While recycling and other advancements have reduced water use in Minnesota’s corn-ethanol plants by a third of the levels of just a few years ago, increased reliance on irrigated corn has pushed water consumption to alarming levels in the desert Southwest and parts of California.
A University of Minnesota report out today notes that Minnesota’s 17 ethanol plants currently average about 3.5 gallons of water for each gallon of ethanol produced. This is down from about 10 gallons per gallon of ethanol just a decade earlier.
Joe Henderson of the Minnesota Pollution Control Agency’s biofuels section said that the newest ethanol plants in the state use about 2.7 gallons of water per gallon of ethanol.
However, over-all water consumption rates rise quickly when ethanol is produced from corn that is irrigated, as it is on 207,000 acres in Minnesota or 3 percent of the state’s 7.8 million acres planted to corn.
The report’s lead author, Sangwon Suh in the university’s College of Food, Agriculture and Natural resources, said that without precipitation, it takes 6,000 gallons of water to produce a bushel of corn that, in turn, produces 2.8 gallons of ethanol.
That means that in the desert Southwest that increasingly relies on water to produce agricultural crops, it takes 1,200 gallons of water to produce a single gallon of ethanol.
Suh said the problem is that reports point to water shortages in the United States, most prominently in the Southwest where a range of uses — including agricultural irrigation — are undergoing scrutiny.
One of the major funders of Suh’s report is the U.S. Department of Energy; another funder is the Legislative and Citizens Commission of Minnesota’s Resources in St. Paul.
When irrigated corn used in ethanol production is factored in, Minnesota averages about 19 gallons of water for each gallon of ethanol produced. Current state-wide ethanol production is about 4 billion gallons, a number that was expected to double this year but the economic downturn has curtailed plant expansion.
‘Bigger elephant is irrigation’
In all, Suh’s report said that Minnesota’s water consumption for ethanol is second lowest of any state. Iowa has the lowest consumption, with six gallons of water required for each gallon of ethanol; South Dakota uses about 96 gallons of water for each ethanol gallon.
As corn production expands into the desert Southwest, the amount of irrigation will dramatically increase, Suh said.
“There’s too much attention on water usage by ethanol plants,” Suh said, “while the much bigger elephant is irrigation.”
Suh’s report will appear in the Journal of Environmetnal Science and Technology. It is the first attempt to compare water consumption for ethanol production on a comparative state-by-state basis.