Comparative life cycle assessment (LCA) of Chlorella vulgaris bio-oil production: assessing the environmental performance of sulfated zirconia vs. zeolite Y catalysts

The environmental performance of bio-oil production from Chlorella vulgaris was comprehensively assessed using non-catalytic pyrolysis and catalytic cracking processes, employing sulfated zirconia and zeolite Y catalysts. Using a life cycle assessment (LCA) model, we examined the energy efficiency, elemental mass balance, and impacts across the entire biofuel production pathway, from the cultivation of microalgae to the product gate. The influence of the process parameters and catalyst selection on environmental outcomes was also explored with the aim of enhancing sustainable microalgal biofuel production and support policy development for emission reduction and industrial scaling. Our findings revealed significant variations in the environmental burden depending on the process route and operating temperature. Although sulfated zirconia demonstrates high catalytic efficiency, it is associated with substantial ecological costs. Zeolite Y offers a balanced approach, whereas non-catalytic routes minimize environmental impacts at the expense of reduced efficiency. Notably, the Global Warming Potential (GWP) varied considerably: non-catalytic pyrolysis yielded a GWP between 7.19 and 9.3 kg CO 2 /kg bio-oil. At the same time, catalytic cracking with sulfated zirconia achieved lower values ranging from 9.4 to 12.7 kg CO 2 /kg compared to 12.6 to 15.2 kg CO 2 /kg for zeolite Y. The environmental impact of the catalyst production primarily drove the higher GWP for the catalytic processes; however, among the catalytic options, the comparatively lower impact of sulfated zirconia makes it the preferred catalyst relative to zeolite Y.