Carbon footprint of microalgae production in photobioreactor

This work aims to evaluate the carbon footprint (CF) of microalgae production in a closed pilot-scale multi-tubular photobioreactor (PBR), on a gate-to-gate approach. Primary data from real production conditions complemented with data from the literature and life cycle inventory databases was used. The carbon embedded in the PBR’s construction materials and nutrients necessary for the microalgae growth were considered. A global CF of 68.34 kg CO2-eq/kg dry biomass was obtained. A CF of 1.72 kg CO2-eq/kg dry biomass was calculated for the PBR construction stage, contributing to 3 % of the overall value. For 74 kg of dry biomass/year produced with this PBR, the CF for this stage was 66.62 kg CO2-eq/kg dry biomass, corresponding to 97 % of the total global CF. In this study, electricity production for the reactor operation is the major contributor (79 %) to the overall CF, followed by the production of nutrients used to prepare the culture medium (21 %). CO2 fixation by microalgae reduces the global value by 3 %.