From Biogas to Biomethane: An In-Depth Review of Upgrading Technologies That Enhance Sustainability and Reduce Greenhouse Gas Emissions Ahinara Francisco López, Telma Lago Rodríguez, Shoeib Faraji Abdolmaleki, Marta Galera Martínez, and Pastora M. Bello Bugallo This review examines recent advancements in biogas upgrading technologies, focusing on physical, chemical, and biological methods to enhance sustainability and reduce greenhouse gas emissions. The technologies are classified based on separation methods, including phase addition, solid agents, phase creation, and biological processes. The review discusses the economic and environmental characteristics, process complexity, and future research prospects of these technologies. It highlights the potential of biogas upgrading in contributing to sustainable development, increasing energy security, and achieving greenhouse gas reduction goals aligned with EU targets. Biogas upgrading involves reducing or removing CO₂ from biogas to produce biomethane, which can serve as a renewable alternative to natural gas. The review covers various upgrading technologies, including absorption, adsorption, membrane separation, and cryogenic separation. These technologies are classified based on their separation methods and are analyzed for their efficiency, cost, and environmental impact. The review also discusses emerging technologies such as in situ methane enrichment, catalytic methanation, and biological technologies. These methods aim to improve the efficiency and sustainability of biogas upgrading. The review highlights the importance of biogas upgrading in reducing reliance on fossil fuels and promoting the use of renewable energy sources. The review emphasizes the need for further research and development in biogas upgrading technologies to enhance their efficiency, reduce costs, and minimize environmental impact. It also discusses the potential of biogas upgrading in contributing to the EU's energy security and climate goals. The review concludes that biogas upgrading technologies play a crucial role in the transition to a low-carbon economy and the sustainable use of renewable energy sources.From Biogas to Biomethane: An In-Depth Review of Upgrading Technologies That Enhance Sustainability and Reduce Greenhouse Gas Emissions Ahinara Francisco López, Telma Lago Rodríguez, Shoeib Faraji Abdolmaleki, Marta Galera Martínez, and Pastora M. Bello Bugallo This review examines recent advancements in biogas upgrading technologies, focusing on physical, chemical, and biological methods to enhance sustainability and reduce greenhouse gas emissions. The technologies are classified based on separation methods, including phase addition, solid agents, phase creation, and biological processes. The review discusses the economic and environmental characteristics, process complexity, and future research prospects of these technologies. It highlights the potential of biogas upgrading in contributing to sustainable development, increasing energy security, and achieving greenhouse gas reduction goals aligned with EU targets. Biogas upgrading involves reducing or removing CO₂ from biogas to produce biomethane, which can serve as a renewable alternative to natural gas. The review covers various upgrading technologies, including absorption, adsorption, membrane separation, and cryogenic separation. These technologies are classified based on their separation methods and are analyzed for their efficiency, cost, and environmental impact. The review also discusses emerging technologies such as in situ methane enrichment, catalytic methanation, and biological technologies. These methods aim to improve the efficiency and sustainability of biogas upgrading. The review highlights the importance of biogas upgrading in reducing reliance on fossil fuels and promoting the use of renewable energy sources. The review emphasizes the need for further research and development in biogas upgrading technologies to enhance their efficiency, reduce costs, and minimize environmental impact. It also discusses the potential of biogas upgrading in contributing to the EU's energy security and climate goals. The review concludes that biogas upgrading technologies play a crucial role in the transition to a low-carbon economy and the sustainable use of renewable energy sources.