Public Opinion Counts on Water

By Holly Jessen | July 15, 2010
"Is ethanol tapping too much water? "
"Biofuels: The water problem"
"Ethanol vs. water: Can both win?"
"University report warns water consumption for corn ethanol on the rise"

When it comes to ethanol's image and water use issues, headlines matter, stressed Nandakishore Rajagopalan, associate director of the Illinois Sustainable Technology Center, in the FEW panel covering water issues. "We've all heard the negative propaganda about ethanol," said Trevor Cassel, vice president and director of operations for Biodynamics Inc. "Just do a Google search and you'll find headline after headline." Rajagopalan and Cassel spoke during a panel titled "Wringing Water out of the Production Equation" as did Mike Mowbray, marketing manager for U.S. Water Services, and Phil Bonneau from Ortman Ethanol Water Resources. Jon Cohen, vice president and technical director of H-O-H Water Technology, served as moderator.

Although there has been a 40 percent reduction in water use in the ethanol production process in the past 12 years, the typical ethanol plant still uses about three gallons of water to produce one gallon of ethanol, Cassel said, a gallon more water than used for gasoline production. As several of the speakers pointed out, cutting back on water consumption or going to zero liquid discharge doesn't exactly translate into increased income. The yield in positive public opinion, however, just might make it worthwhile.

In some cases, zero liquid discharge is the only way to comply with environmental restrictions, which are getting stricter every year, Mowbray said. In addition, zero liquid discharge can result in a 20 to 30 percent decrease in water needs. There is no single design that works for every ethanol plant, he added. U.S. Water Services has four approaches: recycling water using cold lime softening, evaporation or crystallization of the discharge stream, and evaporation ponds, which only work in the Southwest. The method chosen must ensure that any water treatment chemicals used are acceptable to be sold as animal feed. "After all, that's what you guys do, create ethanol and DDGs that are salable on the market," he said. Mowbray cited a retrofit that reduced water usage from about 3.5 gallons per gallon of ethanol, to 2.8 gallons with the addition of cold lime softening. Further conversion to zero liquid discharge decreased water use at the plant to just over 2 gallons of water per gallon of ethanol.

To grow the industry, Rajagopalan said, water usage at ethanol plants can and must be reduced through a number of methods. Water use could easily be reduced by 10 percent, or, with more investment and work, by 25 percent, he said. "It depends how much you want to do and how aggressive you want to be." One water reduction strategy is to focus on boiler water, which accounts for 12 percent of water use. Reusing filter water backwash can save about 4 million gallons of water a year in a 100 MMgy plant. The plant also could increase reverse osmosis recovery, with yearly potential savings of 17.6 million gallons of water. Minimizing cooling tower waste could save about 11 million gallons of water a year. In all, he said, there's a potential to save approximately 40 million gallons of water a year at a 100 MMgy plant.

Cassel talked about recycling thin stillage, resulting in valuable coproducts and energy savings. The average 50 MMgy ethanol plant yields 350 gallons of water per minute as thin stillage—currently sent to the evaporator and then the dryer, both costly and heat-intensive processes. The Biodynamics process uses traditional wastewater treatment processes to remove waste solids, corn oil and other fermentation inhibitors. The water is then recycled to replace thin stillage backset and a fraction of the plant's freshwater needs. Testing shows the process results in greater or equal ethanol yields. The company is awaiting the results of an independent third party review to confirm that, he said. In addition, the resulting distillers grains with solubles (DDGS) has a higher concentration of protein, fat and amino acids. On a dry basis, DDGS has 32 percent crude protein. With Biodynamics, it rises to 42 percent. Crude fat is increased from 8 to 10 percent to an adjustable 9.3 to 30.5 percent, and lysine content rises from 1.2 percent to 5 percent.

Bonneau discussed another angle on water—a failure in the system. Basic failures include electrical (a power surge, lightening or electrical shorts) and mechanical (plugged pump or well, metal fatigue or piping failure). The hydrologist recommended periodic maintenance inspections and suggested ethanol plants do testing to gather data. "You don't have to wait until it's an emergency," he said.