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A Sweet Energy Source

A few years ago, American Crystal Sugar Co. began supplying the University of Florida with sugar beet waste for a research project that, if realized, could change the way the company does business by turning some of its waste into energy. While the project is still in the pilot-plant phase, all signs point toward a successful turnaround from waste product to green energy.
By Kris Bevill / Story and Photos
The idea was fairly simple. Use the organic material left over from processing an agricultural product, such as potatoes or sugar beets, to produce methane. The methane can then be used as a heat source for the processing facility, or turned into electricity and sold back to the power grid.

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."

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
produce enough gas to be used for several options. Malmskog says that sugar beet processing is energy intensive, and that American Crystal has four options for methane use.

The gas can be used to heat boilers, pulp dryers and lime kilns, or it could be cleaned and sold back to the company's energy provider as green gas. This could open up an additional revenue stream and allow the company to profit from carbon credits. Malmskog says he's already received several calls from people interested in obtaining green gas for
that very purpose.

There is some hesitation on the part of Malmskog and Moritz. They are both quick to point out that the process has not even begun yet, and results won't be known until late this year. The grant money will be exhausted after the university runs the facility for 10 consecutive days in the early fall, and then it will be up to American Crystal to continue funding the project. Malmskog says they are curious whether the process will work in the dead of winter when the sugar beet tailings are frozen, or in the spring when the fermentation process has already begun naturally. There is a distinct possibility that the company will provide more money to keep the tests going. But the question will be for how long? "We might find out that it's just too expensive to build [a demonstration plant]," Malmskog says. "We just don't know yet. It's tough for a company even American Crystal's size, which is pretty big, to invest in a demo plant that may never be used." Malmskog hopes the company can come up with more grant money to alleviate some of those expenses and is looking at potential funding opportunities from the recently passed Farm Bill.

The ‘Tail' of the Story
There's no doubt that the use of sugar beet tailings for energy would be a money-saving venture for American Crystal. As the largest sugar beet processor in the country, the company currently operates five processing facilities throughout the Red River Valley of North Dakota and Minnesota. Hundreds of thousands of tons of tailings are left after processing sugar. The company's largest plant, located in East Grand Forks, Minn., produces 400 tons of tailings daily when the plant is in operation from September through May.

The only use, until now, for the tailings has been as animal feed or fertilizer for the sugar beet fields. Some of the plant locations have been giving the tailings away to nearby ranchers, but not all the plants have that option. The East Grand Forks location, for instance, isn't located near any ranchers who are interested in the free feed. The plant has to pay to truck the tailings out to be dumped on fields for fertilizer, which isn't cheap. Malmskog says it costs the company nearly $1 million per year to dispose of the tailings. "That's why this project was especially interesting to us," he says.

Not only would methane production offer a potential low- or no-cost heat source for the plant, but it would also save money by making a "waste" product useful. Another potential byproduct of the tailings would be to use the ash left over after methane is produced as a garden fertilizer or compost material, which would also have value.

Aside from the many benefits, there are a few drawbacks to consider when producing methane using the university's method. Safety is always a concern and the possibility of an explosion exists anytime methane is being produced in a contained atmosphere. American Crystal modified its ventilation system and installed a fan on the top floor of the building to disperse any gas leaks that could occur. "Let's just say the university was comfortable with what we had, and we added to it," Moritz says. "We feel its [potential for explosion] is manageable, but we go a little farther than we have to."

Another downfall is the labor intensiveness of the process and the relatively slow turnaround time. Methane has been produced in the lab in six days-down from an initial 15 days, but those numbers aren't likely to hold up in a larger pilot plant. Malmskog says they'll be happy if they can produce methane in 10 days. At that, they still expect the process to take approximately two people 10 eight-hour work days to produce the gas. But, as Malmskog says, you just never know. That's the whole reason for this facility-to test the technology and see where it leads.

Kris Bevill is a Biomass Magazine staff writer. Reach her at kbevill@bbiinternational.com or (701) 373-8044.
 

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