Prospective LCA of brown seaweed-based bioplastic: Upscaling from pilot to industrial scale

Seaweed-based bioplastics are considered a possible alternative to conventional fossil-based plastics due to their potential environmental advantages. The cultivation of seaweed is a fast-growing practice that requires no arable land, freshwater, or fertilizers, perceiving it as an advantageous option for bioresource production. However, research on the environmental impacts of seaweed-based bioplastics is still limited, highlighting the need for a life cycle assessment (LCA) to evaluate their potential. In this article, a prospective LCA is conducted to assess the environmental impacts of brown seaweed-based bioplastic production, from pilot to industrial scale. Upscaling techniques are combined for each life-cycle stage, using interviews to upscale seaweed production and process simulation for the biorefinery and film fabrication steps, and the end-of-life scenario is modelled as composting. All the processes were upscaled to 4000 tonnes (t) per year in 2030 and 2 million tonnes (Mt) per year in 2035, including marginal suppliers of brown seaweed. The results show that the production of 1 kg of brown seaweed-based bioplastic resulted in approximately 1.37 kg CO₂-eq. in the best-performing scenario, producing 2 Mt per year in 2035 accounting for the carbon uptake, which is lower than low-density polyethylene (LDPE) with an impact of 3.6 kg CO₂-eq. The impact in marine eutrophication in the 2 Mt scenario is −0.009 kg N-eq., and −0.002 kg P-eq. in freshwater eutrophication. This study provides for the first time estimates of prospective industrial-scale impacts of the emerging seaweed-based bioplastic and shows how different upscaling techniques can be successfully combined, i.e., interviews and process simulation, to conduct a prospective LCA of seaweed-based bioplastics. The results demonstrate the potential of seaweed-based bioplastics as a sustainable alternative to conventional plastics.