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Co-firing Coal with Biomass to Reduce Greenhouse Gas Emissions

The federal government and several states are placing greater attention on carbon emissions which is expected to result in rising demand for biomass renewable energy feedstocks, especially among coal-fired heating plants in the northern plains region. These feedstocks will either replace coal directly, or be gasified, to meet impending carbon regulations and/or generate carbon credits. Co-firing with biomass also generates renewable energy credits that enable utilities to meet state renewable energy mandates. Moreover, cellulosic biofuel production is expected to be commercialized, accelerating demand for biomass feedstock.

North Dakota is one of the nation’s primary suppliers of coal. Consequently, electrical utilities, state heating plants, and industrial processing plants throughout the region rely heavily on this energy resource. North Dakota has also the distinction of being leading supplier of biomass renewable energy feedstock (National Renewable Energy Laboratory, 2009). Numerous counties have the potential to supply over 500,000 tons annually. 

National interest in North Dakota feedstock supply availability is especially keen given the perception that large portions of the state’s land are of marginal quality. Collection of biomass from these lands is perceived to have less impact on food production for human consumption.  However, these same individuals fail to realize the additional care required to minimize environmental damage to these fragile lands, native plants, and wildlife. Biomass education programs are needed to inform the public of each view’s merits.

Great River Energy (GRE) is proactively preparing for increased carbon regulation with development of a combined heat and power facility near Spiritwood, ND. The project proposes to develop a biomass supply infrastructure for co-firing up to 10 percent biomass. In addition, GRE has recently signed an agreement with Inbicon to develop a cellulosic biofuel facility on the site which would be an additional market for biomass.

Processing biomass for co-firing requires densification. Show Me Energy (Missouri) grinds all incoming feedstock in a specialized grinder and then pellets the ground material to ¼²size. Cubing biomass has also been found to be a viable densification technology and provide a biomass form that is conveniently handled with existing coal industry equipment. While the coal industry can use ground biomass directly, densification at regional pre-processing centers lowers transportation costs.

To move forward, GRE completed a Biomass Co-firing Feasibility Assessment to determine whether or not a sustainable biomass business model can be developed in the area of Spiritwood, North Dakota (NDIC Contract R001-003). The GRE study evaluated specific types of biomass that may readily exist or be established in the future, along with combustion characteristics, and expected delivered costs.

Focus groups conducted with regional farmers found they were not aware of preferred biomass harvest timing, product qualities or methods to reduce environmental impact. Attendees had expected biomass harvest to conflict with either summer or fall machinery operations. However, the ideal biomass harvest time is late winter before spring field operations begin. At this time preferred moisture was as low as possible and plant nutrients have been passed to the soil which minimizes fertility losses.

Biomass is typically purchased solely on the basis of BTU content, moisture and weight. One third of potential biomass is often left unharvested to preserve environmental quality and soil health. While most biomass is sold in bulk to wholesale buyers (e.g. electric utilities) a sizeable retail market also exists. During the winter of 2009 in Fargo, ND, big box retailers sold biomass pellets to consumers for $200/ton.  Show Me Energy, Missouri has found that pellets produce electricity at a cost of $0.03/kwh. Residual ash from co-firing is high in potash and an excellent fertilizer with a collection cost of $2/ton. Two of the most important challenges facing a co-firing biomass densification plant are silica and embedded metal which are highly corrosive and destructive to processing machinery. 


Broekema, Sandra, “Feasibility Study of a Biomass Supply For The Spiritwood Industrial Park” Final Report, Great River Energy, June 30, 2009.

National Renewable Energy Lab, “Biomass Maps” viewed Nov. 25, 2009.


Cole Gustafson, North Dakota State University

NDSU, Dept. 7620

P.O. Box 6050

Fargo, ND  58108-6050

Phone: 701.231.7261

Fax: 701.231.1008

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