Most of the biofuels on the market now fall into one of two categories: bio-alcohols, such as the ethanol made primarily from corn in the U.S., and biodiesels, which are made from fatty acids. Both are no more than additives in gas or diesel, unless an engine is specially designed to run on them.

The next wave of alternative fuel hopefuls could be synthetic analogues—fuels created by genetically engineered bacteria, designed to be completely compatible with engines that run on fossil fuel. Today in the Proceedings of the National Academy of Sciences, researchers at the University of Exeter led by John Love announced that they've produced one such biofuel with plans to push toward commercial application.