It comes from agricultural waste which is concentrated into charcoal-like biomass by heat­ing it. Very little processing required, low-tech, naturally holds CO2 rather than releasing it into the air. Primarily, biochar has been used as a means to enrich soil by keeping CO2 in it, and not into the air. As fuel, the off-gasses have been used in home heating. There is contro­versy surrounding the amount of acreage it would take to make fuel production based on biochar viable on a meaningful scale. Furthermore, use of agriculture wastes which rich with inorganic elements (NPK—) as compost (fertilizer) in agriculture.