Biochar is a form of charcoal derived from crop residues and forest bi-products like stems, husks and other waste plant materials, which are heated in a low-oxygen environment known as pyrolysis. This locks much of the plant’s carbon into charcoal, which doesn’t easily decompose, preventing most of the trapped carbon from decaying for hundreds or thousands of years. When added back to croplands, some types of biochar can also improve soil health. (N4C)