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With the implementation of China’s Green Fence Policy and the following National Sword Policy, there is a need to divert previously accepted waste materials away from the landfill. Mixed plastic and paper wastes that are too contaminated to be economically recycled can be used for conversion into fuels and products. The effect of common contaminants present in waste streams must be determined to make municipal solid waste (MSW) a viable alternative to agricultural feedstocks for conversion. In this study, MSW was sourced from a dual stream materials recovery facility (MRF) in Emmet County, Michigan and characterized via mass balance. The most common contaminants in mixed paper and plastic were quantified and targeted for decontamination when mixed paper was explored for low temperature conversion pathways and plastics for high temperature conversion pathways. Ink, stickies, and plastic contamination were sorted out of the mixed paper stream and did not have an impact on sugar yields during enzymatic hydrolysis (EH). Although no improvement in yield was found, it was noted that copy paper within the mixed paper stream had an elevated pH and higher concentration of fermentation inhibitors, suggesting that intrinsic properties of some paper types may not be ideal for EH and fermentation conversion. Dilute alkaline pretreatment and mechanical refining of mixed paper increased the EH yield of mixed paper, suggesting this previously established process could be used as a decontamination method. “Dirt” and particulates were washed from mixed plastic using either an aqueous detergent or a non-aqueous chemical washing method. Liquid oil yields were increased during microwave assisted fast pyrolysis. All decontamination techniques met the cost target of less than $30/dry ton with plastic decontamination ranging from $18.16 to $24.81/dry ton. Because dilute alkaline pre-treatment and mechanical refining is considered part of the conversion process, the decontamination cost during feedstock preprocessing was considered $0/dry ton.

Ash in biomass is believed to damage biorefinery equipment due to its abrasive properties. All biomass contains at least some ash, or inorganic content, as a result of normal physiological processes. The concentration of biogenic ash in biomass is largely species dependent; however it can also be affected by weather patterns, irrigation, soil type, and fertilizer applications. Ash concentrations in harvested biomass can also be elevated due to the incorporation of soil and dust during the harvest and collection processes. While ash concentration in biomass is important, so also is the mineral form of the ash. Certain mineral forms of ash can be much harder than the steels used to construct biorefinery equipment and cause excessive wear. In this perspective, the relative concentrations of ash elements, mineral forms of ash, and the hardness of these minerals are considered to identify ash components of concern to biorefinery operators. Strategies are suggested to remove ash from harvested biomass to reduce the risk of excessive wear on biomass processing equipment.