Nano-biochar: Properties and prospects for sustainable agriculture

Biochar is an extremely valuable carbon black material used since the Pre-Columbian Era in Latin America and is known for its properties to promote soil fertility and sustain crop production. Modern civilization has followed the footsteps of ancient civilizations and has prepared nano-sized biochar (nano-BC). The synthesis of nano-BC can be achieved using different feedstock materials via pyrolysis, yielding bulk-BCs which are mechanical transformed into the nano-BCs, the final value-added product. This review provides insights into structural, functional, and elemental properties concerning synthesis, surface properties including functional groups, and carbon stability. Moreover, the prospects of improving soil physicochemical properties including CEC, nutrient availability, soil water retention, and buffering capacity are discussed with agricultural implications. Mechanistic insights have been provided regarding how nano-BC can improve soil health and could promote plant growth and physio-biochemical properties, which further pave the way for its application to improve plant resilience to abiotic stress factors. Last, limited studies have been conducted that elucidate potential negative effects including contaminant mobilization and residual effects and these are also critically discussed. Above all, nano-BC could be used as a beneficial soil amendment to boost crop production and enhance soil fertilities.