Energy is stored in carbon bonds.
Explanation:
It is required to study the carbon bonds and their contents.
The formation of chemical bonds in atomic elements releases energy. For example: Solid carbon has less energy than a cloud of carbon atoms so it could be said graphite has less energy relative to a cloud of atomic carbon atoms. We would describe this energy with the name "bond energy". But this is the energy released by the hypothetical process of forming lists of C-C bonds from isolated carbon atoms. Â The point here is that the double bonds in CO2 are stronger than the combined bonds in oxygen gas and graphite (so they are lower energy) This means that the reaction between carbon and oxygen releases energy (it takes less energy to break all the O-O and C-C bonds than is released when new C=O bonds are formed. So elemental carbon "stores" energy relative to carbon dioxide.
It means: Carbon bonds store energy, they need energy to be bonded.
Finally, we can conclude that Energy is stored in carbon bonds.