To determine if wood is a clean fuel, we must define what clean means. A 'dirty' fuel might include those that produce particulate matter; emit impurities contributing to acid rain or other environmental concerns; are non-renewable resources; and cause lasting environmental damage during the extraction, purification, or transportation process.
No fuel that involves combustion of a material is entirely clean. In comparison with other energy options, wood can be a relatively clean option. However, inefficient burning can produce particulate matter in smoke. The amount of particulates from wood burning can vary by wood stove management or the efficiency, type of wood, and moisture content of the wood.
Burning wood for energy (and all other hydrocarbons, like coal or gas) emits carbon dioxide into the air. However, wood is a renewable resource. Within 50 years, the carbon dioxide emitted from the wood stove can be offset if trees are replanted. Use the U.S. Environmental Protection Agency's Burnwise website to learn more about ways to cleanly and efficiently burn wood.