State of Science :: Environment
"Corn Ethanol Allure Plummets"
February 2009
Author(s): Dr. David Pimentel
Cornell University
CORN ETHANOL ALLURE PLUMMETS
By: Dr. David Pimentel Cornell University
The diminishing supply of oil and high prices is encouraging the conversion of grain or other biomass into ethanol fuel. Using corn or any other biomass for ethanol requires large land areas of fertile soil, and sunlight for green plant production plus significant quantities of water. Total green plants in the U.S., including all crops, forest, and grasses, combined collect only about 32 quads (32 x 1015 BTU) of sunlight energy per year. Meanwhile, the American population uses slightly more than 3 times that amount of energy each year as fossil fuels!
Enthusiasts suggest ethanol produced from corn grain and cellulosic biomass, like grasses, could replace much of the oil used in U.S. Consider that 20% of the U.S. corn crop was converted into 6 billion gal of ethanol in 2007, but that amount replaced only 1% of U.S. oil consumption. If the entire corn crop were used, it would replace a mere 7% of oil consumption–and not make the U.S. independent of foreign oil!
Several up-to-date analyses report that 14 energy inputs typically are required for corn production, then 9 more energy inputs are invested in fermentation and distillation operations, confirming that more than 140% more energy (mostly high value oil and natural gas) is expended to produce a gallon of corn ethanol than is in the ethanol gallon itself. Some investigators omit several of the energy inputs required in corn production and processing, such as energy for farm labor, farm machinery, energy production of hybrid corn-seed, irrigation, and processing equipment. Omitting several fossil energy inputs suggests that a corn ethanol production system provides a positive energy return. Investigators also differ about the energy value of the byproducts from making corn ethanol. In any event, corn ethanol is an inefficient choice from an energy cost and transport standpoint.
Cellulosic ethanol is touted as the replacement for corn ethanol. Unfortunately, cellulosis biomass contains less than 1/3rd the amount of starches and sugars in corn and requires major fossil energy inputs to release the tightly bound starches and sugars for ethanol conversion. About 170% more energy (oil and gas) is required to produce ethanol from cellulosic biomass than the ethanol produced.
The production of corn ethanol is highly subsidized by state and federal governments by more than $6 billion per year according to a 2006 report, "Biofuels --at What Cost? Government Support for Ethanol and Biodiesel in the United States," released by the International Institute for Sustainable Development in Geneva. These subsidies for a gallon of ethanol are more than 60 times those for a gallon of gasoline.
The environmental impacts of corn ethanol are serious and diverse. These include severe soil erosion of valuable cropland, plus the heavy use of nitrogen fertilizer and pesticides that pollute rivers. Large quantities of carbon dioxide are produced and released into the atmosphere because significant amounts of fossil fuel energy are used in ethanol production. Then during the fermentation process, about 25% of the carbon from the sugars and starches is released as carbon dioxide into the atmosphere. These two major releases of carbon dioxide significantly contribute to global warming.
Each gallon of ethanol requires 1,700 gallons of water (mostly to grow the corn) and releases 12 gallons of noxious sewage effluent from the fermentation process into the environment.
Using food crops, such as corn grain, to produce ethanol also raises major nutritional and ethical concerns. Nearly 60% of humans in the world now are currently malnourished, so the need for grains and other basic foods is critical. Growing crops for fuel squanders land, water, and energy resources vital for the production of food for people. The President of the World Bank reported that biofuels have increased world food prices 75%. Jacques Diouf, Director General of the U.N. Food & Agriculture Organization reports biofuels increasing world human starvation.
The world population is currently at 6.7 billion with a quarter million additional people added daily. Energy specialists project that peak oil and natural gas have already been reached and there are only about 60 years of these fuels remaining. Slowly oil and gas supplies will decline until these fuels are exhausted. This will create a critical situation for food production because all food supply currently depends primarily on oil and gas to maintain a highly productive agriculture. The Food and Agriculture Organization reports that cereal grain production per capita has been declining continuously for the past 24 years. This is critical because grains make up 80% of world food.
David Pimentel
(dp18@cornell.edu)
Professor of Ecology and Agricultural Sciences
Cornell University, Ithaca, NY 14853
July 26, 2008
