(395b) Co-Hydrothermal Carbonization (Co-HTC) of Biomass-Plastic Blend: Enhancement of Fuel Quality

Disposal of waste plastics and biomass have been alarming issues for the U.S. over the past few years. A sustainable circular bio-economy has been a prime need to shift towards alternative fuels from traditional fossil fuels. Unfortunately, waste biomass contains high inorganics and low carbon content that makes biomass unfavorable for co-firing. On the other hand, waste plastics e.g., discarded mattress has low bulk density and contains high nitrogen content. Both feedstocks need preprocessing prior to use as fuel. This study focused on converting waste corn-stover into carbon-rich value-added biofuel through blending with waste polyurethane. The biomass-plastic blend was mixed at 95%:5%, 90%:10%, and 85%:15% (w/w dry basis) ratios, and co-hydrothermally carbonized (co-HTC) at 200, 230, and 260 °C. The ultimate analysis was done to determine the elemental composition in the resulting hydrochars and compared with the control runs (HTC of biomass and plastics at the corresponding temperatures). The thermogravimetric analysis was performed both in nitrogen and oxygen environments to observe the thermograms and combustion properties of the hydrochars. The higher heating value was obtained to observe the upgrade in the fuel value via Co-HTC. It is found that the total elemental carbon content of co-HTC hydrochars are higher than the HTC of biomass-only. On the contrary, the total elemental oxygen and nitrogen content also drop in polyurethane which augment the overall fuel value of the blended-biomass. Additionally, the ash content significantly decreases in both biomass and polyurethane. It was found that the fuel value of co-HTC hydrochar increases up to 26 MJ/kg, which is like lignite coal. Low sulfur, nitrogen, and oxygen content of the co-HTC hydrochar along with high energy content make co-HTC hydrochar a viable fuel. This study shows a sustainable route to produce blended biomass-plastic hydrochars with enriched fuel value from waste agricultural residue and plastics.