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October 2007

Water Implications of Production in the

National interests in greater energy independence, concurrent with favorable mar- ket forces, have driven increased production of corn-based in the United States and research into the next generation of biofuels. The trend is changing the national agricultural landscape and has raised concerns about potential impacts on the nation’s water resources. This report examines some of the key issues and identifies opportunities for shaping policies that help to protect water resources.

iofuels— derived from biological materials—are likely Bto play a key role in America’s energy future. In 2007, President Bush called for U.S. production of ethanol to reach 35 billion gallons per year by 2017, which would displace 15 percent of the nation’s projected annual use. By 2030, the administration aims to increase that production to 60 billion gallons per year. Recent increases in oil prices in conjunction with subsidy policies have led to production based on discussions at the collo- a dramatic expansion in production quium, written submissions of participants, the and high interest in further expansion over the peer-reviewed literature, and the best profes- next decade. sional judgments of the committee. Increased use of biofuels offers many ben- efits, such as a decreased reliance on foreign oil, Types of Biofuels but it also presents some challenges. Among Currently, the main in the United the challenges that may not have received ap- States is ethanol derived from corn kernels. Corn- propriate attention are the effects of biofuel de- based ethanol is made by converting the in velopment on water and related land resources. corn kernels to and then converting those Growing and processing biofuel to meet sugars into ethanol. Ethanol derived from sor- America’s energy needs will alter how the na- ghum and derived from com- tion’s water resources are used. However, the prise a very small fraction of U.S. biofuels. Other water implications of biofuels production are potential sources of materials for use in biofuels complex, difficult to monitor, and will vary include field crops such as soy; short-rotation greatly by region. woody crops such as poplar and ; animal To help illuminate these issues, the Na- fats, vegetable oils, and recycled greases; peren- tional Research Council held a colloquium on nial grasses, such as switchgrass; agricultural July 12, 2007 in Washington, DC to facilitate and residues such as and cellu- discussion among representatives from federal losic ; aquatic products such as algae and and state , non-governmental orga- seaweed; and municipal waste such as nizations, academia, and . This report sludge or solid waste. Different biofuel sources examines the water implications of biofuels have unique implications for water resources. One of the most potentially significant new biofu- Water Use for els on the horizon is “,” derived from All biofuel facilities require water to convert bio- fibrous material such as , native grasses, and logical materials into . The amount of water used forest trimmings. Because of technological limitations, in the process is modest compared to the cellulosic ethanol can currently be produced only at pilot water used for growing the used to produce and commercial demonstration-scales; however, produc- ethanol; however, because water use in biorefineries is tion of cellulosic ethanol is expected to begin commer- concentrated into a smaller area, such facilities effects cially within the next decade. can be substantial locally. A that produces 100 million gallons of ethanol per year, for example, Implications for Water Supply would use the equivalent of the water supply for a town Water is an increasingly precious resource used of about 5,000 people. Ethanol producers are increas- for many critical purposes; in some areas of the coun- ingly incorporating water and use-reduction try, water resources are already significantly stressed. measures in order to maximize energy yields while re- For example, large portions of the Ogallala (or High ducing water use. Plains) aquifer, which extends from west Texas up into South Dakota and Wyoming, show water table declines Implications for Water Quality of over 100 feet since about the 1940s. Increased bio- Shifting agricultural practices to incorporate fuels production will likely add pressure to the water more biofuel crops will affect water quality as well as management challenges the nation already faces as bio- water quantity. Converting pastures or woodlands into fuels drive changing agricultural practices, increased cornfields, for example, may exacerbate problems as- corn production, and growth in the number of biore- sociated with runoff and . fineries. Water Use for Irrigation Fertilizer Runoff and Nutrient Whether or not biofuel crops will require more For most crops, it is standard agricultural practice or less water will depend on what is being sub- to apply such as nitrogen and phosphorus, as stituted and where it is being grown. Corn generally well as pesticides, which include herbicides and insec- uses