Question

One example of
solid fuel.
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Answer 1

Answer:

I think the answer is biogas of your question

Answer 2

Answer:

Explanation:

Solid fuels include peat, wood, and coal and can encompass solid rocket fuels as well as metals. The earliest fuels used by man were nonfossil fuels of wood and oil from plants and fats from animals. The windmill and water wheels were other sources of energy.