The most commonly produced liquid biofuels for transportation are biodiesel and ethanol. Chemical and energy characteristics of commercial biodiesel are largely the same as fossil diesel. There are slight differences between biodiesel (or fatty-ester methyl ether; FAME), pure plant oil, and synthetic biodiesel.
Biofuel blends can be burned in conventional combustion engines with or without adaptations, depending on the type of fuel used. Low-percentage blends (5-20%) in conventional diesel can be used in conventional engines. Pure biofuels require engine adaptations to specific characteristics of the fuel. Some biofuels even enable engine adaptations that improve performance or energy efficiency.
Biogas is also expected to be used in road transport, mainly in public transport (city buses) and municipal fleets. Biomethane is already in use in some European countries, fed directly into the natural gas grid (for heat and power generation and for fueling vehicles).
So-called first-generation biodiesels are commonly produced from vegetable oils, extracted from oil palm, rapeseed, sunflowers, soybeans, and so forth. The vegetable oils are converted through transesterification into FAME, which can be used in place of petroleum diesel.