Fast Pyrolysis of Biomass: Effect of Blending Southern Pine and Switchgrass

Fast pyrolysis of biomass is a promising technique to produce a high yield of a liquid product (bio-oil). However, biorefineries are often limited in size based on their ability to collect biomass from farther distances. This study was performed to understand the influence of blending two biomass types on the product distribution and physical and chemical properties of the bio-oil obtained from fast pyrolysis in a fluidized bed reactor. The implication of this study is that a biorefinery does not have to be limited to one feedstock and can benefit from the economy of scale. A biorefinery can also address the seasonality of biomass. Experiments were performed with southern pine, switchgrass, and their blends. Blending switchgrass with southern pine resulted in an improvement in the pH (2.39 to 3.16) and viscosity (12.12 to 6.96 cSt) of the bio-oil, although blending also resulted in increasing water content of the liquid phase. This effect could be attributed to the catalytic effect of the mineral ash contained in switchgrass, which causes secondary cracking of the pyrolysis vapor, thereby altering the quality of the bio-oil produced.