Biofuel is any fuel that is produced from living or once-living matter in a short period of time, days, weeks, or even months. This contrasts with fossil fuels, which take millions of years to form, and with other types of fuel which are not based on hydrocarbons such as nuclear fission. What makes biofuels tricky to understand is that they are not made by a living organism, though they can be. Biofuels can also be made through chemical reactions, carried out in a laboratory or industrial setting, that use organic matter, called biomass, to make fuel.
There IS one requirement that must be met for fuel to be considered a biofuel. That is
A) the starting material must be CO2 that can be fixed or turned into other molecules.
B) the biomass is produced year after year through sustainable farming practices.
C) it does not harm ecosystems, contribute to acid rain, or worsen global warming.
D) they do not produce any greenhouse gases when used.