Reinvention With LESS Innovation

A legacy ethanol plant showcases a new low-energy solids separation system.
By Susanne Retka Schill | October 21, 2014

How can a small ethanol plant be relevant in an industry dominated by 75 MMgy-plus plants? Especially when every producer is striving for maximum efficiency aimed at shaving pennies off the cost of production to compete as a low-cost producer. For the 13-year-old, 18 MMgy facility at Buffalo Lake, Minnesota, the answer is to turn it into a showcase for innovation. The legacy plant, now known as Buffalo Lake Advanced Biofuels LLC,  will be watched closely by the industry as it seeks to drive efficiency to new levels  by cutting the plant’s energy load by a third, eliminating two troublesome systems and utilizing increased syrup solids to generate the plant’s power needs. In a collaboration with plant owners West Ventures LLC and operations specialists at IR1 Group, a new company in the ethanol space, Yield & Capacity Group LLC, has installed its innovative low energy solids separation (LESS) technology at Buffalo Lake Advanced Biofuels LLC.

Like many of the early ethanol plants, the Buffalo Lake operation has struggled in recent years. The Katzen-design ethanol plant, built by Minnesota Energy Cooperative, came online in 1997 at just under 9 MMgy. It had a good run until the deep downturn of 2009 brought production to a halt and idled the plant. Purified Renewable Energy restarted the plant in June 2012, announcing five months later that that it had purchased the facility. Purified quickly ran into problems, however, and filed for bankruptcy in March 2013.

Colorado-based IR1 Group worked for the bankruptcy court in the sale of the assets, and in the end, one of Purified’s main creditors, West Venture LLC, purchased the plant out of bankruptcy. Terry Kulesa, IR1 president, explains that his group has worked with a number of banks and investor groups trying to figure out what to do with the legacy plants that shut down during the economic downturn. “On the small plants that are old, have old equipment and often didn’t keep up with improvements, we tell them they have to do something different. They can’t compete with the 100 MMgy plants, there’s no economies of scale.” For some of those plants, turning to alternative products such as butanol has been the solution. At Buffalo Lake, IR1 introduced the investor group to Mike LoCascio and Ron Dunbar, who had just formed Yield & Capacity Group to commercialize LESS.

LoCascio is known in the ethanol industry as he worked for U.S. Water Services during the ethanol build-out, helping to develop the water balance in the Fagen/ICM plant design. After several years, he left that position, working briefly on biodiesel processes before going out on his own. In 2011, he did consulting work for Ron Dunbar, then manager at White Energy, cleaning up wastewater discharge. “Ron said to me, ‘If you can clean this up, can you clean up thin stillage?’” LoCascio recalls. When LoCascio’s experiments showed promise, the pair formed their company last year to commercialize it. “I provide the science background and Ron provides the operations know-how,” he says. Initial bench-scale experiments were followed by pilot trials at a cooperating ethanol plant willing to let the pair run their experiments onsite using the plant’s thin stillage. Now, the Buffalo Lake installation is serving as the commercial-scale demonstration.

Throughout the summer, as the Buffalo Lake plant was shaken down for restart, LoCascio and Dunbar shook down LESS. Joe Winckler, director of operations for IR1, directed much of the fabrication and modification work required as design improvements were made.

Gentle Extraction
“LESS is not a disruptive technology,” LoCascio says, explaining that it is based on technologies used in waste water treatment. The process uses a commercially available, GRAS-approved (generally regarded as safe) polymer that YCG has worked with two manufacturers to produce to its specific requirements. “The real challenge was in finding a mechanical process to separate liquids and solids in a way that didn’t violate all the patent claims that had been made by as many as 10 other groups,” he adds. “We are the only group to have found a robust, simple process for separating the flocculated solids from the liquid fraction.” 

Besides avoiding patent infringements, the main design challenge was finding a gentle means of extracting water. “We tried centrifuges, screw presses, dissolved air flotation, clarifiers—the four main industry technologies,” LoCascio reports. The biggest issue was each system introduced too much energy, dissipating the polymer effect that separated the solids. When the fourth set of machinery trials still wasn’t satisfactory, he called a friend at a nearby wastewater treatment facility and asked if he could experiment with one of the gravity tables used for dewatering sludge. “We took two 5-gallon pails of thin stillage over and threw them across the belt. It worked. The next day we went back with 15 pails.” A used gravity table was installed at Buffalo Lake, and more trials conducted to work through modifications to improve the system and provide enough separated solids and liquids to test the results.

