A biofuel is a fuel produced from recently living organisms.
[2] The table below includes entries for popular substances already used for their energy, or being discussed for such use.
The final two columns deal with the carbon footprint of the fuel.
The fourth column contains the proportion of CO2 released when the fuel is converted for energy, with respect to its starting mass, and the fifth column lists the energy produced per kilogram of CO2 produced.
But these numbers do not account for other green house gases released during burning, production, storage, or shipping.