charges present on the surface of biochar play an important role in pollutants removal. This review focuses on the mechanisms of biochar production using different waste materials as a feed stock, factors that influence biochar quality as well as application of biochar in agricultural soil and their reclamation as well. This article also discusses knowledge gaps and future perspectives in the field of biochar-based toxic-pollution remediation.

Conventional tillage (CT)-based agriculture is known to be ecologically indiscreet, economically and environmentally unsustainable, and leads to the degradation of soil and the environment in the Indo-Gangetic Plain (IGP). The surface seeding (SS) method was introduced to manage agro-ecosystems for sustaining productivity and increasing farmers’ profits, while sustaining the natural resources. Here, we conducted a systematic literature review on SS of wheat reported in the IGP, with the aim to cover the concept of SS, its impact on wheat yield, soil properties, and the environment, with the potential benefits and constraints. The major findings are: (i) an SS-based rice–wheat system improves productivity (∼10%) and profitability (20–30%),while employing a lesser amount of irrigation water (15–30%) and energy input (20–25%) compared to a conventional system; (ii) an SS-based system is more adaptive to extreme climatic conditions, reduces the carbon footprint, and increases crop production; (iii) an SS approach enhances soil health by virtue of increased soil organic carbon and improved soil aggregation, as well as soil, water, and energy conservation; (iv) SS consisting of no-tillage with substantial crop residue retention offers an alternative to crop residue burning. Strong policies/legislation are required to encourage SS of wheat, in order to limit residue burning, and provide farmers with carbon credits in exchange for carbon sequestration and reduced greenhouse gas emissions.

Biochar is considered as a potential substitute for soil organic matter (SOM). Considering the importance of biochar, the present review is based on the different benefits and potential risks of the application of biochar to the soil. Biochar addition to low organic carbon soils can act as a feasible solution to keep soil biologically active for the cycling of different nutrients. The application of biochar could improve soil fertility, increase crop yield, enhance plant growth and microbial abundance, and immobilize different contaminants in the soil. It could also be helpful in carbon sequestration and the return of carbon stock back to the soil in partially combusted form. Due to the large surface area of biochar, which generally depends upon the types of feedstock and pyrolysis conditions, it helps to reduce the leaching of fertilizers from the soil and supplies additional nutrients to growing crops. However, biochar may have some adverse effects due to emissions during the pyrolysis process, but it exerts a positive priming effect (a phenomenon in which subjection to one stimulus positively influences subsequent stimulus) on SOM decomposition, depletion of nutrients (macro- and micro-) via strong adsorption, and impact on soil physicochemical properties. In view of the above importance and limitations, all possible issues related to biochar application should be considered. The review presents extensive detailed information on the sustainable approach for the environmental use of biochar and its limitations.

AbstractThe iron impregnated fungal bio-filter (IIFB) discs of luffa sponge containing Phanerochaete chrysosporium mycelia have been used for the removal of As(III) from water. Two different forms of same biomass viz. free fungal biomass (FFB) and modified free fungal biomass (chemically modified and iron impregnated; CFB and IIFB) have been simultaneously investigated to compare the performance of immobilization, chemo-tailoring and iron impregnation for remediation of As(III). IIFB showed highest uptake capacity and percentage removal of As(III), 1.32 mg/g and 92.4% respectively among FFB, CFB and IIFB. Further, the application of RSM and ANN-GA based mathematical model showed a substantial increase in removal i.e. 99.2% of As(III) was filtered out from water at optimised conditions i.e. biomass dose 0.72 g/L, pH 7.31, temperature 42 °C, and initial As(III) concentration 1.1 mg/L. Isotherm, kinetic and thermodynamic studies proved that the process followed monolayer sorption pattern in spontaneous and endothermic way through pseudo-second order kinetic pathway. Continuous mode of As(III) removal in IIFB packed bed bioreactor, revealed increased removal of As(III) from 76.40 to 88.23% with increased column height from 5 to 25 cm whereas the removal decreased from 88.23 to 69.45% while increasing flow rate from 1.66 to 8.30 mL/min. Moreover, the IIFB discs was regenerated by using 10% NaOH as eluting agent and evaluated for As(III) removal for four sorption–desorption cycles, showing slight decrease of their efficiency by 1–2%. SEM–EDX, pHzpc, and FTIR analysis, revealed the involvement of hydroxyl and amino surface groups following a non-electrostatic legend exchange sorption mechanism during removal of As(III).

Biological treatment methods are the most important part of the treatment process for domestic wastewater, the amounts of which are increasing every year due to rapid, unregulated urbanization and the rising number of people living in such areas. At the same time, microorganisms existing in treatment facilities should not only effectively utilize organic pollutants, but also be resistant to a variety of organic and inorganic contaminants. This study’s objective is to isolate and identify—using molecular genetic techniques—strains of bacteria that tolerate concentrations of heavy metals (Ni, Cd, Pb, Zn and Cu) in the 3–5 mM range. They were sourced from water and sludge samples obtained from sewage treatment facilities in a large city. Outcomes of phylogenetic analysis of 16S rRNA gene sequences revealed that tolerant strains of bacteria belonged to the genera Pseudomonas, Serratia and Klebsiella; strains belonging to the genus Pseudomonas dominated. Of ten resistant strains, nine were isolated from sludge and water samples of the secondary sedimentation tank, and the other one from a treatment plant’s digester. Changes in the color of microorganisms’ colonies became evident when cultivated on media enriched with heavy metals. Cultivating nonpathogenic strains of these bacteria and their introduction into communities of other activated sludge microorganisms could have practical application to biological decontamination of wastewater.

Current study was conducted to evaluate the effect of important land uses and soil depth on soil organic carbon pools viz. total organic carbon, Walkley and black carbon, labile organic carbon, particulate organic carbon, microbial biomass carbon and carbon management index (CMI) in the north Western Himalayas, India. Soil samples from five different land uses viz. forest, pasture, apple, saffron and paddy-oilseed were collected up to a depth of 1 m (0–30, 30–60, 60–90 cm). The results revealed that regardless of soil depth, all the carbon pools differed significantly (p < 0.05) among studied land use systems with maximum values observed under forest soils and lowest under paddy-oilseed soils. Further, upon evaluating the impact of soil depth, a significant (p < 0.05) decline and variation in all the carbon pools was observed with maximum values recorded in surface (0–30 cm) soils and least in sub-surface (60–90 cm) layers. CMI was higher in forest soils and lowest in paddy-oilseed. From regression analysis, a positive significant association (high R-squared values) between CMI and soil organic carbon pools was also observed at all three depths. Therefore, land use changes and soil depth had a significant impact on soil organic carbon pools and eventually on CMI, which is used as deterioration indicator or soil carbon rehabilitation that influences the universal goal of sustainability in the long run.