Information Is Limited on the Water Supply and Water Quality Impacts of the Next Generation of Biofuels

Our work to date indicates that while the water supply and water quality  effects of producing corn-based ethanol are fairly well understood, less is  known about the effects of the next generation of feedstocks and fuels. The cultivation of corn for ethanol production can require substantial  quantities of water—from 7 to 321 gallons per gallon of ethanol  produced—depending on where it is grown and how much irrigation water  is used. Furthermore, corn is a relatively resource-intensive crop,  requiring higher rates of fertilizer and pesticide applications than many  other crops; some experts believe that additional corn production for  biofuels conversion will lead to an increase in fertilizer and sediment  runoff and in the number of impaired streams and other water bodies. In contrast to corn-based ethanol, our work to date indicates that much  less is known about the effects that large-scale cultivation of cellulosic  feedstocks will have on water supplies and water quality. Since potential  cellulosic feedstocks have not been grown commercially to date, there is  little information on the cumulative water, nutrient, and pesticide needs of  these crops, and it is not yet known what agricultural practices will  actually be used to cultivate these feedstocks on a commercial scale. Uncertainty also exists regarding the water supply impacts of converting  feedstocks into biofuels. Water consumed in  the corn-ethanol conversion process has declined over time with improved  equipment and energy efficient design, according to a 2009 Argonne  National Laboratory study, and is currently estimated at 3 gallons of water  required for each gallon of ethanol produced. For the conversion of cellulosic feedstocks, the amount of  water consumed is less defined and will depend on the process and on  technological advancements that improve the efficiency with which water  is used. Our work to date also indicates that additional research is needed on the  storage and distribution of biofuels. To overcome potential compatibility issues, future research  is needed on other conversion technologies that can be used to produce  renewable and advanced fuels that are capable of being used in the  existing infrastructure. Key Efforts to Reduce Use of Freshwater at Power Plants May Not Be Fully Captured in Existing Federal Data

In our work to date, we have found (1) the use of advanced cooling  technologies can reduce freshwater use at thermoelectric power plants,  but federal data may not fully capture this industry change; (2) the use of  alternative water sources can also reduce freshwater use, but federal data  may not systematically capture this change; and (3) federal research under  way is focused on examining efforts to reduce the use of freshwater in  thermoelectric power plants. For  example, plants using advanced cooling technologies may cost more to  build and operate; require more land; and, because these technologies can  consume a significant amount of energy themselves, witness lower net  electricity output—especially in hot, dry conditions. For these reasons, a number of power plant developers in the United  States and across the world have adopted advanced cooling technologies,  but according to EIA officials, the agency’s forms have not been designed  to collect information on the use of advanced cooling technologies. Use of these  alternative water sources can ease the development process where  freshwater sources are in short supply and lower the costs associated with  obtaining and using freshwater when freshwater is expensive. Because of  these advantages, alternative water sources play an increasingly important  role in reducing power plant reliance on freshwater, but can pose  challenges, including requiring special treatment to avoid adverse effects on  cooling equipment, requiring additional efforts to comply with relevant  regulations, and limiting the potential locations of power plants to those  nearby an alternative water source. EIA collects annual data from power plants on their water use and  water source. In 2008,  DOE awarded about $9 million to support research and development of  projects that, among other things, could improve the performance of  advanced cooling technologies, recover water used to reduce emissions of  air pollutants at coal plants for reuse, and facilitate the use of alternative  water sources such as polluted water for cooling. This task will be particularly  difficult, given the interdependency between energy production and water  supply and water quality and the strains that both these resources  currently face.
Why GAO Did This Study

Water and energy are inexorably linked--energy is needed to pump, treat, and transport water and large quantities of water are needed to support the development of energy. However, both water and energy may face serious constraints as demand for these vital resources continues to rise. Two examples that demonstrate the link between water and energy are the cultivation and conversion of feedstocks, such as corn, switchgrass, and algae, into biofuels; and the production of electricity by thermoelectric power plants, which rely on large quantities of water for cooling during electricity generation. At the request of this committee, GAO has undertaken three ongoing studies focusing on the water-energy nexus related to (1) biofuels and water, (2) thermoelectric power plants and water, and (3) oil shale and water. For this testimony, GAO is providing key themes that have emerged from its work to date on the research and development and data needs with regard to the production of biofuels and electricity and their linkage with water. GAO's work on oil shale is in its preliminary stages and further information will be available on this aspect of the energy-water nexus later this year.

What GAO Found

While the effects of producing corn-based ethanol on water supply and water quality are fairly well understood, less is known about the effects of the next generation of biofuel feedstocks. Corn cultivation for ethanol production can require from 7 to 321 gallons of water per gallon of ethanol produced, depending on where it is grown and how much irrigation is needed. Corn is also a relatively resource-intensive crop, requiring higher rates of fertilizer and pesticides than many other crops. In contrast, little is known about the effects of large-scale cultivation of next generation feedstocks, such as cellulosic crops. Since these feedstocks have not been grown commercially to date, there are little data on the cumulative water, nutrient, and pesticide needs of these crops and on the amount of these crops that could be harvested as a biofuel feedstock without compromising soil and water quality. Uncertainty also exists regarding the water supply impacts of converting cellulosic feedstocks into biofuels. While water usage in the corn-based ethanol conversion process has been declining and is currently estimated at 3 gallons of water per gallon of ethanol, the amount of water consumed in the conversion of cellulosic feedstocks is less defined and will depend on the process and on technological advancements that improve the efficiency with which water is used. Finally, additional research is needed on the storage and distribution of biofuels. For example, to overcome incompatibility issues between the ethanol and the current fueling and distribution infrastructure, research is needed on conversion technologies that can be used to produce renewable fuels capable of being used in the existing infrastructure. With regard to power plants, GAO has found that key efforts to reduce use of freshwater at power plants are under way but may not be fully captured in existing federal data. In particular, advanced cooling technologies that use air, not water, for cooling the plant, can sharply reduce or even eliminate the use of freshwater, thereby reducing the costs associated with procuring water. However, plants using these technologies may cost more to build and witness lower net electricity output--especially in hot, dry conditions. Nevertheless, a number of power plant developers in the United States have adopted advanced cooling technologies, but current federal data collection efforts may not fully document this emerging trend. Similarly, plants can use alternative water supplies such as treated waste water from municipal sewage plants to sharply reduce their use of freshwater. Use of these alternative water sources can also lower the costs associated with obtaining and using freshwater when freshwater is expensive, but pose other challenges, including requiring special treatment to avoid adverse effects on cooling equipment. Alternative water sources play an increasingly important role in reducing power plant reliance on freshwater, but federal data collection efforts do not systematically collect data on the use of these water sources by power plants. To help improve the use of alternatives to freshwater, in 2008, the Department of Energy awarded about $9 million to examine among other things, improving the performance of advanced cooling technologies. Such research is needed to help identify cost effective alternatives to traditional cooling technologies.