Abstract
Poly(limonene carbonate) (PLC) has been highlighted as an attractive substitute to petroleum derived plastics, due to its utilisation of CO2 and bio‐based limonene as feedstocks, offering an effective carbon capture and utilisation pathway. Our study investigates the techno‐economic viability and environmental sustainability of a novel process to produce PLC from citrus waste derived limonene, coupled with an anaerobic digestion process to enable energy cogeneration and waste recovery maximisation. Computational process design was integrated with a life cycle assessment to identify the sustainability improvement opportunities. PLC production was found to be economically viable, assuming sufficient citrus waste is supplied to the process, and environmentally preferable to polystyrene (PS) in various impact categories including climate change. However, it exhibited greater environmental burdens than PS across other impact categories, although the environmental performance could be improved with a waste recovery system, at the cost of a process design shift towards energy generation. Finally, our study quantified the potential contribution of PLC to mitigating the escape of atmospheric CO2 concentration from the planetary boundary. We emphasise the importance of a holistic approach to process design and highlight the potential impacts of biopolymers, which is instrumental in solving environmental problems facing the plastic industry and building a sustainable circular economy.
Highlights
Global demand for plastic has increased considerably in the past decades, with the average annual increase in global plastic production reaching 10 %.[1]
This study focuses on a novel biopolymer production pathway, based on the copolymerisation of carbon dioxide (CO2) and limonene oxide sourced from citrus waste
Previous process designs had large environmental burdens due to the tert-butyl hydroperoxide (TBHP) synthesis route and the requirement for an additional solvent. This epoxidation reaction aims to reduce these effects by utilising H2O2 in the place of TBHP, and excess limonene in the place of an additional solvent, which simultaneously reduces the number of chemicals and reactions involved in the production of Poly(limonene carbonate) (PLC), with water being the only by-product
Summary
Global demand for plastic has increased considerably in the past decades, with the average annual increase in global plastic production reaching 10 % (from 1.5 million tonnes in 1950 to 335 million tonnes in 2016).[1]. The novel epoxidation process modelled in our study is a polytungstophosphate catalysed and solvent-free reaction, demonstrating 100 % selectivity and reduced reaction time of minutes.[10] Such an empirical advance offers a potential sustainable solution: first, it solves the problem with expensive process feedstocks highlighted in previous studies; second, it enables environmental impact reduction by no additional solvent input since excess limonene acts as a solvent, mitigating exothermicity and allowing for higher selectivity The former is due to the decreased overall flowrate, reducing heating duties in separation sequences and electricity use associated with pumping requirements. This environmental contribution is quantified based on our process design
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