Mitigation of greenhouse gases (CO2) generated in the anaerobic digestion of physicochemical sludges using airlift photobioreactors operated with Chlorella spp.

The aim of this study was to evaluate the mitigation of greenhouse gasses generated in the anaerobic digestion process of physicochemical sludges by evaluating the effect of CO2 supply and light intensity requirements on the growth of microalga Chlorella spp. and measuring the consumption of CO2. The best conditions at a laboratory scale were performed in an airlift photobioreactor (PBR) at pilot-scale plant (26 L) during 60 days with a CO2 supply of 2% v v-1 from an electric generator coupled to an anaerobic digestion of physicochemical sludge process. The maximum %CO2 consumed was 91.92% which was reached in the seventh supply cycle and biomass production was 2.18 g L-1. The results obtained showed that airlift-type PBRs are a suitable complement for anaerobic digestion of physicochemical sludge technologies in order to reduce emissions of greenhouse gases produced during the combustion of biogas.