What fuels can be grouped as alternative fuels?

"Alternative fuel" is an imprecise term that seeks to contrast certain fuels with what might called traditional fuels. Traditional fuels would include coal, oil, gas, and wood as a few examples. It is not possible to produce a definitive list of products but here are some suggestions.
Carbon based alternative fuels might include ethanol from bio-mass, recycled bio-mass from agriculture or forestry operations, peat dug from soils rich in organic matter.

Non carbon based alternative fuels include solar energy used to produce electricity or hot water, wind, waves, tidal energy, hydro-electric, hydrogen and more.

Nuclear power can sometimes be considered to be an alternative energy source or a traditional one.