Hate to tell you, but there is a fuel that is formed from methane. Don't remember all the details, but it produces the energy needed to run your car. Just not very people friendly. But smells more and more attractive as the other options get expensive.
It isn't expensive, but the marketing on it didn't work. When they looked into it, and made it public that such a thing existed., most people polled were disgusted with the thought. I wonder if they would be now? Makes sense to me.