Recent advances on photosynthetic biogas upgrading to biomethane

Biogas upgrading using algal-bacterial processes has emerged as a cost-effective and environmentally friendly platform capable of supporting the integral removal of the main pollutants from biogas. These systems are based on CO2 fixation by microalgae using solar energy and the concomitant oxidation of H2S, ammonia, and volatile organic compounds promoted by the oxygen photosynthetically produced. In this biotechnology, residual nutrients from wastewaters can be used to support algal-bacterial growth. In addition, the valorization of microalgal biomass through the production of high-added value commodities fosters its economic sustainability. This chapter aims at providing an overarching overview of the fundamentals and latest advances made in the field of photosynthetic biogas upgrading. Particular attention is devoted to summarizing the key operational and environmental parameters impacting microalgae-based biogas upgrading. Innovative designs, operational strategies, and the latest research results on integrated wastewater treatment technologies driven by photosynthetic biogas upgrading are also presented and discussed in detail. The chapter also focuses on current trends on the latent production of high-added value commodities obtained from biomethane and algal biomass and discusses the economic feasibility of photosynthetic biogas upgrading. Finally, concluding remarks and future outlook in developing photosynthetic-based technologies for the production of biomethane and other marketable products are given.