less water than soybeans in the Pacific and Moun- ticides. However, these chemicals can wash into bodies tain regions, but the reverse is true in the Northern and of water and affect water quality. For example, excess Southern Plains. Therefore, farmers switching from nitrogen washing into the Mississippi River is known soybeans to corn will need more water in some regions to be a cause of the -starved “dead zone” in the and less water in others. As this example demonstrates, Gulf of Mexico, in which marine life cannot survive. there are many uncertainties in estimating the overall Different crops require different amounts of fer- net impacts of biofuel crops on our water resources. tilizers. One metric that can be used to compare wa- Another important consideration is how biofuel ter quality impacts of various crops are the inputs of production might drive the expansion of agricul- ture into regions that currently support little ag- Fuel Feedstock U.S. Production in 2006 riculture. Expansion of agricultural lands, espe- cially into dry western areas, has the potential to Ethanol Corn 4.9 billion gallons dramatically affect water availability. < 100 million gallons The report concludes that in the next 5 to Cane No production (600 million 10 years, increased agricultural production for gallons imported) biofuels will probably not alter the national- No production (one demon- aggregate view of water use. However, there are stration in Canada) likely to be significant regional and local impacts Biodiesel oil Approximately 90 million where water resources are already stressed. gallons Depending on what crops are grown, where the crops are grown, and whether there is an increase Other vegetable oils < 10 million gallons in overall agricultural production, significant Recycled grease <10 million gallons acceleration of biofuels production could cause Cellulose No production much greater water quantity problems than are U.S. production of different types of biofuels in 2006. currently experienced. SOURCE U.S. Congressional Research . fertilizers and pesticides per unit of the captured in a biofuel. Of the potential bio- fuel crops, the greatest application rates of both fertilizer and pesti- cides per acre are for corn. Per unit of energy gained, biodiesel requires a small fraction of the ni- trogen and phosphorous used for corn-based ethanol. All else being equal, converting other crops or non-crop plants to corn will likely lead to much higher application rates of nitrogen. However, there are many management practices that can improve the efficiency of fertilizer application and how it is used by plants. For example, recent ad- vances in have in- creased yields of corn per unit of Existing and planned ethanol facilities (2007) and their estimated total water applied nitrogen and phosphorous. use mapped with the principal bedrock aquifers of the United States and total water use in year 2000. SOURCE: Janice Ward, U.S. Geological Survey. Soil Erosion and Sedimentation Sedimentation occurs when Reducing Water Impacts through Agricul- soil erodes from land and washes down into surface tural Practices water bodies. Sediments impair water quality and also There are many agricultural practices and tech- carry agricultural and other pollutants. The amount of nologies that can simultaneously increase crop yields sediment eroding from agricultural areas is directly while reducing impacts on water resources. These tech- related to —the more intensive the use, the nologies include a variety of water-conserving irriga- greater the erosion. For example, more sediment erodes tion techniques, erosion prevention techniques, fertiliz- from row crop fields, such as corn, than from pastures er efficiency techniques, and precision tools or woodlands. that take into account site-specific soil pH (acidity/al- One of the most likely causes of increased erosion kilinity), moisture, and other measures. Such practices in the near term may be withdrawal of lands from the can have a large, positive environmental impact. U.S. Department of Agriculture’s voluntary Conserva- Surface cover is crucial in reducing sediment in tion Reserve Program owing to an increase in overall runoff and limiting soil erosion. Farmers can employ a agricultural production. The program pays farmers to number of techniques that leave some portion of crop convert environmentally sensitive or highly erodible residues on the soil surface, helping to reduce erosion. acreage to native grasses, wildlife plantings, trees, fil- In “no-till” systems, as the name implies, crops are ter strips, and riparian buffers and provides cost-share simply planted into the previous year’s crop residues. assistance for conservation practices. One of the issues for corn is what to do with the stalks Producing biofuels from perennial crops that and cobs left in the field after the grain has been har- hold soil and nutrients in place and require lower fer- vested—called the corn . This material could po- tilizer and pesticide inputs, like switchgrass, poplars, tentially be converted to cellulosic biofuel, but leaving , or polyculture, is another option for on the fields can