(602aj) Biofuels From Pyrolysis of North-American Grass Species

Native perennial grasses, indigenous to the Midwest, are ideal bioenergy crops due to their potential to be productive on marginal lands. Fast pyrolysis is a simple, flexible process to convert these feedstocks into bio-oil, which is  precursor to liquid hydrocarbon fuels. However, organic acids and oxygenates in bio-oil lead to storage instability and limit its early adoption as a transportation fuel. Biomass constituents such as inorganic salts dramatically alter the speciation of pyrolysis products. Therefore, the objective of this study was to prospect amongst several native grasses for cultivars suitable for pyrolysis to biofuels, by investigating the effects of biomass composition on pyrolysis products.

In this work, the composition of native grasses, including big bluestem, coastal panicgrass, deertongue, indiangrass, miscanthus, sandreed, sideoats grama and switchgrass, was determined. Pyrolysis of the grasses was studied using analytical pyrolysis-GC/MS and TGA. The resulting pyrolysis gas contains hundreds of chemical species. Principal component analysis revealed that only six chemical compounds, glycolaldehyde, acetic acid, acetol, methyl glyoxal, 4-vinyl phenol and levoglucosan, were needed to describe more than 90% of the variability associated with pyrolysis products. Correlation analysis revealed that potassium had a significant effect on production of acetic acid, acetol, levoglucosan, char yield and TGA peak reaction rate temperature. Pyrolysis of extractive-free as well as water-washed biomass was studied and compared with untreated biomass. Bio-oil from the native grasses was produced using a screw-conveyor pyrolysis reactor and bio-oil quality was subsequently assessed.