Decarbonising biofuel pathways: A life cycle assessment of hybrid renewable energy integration in microalgae-based biodiesel production

This study investigates a decarbonising pathway to meet Australia's emission reduction target through the integration of a hybrid renewable energy system for microalgae-based biodiesel production. Carbon hot spots were quantified by integrating a hybrid renewable configuration combining photovoltaic panels, parabolic trough collectors, solar stills, and geothermal technologies to produce 1 MJ of biodiesel from microalgae. A cradle-to-gate life cycle assessment was conducted using the ALCAS Best Practice LCIA carbon neutral V2.05 and ReCiPe 2016 methods to compare the hybrid configuration with a conventional grid-powered system. The hybrid system, applied across all stages from cultivation to transesterification, achieved an 86.7 % reduction in carbon emissions, lowering from 0.6 to 0.08 kg CO 2 eq per MJ of biodiesel. Endpoint assessment revealed a 92.8 % decrease in ecosystem impacts, an 88.5 % reduction in human health damage, and a 14.3 % decline in resource depletion, including fossil and mineral resources. Uncertainty analysis confirmed consistent environmental advantages of the hybrid system across key impact categories. If implemented nationally, the proposed system could reduce annual emissions by 1.9 Mt CO 2 eq, contributing 4.2 % to Australia's 2030 reduction target and saving 47.5 Mt CO 2 eq cumulatively by 2050. These findings highlight the novel potential of hybrid renewable integration to accelerate decarbonised biodiesel production and strengthen Australia's long-term sustainability strategy, with the added advantage of enabling off-grid operation in remote regions. • An assessment of carbon hot spots in microalgae biodiesel production. • A novel mix of geothermal and solar energy was assessed along the production route. • Results indicate a potential 86.7 % reduction in carbon emissions. • Annual emissions of 1.9 Mt CO 2 eq could be reduced if findings are implemented.