There are various liquid, solid, and gaseous fuels, each of them represents an alternative to different, widely used liquids.
Alternative fuels obtained from renewable sources and energy crops can be classified considering their origin and energy power or caloric capacity.
We can consider four categories:
Biogas obtained from anaerobic fermentation
Biodiesel which originates from vegetable oils by the breakdown of a triglyceride obtaining glycerin and fatty acids, the latter are those formed by biodiesel.
Bioethanol is obtained from aerobic fermentation of raw material with high sugar content. a distillation process producing ethanol.
Direct burning biomass, solid fuels such as wood or firewood that are normally used in heating.
Gasoline and diesel have a high density