How does grain-based ethanol compare to cellulosic ethanol?
Cellulosic ethanol is produced from plant parts other than the grain or seed. That partly gets around the issue of cutting into our food supply to drive our cars. Also, perennial vegetation—either grass or trees—can be used as feedstock for cellulosic ethanol. This is a clear benefit from a water quality perspective because perennial crops have a longer growing season and a fully established root system that continually takes up water and nutrients. Perennial crops lose much less nutrients than annual crops like corn, soy, and wheat, which actively grow for only a short time each year. In general, perennial crops also deliver more energy relative to the energy used to produce it. The downside of cellulosic ethanol is that you have to convert the stored energy in the crop to a usable energy product. Right now, with all the focus on liquid fuels, the technology isn’t there. But aggressive research is underway.
