Evaluation of PHA as a replacement for fossil plastics in hemp-based panel composites for vehicle interiors

The climate impact and recycling difficulties associated with fossil-based plastics motivateresearch into bio-based alternatives. Due to the unique properties of plastic, it is irreplaceable in certain applications, which means that the only alternative is bio-based plastic. The study investigates the possibility of improving the recyclability of Polestar's panel concept which is based on polypropylene mixed with hemp fibers and aims to make the panel completely biobased. This would be possible by replacing polypropylene with the biobased and biodegradable alternative, polyhydroxyalkanoate (PHA). PHA can be based on biological waste products, which allows plastic production to become part of an industrial symbiosis where industrial waste streams are used. The report reviews all steps in the production of PHA on a lab scale, from sludge selection to PHA extraction, and the fusion of PHA and hemp fibers into a composite panel. An environmental analysis is also carried out to investigate environmental impact difference between the polypropylene and PHA lifecycle. The environmental analysis also examines whether PHA can be produced without the use of chemicals or substances of fossil origin. Emissions of carbon dioxide equivalent from producing the amount of plastic contained in one ton of panel, which is equivalent with 300 kg of plastic. The study shows that PHA production is theoretically possible without direct fossil emissions. The environmental analysis also shows that the total emissions, which also include electricity and heating-related emissions, from PHA production are 94% lower than the total emissions associated with polypropylene during its life cycle according to this study. In panels produced with 70% hemp fibres and 30% PHA, it was found that PHA acts as a binder for the fibres, but further studies comparing the performance during standardized car interior tests are required to measure whether PHA meets all the requirements set by the automotive industry. Initially, the possibility of using the sludge in the Borgstena textile factory as a substrate for PHA production was investigated, but it turned out to be unsuitable. Therefore, the study also focuses on identifying suitable industrial waste streams so that PHA can be produced as part of an industrial symbiosis. Polestar was also interested in anaerobic PHA production, but such a process was not possible.