Why do somethings contain more heat energy than others???

Question

For example, when wood with the same mass as manure is burnt, the wood has greater heat energy. Why?

Answer 1

might have to do with carbon and density

Answer 2

that is due to many reasons, the first is the atoms itself since some atoms have more energy due to the number of free electons in their outer level ,the second is the bonds since some bonds have more energy than others,for example, a double bond has more energy than the single bond,generally the greater the energy needed to form compounds ,the greater the energy they release when being burned,wood is formed of complicated greatly bonded cellulose fibres while manure consists of simple,loosely bonded hydrocarbons .all that could be evaluated by the different laws and practical procedueres of chemical thermodynamics.

Answer 3

A chemistry book could explain it better than I can, but it has to do with the amount of energy that different compounds can release and that depends on the electron bonding among molecules. Gasoline and kerosene are chemically similar but burn at different temperatures because of the way the electron bonds in the molecules are arranged. You will no doubt get a much better answer than this, but thats the general idea.