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Biofuel crops require large quantities of water, and water pollution is heightened by agricultural drainage that contains fertilizers, pesticides, and sediment, these drawbacks—labeled the “water footprint” by study authors—need to be balanced against the potential gains of developing biofuels as an alternative to foreign oil.

RICE (US)—The new emphasis on biofuels as an alternative to foreign oil must be carefully weighed against the potential damage to the nation’s water resources, scientists warn in a new report.

“The ongoing, rapid growth in biofuels production could have far-reaching environmental and economic repercussions, and it will likely highlight the interdependence and growing tension between energy and water security,” says a report coauthored by Pedro Alvarez, the George R. Brown Professor of Civil and Environmental Engineering at Rice University.

Because fuel crops require large quantities of water, and water pollution is heightened by agricultural drainage that contains fertilizers, pesticides, and sediment, these drawbacks—labeled the “water footprint” by study authors—need to be balanced against the potential gains of developing biofuels as an alternative to foreign oil.

The report analyzed the amount of water needed to grow particular crops used to produce biofuels and noted that certain crops yield more biofuel energy while using less land, fertilizer, and water. For example, the researchers found that to fuel an average car for one mile, it would take about 23 gallons of water to produce enough irrigated-corn ethanol in Iowa, 50 gallons to produce the equivalent of Nebraska-grown corn, and 115 gallons for Texas-grown sorghum.

Raising biofuel crops in some areas will require greater use of fertilizers, with the runoff affecting local aquifers and coastal regions. The authors urged that crops be chosen based on their appropriateness to the local climate and that producers raise crops that can be sustained by rainfall rather than irrigation.

The report calls on policymakers to evaluate the water footprint as they devise an environmentally sustainable biofuels program.

“Through energy conservation and careful planning that includes adoption of agricultural practices and crop choices that reduce water consumption and mitigate water pollution from agrichemicals, and identification of the local and regional water resources that will be needed to meet the biofuel mandate,” the authors say, “we can have our drive and drink our water too.”

The report was supported by a fellowship from the Baker Institute Energy Forum and by the Shell Center for Sustainability at Rice University.

Researchers from Rice University, Clarkson University, and Missouri University of Science and Technology contributed to the report.

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