Comparative analysis of two biorefineries for high-purity phycocyanin, biocrude and biogas production from Arthrospira platensis: a life cycle assessment and simulation approach

Abstract

This study evaluates the environmental performance of a cyanobacterial biorefinery for producing high-purity phycocyanin (PC) coupled with the valorisation of waste biomass (WB) via either hydrothermal liquefaction (HTL, scenario 1 A) or anaerobic digestion (AD, scenario 1B). Both pathways are compatible with cyanobacterial WB but differ in energy demand, chemical requirements, and downstream processing. Life Cycle Assessment (LCA) was conducted using inventory data from process simulation and experimental extraction data. LCA results showed that PC extraction and purification were the most important contributors across all impact categories due to the large consumption of salts and ionic liquid (IL), respectively. Regarding biomass valorisation, AD presented advantages over HTL due to lower chemical and energy requirements. Based on these results, the influence of IL recovery was studied, and scenario 2 (IL recovery 90% + AD) was constructed and analysed from an LCA perspective. The comparison of LCA results for the analysed scenarios showed that increasing IL recovery by 15% (scenario 2) led to impact reductions up to 46% in the extraction step, achieving reductions up to 37% and 12% in the overall process compared to scenarios 1 A and 1B, respectively. Furthermore, scenario 2 yielded a carbon footprint value of 52.07 kg CO eq./kg of dried biomass, within the range reported in the literature for other PC production biorefineries. These results demonstrate the environmental feasibility of integrating highpurity PC production within a cyanobacterial framework, identify AD as the more environmentally favourable residue valorisation pathway and highlight the importance of solvent recovery efficiency.