MADISON, Wisconsin, March 11, 2008 (ENS) - The U.S. demand for corn-based ethanol will add to nutrient pollution in the Gulf of Mexico and expand the annual low oxygen "dead zone" that kills fish and other aquatic life, a computer model run by an international team of scientists shows.
In the first study of its kind, lead author Simon Donner of the University of British Columbia and Chris Kucharik of the University of Wisconsin-Madison modeled the effects of biofuel production on nutrient pollution in an aquatic system.
The researchers looked at the estimated amounts of land and fertilizer needed to meet future production goals for corn-based ethanol.
The new U.S. Renewable Fuels Standard, signed into law in December 2007 as part of the revised energy bill, calls for the production of 36 billion gallons of biofuels, mainly ethanol and biodiesel, annually by 2022.
Not all of those billions of gallons of biofuels will be ethanol made from corn. An estimated 21 billion gallons will come from advanced biofuels, which can be produced using a variety of new feedstocks and technologies. Of this, roughly 16 billion gallons is expected to be from cellulosic biofuels, derived from plant sources such as trees, grasses and agricultural waste.
Still, Donner and Kucharik say their findings suggest that nitrogen loading from the Mississippi River into the Gulf of Mexico would increase by 10 to 19 percent, expanding the dead zone, which each summer already covers more than 7,722 square miles - an area equivalent to the size of New Jersey.
The Gulf of Mexico dead zone near the mouth of the Mississippi River (Photo courtesy NOAA)
"This result confirms our suspicion that there's a significant tradeoff to the expanded production of ethanol from corn grain," says Kucharik, a scientist with the UW-Madison Nelson Institute for Environmental Studies. "It also shows that we need to continue considering our options for other biofuel feedstocks. And when we do, we need to keep the greater impacts on ecosystems in mind."
Nitrogen and phosphorus from agricultural fertilizers have been found to promote excessive growth of algae in water bodies, a problem that is common across North America and in many areas of the world. In some cases, the decomposition of algae consumes much of the oxygen in the water. Inadequate dissolved oxygen in bottom waters forces bottom-dwelling animals to either flee or die.
Fertilizer applied to cornfields in the central United States - Illinois, Iowa, Nebraska and Wisconsin - is the primary source of nitrogen pollution in the Mississippi River system, which drains into the Gulf of Mexico.
Donner and Kucharik arrived at their figures by combining the agricultural land use scenarios required to meet future demand for corn-based ethanol with models of terrestrial and aquatic nitrogen cycling.
Their results call into question the assumption that enough land exists to fulfill the current demand for food and feed crops, while at the same time allowing an expansion of corn production for fuel.
Instead, the scientists conclude that boosting ethanol production from U.S. croplands without endangering water quality and aquatic ecosystems will require a substantial reduction in the amount of corn that is grown for animal feed and meat production.
Because the Mississippi River drains 41 percent of the U.S. land area, some scientists believe only a broad effort at reducing nitrate runoff would reduce the dead zone. Because nitrogen is stored in the soil and continues leaching for many years, any solution must be a long-term effort.
The U.S. ethanol industry produced a record amount of fuel ethanol in 2007 – 6.48 billion gallons - 32 percent more ethanol than in 2006, according to year-end data released by the U.S. Energy Department’s Energy Information Administration.
Capacity for ethanol production is expected to grow another four billion gallons in 2008, according to the Renewable Fuels Association.
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