That's one of the main questions facing all of us as we look to wean ourselves from fossil fuels. The engines that get us and our stuff around have to run on something. But even the initial steps toward corn-based ethanol show that won't work; it shifts the greenhouse gases without eliminating them, does nothing to cut carbon dioxide emissions and is already having an inflationary impact on the price of corn.

Figuring out how to run our vehicles responsibly is the work of the Alternative Fuel Vehicle Institute. Their blog, by Kimberly Taylor, is an excellent place to get the latest thinnking, research and breakthroughs as the planet looks for something to run on that isn't refined from prehistoric plants and animals. It's worth bookmarking and checking regularly.