Making the Most of DDGS
Historically, distillers grains products have served as a revenue source for ethanol producers and a feed product for livestock producers. The Renewable Fuels Association estimates that the nearly 31.5 million metric tons of distillers grains products produced during the 2009-’10 marketing season had a market value of about $3.8 billion. June prices for DDGS ranged from about $195 per ton to nearly $245 per ton, up almost $100 per ton compared to last year, according to CHS Inc. Considering that about 17 pounds of distillers grains is produced from each bushel of corn that enters an ethanol plant, sales of distillers grains can add a significant portion to each plant’s bottom line. But as diversification is seen as a necessary strategy for continued profitability in the ethanol industry, researchers see a time when distillers grains will be used for more than feed. Diversifying uses for distillers grains can provide multiple revenue streams and contribute to the increasing need for renewable fuels. Several projects currently are exploring how to make the most of ethanol’s most abundant coproduct.
Take All You Can Get
“The economics of ethanol plants is softening,” says Pavel Krasutsky, chemical engineer and director of the Chemical Extractives Program at the Natural Resources Research Institute at the University of Minnesota Duluth. “If we can find some additional value-added products, we can improve the economics and make it sustainable.”
In 2004, Krasutsky began researching methods to produce other products from DDGS, firmly intent upon not destroying the DDGS as a feed product in the process. He wanted to improve its feed quality so as to increase its market value, and he wanted the DDGS to serve as a fuel. His project quickly yielded some unexpected results. “We found that if we extract products from DDGS using ethanol, we have two parts valuable for biofuel—fat material, which can be used for biodiesel production, and solubles, which can be converted to more ethanol,” he says. “At the same time, after extraction of these products from DDGS, we increased the protein level of DDGS from 28 percent to nearly 40 percent.” Lab and early pilot plant test results indicate that corn ethanol plants could increase their ethanol production using this method by nearly 10 percent. Add to that another 10 percent of biodiesel, and the overall increase adds up to a process which Krasutsky says could “dramatically change” the economics of ethanol production. Krasutsky is also exploring the potential of zein production using his extraction method, which would provide another revenue source for producers.
The higher protein DGs produced as a result of this process should also provide a significant income boost to ethanol producers. In addition to having increased levels of the protein, the leaching process used to extract corn oil and glycerin from the DDGS also removes any residual antibiotics and water, which may be attractive to some feeders. High-protein distillers grains are also more concentrated, consisting of about 70 percent of the initial product, making them less costly to ship. A trace of the microbiocidal ethanol used as a solvent in the extraction process remains in the final distillers product, which helps maintain the product’s shelf life and as a result, further improves the logistics of long-distance transport.
Doug Tiffany, an extension production economist at the University of Minnesota who specializes in analyzing renewable energy technologies, has been working with Krasutsky on the project and says early analysis of the overall process “looks favorable,” but he hesitates to provide an expected market cost for the high-protein DGs quite yet. “We’re being conservative on what we think this high-protein distillers product would be worth,” he says. Feed trials will be part of the research effort during the pilot phase to help determine the market price and demand for the new product. “You just can’t show up to the market and say, ‘We’ve got something new, start using,’” Tiffany says. “That’s a great thing about the pilot facility. We’ll have the opportunity to make substantial amounts so we can see how it performs in feed trials.”
Grants received from the Minnesota Corn Growers Association and the Institute of Renewable Energy and the Environment have helped the project move into the pilot phase, begun earlier this year with completion expected in July. Pilot operations are being conducted at Crown Iron Works Co. in Minnesota. Krasutsky recently received a patent for the biodiesel production process and is also working with Glycos Biotechnologies Inc. to produce ethanol from the solubles extracted from the DDGS. Paul Campbell, chief science officer at GlycosBio, says the company’s proprietary technology will be used to convert this low-value mixture of glycerol and sugars to ethanol first, but eventually the goal is to produce renewable chemicals such as lactic acid or isoprene. Krasutsky and others involved in the project believe that ethanol produced from the DDGS could qualify as an advanced biofuel, making it even more valuable for producers, but that remains to be determined. “Glycerol has never been used as a feedstock for ethanol production,” Campbell says. “If converting DDG to ethanol in a cellulosic process counts as an advanced biofuel, we hope the same logic will apply to our process as well.”
