Exploring the future of photosynthetic biogas upgrading process

The increasing demand for biomethane in Europe requires the urgent development of sustainable and cost-effective technologies to meet the ambitious target of producing 35 bcm of biomethane by 2030. Biological technologies stand as a promising integrating platform to purify biogas and valorize biogenic CO 2 , while producing high-value chemicals. Photosynthetic biogas upgrading has demonstrated to be an attractive platform as microalgae can fix CO 2 while producing biomass that can be further valorized for biofuel, biofertilizer or biostimulant production. However, its high investment cost and the low microalgae biomass productivities have limited commercialization. Recently, the supplementation of nanoparticles obtained from olive-mill wastewater, has demonstrated to be a promising technique to improve biomass productivity, CO 2 removals, and the overall stability of the system. This review summarizes the current trends and future outlooks of this sustainable platform aiming at the development of novel integrated microalgae biorefineries devoted to biogas upgrading and high-value compounds production.