Biochar is a type of charcoal, made by burning organic matter WITHOUT much air/oxygen. When organic matter burns, most of the fire is gas that comes from the organic matter when it gets hot. The remaining charcoal is mostly carbon, with millions of very very small holes (pores). Biochar to keep carbon in the soil long-term (instead of CO2 in the air) - reducing climate change, to store nutrients, to store water...