Enhancing Coproducts

By Ron Kotrba | July 15, 2010
Panel speakers at the FEW discussed back-end coproduct optimization for ethanol plants, including extraction of post-fermentation corn oil from stillage that has been finding a home among biodiesel producers. The chief technology officer for Greenshift Corp., David Winsness, said only about 4 MMgy of post-ferm corn oil was being extracted from whole stillage at U.S. ethanol plants in May 2007. Two years later, that number grew to 33 MMgy and by May 2010 as much as 44 MMgy of post-ferm corn oil was removed and sold as biodiesel feedstock or for other uses. Winsness said by 2022, it is expected that up to 680 MMgy of post-ferm corn oil will be siphoned from the back-end of U.S. ethanol plants.

Winsness said the earlier Greenshift extraction modules were able to secure up to 0.9 pounds per bushel (lbs/bu) of corn oil, but by applying the company's latest advanced method, up to 1.7 lbs/bu of post-ferm corn oil can be extracted. He said ethanol producers can make up to 7.9 cents per gallon of ethanol produced by selling their post-ferm corn oil. "This could mean $830 million of new money to this industry." While most corn fractionation processes involve front-end component separation after which the non-starch streams can be sold into various higher-value markets, Greenshift has trademarked the term Backend Fractionation to represent the selective and efficient removal of valuable components within the whole stillage. "It's barbaric to use a hammer and chisel approach to separating corn components," said Winsness of some front-end frac processes.

Ryan Heuer, with ICM Inc.'s business development unit, discussed Flottweg's Tricanter technology, which is a three-phase separator isolating the solid "peanut butter-like material" from the two immiscible liquids with different densities, oil and water. Heuer said unlike competitors' separation equipment, which use disk stack centrifugation similar to that used for skim milk production, Tricanter technology does not leave entrained solids in the extracted corn oil. He also said the downtime of Tricanter technology is significantly less than with competing oil extraction units. "There's a 40 to 60 second delay every six or seven minutes," Heuer said referring to disk stack units. "That equals a downtime of about 10 percent," whereas Heuer said downtime for the Tricanter is only about 1.2 percent. He said the purity of the extracted oil product is comparable to yellow grease and actually trades at a premium to yellow grease.

Radhakrishnan Srinivasan, assistant research professor at Mississippi State University, spoke on the so-called Eluseive process, whose name comes from combining elutriation and sieving. Using the system, Srinivasan said it is possible to make lower-fiber, higher-protein/fat-enhanced distillers grains for chicken and poultry. The separated fiber can be sold to ruminant feed markets. Using four sieve sizes, the DDGS are first separated according to particle size. Air is then blown into each batch, effectively removing the fiber for enhanced DDGS. A one-ton-per-hour Elusieve pilot plant is operating at University of Illinois-Urbana Champagne.