Biogas upgrading using algal-bacterial processes

Photosynthetic biogas upgrading constitutes, to the best of our knowledge, the only biotechnology capable of simultaneously removing CO2 and H2S from raw biogas. Recent studies at the pilot scale confirmed the potential of algal-bacterial processes to obtain a biomethane with sufficient quality to be injected into natural gas networks. The main limitation identified in this novel biotechnology is the large land requirement for microalgae to fix all CO2 removed from biogas, which would eventually limit its applicability to biogas design flow rates < 500 Nm³ h− 1. Algal-bacterial photobioreactors also exhibit a high-water footprint, which can compromise the environmental sustainability of the process. The latter limitation can be overcome by coupling biogas upgrading to wastewater/digestate treatment, which would allow reducing the eutrophication impact of these wastewaters while producing a valuable algal biomass. The valorization of the algal biomass using a biorefinery approach would also contribute to the sustainability and economic viability of this technology.