why is it neccesary for an alternative fuel to be formed in an endothermic reaction?

Question

for example:

ethanol

C6H12O6 (s) → 2 CH3CH2OH (l) + 2 CO2 (g)
is delta H = 260kJ/mol

this is an endothermic reaction

Answer 1

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When we burn a fuel, we are using its chemical energy. Thus chemical "burning" is always exothermic. The fuels must be some chemicals with high internal energy. But the natural resource is limited. Therefore we have to make chemicals with high internal energy from some chemicals with low internal energy. From the principle of energy concervation, we have to STORE the energy into the chemicals to make the internal energy high. That is why it is neccesary for an alternative fuel to be formed in an endothermic reaction.

Answer 2

In your example, the delta H energy is stored in the ethanol until it is released by burning. Just as batteries store electrical energy, fuels store chemical energy. Just as you have to add energy to charge a battery, so too you must add energy to form a fuel. Unless energy is added, there is no energy stored and then there is no energy to be released later.