Assessment of municipal solid waste as a blend feedstock to lower biomass feedstock costs

Biomass feedstocks costs remain a large contributor to biofuel production costs.  Biomass feedstock costs could be reduced by blending more expensive high quality feedstocks with lower cost, lower quality feedstocks such that the overall quality still meets specifications required by the biorefinery and the final costs are reduced.  Municipal solid waste (MSW) represents an attractive low cost feedstock with year-round availability, an established collection infrastructure and potential availability at negative cost.    

In this study, a blend of MSW and corn stover was examined for its ability to meet DOE cost and quality targets ($80/ton, 59% total carbohydrates and 5% total ash).  The Idaho National Laboratory Least Cost Formulation model was utilized to determine a corn stover/MSW blend with total feedstock costs below $80/dry ton.  The best blend ratio was determined to be 80% corn stover and 20% MSW.  The MSW fraction consisted of a paper waste stream collected from an office building which included cardboard, office paper, food packaging, magazines and catalogs.    Chemical analysis of the blend showed 5.5% total ash and 61.6% total carbohydrates.  Both corn stover and the corn stover:MSW blend were pretreated with ionic liquid and enzymatically hydrolyzed for 72 hours.  Glucose yields for both corn stover and the corn stover:MSW blend were 90% of theoretical while the xylose yields for corn stover and the blend were 48% and 55%, respectively. This study demonstrated that lower cost/quality feedstocks can be blended with higher cost/quality feedstocks to reduce overall feedstock costs without affecting quality targets or sugar yields.