Microalgae–Nanoparticle Systems as an Alternative for Biogas Upgrading: A Review

Anaerobic digestion is a well-established technology for the sustainable production of biogas. However, to be used as a substitute for natural gas or as vehicle fuel, it is necessary to remove carbon dioxide (CO2) and other contaminants from biogas that can compromise the useful life of combustion engines. Upgraded biogas is known as biomethane (>95% methane content). This work reviews the different technologies used for upgrading biogas, emphasizing microalgae–nanoparticle systems, representing a more sustainable and environmentally friendly system. Parameters affecting these systems performance are discussed, and the trends and areas of opportunity for subsequent work are evaluated through a bibliometric analysis.