Effect of pelletizing herbaceous grasses on chemical composition and conversion properties

Warm season perennial grasses are promising candidates as bioenergy crops because of their high productivities and carbohydrate contents. However storage and transport are challenging because of their low bulk density and poor flow properties. Pelletizing is a standard method for increasing bulk density of biomass. Field grown switchgrass, big bluestem, and a low diversity mixture were either milled or pelletized. Samples were analyzed for chemical composition using the dietary fiber method. Pelletized samples appeared to have lower overall structural carbohydrates and increased ethanol/water extractable materials. Samples were pretreated with low moisture ammonium hydroxide and evaluated for enzymatic sugar extraction. Pelletizing led to increased glucose yields for the big bluestem and low diversity mixture but not for the switchgrass. When pretreated with liquid hot-water, pelletizing was associated with increased glucose yields only for the low diversity mixture.