The best biofuel--The Food, Energy, and Environment Trilemma

"The search for beneficial biofuels should focus on sustainable biomass feedstocks that neither compete with food crops nor directly or indirectly cause land-clearing and that offer advantages in reducing greenhouse-gas emissions. Perennials grown on degraded formerly agricultural land, municipal and industrial sold waste, crop and forestry residues, and double or mixed crops offer great potential. The best biofuels make good substitutes for fossil energy. A recent analysis suggests that more than 500 million tons of such feedstocks could be produced annually in the United States (Science)"