Life cycle assessment of pilot and real scale photosynthetic biogas upgrading units

Abstract

In the present study, the sustainability of the simultaneously upgrading of biogas and high-value algal biomass production was evaluated in terms of energy consumption, CO2 emissions and environmental impacts. Two pilot-scale biogas upgrading units and a simulated real scale plant were considered. The study included the creation of an inventory of all sub-processes involved in the production of algal-biomass and biomethane. A comprehensive analysis using a life cycle methodology of the whole process was also conducted. The whole process was divided in three main sub-systems: the gas absorption unit (biogas upgrading), microalgae biomass production unit (HRAP, High Rate Algal Pond) and the biomass recovery unit (for its valorization). The analysis of environmental impacts was carried out for the real scale plant using the software SimaPro, considering the ReCiPe endpoint (H) and midpoint (H). For the two pilot-scale biogas upgrading, as expected, artificial illumination in the indoor HRAP was responsible for ≈ 90% of the total energy demand. For the simulated real-scale plant, the biomass recovery step (harvesting and drying processes) exhibited the highest environmental impacts, while the biogas upgrading unit showed high impacts on climate change and low impacts on fossil and water depletion.