Ethanol fuel presents a corn-undrum
Corn ethanol yields an energy dividend but gains are higher with soy biodiesel, a new study shows
A definitive study of ethanol derived from corn reveals its pros and cons compared with biodiesel fuel from soybeans and points the way toward new sources of renewable energy.
By Deane Morrison
July 18, 2006; updated Sept. 18, 2006
Five University researchers have taken a stand in the long-running debate over whether ethanol from corn requires more fossil fuel energy to produce than it delivers.
Their answer? It delivers 25 percent more energy than is used (mostly fossil fuel) in producing it, though much of that 25 percent energy dividend comes from the production of an ethanol byproduct, animal feed.
But the net energy gain is much higher -- 93 percent -- from biodiesel fuel derived from soybeans. And alternative crops such as switchgrass or mixed prairie grasses, which can grow on marginal land with minimal input of fossil fuel derived fertilizers and pesticides, offer the best hope for the future.
U dean gives North American perspective at EU biofuels conference
College of Biological Sciences dean Robert Elde presented the North American perspective on biofuels development at a European Union conference on bioenergy, held in Norway Sept. 13-14, 2006.
At "Bioenergy in a Cross-Europe Perspective," a conference sponsored by European Cooperation in the Field of Scientific and Technical Research (COST), Elde spoke during a session about the impact of biofuels on the energy market. His presentation included details about research under way at the University of Minnesota.
COST is affiliated with the European Union, which now includes 25 member nations representing 450 million people.
Elde and a delegation of U of M faculty and staff members also met with scientists at the conference's host institution, the Norwegian University of Life Sciences, to review collaborative research projects and explore new partnership opportunities. Growing U ties with Norway are bringing the University into European policy discussions about renewable energy.
"Corn ethanol and soybean biodiesel have proven that we can make viable biofuels," says David Tilman, a coauthor of the study and Regents Professor of Ecology. "This is an important first step toward developing a renewable and environmentally friendly biofuel energy supply, but the challenges ahead are still immense."
A major challenge is getting enough biofuel. Already, 14.3 percent of corn grown in the United States is converted to ethanol, replacing just 1.72 percent of gasoline usage. Even if all the remaining corn were converted to ethanol, the total ethanol would only offset 12 percent of gasoline. The entire soybean crop would replace a much smaller proportion of transportation fuels--only 6 percent of current diesel usage, which itself amounts to a tiny fraction of gasoline usage.
With world energy and food demands increasing, the study fills a need for guidance in choosing the best alternative energy strategies. That's why the University's Initiative for Renewable Energy and the Environment (IREE), which aims to make Minnesota a national leader in the development and production of renewable fuels to reduce greenhouse gas emissions and other forms of pollution, helped fund the work.
"Quantifying costs and benefits of biofuels throughout their life cycle allows us to make rational choices and identify better alternatives," Hill says in a news release.
"The reason for doing this study was to learn from our first two successful biofuels how we could do it better," says Tilman. "It's a bit like the Wright Brothers--a good first start, but if I'm flying across the Atlantic, I want a jet." Besides Hill and Tilman, who is the world's most cited ecologist, study authors were Stephen Polasky and Douglas Tiffany, professors of applied economics; and Erik Nelson, a graduate student in applied economics.
The researchers examined every stage of the biofuels' production and use. They considered such costs as the effort to raise crops, environmental effects of fertilizers and pesticides, transportation and the energy required to distill ethanol.
Already, 14.3 percent of corn grown in the United States is converted to ethanol, replacing just 1.72 percent of gasoline usage. Even if all the remaining corn were converted to ethanol, the total ethanol would only offset 12 percent of gasoline.
The analysis showed that growing both corn and soybeans caused soil and water pollution from such chemicals as the nitrogen and phosphorus in fertilizer and from pesticides, with the pesticides used in corn production being especially harmful. But biodiesel used, per unit of energy gained, only 1 percent of the nitrogen, 8.3 percent of the phosphorus and 13 percent of the pesticide (by weight) of corn production.
The researchers also compared greenhouse gas emissions from the two biofuels with emissions caused by producing and burning enough gasoline or diesel to yield the same amount of energy. Emissions from the production and use of corn grain ethanol were 12 percent lower than the net emissions from gasoline; the reduction was 41 percent for biodiesel from soybeans. These figures show that biofuels have the potential to provide significant environmental benefits.
However, the benefits will only be substantial when much more biofuel is produced and when it has much greater greenhouse gas reductions. For example, if one replaced a total of 5 percent of gasoline energy with ethanol energy, greenhouse gas emissions from driving cars would be a bit more than a half percent lower (5 percent times 12 percent). It must be borne in mind, too, that these figures are only for transportation-related energy usage. Considering total energy use, which includes building heating and electricity, the fraction of savings from transportation biofuels drops by two-thirds.
Also, these reductions hold only for crops grown on land already in production.
"Converting intact ecosystems to production would result in reduced greenhouse gas savings or even net greenhouse gas release from biofuel production," the researchers write.
The researchers point to nonfood plants that can grow on marginal lands with minimal input of fertilizers and pesticides as the best hope for bio-based energy. Crops like switchgrass, diverse prairie grasses, and woody plants may offer the best prospects for supplying biofuels.
The researchers noted that rising gasoline and diesel prices have made the development of biofuels more economically advantageous, and that biodiesel's environmental benefits seem strong enough to merit subsidy. Yet ethanol also plays an important role as an additive by oxygenating gasoline and making it burn more cleanly.
"New and better transportation biofuels and greatly increased energy efficiency are essential for our economy and our environment," says Tilman. "We also need renewable electricity, including both wind energy and renewable biofuels that take the place of coal. Coal is a major source of electricity and of greenhouse gases."
The researchers point to nonfood plants that can grow on marginal lands with minimal input of fertilizers and pesticides as the best hope for bio-based energy. Crops like switchgrass, diverse prairie grasses, and woody plants may offer the best prospects for supplying biofuels. Researchers at the University and elsewhere are hard at work finding ways to tap the energy of such plants, which is locked up in difficult-to-digest cellulose and related plant materials. One thing that made corn and soybeans so attractive in the first place was the relative ease of extracting energy from the carbohydrates and oils in those crops. But with global warming rapidly changing the world environment, and energy prices soaring, there is no choice but to find alternative sources of energy, and fast.
Source: www1.umn.edu
No comments:
Post a Comment