Encouraging numbers for corn oil feedstock

Posted June 22, 2010

Panel speakers discussed back-end coproduct optimization for ethanol plants at the 2010 International Fuel Ethanol Workshop & Expo in St. Louis last week. In recent times, more biodiesel producers have incorporated use of post-fermentation corn oil, extracted from ethanol plant stillage, as a biodiesel feedstock.

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, however, that number grew to 33 MMgy. 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/bushel) of corn oil, but by applying the company's latest advanced method, up to 1.7 lbs/bushel of post-ferm corn oil can be extracted. He said ethanol producers can make up to 7.9 cents per gallon of ethanol produced off of selling their post-ferm corn oil. "This could mean $830 million of new money to this industry," Winsness said.

While most corn fractionation processes involve front-end component separation after which the nonstarch 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 what's used for skim milk production, Tricanter technology does not leave any 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, gave an interesting talk on the so-called Eluseive process, whose name comes from combining elutriation and sieving. Using blowing air and different sized sieves, Srinivasan said it is possible to make enhanced DDGS, which is low-fiber, higher protein/fat distillers grains for chicken and poultry, an application developed to increase the utility of the feed in nonruminant markets. The separated fiber can be sold to ruminant feed markets.

Using four sieve sizes-large, medium, small and pan-the DDGS are first separated according to particle size. Once separated, air is blown into the size-separated batches of DDGS, effectively removing the fiber, leaving behind a relatively fiber-free enhanced DDGS. A one ton per hour Elusieve pilot plant is operating at University of Illinois-Urbana Champagne.