A team of researchers in the University of Florida’s biological engineering department thought it would be an environmentally friendly way for processors to use waste material and to add another source of revenue. The researchers contacted American Crystal Sugar Co., a sugar beet processing cooperative headquartered in Moorhead, Minn., to provide them with the feedstock and set to work so they could prove their theory.
From the Lab to the Plant
According to Jeff Moritz, facility services superintendent of technical services at American Crystal, the partnership started when the sugar processing plant began sending samples of sugar beet tailings to the university’s lab. The “tailings” consist of all of the organic material that remains after the sugar is processed from the beet—plant skins, greens from the tops that weren’t cut off during the harvesting, stray weeds, etc.
Initial university lab results were positive, as expected. “It’s a simple process,” Moritz explains. “It’s basically the same thing that would happen eventually in nature, in a compost bin or something.”
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The process uses anaerobic digesters to break down the tailings at an accelerated rate, resulting in the production of methane gas. Methane fermentation occurs naturally when groups of microorganisms in the plant go through a series of metabolic interactions. The university’s process just speeds things up by supplying the microorganisms needed to “eat” the food and the ideal environment for them to work in.
Even though tests showed the process was feasible, the lab was too small an environment for researchers to accurately predict what might happen in a commercial-scale facility. A larger test site was needed to prove it could be done on the scale needed for a processing company to commit to such a project. And for that to happen, an injection of money was needed.
The partners applied for a grant from Xcel Energy, a regional electricity and natural gas provider that services American Crystal’s sugar beet processing facilities. Xcel has funded various renewable energy projects since 2001 through a program called the Renewable Development Fund. Money for the program is provided by Xcel ratepayers and used to establish renewable energy sources in the company’s service area. Through that fund, the sugar beet tailing project was awarded $1 million for further research and to operate a pilot methane-producing plant.
It was decided that the pilot facility would be located at American Crystal’s Moorhead processing plant because the site already contained stainless steel tanks from an abandoned fiber project that could be reincarnated for the methane project. Having those tanks in place was a money saver for the project. “Although $1 million dollars sounds like a lot, when you’ve got a two-year research project, most of it goes to the lab and salaries for people working in it,” says Dave Malmskog, business development and economic analysis director for American Crystal.
The old tanks were the perfect solution, except for one problem. Three of them, ranging in size from 1,500 to 11,000 gallons, are located on the fifth floor of the building that houses the facility, while the collection tank and feedstock storage bins are on the ground floor. With a little ingenuity and lab work, however, that problem was solved. The solution was to create slurry from the tailings that could be pumped up to the tanks on the fifth floor to continue the methane fermentation process in the digesters.
The university researchers oversaw the setup of the equipment from Florida, with Moritz acting as their eyes and ears at American Crystal. He remains the point person for the project, although the researchers regularly visit Moorhead for testing and continued equipment work. American Crystal provides its technical expertise in processing organic material, the building and equipment and, of course, the feedstock. “It’s a learn as you go project,” Malmskog says, adding that a project like this has never been done at the scale they are attempting.
When the plant starts processing sugar beets in mid-September, the pilot facility will begin testing its tailings-to-methane process. Moritz says they plan to process 1.5 tons of tailings per day at the facility. Tailings will be trucked a few hundred yards from the processing facility to the pilot facility before being transferred into the feed pumping bin to begin the methane fermentation process.
The methane produced at the pilot plant is a small amount,—about 2,000 cubic feet per day—which Moritz calls “Bunsen burner-type stuff.” That small an amount isn’t worth sending to one of the plant’s burners, so the methane will simply be released into the atmosphere in safe doses. However, if the process is proven effective, a larger facility would
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