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AURI Energy Center News

University of Minnesota shows favorable results testing emissions

Minneapolis, Minn. – Oat hulls could soon help warm the halls of the University of Minnesota’s Minneapolis campus.

U of M steam and electrical plant operators want to use more renewable fuels in their plants. The boilers in one plant are already designed to cogenerate power from coal and biofuels, as part of an energy and environmental upgrade completed five years ago. Faced with rising energy costs for 18 million square-feet of building space, officials designed more efficient systems with lower emissions at both St. Paul and Minneapolis campuses.

Wood is the only alternative fuel burned so far, as it was the only biofuel available in 1996 when the plant’s emissions permit was granted. Since then, the U of M has increased its wood consumption to about 32,000 million Btu – outpacing the local wood supply that meets its cogenerator’s specifications.

Because of erratic fuel supplies, fluctuating costs and original boiler-design intent, University officials have been seeking other biofuels to supplement the mix.

They identified oat hulls, the outside husk of the oat kernel left after processing, as a viable fuel to evaluate.

“We had tested a number of agricultural products for Btu value,” and knew that “many ag products compared favorably on cost … compared to traditional fuels,” says Alan Doering, AURI technical services specialist. “But we didn’t have much information about emissions. The University has the capacity to measure emissions, so we were very interested in working together.”

In early 2003, University officials negotiated a test burn with the Minnesota Pollution Control Agency to evaluate emissions using oat hulls. Emissions can vary by fuel source as well as technology and equipment used to burn them, making regulatory permitting difficult.

AURI’s coproducts utilization lab in Waseca helped produce hull pellets to address potential storage, dust and handling concerns, although they were not used in the actual test burns.

In early 2004, University officials tested two fuel blends: one with 9 percent oat hulls and 91 percent coal; the other with 35 percent oat hulls. Both yielded positive results.

The 35-percent oat-hull blend reduced sulfur-dioxide, carbon-monoxide and particulate emissions by nearly two-thirds over 100 percent coal. The blend did slightly increase nitrogen-oxide emissions, but well within permitted levels. The 9-percent oat blend showed a significant reduction in sulfur-dioxide and nitrogen-oxide emissions, but a slight increase in carbon-monoxide and particulate emissions – both well under permit thresholds.

Based on the favorable test data, the U of M has applied for an MPCA permit amendment that would allow for burning oat hulls and testing of other biofuels. The application is under review.

The University estimates it could burn 15,000 tons of oat hulls per year, and with new material-handling and burning equipment, up to 30,000 tons. Officials say General Mills’ two metropolitan-area plants could supply up to 60,000 tons of hulls year round.

“The emission (test) results enhance the attractiveness of oat hulls as a fuel,” Doering says. “It could also be valuable information to help encourage others to take a serious look at ag-based fuels.”

“Many other agricultural products have the potential to be used as biofuels. If the University can generate and share the emissions information we need, it will help improve the acceptance of ag products as viable fuels.”