Comment▼ Biofuels and the environment
F
armers grow the three Fs—food, feed, and fiber— for the world. Now, for the first time, they are being called upon to produce a fourth F: fuel. But the burgeoning growth of corn and soybeans for biofuels could gravely impact the environment, increasing soil and nutrient runoff from the land, adversely affecting water quality, and causing conservation reserve lands to be brought back into production. Biofuels in the U.S. are produced principally from corn kernels, which are fermented and distilled to ethanol and blended with gasoline as a transportation fuel. Soybeans are processed to form biodiesel, which is often blended with petroleum diesel for fuel. Potatoes, sugar beets, and sugarcane could also be used as feedstocks for ethanol, but presently corn has the lion’s share of the market in the U.S. because of its relatively low price ($2 per bushel). Likewise, soybeans have cornered the biodiesel market, even though canola or most other vegetable oils would do. Biofuels have become recognized as renewable sources of energy in the sense that modern ethanol and soydiesel industries capture somewhat more energy from crop photosynthesis than is used in the life cycle of its production. In addition, the quality of liquid biofuels is much greater than that of the solid wastes, corn stover, or coal that is sometimes burned in its production. Most biofuel plants are located in the agricultural Midwest, where corn is grown efficiently by rain-fed agriculture and where the co-products (wet and dry distillers’ grains) can be used as local animal feed. Waste from the animals, in turn, is applied on farmland to recycle nutrients back to the land. It is a form of industrial ecology where the waste from one industry (animal agriculture) is used as the nutrient input to another (corn agriculture for ethanol), and the co-products from biofuels production are recycled to feed animals. Big grain-processing companies love the idea of biofuels. Oil companies hate it. Automobile manufacturers are slowly seeing the greening possibilities through the sale of flex-fuel cars. Most everyone else supports a vigorous campaign to produce more biofuels for greater energy security. But biofuels will also help to curb greenhouse gas emissions, create jobs, reduce our balance-ofpayments deficit, support crop prices, and strengthen the farm economy. If the U.S. were more energy-independent, it wouldn’t need to deploy troops to the Middle East to protect oil supply lines; this enrages people there, creates terrorists, and costs tens of billions of dollars per year in taxes. With all those benefits to biofuels, what could possibly be the problem?
4042 ■ ENVIRONMENTAL SCIENCE & TECHNOLOGY / JULY 1, 2006
BIOFUELS ARE NOT SUSTAINABLE. At least not in the way we practice row-crop agriculture today. Far too many nutrients run off the land, thus causing eutrophication and Gulf hypoxia, and far too much soil erodes for biofuels to be considered sustainable in the long run. We need a cropping system that is perennial, in which tillage is minimized (or nonexistent) and soils and nutrients are held in place. Perennial switchgrass could fill the bill. Switchgrass was one of the most ubiquitous prairie plants of the Great Plains and could become so again, enhancing bird habitat and improving water quality while sequestering CO2 in soils. But to reach the full potential of switchgrass, we need a breakthrough in technology that may still be several years off. Ideally, ethanol should be made from the cellulose in perennial crops and wastes, and it will require development to efficiently break down cellulose into starch and sugar for fermentation using specialty enzymes (Environ. Sci. Technol. 2006, 40, 1722; 4052). Are biofuels a panacea for our energy problems? No. Unfortunately, our gluttony for liquid fossil fuels is so gargantuan that we cannot grow our way out of this problem. The U.S. consumes 21 million barrels of petroleum each day (3 gallons for every man, woman, and child). Even if we utilized all 72 million acres of corn planted in the nation for ethanol and biodiesel, it would satisfy only 10% of our current petroleum consumption. And it would leave us with little room for the other three Fs. Clearly, conservation and energy efficiency are still our greatest energy resources if we choose to get serious about the problem. Wind and solar can help, too. So we desperately need a new energy mix in the U.S. Food, feed, fiber, and (yes) biofuel will be produced on the farm. But it must be done in a sustainable manner, and it must be part of a comprehensive energy and farm plan. We are not running out of oil, rather we are running out of $50-per-barrel oil. Most of all, we are running out of an atmosphere where we can continue to store the exhaust from our profligate use of fossil fuels. Biofuels are one element of a rational and strategic response to the problem.
Jerald L. Schnoor Editor
[email protected] © 2006 American Chemical Society
