Indigenous North Americans and early explorers utilized cottonwood for heating and cooking fires. Meriwether Lewis and William Clark, for example, relied on riparian cottonwoods in otherwise treeless stretches of the Great Plains for these purposes. In general, however, cottonwood has a mediocre reputation as a firewood.
Because of its lightness, cottonwood does not produce a lot of heat, and it tends to burn out fairly quickly. The California Energy Commission reports that the tree generates between 15.8 and 16.8 BTUs (British thermal units) per cord.
Properly cured cottonwood is easy to cut and quick to light, so it can be a good choice for kindling, incorporated into fires with hotter and longer burning logs such as those of ash or oak.
Smoke and Ash
Burned cottonwood tends to produce quite a bit of ash. Wet cottonwood may smoke prolifically, but well-dried logs often don’t produce much smoke at all. As with any firewood, it’s important to season logs adequately to allow them to dry out -- often six months to a year.