Mechanisms and applications of biochar in environmental remediation, energy, and catalysis

Biochar is a carbonaceous material produced from the thermochemical treatment of biomass in the absence or with a limited supply of oxygen. Despite the use of carbonized biomass to improve agricultural soils over centuries, the application and interest in biochar have grown dramatically owing to its diverse applications in the environment, energy, industry, etc. This review focuses on key technologies of biochar production, comparing their advantages, disadvantages, and their effect on biochar properties. Emphasis has been placed on the physical-chemical properties of biochar (pore structure, surface chemistry, element composition, specific surface area, etc.) as well as the production parameters that control them. Approaches for modifying and activating biochar to improve performance in targeted applications are also discussed. The review further examines the growing role of biochar in pollutant removal, renewable energy systems, and catalytic transformations. In addition, recent advances in nanobiochar are highlighted, emphasizing how reducing particle dimensions to the nanoscale alters surface reactivity, adsorption behavior, and functional performance. Nanomaterials, generally defined as materials with dimensions below 100 nm, possess exceptionally high surface-to-volume ratios that can result in unique physicochemical properties not observed in their bulk counterparts. Finally, current challenges, emerging opportunities, and future pathways for the development and application of biochar-based materials are critically evaluated.