NextGen, ISU test biomass in coal boilers

By Lisa Gibson
NextGen Biofuels Inc. and Iowa State University will conduct cofiring trials with coal, wood chips and wood pellets at ISU's coal-fired combined-heat-and-power (CHP) plant, as the school contemplates switching to a biomass-coal blend.

Instead of spending millions on retrofitting, the project is designed to evaluate the efficiency of burning biomass in an existing coal boiler. "We're trying to demonstrate that you can run wood biomass through a currently operating coal plant," said Bob Ravlin, president of NextGen. The fuel does, however, need to be tailored to the boiler type, he added. NextGen procured pine wood pellets and wood chips from Rocky Mountain Pellet Co. in Colorado for the 3-month tests, which began June 28, Ravlin said.

The tests were to begin with a 5 percent biomass blend, gradually increasing to 10 percent, 15 percent and 20 percent. Separate testing would be done for the two different forms, as they are handled differently for the boiler. "Each feedstock has its own benefits and drawbacks," Ravlin said.

ISU has also done similar tests with construction and demolition waste, but the feedstock proved too dirty and was loaded with impurities, according to Jeff Witt, assistant director of utilities for ISU. "We are looking to displace some of our coal," he said. "We've been looking around in the past couple years." Although most biomass products will be more expensive than fossil fuels, there are clear benefits to the switch, Witt said.

The testing is preliminary and the school has not looked deeply into supply chains or sustainability as of yet. "There's probably enough product, but there's nobody making it right now," Witt explained, using a cart before the horse metaphor. If any other kinds of biomass feedstock seem applicable, they will be tried also, he said.

Once testing is complete, results will be evaluated and the school will decide whether to proceed with further research into the wood chip and pellet feedstocks for the long term. "It's a work in progress," Ravlin said. "You've got to start somewhere. You've got to start simply and build up from there." Besides demonstrating that it is possible to burn wood in existing coal boilers, NextGen has other goals for the project. "We want to jump-start the local economy," Ravlin said, adding that the logistics, know-how and equipment for lumber are already established. "You've got to get that area started." Fortunately, the tests have garnered a lot of attention from local utilities looking into the benefits of cofiring biomass, Ravlin said.