How do fossil fuels release energy?
fossil fuels are oxidized by the combustion process. This chemical process releases high quantities of heat. 14,560 btu/lb for carbon which is oxidized to carbon dioxide. 62,000 btu/lb for hydrogen to water and 4050 btu/lb for sulfur to sulfur dioxide. These are comparable to 8081 cal/g, 34,414 cal/g, and 2248 cal/g respectively.