(332d) Using Municipal Wastes with Conventional Feedstocks for Biofuel Production

The U.S. Department of Energy promotes production of advanced liquid transportation fuels from a variety of biomass feedstocks by funding fundamental and applied research. Supply system designs depend on the properties of the materials and variability in feedstock quality. Meanwhile, increasing generation of municipal solid wastes (MSW) presents a problem of waste accumulation in landfills and oceans accompanied by a wide range of negative environmental consequences. MSW also exhibits some of the same challenges associated with terrestrial biomass feedstocks including material heterogeneity, inconsistency in feedstock quality, and issues around handling during preprocessing. In this study, we evaluated the potential to use ”cost advantaged” MSW (grass clippings and mixed paper) along with a conventional biomass feedstock (corn stover) to evaluate the potential to meet specific quality targets for downstream conversion (≥ 59 wt% total carbohydrates and ≤ 4.93 wt% ash). Feedstocks such as grass clippings and mixed paper have relatively unfavorable quality characteristics such as high ash content that necessitate an alternation of the biomass supply logistics system. Grass clippings have average carbohydrate and ash contents of 28.1% and 13.1%, respectively, whereas mixed paper contains on average 61.4% carbohydrate and 10.1% ash. Our analysis indicates that it is possible to meet the quality requirements for conversion by delivering to the biorefinery a blend of pellets comprising 88.9% two-pass corn stover pellets, 7.7 % grass clipping pellets, and 3.3% mixed paper pellets (with a starch binder 2 wt%) at a delivered cost of $82.57/dry ton (2016$) for the blend including the binder. Moreover, it is also possible to deliver a pellet blend that exceeds the quality requirements by blending 86.7% two-pass corn stover pellets and 13.3% mixed paper pellets with a resulting carbohydrate content of 61% and an ash content same as the previous scenario at 4.93%. The blend, which excludes grass clippings, also results in a small cost saving as the per ton cost of the feedstock blend was $82.18/dry ton (2016$). Our analysis indicates that it is possible to use MSW to support future fuel production pathways, including the production of sustainable aviation fuels.