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U of I Corn Processing Research Reduces Ethanol Production Costs, Improves Quality of Resulting DDGS
Urbana—Corn processing research currently under way at the University of Illinois is changing how ethanol is made across the U.S. The discoveries are lowering the costs of fermenting corn into ethanol by isolating only the components needed for fermenting, eliminating the need to add a certain enzyme because it is bred right into the corn and reducing the amount of energy needed to produce ethanol via use of the Raw Starch Hydrolyzing Enzyme.
The U of I research also is improving the quality of an ethanol coproduct, Distillers Dried Grains with Solubles (DDGS), making it potentially more suitable as feed for non-ruminant animals such as poultry and swine as well as the beef and dairy cattle it now feeds.
U of I Associate Professor of Agricultural and Biological Engineering Vijay Singh said in a recent interview that of the two primary ways to make ethanol—dry grind or wet mill—the number of dry grind ethanol plants is growing at a very fast pace and all new ethanol plants built in the past 10 years utilize the dry grind process.
One reason for the preference of the dry grind option is that such plants cost about one-third less than wet milling plants to construct. However, in a wet milling plant, the ethanol producer separates the corn completely into four components—fiber, protein, germ (and oil) and starch--before starting the fermentation process to turn only the starch into ethanol. The fiber, protein and germ (and oil) that are removed initially can be marketed separately. In the now more popular dry grind plant set-up, the entire corn kernel is ground and mixed with water to produce slurry that is cooked. The slurry starch is liquefied, saccarified (turned into sugar) and fermented to produce ethanol, while the remaining nonfermentables (germ, fiber and protein) are recovered at the end of the process in the form of an animal feed known as DDGS.
“It costs a lot to process all of the components rather than just the starch, and the value of DDGS is less than ethanol or even corn itself. About one-third of what is being processed in a conventional dry grind plant is going to end up as DDGS,” he said. And, the type of DDGS being produced is high in fiber to be a really good replacement feed for non-ruminants. It is best fed to ruminants, including dairy and beef cattle.
To further compound the DDGS situation, Singh noted that the largest dairy and beef cattle concentrations, and therefore attractive markets for DDGS, are in Texas, California and New York.
“The DDGS is selling at about $80 to $120 a ton but it’s costing ethanol producers about $30 to $40 a ton to transport it to areas of the country with high beef and dairy concentrations. That reduces the profit on DDGS by almost half,” Singh said.
Dry Grind Process Modifications
New dry grind process modifications utilizing corn fractionation have been uncovered by U of I researchers working in collaboration with scientists at the U.S. Department of Agriculture (USDA) Eastern Regional Research Center (ERRC), The process isolates and removes corn germ and fiber before the fermentation process begins, leaving only the starch and protein to undergo the fermentation stage.
The new Modified Dry Grind Corn process, known as the enzymatic dry grind or E-Mill corn process, produces 70 percent less DDGS than the conventional dry grind process. The resulting DDGS—called Enzymatic Dry Grind DDGS or E-Mill DDGS—is lower in fiber and higher in protein than conventional process DDGS. It currently is being studied as a possible feed for poultry and swine, which are both plentiful in the Midwest so would open new, closer markets for ethanol producers. So far, feeding trials conducted in the Department of Animal Sciences at U of I look promising, according to Singh.
How is the Modified Dry Grind process accomplished? In simple terms, corn is brought into the plant and soaked in water for a short time, about four to six hours. Then, the corn-water slurry is incubated with specific enzymes that break down the raw starch and change the specific gravity of the slurry and make it thicker. The germ component, because it has a high oil content, will float on top of the slurry and can be recovered by a hydrocyclone (equipment used to separate components based on density difference). If the specific gravity of the slurry is further increased, pericarp fiber also floats along with germ and can be recovered with the germ fraction. Remaining components (endosperm fiber, protein and starch) settle to the bottom. Endosperm fiber is recovered via the use of screens. Starch and protein are processed for ethanol production. Starch gets converted into ethanol and protein is recovered as E-Mill DDGS.
