Gas from Grass
Ethanol production has sparked a hot debate among environmental scientists and farmers. It's true that ethanol burns cleaner than conventional gasoline, emitting less carbon dioxide and benzene into the air. It's also true that corn and other plants used as ethanol feedstock absorb atmospheric carbon dioxide in their growth stage, greatly reducing carbon dioxide levels over the entire fuel life cycle [source: U.S. Department of Energy]. But the dependence on corn as an ethanol feedstock in the United States has created problems, both with the food supply and fossil fuel consumption.
Humans directly consume only two out of every 10 ears of corn grown in the U.S., either as fresh corn, corn syrup, corn meal or other corn derivatives. The other eight ears traditionally became feed for livestock like cows, pigs and chickens, but that was before the ethanol boom. Thanks in part to government subsidies, more corn was grown for ethanol from August 2011 to July 2012 than for livestock [source: Lott]. That was a first in American farming history. In a year when drought conditions lowered total corn yield, critics blame ethanol production for even higher food prices [source: McDonald].
Corn and soybeans, another popular ethanol feedstock, also require large amounts of fossil fuel energy to produce. Tractors burn up their fair share of fossil fuels, but the biggest culprit is synthetic fertilizer. Nitrogen fertilizer, for example, requires 1.5 tons (1360.7 kilograms) of fossil fuels -- usually coal and natural gas -- to produce one ton (907.18 kilograms) of nitrogen [source: Oliver].
Thankfully, researchers and farmers have identified a number of non-food sources of ethanol feedstock that can grow just about anywhere without any additional fertilizers. In the U.S., the best options are tall grasses like switchgrass and miscanthus. These grasses grow more than 10 feet (3.05 meters) high in thick strands, and they're perennials, which means they can be harvested in the fall and grow back in the spring. Fewer plantings means less fossil fuel burnt in the tractor. In tropical climates like Hawaii and Southeast Asia, researchers are experimenting with bana grass, sweet sorghum and an inedible oil nut called jatropha [source: Smith].
These grasses can grow in poor soils with little irrigation or fertilizer input. And they pack a biomass punch. According to tests by the Argonne National Laboratory, switchgrass has an energy output ratio of 1 to 10, meaning every unit of energy consumed to produce switchgrass ethanol results in 10 units of available energy. Corn ethanol, on the other hand, produces only 1.36 units of energy output for every unit of energy input [source: Wang].
The switch to "grassoline" is ingenious because it doesn't compete with existing food crops, can be grown on marginal land, doesn't rely on synthetic fertilizers and produces a far greater amount of energy per unit of biomass. That helps to keep food prices down, fuel costs down, and pollution levels low -- a win for everyone!