Central Minnesota Ethanol Co-op (CMEC) in Little Falls, Minn., has begun using natural wastes from the forests that surround it to power its ethanol production plant. North-central Minnesota is a strong supply source for the forestry industry, so wood waste was chosen as the fuel for CMEC's new biomass gasifier. It is abundant, cheap and easily obtainable in the long-term as almost all of the landscape northeast of the plant is wooded. But the gasifier is not limited to relying on this source. "It's been tested on almost 20 different fuels," said Cecil Massie of Sebesta Blomberg, the company that integrated the gasifier into the design of the plant. The secondary fuel for this equipment is natural gas, and the tertiary fuel is distillers grains.

Tulsa, Okla.-based Primenergy LLC, which engineers and constructs biomass conversion systems, built the gasifier. "The installation went very well; we got blessed with good weather last winter," said Bill Scott, president of Primenergy. "We had anticipated a long, cold winter, but that didn't happen last year."

The extent of the environmental improvements that the gasifier will provide won't be fully understood until more tests are conducted. "We will know a lot better when we get our stack test done," Scott said. "That is the next major hurdle that we need to get by, and then we will all feel good."

The gasification system is designed to play a very specific role and alleviate some particular problems. "CMEC had a problem with [its] dryer, so we are sending this gas from the gasifier to the thermal oxidizer," Scott said. "That was the first goal; the second was to get [the plant] off natural gas." The wood-burning Primenergy gasifier provides all of the heat for the dryer and all of the steam for the process.

"We're making progress, and as far as I know, there isn't reason to believe that we won't meet all of our objectives," Massie said. "We haven't settled into the kinds of things that would lead to an emissions test; it is still a matter of learning how to handle the fuel and equipment—what it does when this happens or what it does when that happens."

Construction to integrate the biomass burner into CMEC operations began in July 2005. "It is in start-up, and I would characterize it as encountering some of the normal glitches that you run into," Massie said. "So far, there have been no problems with the operations, but some minor modifications have been made." Massie wouldn't specify as to what additional or unexpected work had actually been performed on the machinery.

To feed the biomass combined-heat-and-power (CHP) unit, the facility will burn approximately 280 tons of wood waste per day and allow the delivery of wood day-in and day-out. EPM has reported that with the new equipment, the plant will be producing ethanol with an energy balance of 3.15:1, compared with the industry average ratio of 1.67:1.