Wood is less and less used as fuel because of its increasing scarcity and because coal is abundant and easily handled. Charcoal, made from wood, is now used only for special purposes because of its high cost. Charcoal is prepared by heating wood to a high heat and thereby distilling off nearly all water and volatile gases, leaving only carbon and non-combustible mineral salts. The heating must be done under a covering which will exclude air.

In later processes, charcoal is produced in kilns, or in closed retorts in which wood is distilled for pyroligneous acid and wood alcohol, and charcoal is a by-product.