Glucose is a hydrocarbon which is used by the cells to obtain energy and the oxidation of glucose results in the production of CO2, H2O, and energy. Some of the energy is released in the atmosphere and some are trapped in the form of ATP. This process is called respiration.
Burning of fossil fuel also involves a reaction that is similar to this reaction because fuels are hydrocarbons that were made by buried fossil after thousands of years.
Therefore when fossil fuels are burned the carbon and hydrogen are released in the atmosphere which reacts with oxygen and converts into CO2 and H2O and as it is an exothermic process so energy is released in this process.
