## 3 Results and Discussion
### Demonstration-Scale (140 L)
Furthermore, the environmental profiles of each subsystem appeared again as a considerable hotspot for the energy consumption for the drying processes (freeze-drying in dewatering and extraction II and rotavapor in extraction I). In contrast to the laboratory scale environmental results, the total batch impact (Table 5) showed a reduction in 9 of the 11 impact categories assessed, a result even more pronounced for the impact of 1 litre of culture broth, where the demonstration scale showed a drastic reduction in impact. The reason for this is mainly due to the change in the photobioreactor. A growth chamber with artificial lighting, ideal for optimisation processes, consumes a large amount of energy; in contrast, an open-air system consumes less than half of the energy, even though it is heated all day and illuminated during the night. On the other hand, scale-up processes can generally lead to losses in biomass productivity [49]; here, one of the main assumptions was that productivity would be the same, as the reactor showed similar volumetric productivity in the experimental study with _Arthrospira platensis_[35]. However, it is important to note that the use of different species can have a large impact on the efficiency of the system: approximately 20% for a demonstration scale and up to 50% for a large production scale [49]. Regarding sterilisation procedures, identified as an expressive hotspot for the demonstration scale, ozone sterilisation has been proposed as a viable alternative to heat sterilisation in large-scale microalgae production [8], which could reduce the high impact caused by this step. Furthermore, [PERSON] et al. [43] proposed the same ozone sterilisation for the reactor cleaning stage, although no differences were found in the environmental profile, when compared to the reverse osmosis and UV filtration for the sterilisation of the culture medium. Figure 4: Relative contribution (in %) per subsystem of the demonstration-scale process (140 L) to each impact category: global warming (GW), stratospheric ozone depletion (SOD), terrestrial acidification (TA), freshwater eutrophication (FE), marine eutrophication (ME), terrestrial ecotoxicity (TET), freshwater ecotoxicity (FET), marine ecotoxicity (MET), human carcinogenic toxicity (HCT), human non-carcinogenic toxicity (HNCT), fossil resource scarcity (FRS). For a better interpretation and proposal of a more efficient process, a sensitivity analysis was performed based on four different scenarios for the demonstration scale process, taking into account the identified critical points of the life cycle of the process: (D1) the use of ozone sterilisation for cleaning (0.12 kWh m\({}^{-3}\) + 10 g m\({}^{-3}\); [PERSON] et al. [43]); (D2) the use of ozone sterilisation of the culture medium (0.27 kWh m\({}^{-3}\) + 10 g m\({}^{-3}\) ozone; [PERSON] et al. [8]); (D3) the use of reverse osmosis (7.71 kWh m\({}^{-3}\)) and UV sterilisation (0.35 kWh m\({}^{-3}\)) of the culture medium ([PERSON] et al. [43]); (D4) reducing the biomass productivity by 20 %. The results of the sensitivity analysis are shown in Figure 5.  
The use of ozone sterilisation for reactor cleaning (Scenario D1) reduces environmental loads by approximately 10% of all impact categories assessed, except for SOD, where the reduction was 20%. This scenario was proposed by [PERSON] et al. [43], although the authors did not observe significant differences between ozone sterilisation and chemical sterilisation, contrary to the _Cyanobium_ bioprocess. Moreover, the authors proposed the use of ozone sterilisation for large-scale production due to the higher feasibility of this method compared to chemical sterilisation. The use of ozone (Scenario D2) or reverse osmosis and UV filtration (Scenario 3) for medium sterilisation showed a similar impact between the two, and large impact reductions compared to the baseline scenario (heat sterilisation), mainly in GW (20%), TET (30%) and FRS (25%).