Life cycle assessment and cost analysis of innovative agar extraction technologies from red seaweeds

Developing efficient and sustainable extraction technologies for valuable biocompounds from seaweed is crucial to overcome the limitations of conventional technologies. This study aims to compare three innovative technologies for agar extraction from two red seaweed species, G. sesquipedale and G. vermiculophylla: subcritical water extraction (performed at 125 °C, 2.5 atm, 1 min, and at 140 °C, 3.8 atm, 1 s), moderate electric fields (applied at 85 °C for 120 min and 95 °C for 180 min), and a combination of both methods. The comparison used life cycle assessment and life cycle costing methodologies, considering a gate-to-gate approach. The combined technology demonstrated the lowest energy consumption, with 67 MJ/kg_agar for G. vermiculophylla and 100 MJ/kg_agar for G. sesquipedale. A carbon footprint reduction of up to 94 % was obtained when compared to the control, with 15.9 kg_{CO2 eq.} /kg_agar for G. vermiculophylla and 20.4 kg_{CO2 eq.} /kg_agar for G. sesquipedale. Using photovoltaic panels as alternative energy further cut carbon emissions by 50 %. The cost analysis showed that the combined technology was the most cost-effective extraction method.