While optimization of the process remains to be completed, Tiffany says early numbers indicate that a 55 MMgy ethanol plant could improve its annual profits by about $19 million using Krasutsky’s integrated process. “We don’t have all the answers yet, but what we see looks pretty good,” he says. “We’re looking at a pretty rapid payoff of this technology under a variety of market conditions. In the end, ethanol plants will have a broader portfolio of products to sell as they extract more value from every bushel ground.”
Krasutsky admits that while the numbers look promising, there may not be many producers in the position to front the capital required to install the equipment to produce these varied products. One possible solution is for producers to team up to establish regional processing facilities. Because ethanol is used as a solvent, it would make sense to co-locate the DDGS facility with an ethanol plant and other plants could then sell their DDGS for processing. It’s an idea that should be familiar to the many ethanol plants currently owned and operated by farmer cooperatives. “Every plant could have something like this, but it may be more practical for there to be one of these at a regional ethanol facility,” Tiffany says. Krasutsky plans to begin work on the engineering of a commercial facility immediately following the completion of the pilot project and says he expects the process to be commercially available in about two years.
While Krastusky and others have geared their efforts towards coaxing as many products out of DDGS as possible, other projects are more singularly focused. At the U.S. DOE’s Great Lakes Bioenergy Research Center, based at the University of Wisconsin and Michigan State University, researchers are tasked with one goal: making cellulosic ethanol production cost effective. It’s a project with many possible means to the end, and one of the means being explored is DDGS. Jonathan Walton, professor of plant biology at Michigan State University and associate director of GLBRC’s activities at MSU, is responsible for the basic research and says his team is interested in the feasibility of using DDGS as a lignocellulosic ethanol feedstock. “After it comes out of the distillery, there’s a lot of polysaccharide left there, sometimes a significant amount of starch, say 3 to 5 percent, but then all of the cell walls,” he says. “So we’re treating it as a lignocellulosic material. I’ll be the first to admit that we don’t think that currently it’s going to be economical. I think everybody who works with DDGS and thinks about it recognizes this problem—in a ton of DDG there’s about 220 kilograms of glucose, which could produce about 37 gallons ethanol, and that comes out to about $5.10 a gallon. That’s clearly not economical, but the price of DDG might change, the price of gas might change. If gas were $6 a gallon, that would look pretty good.”
Walton’s process would also leave behind protein for high-value animal feed and corn oil for other uses. He agrees that the best way to make DDGS conversion economical is to produce a suite of products, but his research at the GLBRC focuses only on the ethanol conversion. The first step in that process is to break down the DDGS samples. To do this, Walton and his team are using a machine they designed, dubbed the GENPLAT, for GLBRC Enzyme Platform, that helps determine which particular enzymes are most effective at breaking down materials for cellulosic ethanol conversion. GENPLAT is able to perform 96 assays in one test, which vastly improves the rate at which enzymes can be evaluated. Initial GENPLAT tests have indicated that beta-mannanase is a surprisingly important component of an enzyme mixture needed to break down DDGS. Walton says this finding was peculiar because DDGS contains little mannose. His theory is that mannan forms a barrier to those ever-important glucose-containing polymers, cellulose and hemicellulose, and therefore the mannanase is necessary to break that barrier apart. Much of it remains a mystery, but Walton believes GENPLAT will play an important role in finding the answer.
There are many potential feedstocks for cellulosic ethanol, but aside from corn stover, switchgrass and miscanthus, most have only small-scale potential. Distillers grains offers an ample amount of feedstock already conveniently located at ethanol production facilities, which makes it extremely attractive. “You don’t have to develop a new crop or a new infrastructure to grow and transport it,” Walton says. “It fits into the current industrial infrastructure scenario quite well. It’s just a matter of squeezing a little more value out of material that we already have.”
Author: Kris Bevill
Associate Editor, Distillers Grains Production & Markets