Extensive studies are needed to understand the water needs of biofuel production from cellulosic feedstocks or other next-generation sources, federal auditors said in a preliminary report released yesterday.
The effects of corn-based ethanol production on water quantity and quality are well understood, the Government Accountability Office report says, but less is known about next-generation feedstocks that have not been grown on a commercial scale.
"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," the report says.
The report was released following a House hearing yesterday on the impact of energy generation on water (E&E Daily, July 10).
"There are many uncertainties in the energy and water nexus," said Anu Mittal, GAO's director of natural resources and the environment.
Another uncertainty: the potential water-supply impact of converting cellulosic feedstocks into biofuels.
In addition to its use for growing crops, water is also needed for biorefining. Current estimates say 1.9 to 5.9 gallons of water are needed to produce a gallon of biofuel from cellulosic feedstocks, the report says.
"Some experts we spoke with said that greater research is needed on how to manage the full water needs of biorefineries and reduce these needs further," the report says. "Similar to current and next generation feedstock cultivation, additional research is also needed to better understand the impact of biorefinery withdrawals on aquifers and to consider potential resource strains when siting these facilities."
Storage and distribution of biofuels also deserves further research, the report says. Ethanol is highly corrosive and could damage pipelines and storage tanks, which could lead to groundwater contamination, the report says. It recommends an evaluation of the compatibility of higher blend fuels -- such as those containing 15 percent ethanol -- with existing fuel infrastructure.
Algae-derived biofuels' impact on water warrants further research, as well, the report says.
"Algae have the added advantage of being able to use lower-quality water for cultivation, according to experts," the report says. "However, the impact on water supply and water quality will ultimately depend on which cultivation methods are determined to be the most viable."
The report identifies two areas that require immediate attention: oil extraction and contaminants. Research is needed on the oil extraction process to preserve the water contained in the algal cell with the oil for recycling. And more information is needed on how to best manage contaminants found in the algal cultivation water.
"While we recognize that DOE currently has a number of ongoing research efforts to develop information and technologies that will address various aspects of the energy-water nexus, our work indicates that there are a number of areas to focus future research and development efforts," the report concludes.
The final report should come out later this year, Mittal said.
Click here to read the report.