Novel seaweed-based bioplastic: A prospective Life Cycle Assessment

The PhD thesis focuses on assessing the environmental impacts of bioplastic production from brown seaweed within the context of the emerging field of Blue Bioeconomy as a consequence of an increasing interest in biomaterials. The research is conducted in parallel with the PlastiSea project, which aims to develop bioplastics using alginate extracted from brown seaweed. The main objective of the PhD is to evaluate the environmental consequences of producing bioplastics from brown seaweed through a consequential Life Cycle Assessment (LCA) perspective.The thesis is a compilation of scientific articles and the research is structured into four parts, each addressing a specific aspect of the study and corresponding to an article. The first part involves identifying marginal suppliers of brown seaweed, analysing the supply chain and determining key suppliers in the market. The second part focuses on evaluating the environmental impacts of the pilot-scale seaweed-based bioplastic production system and the potential of re-circulating seaweed co-products and different end-of-life pathways, while the third part examines the impacts of an industrial-scale system. The fourth part takes a broader perspective by considering seaweed-based bioplastic production from a supply chain standpoint.The thesis presents relevant results in different areas. In terms of marginal suppliers, China emerged as the primary supplier and is projected to maintain its significance. Additionally, suppliers from northern Europe and America are anticipated to witness a moderate increase in their market share, but in smaller proportions.The LCA at the pilot scale identifies the potential for recovering mannitol from seaweed, which could be utilized in the subsequent seaweed-based bioplastic production step. This approach exhibits a slight advantage compared to the base scenario; however, the observed difference is not deemed significant. The assessment of the end-of-life scenarios shows a significant advantage of composting end-of-life compared to incineration. Moreover, the prospective LCA, which involves upscaling the processes to larger scales, reveals a noteworthy trend of decreasing environmental impacts. As the processes increase in volume, the impacts associated with their operation lower, emphasizing the potential benefits of scaling up production in terms of reducing environmental burdens. The inclusion or exclusion of biogenic carbon shows a substantial impact on the results, showcasing the importance of accounting for this factor in the assessment. The disparities in the outcomes highlighted the significance of considering the biogenic carbon component in LCA analyses.The findings of the PhD reveal promising potential for brown seaweed-based bioplastics, particularly in terms of greenhouse gas emissions, which show lower impacts compared to conventional fossil-based plastics at larger scales. Moreover, seaweed-based bioplastic exhibits significant advantages in other impact categories, such as marine and freshwater eutrophication. The results collectively also provide valuable insights into the dynamics of marginal suppliers, the potential recovery of seaweed co-products and the assessment of different end-of-life pathways, the influence of biogenic carbon accounting, and the environmental implications of upscaling processes. However, some constraints need to be considered, including competition with other uses of the seaweed biomass and the specific properties and limited applications of the seaweed-based bioplastic, such as its high moisture absorption.In conclusion, the thesis highlights the challenges and opportunities associated with the production of bioplastics from brown seaweed. It emphasizes the need for further research to address the identified constraints and explore potential solutions. The discussion and conclusion provide a comprehensive overview of the research outcomes, implications, and future directions for the development and utilization of brown seaweed-based bioplastics from an environmental perspective.