American Crystal Sugar Co., headquartered in Moorhead, Minn., is gearing up to test the use of sugar beet waste as an energy source. Traditionally the company has distributed the tailings over farm land, a several hundred-thousand dollar yearly expenditure.
American Crystal has six sites in the Red River Valley of North Dakota and Minnesota, some of which generate hundreds of tons of waste daily. The sites in East Grand Forks, Minn., and Hillsboro, N.D., are the company’s largest factories and produce the most tailings East Grand Forks incurs the highest waste disposal expenses.
Researchers from the University of Florida have been experimenting with the tailings-to-methane process, and contacted the beet processing company to test it on a much larger scale. The project received $1 million from the Xcel Energy Renewable Energy Development Fund. If successful, a project could be granted up to $2 million if certain commercial criteria are met.
The process being tested, which was originally developed for NASA in order to aid future Mars astronauts in generating energy, uses microorganisms to anaerobically digest the sugar beet tailings and generate methane which can be converted to electricity. This can be done effectively with careful monitoring of the moisture, pH and temperature levels of the tailing storage containers.
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A seven story pilot plant is being built near Moorhead, Minn., and will be completed later this year. The plant will be able to convert approximately 10 tons of beet tailings weekly, and also capable processing other feedstocks.
Although small and solvable, a few problems have surfaced with the plant. “This is because a pilot plant by its nature is unique from anything else that has ever been built,” Dave Malmskog, American Crystal Sugar director of business development, told Biomass Magazine. “For example, we are utilizing some old tanks at our Moorhead factory as digesters for the system. The problem, however, is that the tanks are located on the 5th floor of the building and there isn’t room or budget to convey the tailings upstairs.”
The solution to the problem was to macerate the tailings on the first floor, and then pump them up to the fifth floor. “Of course, the University of Florida had to run tests back at their lab to make sure a macerated feedstock would generate methane as quickly as our previous tailings mixture,” Malmskog said. “It turned out, maceration worked even better in the lab so we’ve incorporated the maceration pump into our system. The team from the University of Florida has done a truly great job in hammering out solutions for numerous problems like this over the past several months.”
Malmskog said preliminary calculations show that 125 billion British Thermal Units (BTUs) could be produced annually from tailings at the East Grand Forks site. "Ideally, where I would like this to go — where it would probably provide the most benefit — is if we could find a way to clean it up and inject it into the natural gas pipeline." Malmskog added that in the future, American Crystal Sugar may look for other biomass to use as a feedstock.
Officials hope the pilot project near Moorhead, Minn., will lead to a commercial project in the next couple years. “It will be a win-win situation,” Malmskog said. “We will win because we will save on disposal costs and energy costs. Secondly, the United States will win because the biogas produced will be made in America and renewable. Finally, the environment will win because the carbon footprint of our factory could be reduced.”
Malmskog said that it will be at least two years before the project can be rendered commercially viable.