Review of the Utilisation of Microalgae for Bioenergy and Food in a Circular Economy

Abstract

Spirulina (Arthrospira platensis) is increasingly positioned as a dual-purpose biomass platform that can support both sustainable food  production and renewable energy generation. This review evaluates Spirulina within a circular economy framework by linking cultivation  conditions, product valorisation, and downstream conversion routes. The food pathway is motivated by Spirulina’s high protein density  and micronutrient content, alongside its potential for low land use and net carbon uptake during growth. The biofuel pathway is assessed  through cultivation strategies that modify biomass composition and improve conversion performance, including staged operation, carbon  delivery control, nutrient management, and monitoring approaches that stabilise feedstock quality. An integrated facility concept is then  discussed using the selected block flow diagram, which couples CO2 utilisation, reverse osmosis water recovery, biomass separation, food  processing, and bioenergy conversion. In this configuration, algae-based food processing waste is treated as a process intermediate for  energy recovery, while by-products are routed to external value chains to improve overall resource efficiency. The analysis indicates that  commercial feasibility depends on co-product revenue, low-carbon utilities, and tight quality assurance boundaries that protect food grade streams while enabling robust conversion of residual biomass to energy.