Comparative life cycle assessment of astaxanthin production with Haematococcus pluvialis in different photobioreactor technologies

Haematococcus pluvialis is one of the most abundant sources of natural astaxanthin when compared with other microorganisms, and has attracted the interest of the market thanks to its health benefits. We investigated the environmental performance of the cultivation of H. pluvialis and the astaxanthin production processes through a comprehensive Life Cycle Analysis (LCA). This study compares the potential environmental impact of three photobioreactors (PBR) available on the market: the flat panel airlift, the green wall panel, and the unilayer horizontal tubular PBR. These systems have different technical settings: the flat panel airlift has a double-sided light emitting diode (LED) illumination system and is placed inside a building; the green wall panel is located outside and equipped with one-side LED lighting; the unilayer horizontal tubular is placed outside without any artificial lighting. Two different functional units were considered: one kg of H. pluvialis (80% dw) and 1 kg of astaxanthin. Where 1 kg of astaxanthin was selected as functional unit, as the content of astaxanthin in the biomass is low, the system expansion method was applied. The LCA results, based on original data from pilot-scale production, indicate that the system design, and the energy mix used have a significant environmental impact, due to differences in algae productivities and energy demand. For indoor systems, even with light-emitting diodes (LED), the energy demand for lighting is the main contributor to climate change. This contribution decreases significantly if the share of renewable energy increases. In the case of the green wall panel another main climate change contributor is the material used for the diode production, including tin and molybdenum. Although the astaxanthin yield is higher in the flat panel airlift and green wall panel, electricity production systems still constitute an environmental burden. For this reason, the system with the lowest environmental impact is the unilayer horizontal tubular, i.e. the photobioreactor where no artificial light is used.