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
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.