E-Mill process helps isolate and separate the two basic kinds of corn fiber: pericarp fiber and endosperm fiber. These two kinds of fiber can be used to make high-fiber drinks and high-fiber cereals for human consumption, and to produce corn fiber oil, a nutraceutical product that can reduce serum cholesterol in humans.
According to Singh, recovering the germ, pericarp fiber and endosperm fiber increases the amount of starch during fermentation and increases the final ethanol concentration in the dry grind process. Fibers recovered in the E-Mill process can also be used as feedstocks for making cellulosic ethanol.
“The E-Mill process improves the dry grind ethanol process of ethanol in three ways,” said Singh. “First, valuable coproducts (corn germ, pericarp fiber and endosperm fiber) result from the process. Second, it increases the plant capacity. Third, it increases the amount of protein and reduces the amount of fiber in the resulting DDGS, which has a wider market than conventional DDGS.” U of I and USDA/ERRC have a joint patent on the E-Mill process.
The Elusieve Process
In addition, another new procedure known as the Elusieve Process has been researched by U of I scientists. It is used to separate fiber from DDGS produced using the conventional dry grind process, and the resulting fiber can be used for the recovery of other value-added co-products. The Elusieve Process uses a series of five different sizes of sieves and elutriation, a process of separating lighter particles from heavier ones using a vertically-directed stream of air. The resulting DDGS has a lower fiber and higher protein and fat content, similar to that produced by the E-Mill process. The U of I has a patent pending on this process.
Raw Starch Hydrolyzing Enzyme
A third innovation being studied at the U of I involves the use of the Raw Starch Hydrolyzing Enzyme which can help ferment starch even when it is still crystalline in nature and reduces the use of heat in the dry grind process.
Singh explained that in a conventional ethanol plant, producers grind corn and then add water to make a mash that is heated to high temperatures. The mash must be heated because starch cannot be broken down by conventional enzymes unless the crystal structure of the starch is broken. Heating disrupts the crystalline structure of starch. Then two enzymes—alpha-and gluco-amylase --are added in sequential steps requiring specific acidity and temperatures before the fermentation process gets under way.
In the new enzymatic process, however, corn is ground, water is added and the recently developed Granular Starch Hydrolyzing Enzymes are added so fermentation can begin immediately. These enzymes have been recently developed by two major enzyme companies. Some 20 ethanol plants across the U.S. now use this process, and interest in the process is increasing, Singh noted.
“It’s a beautiful technology because it simplifies the process and doesn’t require the use of heat,” Singh noted.
A New Corn For Ethanol
Finally, U of I researchers have been involved in testing a new kind of genetically modified corn produced by Syngenta Biotechnology, Inc., that has the alpha-amylase enzyme produced inside the corn, thus eliminating the need to add it during processing.
“Now you can grow a superior corn that can go right to a dry grind ethanol plant” Singh said. While the U.S. Food and Drug Administration has OK’d the use of the new genetically modified corn as a feed for animals destined for human consumption, it is still waiting for USDA approval to be grown widely.
According to Singh, the addition of only 3 percent amylase corn to dent corn is required for ethanol production, and he and others have found no differences in the DDGS such a combination produces at the end of the ethanol production process.
“We have tested it and found it works very, very well and produces the same amount of ethanol,” he said. “And, this is only a first generation product. Think about what could be next? The possibilities are endless.”
Syngenta, one of the world’s biggest makers of agrichemicals and plant seed, previously announced it would introduce the first enzyme-enhanced corn seed designed to cut the cost of the production of ethanol into the U.S. market in 2007.
Syngenta modified the seeds genetically to express high levels of a novel alpha-amylase enzyme—a thermal-tolerant digestive enzyme that turns the corn’s starch into sugar for ethanol. The company expects sales to be “significant,” according to David Jones, Syngenta’s head of seed development. Syngenta has estimated that the high-amylase seeds could cut production costs by 10 percent.
Collaborators working with Singh on innovations in corn processing include David Johnston and Robert Moreau, both with the USDA/ARS /ERRC; Bruce Dien, USDA Agricultural Research Station (ARS)/ National Center for Agricultural Utilization Research (NCAUR) and Kent Rausch, U of I Associate Professor of Agricultural and Biological Engineering.