According to the U.S. Department of Energy, three other possible biofuels are emerging — biogas, biobutanol and hydrogenation-derived renewable diesel. Biogas makes use of organic material, like manure or solid waste, which is decomposed and refined into a substitute for natural gas. One of the plusses for biogas is that it could be transported through the current natural gas infrastructure.
Biobutanol is butanol alcohol concocted from crops, grass or waste. Because it's so similar to ethanol, biobutanol can also be used in today's engines. With a few changes, existing ethanol plants could make biobutanol, and it could be distributed the same way as gasoline.
And, lastly, there's hydrogenation-derived renewable diesel, fuel made by refining vegetable oil or fat in an oil refinery. This fuel can stand on its own or be mixed with petroleum. Development of hydrogenation-derived renewable diesel is still in its early stages, but it could probably be distributed through existing systems.