Dec. 16, 2010

DNR, ISU eye results of wood-coal combo

by Diana Pounds

In a few weeks, university officials hope to find out if it's feasible to begin adding wood pellets or chips to Iowa State's coal-fired boilers.

Intermittently since July, facilities planning and management staff have been testing various wood-coal combinations in the boilers. The test included monitoring air emission levels and the makeup of ash produced during the burning.

Those numbers recently were turned over to the Iowa Department of Natural Resources for review. The DNR regulates both air emissions and solid waste (ash) that's produced during burning.

"The next step in this process is getting input from the DNR on what requirements Iowa State would have to meet to get a permit to burn wood in its boilers" said Jeff Witt, FPM director for utilities. "We'll meet with DNR officials sometime after the first of the year to discuss these issues."

Armed with the DNR's conclusions and the test results, Iowa State officials will further explore the feasibility of adding wood to its fuel sources.

Pellet pros and cons

The idea is appealing, Witt said, because wood is considered renewable and its emissions are cleaner. University officials also are looking for ways to reduce reliance on coal.

However, Witt added, wood fuel is considerably more expensive than coal. Driving up the price are transportation costs (central Iowa doesn't have a ready source of wood). In addition, wood contains less energy and density than coal. By volume, it takes four times more wood than coal to produce the same amount of energy.

Emissions results

Witt said Iowa State tested wood-coal blends that ranged from 5 percent to 15 percent wood. Emissions results on the final 15 percent wood test revealed mixed results. Some air emissions increased and some decreased, but overall the results were promising. Specifically:

  • Air emissions of sulfur dioxide and particulate matter decreased.
  • Air emissions of nitrogen oxides increased slightly.
  • No significant changes were noted in carbon dioxide and carbon monoxide emissions.

Anything that reduces air emissions is considered beneficial; however, increases can be problematic. Based on the test data, the DNR will determine what permit modifications will be required. These permit changes will be part of the evaluation criteria used by university leaders to determine whether to proceed with wood as a fuel source.

Wood from beetle-decimated pines

The Rocky Mountain Pellet Co., Walden, Colo., and Nextgen Biofuels, Underwood, Iowa, supplied pellets and chips for the tests at no cost. The wood came from Colorado pine trees ravaged by pine beetles. The beetles have been chomping on Colorado forests for more than a decade.