Biochar, a low-cost material produced from the thermal pyrolysis of biomass, has multiple applications in the environment, energy, and agriculture sectors. These biochar applications have attracted global attention in the context of preparation, behaviour in a particular environment, modification, and especially aging processes. Biochar undergoes certain changes in their physical and biochemical characteristics due to different factors which are called aging and are triggered by biotic and abiotic processes. Numerous studies have focussed on the effectiveness of biochar by improving their properties using rapid and controlled laboratory conditions to scale up their applications. However, the impact of biotic- and abiotic-derived aging processes, their possible impact on biochar physicochemical properties, and how they affect the eco-toxicity and long-term stability of biochar in the environment has not been discussed in detail. This review mainly focused on the biotic- and abiotic-derived alterations in pore volume, surface area, elemental composition, surface functional groups, and molecular structures of biochar, leading to higher adsorption capacity, improving soil fertility, and possible changes in biochar stability. Extrapolation of biotic- and abiotic-derived changes in the biochar properties will help to understand the environmental risk of biochar and their sustainable field application for soil remediation and improving agricultural productivity.
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