greatly reduce soil ero- reducing the deleterious effects of biofuel crops. There sion. are, however, large uncertainties surrounding the pro- duction of cellulosic ethanol from such crops: such Key Policy Considerations crops have very little history of use in large-scale culti- vation. Therefore, even basic information such as water The water implications of biofuels production are or nitrogen inputs needed, herbicide use, impact on soil complex, difficult to monitor, and will vary greatly by erosion, and even overall yields is preliminary. region. In general, however, crops that require less ir- rigation, less fertilizer and pesticides, and provide • Alternative subsidies to reduce impacts of biofu- better erosion protection will likely produce fewer els production on water use and quality. To meet negative water impacts. Therefore, policy decisions goals regarding overall water use, for example, that encourage such measures can have a significant performance incentives could be developed that positive impact on the protection of water resources encourage producers to increase water recycling as the demand for biofuels expands. in ethanol plants and farmers to adopt improved This report describes factors that shape the cur- irrigation . rent policy context and raises some important con- • Policies to encourage best agricultural practices. siderations for future policy; however, it does not Several existing programs provide incentives to evaluate specific policy options or make any recom- farmers specifically for improved nutrient manage- mendations about policies to be implemented. ment, for example. In addition, about $4 billion is Current Policy Framework spent annually on incentives for farmers to engage The dramatic expansion of corn ethanol pro- in practices to reduce soil erosion. Greater imple- duction over the past several years has largely been mentation of agricultural best practices could help driven by subsidy policies for corn ethanol produc- maintain or even reduce water quality impacts. tion coupled with low corn prices and high oil pric- • Policies to encourage biofuels produced from cellu- es. These policies have been targeted to improving losic alternatives. It is likely that cellulosic biofuels and providing a clean-burning ad- will have less impact on water quality per unit of ditive for gasoline. Staying the current policy path energy gained; therefore, water quality would like- would likely result in the continued trend of expan- ly benefit from the transition from corn ethanol to sion of corn-based ethanol production, driven by the the next generation of biofuels. The extent and in- economics of input costs and ethanol prices supple- tensity of water quality problems from biofuels will mented by the subsidy. be partially driven by the conditions under which the cellulosic biofuels industry develops. Future Policy Options As biofuel production expands and technology If projected future increases in use of corn for advances, there is a real opportunity to shape poli- ethanol production do occur, the increase in harm cies to also meet objectives related to water use and to water quality could be considerable. In addition, quality impacts. To move toward a goal of reducing expansion of corn production on fragile soils can water impacts of biofuels, a policy bridge will likely increase loads of both nutrients and sediments. It be needed to encourage growth of new is vitally important to pursue policies that prevent that develop both traditional and cellulosic crops re- an increase in total loadings of nutrients, pesticides, quiring less water and fertilizer and are optimized and sediments to waterways. From a water quantity for fuel production. perspective, measures to conserve water and prevent the unsustainable withdrawal of water from depleted Policy options that could help protect water aquifers could be critical. resources include:

Committee on Water Implications of Biofuels Production in the United States: Jerald L. Schnoor, (Chair), University of Iowa, Iowa City; Otto C. Doering III, Purdue University; Dara Entekhabi, Massachusetts Institute of Technology; Edward A. Hiler, Texas A&M University; Theodore L. Hullar, Cornell University; G. David Tilman, University of Minnesota, St. Paul; William S. Logan (Study Director), Nancy Huddleston ( Officer), and Michael Stoever (Sr. Project Assistant), National Research Council. This report brief was prepared by the National Research Council based on the committee’s report. For more information or copies, contact the Water Science and Technology Board at (202) 334-3422 or visit http://nationalacademies.org/wstb. Copies of Water Implications of Biofuels Production in the United States are available from the National Academies Press, 500 Fifth Street, NW, Washington, D.C. 20001; (800) 624-6242; www.nap.edu. Support for the study was provided by the McKnight Foundation, Energy Foundation, National Science Foundation, U.S. Environmental Protection Agency, and the National Research Council Day Fund.

Permission granted to reproduce this brief in its entirety with no additions or alterations.

© 2007 The National Academy of Sciences