Abstract
The present study comparatively investigates the potential of waste plastic utilization as a feedstock for the production of liquid fuels to satisfy the rising liquid fuel demands of the transportation industry while simultaneously resolving the global plastic waste pollution challenge. For the first time, therefore, conceptual models simulating the production of transportation fuels of ethanol and gasoline from waste plastics via the technologies of thermo-syngas fermentation and hydrothermal liquefaction were assessed using classic technoeconomic assessment methods. The conceptual models were developed based on existing experimental data as obtained from the literature and simulated using ASPEN Plus as the preferred process simulation tool. This study demonstrated the technical viability of both conversion pathways with the hydrothermal liquefaction (HTL) of waste plastics for gasoline production shown to constitute a more economically preferable pathway. This was because the HTL of waste plastics presented a higher internal rate of return (IRR) value and a lower unit processing cost of 51.3% and USD 0.38 per kg compared to the thermo-syngas fermentation pathway that presented an IRR value and a unit processing cost value of 22.2% and USD 0.42 per kg, respectively. Payback periods of 5 years and 2 years were also determined as vital to recoup initial capital invested in the thermo-syngas fermentation project and the HTL project, respectively. Therefore, this study provides a basis for further work regarding waste plastic management strategies while offering a useful guide for policy makers in determining the most cost-effective way to utilize waste plastic and thus promote favorable environmental outcomes.
Highlights
It is well acknowledged that anthropogenic activities exacerbate global warming and climate change challenges while simultaneously depleting global fossil resources
This is because the transport sector is highly energy intensive and constitutes a corner stone of all sectors of the global economy, notably the agricultural sectors which is characterized by an overwhelming dependence on fossil fuels [1,2]
Plastic waste consists of an array of polymers which include polyethylene (PE), polypropylene (PP), polyethylene tetraphthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), and polycarbonate (PC) [8]
Summary
It is well acknowledged that anthropogenic activities exacerbate global warming and climate change challenges while simultaneously depleting global fossil resources. The low degradability of waste plastic often poses many challenges to its management; a robust management option must, include an opportunity for upcycling and energy recovery [12,13] It is, imperative to consider sustainable management options for these waste products into valuable resources such as alternative fuels, energy, and chemicals [14,15]. The commonly employed incineration approach leads to the emission of toxic substances into the environment resulting in environmental pollution from the release of poisonous gases such as dioxins, furans, and polychlorinated biphenyls [18,19], with thermochemical recycling usually preferred This is because thermochemical recycling of waste plastic is a sustainable option since the approach facilitates the depolymerization of the plastic polymers to produce high-value products and lower waste residue [17]. This, implies that the need for additional hydrogenation steps will be redundant [27]
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