Landfill gas is a source of CH₄ emission, also rich in CO₂ (up to 50 vol%). It can be upgraded to renewable natural gas (RNG) by separating CO₂ and impurities. Alternatively, the CO₂ contained in biogas can be converted into CH₄ via the Sabatier reaction, using H₂ generated by water electrolysis. For industrial applications, it is beneficial to eliminate the energy intensive CO₂ separation step, converting biogas to RNG directly. In this work, a series of 0.02-1 wt% Ru/γ-Al₂O₃ catalysts were prepared by wet impregnation and evaluated for a single-pass conversion of CO₂-CH₄ mixtures. Through the catalytic performance evaluation and characterization studies, the optimal Ru loading was identified as 0.1-0.5 wt%. For these catalysts, CO2 conversion of 80-87% was achieved at 450 °C and 90,000 mL/(g h), maintaining 95-99% selectivity to CH₄ production. These catalysts also showed excellent stability over 100 h on stream, while maintaining 99-100% CH₄ selectivity.