Are certain feedstocks more efficient for biofuel production than others?
Ethanol in the United States is mainly produced from the starch in corn grain. There has been much debate as to whether using corn as feedstock yields a positive or negative energy balance, however. Much depends on the relative productivity of feedstocks, the nature of the technologies that are used for conversion, and how these feedstock crops are grown—whether or not they are farmed in an energy-intensive way. Corn-based ethanol tends to be at the bottom end of most efficiency estimates, especially if there is high fertilizer use, energy-intensive irrigation, and machine-heavy cultivation involved. Ethanol made from sugarcane tends to require less energy than that made from corn—especially that from Brazil, since much of it is rainfed, and the waste products from cane crushing (bagasses) are used as energy inputs. In addition, once the technology to produce cellulosic ethanol becomes widely available, the energy lifecycle balance of ethanol is expected to improve significantly.
