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.

The increasing rate of industrialization, anthropogenic, and geological activities have expedited the release of heavy metals (HMs) at higher concentration in environment. HM contamination resulting due to its persistent nature, injudicious use poses a potential threat by causing metal toxicities in humans and animals as well as severe damage to aquatic organisms. Bioremediation is an emerging and reliable solution for mitigation of these contaminants using rhizospheric microorganisms in an environmentally safe manner. The strategies are based on exploiting microbial metabolism and various approaches developed by plant growth promoting bacteria (PGPB) to minimize the toxicity concentration of HM at optimum levels for the environmental clean-up. Rhizospheric bacteria are employed for significant growth of plants in soil contaminated with HM. Exploitation of bacteria possessing plant-beneficial traits as well as metal detoxifying property is an economical and promising approach for bioremediation of HM. Microbial cells exhibit different mechanisms of HM resistance such as active transport, extra cellular barrier, extracellular and intracellular sequestration, and reduction of HM. Tolerance of HM in microorganisms may be chromosomal or plasmid originated. Proteins such as MerT and MerA of mer operon and czcCBA, ArsR, ArsA, ArsD, ArsB, and ArsC genes are responsible for metal detoxification in bacterial cell. This review gives insights about the potential of rhizospheric bacteria in HM removal from various polluted areas. In addition, it also gives deep insights about different mechanism of action expressed by microorganisms for HM detoxification. The dual-purpose use of biological agent as plant growth enhancement and remediation of HM contaminated site is the most significant future prospect of this article.

The treatment of wastewater is an expensive and energy-extensive practice that not only ensures the power generation requirements to sustain the current energy demands of an increasing human population but also aids in the subsequent removal of enormous quantities of wastewater that need to be treated within the environment. Thus, renewable energy source-based wastewater treatment is one of the recently developing techniques to overcome power generation and environmental contamination issues. In wastewater treatment, microbial fuel cell (MFC) technology has demonstrated a promising potential to evolve as a sustainable approach, with the simultaneous recovery of energy and nutrients to produce bioelectricity that harnesses the ability of electrogenic microbes to oxidize organic contaminants present in wastewater. Since traditional wastewater treatment has various limitations, sustainable implementations of MFCs might be a feasible option in wastewater treatment, green electricity production, biohydrogen synthesis, carbon sequestration, and environmentally sustainable sewage treatment. In MFCs, the electrochemical treatment mechanism is based on anodic oxidation and cathodic reduction reactions, which have been considerably improved by the last few decades of study. However, electricity production by MFCs remains a substantial problem for practical implementations owing to the difficulty in balancing yield with overall system upscaling. This review discusses the developments in MFC technologies, including improvements to their structural architecture, integration with different novel biocatalysts and biocathode, anode, and cathode materials, various microbial community interactions and substrates to be used, and the removal of contaminants. Furthermore, it focuses on providing critical insights and analyzing various types, processes, applications, challenges, and futuristic aspects of wastewater treatment-related MFCs and thus sustainable resource recovery. With appropriate planning and further studies, we look forward to the industrialization of MFCs in the near future, with the idea that this will lead to greener fuels and a cleaner environment for all of mankind.

Anti-microbial resistance (AMR) has recently emerged as an area of high interest owing to the rapid surge of AMR phenotypes. Metal oxide NPs (MeONPs) have been identified as novel phytomedicine and have recently peaked a lot of interest due to their potential applications in combating phytopathogens, besides enhancing plant growth and yields. Numerous MeONPs (Ti₂O, MgO, CuO, Ag₂O, SiO₂, ZnO, and CaO) have been synthesized and tested to validate their antimicrobial roles without causing toxicity to the cells. This review discusses the application of the MeONPs with special emphasis on anti-microbial activities in agriculture and enlists how cellular toxicity caused through reactive oxygen species (ROS) production affects plant growth, morphology, and viability. This review further highlights the two-facet role of silver and copper oxide NPs including their anti-microbial applications and toxicities. Furthermore, the factor modulating nanotoxicity and immunomodulation for cytokine production has also been discussed. Thus, this article will not only provide the researchers with the potential bottlenecks but also emphasizes a comprehensive outline of breakthroughs in the applicability of MeONPs in agriculture.

The modern agricultural system is facing the unprecedented task of contriving the extensive demand for agrarian production owing to population explosion and global climate change. The employment of Nanotechnology in agriculture has gained immense interest in recent times for the development of sustainable agricultural technologies and environmental remediation strategies. Nanotechnology pertains to the employment of nanoparticles and furnishes the potential to fabricate novel materials and products possessing improved quality. The nanomaterials may be used as; nanosensors, nanocides, nanofertilizers, nanobarcodes, and nano-remediators, which play a significant role in modern agricultural practices. However, the physical and chemical processes of nanoparticle production is neither economical nor environmentally sustainable. Therefore, the need for green or biogenic nanoparticles obtained from plants, bacteria, fungi or their metabolites has emerged as novel, sustainable, economical, biocompatible, and eco-friendly technology. In this perspective, the production and sources of biogenic nanoparticles and their implication in agro-ecosystems for crop productivity, soil health management, biocontrol, and environmental remediation have been focused on in this review. The potential development and implementation challenges are also explored.

Water scarcity due to contamination of water resources with different inorganic and organic contaminants is one of the foremost global concerns. It is due to rapid industrialization, fast urbanization, and the low efficiency of traditional wastewater treatment strategies. Conventional water treatment strategies, including chemical precipitation, membrane filtration, coagulation, ion exchange, solvent extraction, adsorption, and photolysis, are based on adopting various nanomaterials (NMs) with a high surface area, including carbon NMs, polymers, metals-based, and metal oxides. However, significant bottlenecks are toxicity, cost, secondary contamination, size and space constraints, energy efficiency, prolonged time consumption, output efficiency, and scalability. On the contrary, green NMs fabricated using microorganisms emerge as cost-effective, eco-friendly, sustainable, safe, and efficient substitutes for these traditional strategies. This review summarizes the state-of-the-art microbial-assisted green NMs and strategies including microbial cells, magnetotactic bacteria (MTB), bio-augmentation and integrated bioreactors for removing an extensive range of water contaminants addressing the challenges associated with traditional strategies. Furthermore, a comparative analysis of the efficacies of microbe-assisted green NM-based water remediation strategy with the traditional practices in light of crucial factors like reusability, regeneration, removal efficiency, and adsorption capacity has been presented. The associated challenges, their alternate solutions, and the cutting-edge prospects of microbial-assisted green nanobiotechnology with the integration of advanced tools including internet-of-nano-things, cloud computing, and artificial intelligence have been discussed. This review opens a new window to assist future research dedicated to sustainable and green nanobiotechnology-based strategies for environmental remediation applications.