Report: Boom in Ethanol Production Could Threaten Water Supplies

The push to develop ethanol could result in significant harm to water quality, according to a new report released on Oct. 10 by the National Research Council.

The committee that wrote the report also identified opportunities for new agricultural techniques and technologies to help minimize effects of biofuel production on water resources.

Recent increases in oil prices have led to a dramatic expansion in corn ethanol production and high interest in further expansion over the next decade. Prompted by strong national interest in greater energy independence, President Bush has called for the production of 35 billion gallons of ethanol by 2017, which would equal about 15 percent of the U.S. liquid transportation fuels.

A National Research Council committee found that agricultural shifts to growing corn and expanding biofuel crops into regions with little agriculture, especially dry areas, could change current irrigation practices and greatly increase pressure on water resources in many parts of the United States.

The amount of rainfall and other hydroclimate conditions from region to region cause significant variations in the water requirement for the same crop, the report finds. For example, corn generally uses more water than soybeans and cotton in the Northern and Southern Plains. Water demands for drinking, industry and other uses as hydropower, fish habitat, and recreation could compete with, and in some cases, constrain the use of water for biofuel crops in some regions. Consequently, growing biofuel crops requiring additional irrigation in areas with limited water supplies is a major concern, according to the report.

Although a large body of information exists for the nation's agricultural water requirements, fundamental knowledge gaps prevent making reliable assessments about the water impacts of future large-scale production of feedstocks other than corn, such as switchgrass and native grasses.

The quality of groundwater, rivers and coastal and offshore waters could be impacted by increased fertilizer and pesticide use for biofuels, the report finds. High levels of nitrogen in stream flows are a major cause of low-oxygen or "hypoxic" regions, commonly known as "dead zones," which are lethal for most living creatures and cover broad areas of the Gulf of Mexico, Chesapeake Bay and other regions. According to the report, there are a number of agricultural practices and technologies that could be used to reduce nutrient pollution, such as injecting fertilizer below the soil surface, using controlled-release fertilizers that have water-insoluble coatings and optimizing the amount of fertilizer applied to the land.

A possible metric to gauge the impact of biofuels on water quality would be to compare the amount of fertilizers and pesticides used on various crops, the committee suggested. For example, corn has the greatest application rates of both fertilizer and pesticides per acre, higher than for soybeans and mixed-species grassland biomass.

Nutrient and sediment pollution in streams and rivers also could be attributed to soil erosion. High sedimentation rates carry financial consequences as they increase the cost of often-mandatory dredging for transportation and recreation. The committee states that farming could be improved, such as conservation tillage and leaving most or all of the cornstalks and cobs in the field after the grain has been harvested.

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