Conceptual image of biochar (black) being used to enhance soil quality and promote plant growth (green shoot). Biochar is a form of charcoal (mostly carbon) produced by heating organic matter in the absence of oxygen, a process called pyrolysis. This avoids the production of carbon dioxide and locks up the carbon in the biochar. In this form, the carbon can remain in soils for thousands of years, increasing the soil fertility and acting as a carbon sink. This sequestration of the carbon helps to meet targets to reduce emission of carbon dioxide, a cause of climate change.