Petroleum is a limited resource. Only so much was made, and as our use of it goes on, only the more expensive to get, and harder to get, stuff remains. To claim otherwise is to deny thermodynamics. (And yes, people have denied thermodynamics to my face.) Petroleum is also the source of gasoline, and when gasoline gets expensive, people get really, really freaky about it.
Discovery News is reporting today that a source can be found in our agricultural fields. Well, with a little chemical modification. Apparently nitrogen fixing bacteria, the kind that favors the roots of legumes and provides a major organic boost to nitrogen in the soil, can produce propane if exposed to carbon monoxide.
But carbon monoxide is a deadly poison, and propane isn't quite energy-dense enough to power your car. (Though you can cook with it, or heat with it.) So, biochemists are hoping to extract this process, and modify it to turn carbon dioxide into bio-buteral, which would function like gasoline in your car's engine. Not only would such a process be endlessly renewable, but it would leech carbon from the air. (Okay, admittedly that carbon would come right back when you drove, but it would change a carbon-producing process into a carbon-neutral one.)
I'm not entirely clear on what the energy source of this process would be. Bacteria use their stored ATP (the fuel of biological life) to fix the nitrogen, as a way of making protein for themselves, and feeding the plants that house and shelter them. If we used genetically engineered bacteria to produce gasoline, they would need to be fed. Probably with sugar. If we used a chemical process, energy would probably have to be added by some means. Which, knowing this economic environment, would be coal. In both cases, no longer carbon neutral. Sugar has to be grown, and shipped, with, you guessed it, gasoline. And coal? Coal is basically purified fossil carbon.