Biochar: An emerging material for the improvement of biological treatment of organic waste

Biochar is a carbon-rich material that can be produced from waste biomass, making it a sustainable alternative to activated carbon. Biochar production is a carbon capture and storage strategy, and its physicochemical characteristics make it a useful additive for many processes, including the biological treatment of organic waste. Particularly, biochar has a high adsorbent capacity due to its high porosity, surface area and functional groups, which makes this material especially attractive in technologies with the presence of known inhibitors or that imply the emission of polluting compounds. In anaerobic digestion, its application improves the stability of the system against inhibition, increases the efficiency of the process, and allows the purification of biogas in situ. In composting, it reduces greenhouse gas and odor emissions and improves the quality of the compost obtained, increasing the nutrient content, immobilizing heavy metals, and reducing the presence of pathogenic microorganisms. Even so, the use of biochar in the biological treatment of organic waste is still an incipient field that requires research and consensus on key aspects such as the optimal dose of biochar, the transformation of the organic material over time, and its subsequent application as an amendment for the improvement of agricultural soils.