Life cycle assessment and techno-economic analysis of a macroalgal-derived biopolymer film coupled with carbon capture

Abstract

In this study, an attributional life cycle assessment (LCA) and techno-economic analysis (TEA) were used to determine the performance of a seaweed biorefinery producing a biopolymer film integrated with biochar carbon capture and storage. In the LCA, a total of 72 scenarios were modelled, investigating the system’s sensitivity to various plant production scales, energy mixes, product uses, and end-of-life pathways. The system was not particularly sensitive to plant production scale, though the application of a green energy mix afforded a ∼ 40% reduction in overall greenhouse gas emissions. Cradle-to-gate impacts ranged from −3.71 to −2.17 kg CO2 eq kg−1 when the biochar route was included, as opposed to −1.30 to −2.43 kg CO2 eq kg−1 without. When also accounting for the end-of-life disposal of the polymer, cradle-to-grave impacts remained extremely low, ranging from −3.64 to −1.24 kg CO2 eq kg−1 (anaerobic digestion), −2.27–0.14 kg CO2 eq kg−1 (incineration), and −1.82–0.59 kg CO2 eq kg−1 (composting). However, if the polymer was disposed of in landfill, this increased to between 2.99 and 5.40 kg CO2 eq kg−1. The results from TEA showed that at an operational scale of 10 000 t yr−1, the optimal biopolymer selling price was $9.36/kg (USD) for a seaweed price of $2000/t, although this was reduced to $4.09/kg (USD) if the seaweed price was reduced to $500/t. Interestingly, including the cost of biochar production only increased the price of the biopolymer by between 1% and 4% at this scale. Therefore, producing biopolymers from seaweed is not only economically comparable to alternative biopolymer production methods, but when combined with a biochar carbon capture process, it becomes a highly cost-effective way to reduce the environmental impact of biopolymer manufacturing.