Biofuels based on corn are our first effort to grow green oil, but they have clearly not succeeded. Current biofuels take too much land and too much energy to grow, and too much of that energy goes into building parts of a plant that we can’t easily convert into fuel. The answer will come from simple engineered organisms that can soak up energy in a vat in any sunny spot and turn that sunlight straight into a precursor for fuel, preferably a precursor that con go straight into an existing oil refinery.