Cobs plus coal could help Willmar meet renewables goals

Willmar piled the cobs for the test burn on a runway at the city's old municipal Airport. Corn cobs do not require any special storage facilities. (Photo by Steve Downer, Minnesota Municipal Utility Association)

Long before ethanol plants began to spring up across the Midwest, corn was widely used as a biofuel in farming communities—a tradition Willmar Municipal Utilities may revive on a utility scale.

The utility's 60-year-old, municipal powerplant received a permit from the Minnesota Pollution Control Agency (MPCA) in February to test burn a new "recipe'' for producing energy: corn cobs and coal. If the pilot project is successful, corn cobs could become part of Willmar's power portfolio—and a new source of income for local farmers. "Burning cobs may be able to help us meet our renewable energy goals and support the local economy at the same time,'' says Willmar General Manager Bruce Gomm.

Bringing renewables into the mix

Minnesota's renewable portfolio standard mandates that all state utilities meet at least 25 percent of their energy needs with renewable resources by 2025. A $10 million wind project Willmar is developing may contribute as much as 3 percent toward that goal. The utility set the foundation for two 2-MW turbines last fall, and expects delivery of the DeWind D 8.2 units in May. 

The percentage of Willmar's power mix that corn cobs would represent is based on the total fuel that goes into the powerplant's boiler. "If the mix is 20 percent cobs to 80 percent coal at a 10-MW plant, we are getting two megawatts from renewable resources," Gomm explained.

Burning 450 tons of cobs in the 20-to-80 ratio will take about two weeks to a month. Gomm anticipates that the power plant will need to start up and shut down a few times for fine-tuning. "We are testing with the equipment that's in place, so the system is not fully designed around this kind of fuel," he acknowledged. "There will probably be a few bugs to work out."

In addition to determining if cobs and coal burn efficiently in combination, the test will provide data to the MPCA for issuing a permit to allow Willmar to permanently burn the cob/coal mix. Permitting biomass projects poses a challenge to the agency because of the variability in materials. Several sets of rules and regulations may apply to a given project. "The MPCA is working very closely with us to develop testing procedures for this kind of burn," said Gomm. "Favorable results would be good news for growers and the state," he added.

Boost to local agriculture industry

That's because farmers in Kandiyohi County alone planted 150,000 acres of corn last year, according to Minnesota Municipal Utilities Association. Willmar Utilities would need to purchase 20,000 to 40,000 acres annually to supply its municipal powerplant. At a rate of $30 to $60 per ton, it is no wonder that the community is so supportive of the test burn, or that several growers volunteered for the harvest.

Ultimately, it was easier for one farmer to supply all the cobs for the test, but Gomm noted that he received calls from people across the country. The corn came from 650 acres farmed by a local couple, Ryan and Lonnie Fosso. "Our plan would be to contract directly with the farmers to buy the cobs," Gomm said. "That way, the money stays in the county."

Harvesting cobs requires a specially-designed collector inventor Vernon Flamme calls the Cob Caddy. Flamme was brought into the project by consultant Jon Folkedahl of Willmar who originally proposed the idea of burning cobs to the utility. The Vermeer Corporation recently bought the patent for the collector and renamed it the Cob Harvester. "We hope that we can start out small, and as the market for corn cob grows, farmers will invest in the harvest equipment,'' Folkedahl said in an interview with the West Central Tribune.

Selling cobs is a better proposition for growers than turning them back into the soil, Gomm observed. Unlike stover, cobs have low nitrogen content, but take nitrogen from the soil to break down. "Basically, that makes them nitrogen neutral," he said.

Excellent fuel potential

On the other hand, there are several factors that make cobs a good biofuel source. The slow-decomposing cobs have an energy value of 75 to 80 percent of Powder River Basin coal Willmar burns at its powerplant. The CO2 released by burning has been recycled from the air, and the sulfur and ash content of the emissions is low. Perhaps most important, Gomm pointed out, is that cobs are abundant in Minnesota. "The best way for a biomass project to be economical is for the fuel to be a fuel of opportunity," he said.

Storage, frequently a logistical obstacle to biomass projects, has not posed a problem to Willmar so far, even though the cobs cannot be mixed with coal. "The difference in density causes the cobs to migrate to the top and the edges of the bin," Gomm explained. "It creates handling problems."

So the cobs were trucked to an old municipal airport, and piled on a runway. Sitting in the open air, the cobs only become drier and more flammable over time. "It's doubtful that we would build a dedicated storage facility," said Gomm.

With so many advantages, it is not surprising that other facilities in the area are harvesting corn cobs. The Fosso farm also supplied cobs to the Chippewa Valley Ethanol Company, which plans to gasify the fuel at its plant in nearby Benson. The University of Minnesota-Morris may also use cobs as part of the fuel mix firing its new biomass gasification plant, launched in October 2008.

Gomm is not worried about the competition for feedstock, however. "We are hoping that the higher demand will cause more interest in harvesting cobs and therefore create a more stable market," he said. "There is more than enough supply in this part of the state to support all of these potential markets."

Resources

Willmar Municipal Utilities

Minnesota Pollution Control Agency

Composite Technologies DeWind wind turbines

Minnesota Municipal Utilities Association

Vermeer Corporation

People

Bruce Gomm

Jon Folkedahl

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