The US government is encouraging the use of biofuels in response to concerns about the country's dependence on imported oil, climate change, and other issues. Water plays a crucial part in all stages of biofuels production, and the Government Accountability Office is studying implications of expanded biofuels production's water use.
The extent to which more biofuels production affects US water resources will depend on the feedstock type selected and how and where it is grown, GAO said in a Nov. 30 report.
It said experts believe that if corn or other conventional feedstocks are used extensively, the impact would be greater than if next generation feedstocks, such as perennial grasses and woody biomass, are used.
"This is because corn is a relatively resource-intensive crop, and in certain parts of the country requires considerable irrigated water as well as fertilizer and pesticide application," GAO said.
The same experts and officials noted that next generation feedstocks' impact on water resources aren't fully known yet because they haven't been grown commercially.
Efficiency questions
The process of converting feedstocks to biofuels also uses water, the report noted. While biorefineries producing ethanol from corn have grown more efficient, the amount of water needed to convert new feedstocks is not known, it said.
"Finally, experts generally agree that it will be more important to take into account the regional variability of water resources when choosing which feedstocks to grow and where to expand their production," GAO said.
Using certain agricultural practices, alternative water sources, and technologies could mitigate biofuels production impacts on water, GAO said, but it also found barriers to their widespread adoption.
For example, it noted that brackish water or other alternative sources might work for some biofuel conversion phases and reduce refineries' reliance on fresh water.
'Remain untested'
Similarly, innovations such as dry cooling systems and thermomechanical processes could reduce water demand, "but many of these innovations are currently not economically feasible or remain untested at the commercial scale," it said.
GAO said many experts identified two main areas where additional research is needed: feedstock cultivation and biofuel conversion, and data on water resources. "For example, some experts noted the need for further research into improved crop varieties, which could help reduce water and fertilizer needs," it said.
It said that several mentioned finding ways to increase algae cultivation commercially and controlling potential water quality problems. Others recommended researching ways to optimize conversion technologies for maximum water efficiency.
"Finally, some experts said that better data on water resources in local aquifers and surface water bodies would aid in decisions about where to cultivate feedstocks and locate biorefineries," GAO said.
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