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The aim of this study was to assess the social impacts of microalgae-based systems for wastewater treatment and bioproducts recovery by using the Social Life Cycle Assessment (S-LCA) tool. In particular, two systems were analysed: 1) a system treating urban wastewater, and 2) another system treating wastewater from the food industry. Moreover, these alternatives were compared to 3) a system for bioproducts production from microalgae grown in a standard growth medium. The recovered bioproducts in all the systems considered were: natural pigments, biogas and digestate, which can be reused as biofertilizer. Results showed that the scenario using standard growth medium was the one showing the best results in all impacts and stakeholder categories (up to 24-fold lower impacts depending on the impact category). This was mainly due to: i) the simplicity of the system, which consequently improves health and safety for workers; ii) the absence of contaminants which consequently improves health and safety, acceptability and olfactory impact for both consumers and the local community; iii) the presence of well-established legislation, regulatory frameworks, and full-scale deployment, which benefit value chain actors and society. Overall, this study also identified several social factors hindering a transition towards a circular bioeconomy in the microalgae-based systems for the wastewater treatment and resource recovery sector. [Display omitted] • Social Life Cycle Assessment of microalgae-based systems was carried out. • Microalgae-based systems recovered natural pigments, biofertilizer and biogas. • Microalgae-based systems using wastewater and standard growth medium were compared. • Scenario using standard growth medium showed up to 24-fold lower impact. • Bottlenecks for full-scale deployment of microalgae-based systems were identified. [ABSTRACT FROM AUTHOR]

Abstract: A life cycle assessment to evaluate the environmental impact of urban sewage sludge use as alternative fuel or raw material in clinker production was carried out. In order to quantify in detail the overall environmental impact of both scenarios, the sewage sludge treatment process and the transport to cement facilities for both alternatives were considered. The substitution ratio of fuel (petcoke) and raw material (limestone) was fixed between 5 and 15% according to the cement production plant limitations. Both scenarios show CO2 savings when compared to the clinker production without substitution. The mid-point and end-point analysis were favourable to the fuel substitution with savings ranging from 3 to 7% compared to the raw material substitution and also to base case without substitution. The influence of the amount of sewage sludge used for both scenarios indicates that fuel substitution reduced the CO2 emissions when the amount of substitution is increased, while other mid-point and end-point categories were proportionally favourable to the fuel substitution scenario. Additionally, the influence of the substituted material characteristics showed that low heating value (fuel substitution) and CaO addition in lime stabilized sludge (raw material substitution) are critical parameters in terms of environmental impact in clinker production. The fuel substitution represents a significant environmental improvement compared to the raw material substitution scenario and clinker production without substitution. [Copyright &y& Elsevier]