A Biomass Fuel Assessment for Duke University’s Chilled Water Plant #2

This Masters Project identifies the University’s biomass fuelshed and locates potential supply sources and probable fuel quantities. An Excel workbook couples user-defined transportation, processing, collection and handling, and purchase premium expenses within fuel classes to establish probable purchase costs for each supply source. Results are optimized for a lowest cost fuel mix to meet modeled plant demand based on user defined plant parameters. Finally, total biomass fuel costs are compared to fossil options to determine if biomass is a financially justifiable fuel for Duke to pursue.

The results of this study indicate that the university fuelshed likely contains supply for more than 4 times the steam plants fuel requirements. The cost per million British thermal units combusted within the fuelshed is highly variable, ranging from approximately $1.01 for construction / demolition material to over $29 for forest thinnings. Several fuel classes are more economic than current prices for natural gas, ranging from less than a quarter to three quarters of the price of natural gas.

The preliminary assessments of purchasing biomass fuel for use in the plant resulted in costs significantly lower than natural gas, and even potentially lower than coal. It is anticipated that the annual fuel costs for a biomass plant could be met for around $2.25 million based on plant parameters modeled and the estimated biomass characteristics (collection, base cost, etc.). Fuel costs are demonstrated to be highly sensitive to changes in fuel properties (mainly distance and moisture content) and plant operating parameters. A large portion of the biomass estimates are derived using employee based proxy equations, and the author was unable to confirm the accuracy of these supply estimates. Finally, the cost modeled is for fuel supply only. This paper does not take into consideration storage, operating / maintenance, or capital outlay, all of which are traditionally higher for biomass than fossil fuels. Despite these uncertainties there is a clearly demonstrated opportunity to fuel the plant with biomass at a cost less than natural gas. Additionally, the large and diverse biomass supply will lend resiliency to market fluctuations.