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 const tute 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.

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Renewable energy powered membrane systems operate with fluctuating energy. Such fluctuations affect pressure and feed flow and as such the hydrodynamic conditions in a membrane system. Hydrodynamic variations alter the membrane surface concentration and boundary layer thickness which in turn determines permeate water quality. In this work this is calculated using computational fluid dynamics (CFD) for the three most predominant energy levels obtained during such fluctuations and compared with experimental data. A 2D-CFD simulation was performed using OpenFOAM to calculate the wall concentration and boundary layer thickness over the length of a module. The influence of module type was investigated using two system configurations, namely three 2.5″ modules in series (BW30-2540 or NF270-2540) and one 4″ module (BW30-4040 and NF270-4040) with similar total membrane areas. Energy levels were extracted from experimental data at three solar irradiance, maximum intensity (1 kW/m 2), light cloud (360 W/m 2) and heavy cloud periods (190 W/m 2). At the highest energy level, in the system with three 2.5″ modules the wall concentration was closer to the bulk concentration due to the higher flow velocity in a smaller channel. The resulting boundary layer thickness for BW30 was constant and almost zero. At the medium energy level, the simulation results show that the permeate flux decreased significantly due to the lower pressure and for the BW30 it was almost zero due to the low pressure. At the lowest energy level, the feed pressure was well below the osmotic pressure and no permeation was possible. Results from this study show that the model is able to describe the filtration process in spiral wound membrane modules under fluctuating energy conditions. Further investigations on the possibility to improve the boundary conditions of the model are required.