LoCascio says the tests showed dramatic improvements. The clarified thin stillage is mostly free of fatty acids, total suspended solids are reduced to 85 to 90 percent compared to normal thin stillage levels and total solids are reduced 30 percent. Total solids would contain things like glycerol, lactic or acetic acid, LoCasio explains. The spent yeast in the clarified thin stillage could be isolated as a new source of protein feed or returned to cook as a nutrient. While the syrup solids recovered from the thin stillage can be reintroduced into the distillers grains, they could also be treated to capture additional corn oil. “What we don’t have data on yet is the net effect on fermentation,” he adds. Once Buffalo Lake is running at steady state, they expect to see positive effects on fermentation, plus an increase in capacity. 

Besides improving backset, the LESS system does an impressive job of reducing energy requirements. Instead of removing water through evaporation to concentrate the thin stillage to a syrup, the polymer-delivery system and gravity table at the heart of the LESS process use just 20 horsepower total, replacing 13,000 pounds-per-hour of steam and more than 300 horsepower in pumps.

The initial plan for Buffalo Lake was to treat 100 percent of the thin stillage, bringing a significant cost savings with the reduced steam use, lowered electricity requirement and by reducing a third of the cooling load in the evaporator condenser. Additionally, treating all the thin stillage would significantly reduce evaporator fouling and downtime. But, as the team continued to repair the legacy plant, one of the most expensive projects was to repair or replace the evaporators. So, the question was posed, if LESS works so well on thin stillage, would it work on whole stillage?

It did, ultimately allowing the plant to bypass the centrifuges and evaps entirely. The LESS system produces a distillers grains that augers and piles like DDGS, while having moisture levels comparable to wet grains. The whole stillage leaves the LESS system at about 23 percent solids. When it didn’t auger well up the 45 degree angle at the Buffalo Lake plant to be piled on the wet cake pad, a screw press was added to remove more moisture, down to a range between 33 and 43 percent solids. LoCascio reports they’ve had the nutritional value tested by a laboratory and local feeders who’ve tested it in livestock rations reported it worked well. “The thing that surprised us early on in our testing was the quality of the distillers grains versus something that’s been through the dryer,” LoCascio says. “Our amino acids are higher across the board and more bioavailable.” Further work is needed to figure out the best use for the unique distillers grains and how it should be valued, as well as to test how the distillers grains performs when dried.

Bypassing the centrifuges and evaporators has a big effect on energy use, LoCascio reports. “Overall, we reduce the Btu required to produce a gallon of ethanol by a third. The energy savings annually is estimated at $1.8 million for this18 MMgy plant.” The $600,000 installation cost is expected to have a four-month payback.

Off-Grid Goal
LoCascio’s not done there, though. “Once we figured out how to separate the solids from the liquid, we started focusing on what to do with the syrup solids. The oil can be easily recovered, but in a traditional plant the additional syrup represents a problem, since most plants that dry the DDGS don’t have additional dryer capacity to be adding in more syrup,” he explains. “That’s when we looked at biodigestion.”  Once Buffalo Lake is running at steady state and they have the LESS system fine-tuned, YCG will partner with the developer of an anaerobic digester system that handles high fatty acid materials. The syrup solids, when properly treated with enzymes, are a dense, balanced feedstock for the digester and would not need additional feedstocks to be brought in to balance the process, LoCascio says. The digester is expected to produce a high-quality biogas with 70 percent of the Btu content of natural gas that would be usable without cleanup in a boiler or generator. Initial tests and calculations indicate that about 20 percent of the syrup solids will generate enough steam and electricity to power the plant, taking it off the grid.

First, though, LESS needs to be demonstrated in steady-state operation. Since June, the Buffalo Lake Advanced Biofuels plant has been started up several times to test systems and to produce enough stillage for the LESS trials, reports plant manager Kyle Peik. In September, he was hoping to see the plant operating 24-7 once again. Beyond the LESS installation, other changes in preparation for restarting the long-idled plant were more routine. Upgrades were made to utilize heat load more efficiently, make systems more user friendly and replace aging components such as sticky valves, he explains. Peik has been with the plant since the beginning in 1997 when he started as low man on the totem pole. During the extended shutdown starting in 2008, he served as property manager. Today, as the plant manager, he’s pleased to be training in a new crew to run the plant. About 35 people have been working to bring the plant back up, he reports, which includes the IR1 and YCG crews, as well as the administrative team at the investor group’s offices in New Jersey.

For Peik and the small, western Minnesota community of 700-some people, seeing the steam rise from the plant’s stack once again is a welcome sight above Buffalo Lake.

Author: Susanne Retka Schill
Senior Editor, Ethanol Producer Magazine