Biochar refers to the black solid(charcoal) obtained by thermally decomposing biomass such as wood, in a low oxygen(O₂) condition.
The biochar in soil can store its carbon(C) for 100 to 10,000 years, depending on the temperature during its thermal decomposition(pyrolysis). When compared to planted trees which can generally fix carbon for about 60 years, biochar can stably maintain its form, hence store carbon longer.
Carbon dioxide(CO₂) sequestered from the atmosphere through plant photosynthesis can be stored in farmland by burying biochar. Carbon capture and storage using biochar can reduce the total amount of circulating carbon on the surface, which leads to the reduction of CO₂.