Advanced Strategies for Upgrading Raw Biogas into High-Quality Biomethane for Domestic Applications.

Biogas produced from the anaerobic digestion of organic matter holds much promise as a renewable energy source for decentralized systems. However, raw biogas contains substantial volumes of carbon dioxide, hydrogen sulfide, water vapor, and other trace impurities. These impurities can reduce the calorific value of biogas and limit its direct use for household energy needs. Purifying biogas to high-grade biomethane (≥95%) is therefore important to improve methane (CH4) content and combustion characteristics. This is a guarantee of its safe utilization in domestic appliances, including cooking, heating, lighting, and electricity generation. This article reviews and evaluates novel approaches for upgrading raw biogas into high-purity biomethane that can offset natural gas in domestic applications. It further examines recent developments in conventional and innovative upgrading technologies such as water scrubbing, chemical scrubbing, pressure swing adsorption, membrane separation, cryogenic separation, and biological upgrading. Particular emphasis is placed on low-cost and small-scale solutions suitable for off-grid or mini-grid rural energy systems. Moreover, the role of process optimization, intelligent monitoring, and data-driven control methods in increasing CH4 recovery and process efficiency is discussed. Despite their relatively high capital costs and energy needs, conventional technologies such as water scrubbing, pressure swing adsorption, and membrane technology continue to dominate biogas purification systems. The findings show that coupling advanced separation technologies, including cryogenic separation, biological upgrading, and hybrid technologies, with optimized process control can significantly improve CH4 purity, save energy use, and enhance the overall consistency of biogas purification systems. These innovative strategies have strong potential to promote the full-scale adoption of biomethane as a clean, sustainable, and affordable energy source for decentralized applications, particularly in the developing world.