Liquid Biofuels, and ethanol in particular, have been touted as the solution to U.S. dependence on foreign oil. But most biofuels actually require almost as much energy to produce as they provide. Despite years of development, biofuels remain uncompetitive with fossil fuels.
Biofuels are derived from plant material and fall mainly into two categories: ethanol and biodiesel. In the United States most ethanol comes from corn, but globally it is produced from a variety of plants, including corn, sorghum, sugar, sugar beets, and switchgrass. In a simple chemical process, biodiesel is made from vegetable oil.
The United States currently produces roughly 13 billion gallons (300 million barrels) of ethanol a year, almost entirely from corn—nearly a tenfold increase in over a decade. The ethanol industry has benefited from both an import tariff of 54 cents per gallon on foreign-produced ethanol as well as a subsidy of 45 cents per gallon, costing U.S. taxpayers billions of dollars. The ethanol industry also benefits from laws mandating the blending of ethanol with gasoline.
Unfortunately, producing ethanol is at best a poor use of resources, and at worst a net energy loser. The energy content of ethanol is about two-thirds that of gasoline. An analysis by the think tank Environmental Working Group indicates that blending 10 percent ethanol with 90 percent gasoline (the ratio mandated by the renewable fuel standard) reduces the miles per gallon achieved by almost 4 percent on average. From an energy standpoint, this means that the 10.6 billion gallons of ethanol produced in 2009 in the United States replaced the equivalent of only 7.1 billion gallons of gasoline.
The net energy ratio (energy return on energy invested, or EROEI) for biofuels in general, and corn ethanol in particular, is abysmal. Various studies have estimated the EROEI of corn ethanol at between 0.8:1 and 1.3:1, meaning that we get between 0.8 and 1.3 joules of energy from ethanol for every joule of energy invested in producing that ethanol. The EROEI of gasoline, by comparison, is between 5:1 and 30:1, depending in part on the source of the petroleum.
Additionally, in recent years the ethanol industry’s huge purchases of corn as a feedstock for fuel production have caused corn prices to increase, raising the cost of basic food items for the global poor. In response, many ethanol advocates are optimistic about cellulosic ethanol (in particular, switchgrass), since it supposedly would not compete directly with food crops. But cellulosic ethanol also has low net energy, and carries the potential for increased competition for food-growing land.
The EROEI of biodiesel is only somewhat better than that for ethanol. While biodiesel produces fewer emissions (except for nitrogen oxides) than petroleum diesel, its production at industrial scales would inevitably mean further increased competition for arable land and possibly for certain food crops, such as soybeans.