October 20, 2009 | General

By-Products To Biomass Energy In Minnesota

BioCycle October 2009, Vol. 50, No. 10, p. 34
Rahr Malting joins forces with the Shakopee Mdewakanton Sioux Community to form Koda Energy, owner and operator of a 24.1 MW biomass power plant.
Dan Emerson

KODA Energy, LLC recently opened a biomass facility in Shakopee, Minnesota that converts oat hulls, barley waste and wood into steam to power a 24.1 MW turbine generator. The $60 million, 17-story plant – a partnership of the Shakopee Mdewakanton Sioux Community (SMSC) and Shakopee-based Rahr Malting – began generating electricity and heat in March. After its “shakedown” period, the plant has been operating nearly continuously since May.
Minneapolis-based Xcel Energy Inc. is buying nearly two-thirds of the electricity generated by Koda Energy to help it meet a state-mandated requirement that electric utilities provide 25 percent of energy used from renewable resources by 2025. The biomass burner is fueled by oat hulls from General Mills, barley malt dust from nearby Rahr Malting and wood chips. Eventually, prairie grasses could be used, according to Joe Johansen, Koda Energy’s General Manager. In the future, the SMSC may also receive wood harvested from road construction projects.
Situated on a 2.5-acre site, the plant is designed for a 60- to 70-year operational life, running 51 weeks a year. Along with the boilers, the plant has six steel silos, two each for the oat hulls, barley waste and dry wood. The Koda plant can combust up to 7 tons/hour of dry wood, and is designed to process 170,000 tons of biomass fuel annually.
The six silos hold enough fuel for four days. The biomass plant is over 70 percent efficient, according to Johansen, more than twice the efficiency of conventional coal-fired plants.
The initial idea for the project came from Rahr Malting, which had been using electricity and natural gas for its malting process. “Several years ago, we began looking for ways to control the cost of producing Rahr’s malt, which is sold to brewing companies,” says Paul Kramer, vice president of malting operations. The company saw the advantage of combined heat and power to generate baseload electricity, which would deliver process heat to the company’s production malting operation.
Rahr’s Shakopee production facility annually produces 370,000 MT (24 million bushels) of malt, making it the largest single site malt producer in the world. The campus consists of five individual malt houses. Rahr uses the process heat to replace natural gas for its malting process which can last from 6.5 to 7.5 days for the three stages: steeping, germination and kilning/drying.
Before the plant opened, Rahr sold its malt husks to animal-feed manufacturers, although “it was not a big source of income,” says Kramer. “The material was a really low-grade feed product, at best. The husks and dust have far greater value as fuel.” Kramer declined to say how much Rahr will save on energy costs, but burning waste rather than natural gas “represents a long-term investment we feel very comfortable with. The higher the price of natural gas, the better this project will pay back. Natural gas is a very volatile, manipulated market.”
SMSC and Rahr Malting formed Koda Energy, a Limited Liability Company, in December 2005 to build and operate the facility. SMSC holds a 51 percent stake in the partnership; Rahr Malting Co. has the remaining 49 percent stake. The plant was designed, built and tested over an 18-month period.

Rahr uses a pneumatic system to convey the malting by-product to the adjacent biomass plant. General Mills provides 136 tons of oat hulls daily to Koda Energy, which is waste product from Cheerios and other cereals. Koda contracts with a local trucking company to haul the oat hulls from the General Mills plant about 45 minutes away.
Incoming biomass cannot be larger than the size of a jellybean and “comes in as dry as possible, under 11 percent moisture,” explains Johansen. “Moisture in the material has to be dried out before it will ignite.” The biomass is ground into a powder using hammermills made by Bliss Industries, Inc. Three of four mills are used at a time to grind 21 tons/hour of material, resulting in a finished size of no more than 9/64-inch, comparable to talcum powder.
The Koda plant has six burners; the firebox heats up to 1,600° to 1,700°F. Dust is controlled at various steps along the process. An electrostatic precipitator removes the fine particulate matter. Emissions meet all Environmental Protection Agency and Minnesota Pollution Control Agency (MPCA) standards.
A 2-drum, top-supported boiler is used to heat the water and produce steam. The boiler can handle up to 900 lbs/square-inch of pressure. It produces 220,000 lbs/hour of steam. Electricity is generated when steam from the biomass burner turns a 38-foot-long Siemens turbine, capable of generating 24.1 megawatts of energy. “Under our contract with Rahr, we provide them with heat for malting and also megawatts to run their fans and plant,” says Johansen. “We also use some of the power to run our own operation. Koda has also contracted with Xcel Energy to feed 12.5 MW/hour into the grid.”
Under the air quality permit issued by the MPCA, Koda is allowed to combust barley products, wood (no manmade wood products) and the oat hulls obtained from General Mills. The plant is also scheduled to do test-burning of agricultural grasses in late August, as mandated by the MPCA. Koda plans to recycle the fly ash left over from the burning process, and has applied for Minnesota Department of Transportation approval to supply fly ash for road-building concrete. Currently, it is hauled to a nearby landfill.


Koda Energy is one of several renewable energy initiatives the tribe has underway, according to SMSC Tribal Administrator Bill Rudnicki. More renewable energy is scheduled to be added this fall, when a 1.7-megawatt wind turbine is installed at the SMSC Pow Wow Grounds near the tribe’s Mystic Lake Casino. Electricity from that turbine will be piped into a substation, where it will be metered against SMSC usage. “We are in a fair to marginal wind area,” Rudnicki points out. “Most projects are located in good to excellent wind areas. But this will demonstrate how you can do these type of projects in fair to marginal wind settings, in a somewhat urban setting.”
In 2008, the SMSC planted 200 acres of prairie grasses for use as energy crops. Two different seed mixes were used to research the best mix to yield the highest BTU to burn in the Koda Energy plant. Initial harvesting of those fields is expected in late fall of 2009.
The tribe also will begin operating a biodiesel production facility, utilizing used cooking oil from the casino complex to make 25,000 to 28,000 gallons/year of biodiesel. It will be used to fuel SMSC’s vehicle fleet.
“We are already using 24 passive solar panels to heat water for our new ice arena and for our fire station,” Rudnicki notes. “We haven’t done photovoltaic yet because the return on investment is less, but maybe that will change, down the road. We’re also considering other demonstration projects. Right now we are building two office buildings using geothermal for heating and cooling.”
Adds SMSC Chairman Stanley R. Crooks, who is also Koda Energy’s Chairman of the Board: “Energy independence is a priority for the tribe. Whenever we can provide our own services, when we can be self-sufficient, it increases our sovereignty. This is a small scale version of what this country is trying to do.”

Dan Emerson is a freelance writer in Minnesota.

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