Distillers dried grains (DDGs), coproducts of converting corn into ethanol, are usually fed to livestock, but DDGs may soon be used to fight weeds and reduce herbicide. 

Plant physiologist Steve Vaughn and colleagues with the Agricultural Research Service (ARS) at the National Center for Agricultural Utilization Research (NCAUR) are seeking to identify new, value-added uses for farm-based commodities like DDGs and help bring them to commercial fruition by developing novel processing technologies.

Vaughn’s work over the past few years has shown that applying DDGs to soil as a surface mulch can not only suppress weeds, but also bolster the growth of tomatoes and some turfgrasses.  In one study, for example, Roma tomatoes in DDG-treated plots yielded 226 pounds, compared to 149 pounds from untreated control plots.

Vaughn attributes some of the increase to nitrogen, phosphorus, and other nutrients released by the DDG mulch as it decayed.

In another study, using various analytical methods, NCAUR collaborator Mark Berhow is seeking to identify, measure, and monitor the activity of the chemicals in the DDG mulch that may have kept chickweed, annual rye, and other weeds from germinating.  Rick Boydston, an ARS collaborator at Prosser, Wash., tested the mulch’s weed control in potted ornamentals, including roses. He observed that DDGs worked best when applied to the soil surface, because mixing them into the soil harmed both ornamentals and weeds alike.

On another front at Peoria, ARS chemist Rogers Harry O’Kuru is examining DDGs for phytosterols, lecithin and other substances with potential use as health-promoting food ingredients.

The team’s efforts to expand the market for DDGs are timely.  In the Midwest, ethanol producers generate 10 million tons of DDGs annually. Farmers buy most of it for about $80 per ton and feed it to cows and other ruminants, but the nation’s increasing production of ethanol may create a DDG surplus that exceeds the current demand, Vaughn notes.
 

John Nowatzki, a North Dakota State University Extension Service agricultural machine systems specialist, says that using biodiesel in diesel engines helps reduce harmful emissions.

“With the increasing availability of biodiesel for both on- and off-road use in diesel engines, there also is increasing interest in the effect of its use on the environment,” he says.

In 2002, the EPA conducted a comprehensive analysis of biodiesel impacts on exhaust emissions and found that tailpipe emissions from engines using biodiesel are significantly lower than the emissions from similar engines operated on petroleum diesel.  Particulate matter, hydrocarbon emissions, and carbon monoxide emissions from engines using biodiesel were all less than those using petroleum diesel.

“The pollutant that is more serious from engines operated on biodiesel, compared with petroleum, is nitrogen oxide,” Nowatzki says. “Nitrogen oxide emissions are about 10 percent higher using biodiesel. Reducing nitrogen oxide emissions is a crucial component of EPA’s strategy for cleaner air and reducing acid rain. There is an effort to modify diesel engine combustion and exhaust systems to reduce nitrogen oxide emissions.”

CO2 emissions are similar from engines operated on biodiesel or petroleum diesel, but the CO2 produced from burning petroleum diesel and emitted to the atmosphere comes from sources long sequestered in the earth. Oil seed crops actually take carbon from the atmosphere during their growth cycles and store that carbon in the ground.

“When comparing the total life cycle of carbon emissions from the two fuels, petroleum diesel has a more negative effect on the environment,” Nowatzki says. “A study of the biodiesel and petroleum diesel life cycles jointly found that because biodiesel production requires such small amounts of fossil fuel, its CO2 life cycle emissions are much lower than those of petroleum diesel. Biodiesel reduces net CO2 emissions by more than 78 percent compared with petroleum diesel. A primary conclusion of the study is that displacing petroleum diesel with biodiesel in urban buses is an extremely effective strategy for reducing CO2 emissions.”  The aforementioned study was conducted by the USDA and Department of Energy.

Carnegie Mellon University researchers have used advanced process-design methods, combined with mathematical-optimization techniques, to reduce the operating costs of corn-based bio-ethanol plants by more than 60%.
   
Redesigning the distillation process by using a multicolumn system together with a network for energy recovery that ultimately reduces the consumption of steam, a major energy component in the production of corn-based ethanol, has been the key to the Carnegie Mellon strategy.
   
“This new design reduces the manufacturing cost for producing ethanol by 11 percent, from $1.61/gallon to $1.43/gallon,” said chemical engineering professor Ignacio E. Grossmann. “This research is also an important step in making the production of ethanol more energy efficient and economical.”