The process goes something like this: Cows excrete their spent fuels as manure, which is then flushed out into a lagoon where microbes begin breaking it down, resulting in the production of methane gas. The gas is then further purified at a local refinery that strips out unwanted bits like carbon dioxide and hydrogen sulfide. After this final refining, the fuel is pressurized and fed into Cummins diesel engines that have been converted to run properly on methane gas.
Proponents of this technology suggest that there is enough manure to displace the gasoline requirements of up to 16 million gas or diesel vehicles. It's both gross and brilliant all at once.
[Source: Wired | Photo: JelleS, CC 2.0]