A new study by researchers at Rice University in Houston, Texas warns that expanded production of crops to produce biofuels could damage water resources. The researchers suggest policy makers take into account what they call the "water footprint" when encouraging biofuel development.

The study is titled The Water Footprint of Biofuels: A Drink or Drive Issue? The suggestion is that by using too much water to produce fuel, humankind might leave itself with not enough water to drink or to grow food.

The lead author of the study, Rice University Professor of Civil and Environmental Engineering Pedro Alvarez spoke to VOA by telephone from France, where he is attending an academic meeting. He says the water footprint consists of two elements. "Water shortages caused by a significant increase in fuel crop irrigation, and increased water pollution from related agro-chemical drainage and increased erosion and so on. The two impacts we refer to as the 'water footprint,'" he said.

Alvarez says there are good reasons to continue programs to produce biofuels, such as reducing the need for imported oil and diversifying our sources of energy. But he says policy makers should provide incentives to producers to use crops that use less water and have less impact on the environment in the form of runoff of pesticides, fertilizers and other chemicals.

"We want to try to use crops that deliver more energy with lower requirements for not just water, but also land and agro-chemicals. These are usually non-edible cellulosic crops," he said.

Corn is one of the main ingredients for the alcohol fuel ethanol

The Rice University study also suggests that using corn to produce the alcohol fuel ethanol may not always be cost effective, especially in states where farmers have to use large amounts of fertilizer to produce the grain.

But Kristen Brekke of the American Coalition for Ethanol in Sioux Falls, South Dakota says the study does not take into account the growing yields farmers are producing by using technology and improved agricultural practices.

"They are getting a lot more efficient; they have a lot better crop genetics and agronomic practices like no-till farming and things like GPS [satellite-dependent global positioning system]. That sort of technology allows them to put only the amount of fertilizer that is needed on a field and in the exact location that it is needed. USDA [the U.S. Department of Agriculture], for example, says that corn yields are expected to double in the next 25 years," she said.

But Brekke agrees with the Rice University study in that using corn for ethanol may not work well everywhere and that development of cellulosic ethanol from waste products and other plants makes sense. "The nice thing about cellulosic ethanol is that all areas of the country will be able to participate in that. Where it makes sense to grow corn, some of that corn is going to ethanol production, but in other areas of the country they will be able to use what they have locally available," she said.

The ethanol industry backs the use of the alcohol additive to gasoline as way of reducing petroleum consumption nationwide.

But Pedro Alvarez argues that it might be better for the environment as well as farmers to use the alternative fuel locally and not try to transport it long distances. He says that the growing world population might force policy changes not only in terms of water used for fuel crops, but also in terms of how water is used to produce the food we eat.

"To make one kilogram of bread, let's say, you need 1,000 liters of water and to make one kilogram of meat you need 10,000 liters of water. The point here is that water is going to be a severe limiting factor - not only to economic development, but just to feed a growing population," he said.

Alvarez says population growth will drive the need to allocate water carefully for various food crops as well as livestock. Likewise, he says, it will be necessary to balance the goals of reducing oil consumption and supporting the income of farmers with the need to preserve the water that makes agriculture possible.