Cellulose is not a hydrocarbon; it is a carbohydrate. Hydrocarbons are made of carbon and hydrogen exclusively. Carbohydrates contain carbon, hydrogen and oxygen. The amount of oxygen in a typical carbohydrate is about 50% by weight. The oxygen in the carbohydrate has, in effect, already reacted with the fuel species hydrogen and carbon and is therefore inert with respect to combustion. Similarly, most of the hydrogen and carbon have also already reacted by forming bonds with the oxygen. The result is that carbohydrates release far less energy per unit weight than do hydrocarbons during combustion.

Hydrocarbons are usually volatile, carbohydrates are not. Carbohydrates must be pyrolized to create combustible gases.