Fuel property changes of switchgrass during one-year of outdoor storage

Like all biomass, both quantitative and qualitative changes in switchgrass may occur during outdoor storage. Evaluating the effects of long-term storage on the qualitative properties of energy crops provides an understanding of maintaining fuel quality. Two upland varieties of switchgrass, Cave-In-Rock and Trailblazer, were harvested, baled and stored outdoors under a protective tarp. Core samples from each variety were taken monthly for one year; on-site moisture was recorded and fuel analyses (proximate, ultimate and mineral/ash) were evaluated every three months during the storage period to determine storage and variety effects. In ad- dition to fuel analyses, fuel quality parameters of fouling and slagging indices, T-250, silica value and alkali% as Na2O were determined for the first and final months of storage. Average on-site moisture for the Cave-In-Rock and Trailblazer varieties were 12.4 and 12%, respectively for the whole year. Trends in fuel analysis only showed decreasing ash and increasing oxygen for both varieties over the storage period. Storage time significantly in- fluenced carbon content; the energy value was also significantly different for both varieties as values varied from 17.7 to 18.4 MJ/kg for both varieties. Significant differences between varieties were observed for ash, volatiles, carbon, nitrogen and oxygen contents. The fuel quality parameters show that the Cave-In-Rock variety maintains a higher melting point and reduced heat transfer in addition to a less and more stable susceptibility to boiler fouling. However, the Trailblazer variety had favorable silica values and percentage of alkali as Na2O compared to the Cave-In-Rock variety.