Solid fuel refers to various types of solid materials that are used to produce energy and generate heating , usually emitted by combustion .
Dry fuels include wood (see firewood ), charcoal , peat , charcoal , hexamine fuel pellets, and pellets made from wood (see wood pellets ), corn , wheat , rye and other grains . Solid fuel rocket technology also uses solid fuel (see solid propellants ).
Humans have used solid fuels for centuries to make fire . Coal was the source of energy that enabled the industrial revolution , from igniting an oven , to running a steam engine . Wood was also used extensively to operate steam locomotives . Both peat and coal are still used to generate electricity today.
The use of solid fuels (such as coal) is restricted and banned in some urban areas , due to unsafe levels of toxic emissions. While other solid fuels such as wood (firewood) are increasingly being used as a heating technology, the availability of high-quality fuels is increasing. In some areas, smokeless coal is the only solid fuel used. In Ireland, peat pellets are used as smokeless fuel. They are also used to start coals.