Amid a U.S. ethanol boom, new research offers another take on the long-debated question of whether corn grain ethanol provides more energy than its production consumes. A recent study that takes into account all the energy used in farming and processing corn to make ethanol concludes that there is a small energy gain, but that the gain from using soybeans to make diesel is far greater--and that biodiesel is less of a greenhouse-gas polluter, too.

Energy in, energy out
Farming and processing corn grain to make ethanol yields about 25 percent more energy--in ethanol and co­products such as animal feed--than it consumes. In contrast, biodiesel and coproducts yield 93 percent more energy.