Compressed natural gas (CNG) vehicles have been around a while and have had a great deal of success — look at all those NYC Crown Vic cabs adapted to use CNG. Though the fuel is abundant and relatively cheap, one of the biggest limiting factors has always been how to package the bulky cylindrical tanks used to store the fuel.
There may be an answer, and you can feel it in your gut. Literally, because the solution proposed by Tucker Gilman of Otherlab is to design the tanks like intestines, which allows for a much more efficient use of space.
I really like this idea, partially because of how amazing these things will eventually look in a junkyard. I just hope nobody cheaps out on the material of these gas-guts, because tracking down and repairing a leak looks like it'd be a nightmare.
Also, the analogues between exhaust and farting just get better and better.