In this study we compare techno-economics and life cycle assessment of thermochemical depolymerization technologies, including pyrolysis, gasification, hydrocracking, hydrothermal liquefaction, and hydrogenolysis, to generate various products from low-density polyethylene (LDPE) waste. We elucidate the effects of production scale, collection cost, and concentration of LDPE in plastic waste. Pyrolysis of LDPE to olefins followed by their conversion to lubricant oils is the most profitable technology. Hydrogenolysis, producing a small fraction of lubricant oils, becomes profitable at plant sizes above 25 kt/y and produces the lowest CO 2 emissions. Hydrocracking is the second most environmentally friendly technology but becomes economically competitive at sufficiently large scales, and the supply chain for collecting plastics is optimized. Gasification of LDPE to H 2 produces high emissions, and the price of H 2 of ∼3 $/kg is higher than current markets and recently announced goals. Similarly, hydrothermal liquefaction also gives high emissions, making carbon capture systems imperative for both technologies. Our results demonstrate that lowering the cost of sorting LDPE from plastic waste, collecting waste near big cities, building sufficiently large plants, and achieving high selectivity to value-added products are critical to successful plastic waste management.
The growing amount of plastic waste endangers the environment. Polyethylene terephthalate (PET) is among the most widespread plastics due to its extensive use in fibers and packaging. Recently, chemical recycling and upcycling approaches have been proposed to produce valuable products from bale PET feedstocks. This work performs techno-economic analysis and life cycle assessment to evaluate the environmental and economic performances of various technologies, including electrification via microwaves over a heterogeneous catalyst. We demonstrate that using a microwave-assisted heterogeneous glycolysis process to produce bis(2-hydroxyethyl) terephthalate (BHET) could have lower production costs and emissions than the traditional dimethyl terephthalate (DMT) route due to the high reactivity and excellent reusability of the catalyst. The fast reaction rate and high selectivity render this process ideal for handling spatially distributed PET waste effectively.
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