Biochar is charcoal created by pyrolysis of biomass. The resulting charcoal-like material can be used as a soil improver to create terra preta, and is a form of carbon capture and storage. Charcoal is a stable solid and rich in carbon content, and thus, can be used to lock carbon in the soil. Biochar is of increasing interest because of concerns about climate change caused by emissions of carbon dioxide (CO2) and other greenhouse gases (GHG).
Biochar is a way for carbon to be drawn from the atmosphere and is a solution to reducing the global impact of farming (and in reducing the impact from all agricultural waste). Since biochar can sequester carbon in the soil for hundreds to thousands of years, it has received considerable interest as a potential tool to slow global warming. The burning and natural decomposition of trees and agricultural matter contributes a large amount of CO2 released to the atmosphere. Biochar can store this carbon in the ground, potentially making a significant reduction in atmospheric GHG levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity and reduce pressure on old growth forests.
Current biochar projects are small scale and make no significant impact on the overall global carbon budget, although expansion of this technique has been advocated as a geoengineering approach. Further research is in progress, notably by the University of Edinburgh, which has a dedicated research unit.