Ethanol vs. Biodiesel: Life Cycle Impacts
To add fuel to the fire that is the ongoing debate comparing the big two biofuels: ethanol and biodiesel (here's our first go at it). An analysis by University of Minnesota researchers of the full life cycles of soybean biodiesel and corn grain ethanol concludes that biodiesel has much less of an impact on the environment and a much higher net energy benefit than corn ethanol, but that neither can do much to meet US energy demand. The researchers tracked all the energy used for growing corn and soybeans and converting the crops into biofuels. They were fairly dilligent about the life cycle impacts, also looking at how much fertilizer and pesticide corn and soybeans required and how much greenhouse gases and nitrogen, phosphorus, and pesticide pollutants each released into the environment. The study showed that both corn grain ethanol and soybean biodiesel produce more energy than is needed to grow the crops and convert them into biofuels. This finding flies in the face of other studies claiming that these biofuels require more energy to produce than they provide. The amount of energy each returns differs greatly, though: soybean biodiesel returns 93% more energy than is used to produce it; corn grain ethanol currently provides just 25% more energy.
Still, the researchers caution that these biofuels are not the silver bullet we're hunting to help insure a greener future; neither can come close to meeting the growing demand for alternatives to petroleum, but they think it's a good start. Alternatively, biofuels from feedstocks such as switchgrass, mixed prairie grasses and woody plants produced on marginally productive agricultural land or biofuels produced from agricultural or forestry waste have the potential to provide much larger biofuel supplies with greater environmental benefits than corn ethanol and soybean biodiesel. So, the jury may still be out on the efficiency and future of biofuels. via ::Green Car Congress