The aim of the present work is to study the effect of different activation methods for the production of a biomass-based activated carbon on the CO ${}_2$ and CH ${}_4$ adsorption. The influence of the activation method on the adsorption uptake was studied using three activated carbons obtained by different activation methods (H ${}_3$ PO ${}_4$ chemical activation and H ${}_2$ O and CO ${}_2$ physical activation) of olive stones. Methane and carbon dioxide pure gas adsorption experiments were carried out at two working temperatures (303.15 and 323.15 K). The influence of the activation method on the adsorption uptake was studied in terms of both textural properties and surface chemistry. For the three adsorbents, the CO ${}_2$ adsorption was more important than that of CH ${}_4$ . The chemically-activated carbon presented a higher specific surface area and micropore volume, which led to a higher adsorption capacity of both CO ${}_2$ and CH ${}_4$ . For methane adsorption, the presence of mesopores facilitated the diffusion of the gas molecules into the micropores. In the case of carbon dioxide adsorption, the presence of more oxygen groups on the water vapor-activated carbon enhanced its adsorption capacity.

Global energy supply remains, to this day, mainly dominated by fossil fuels, aggravating climate change. To increase and diversify the share of renewable energy sources, there is an urgent need to expand the use of biofuels that could help in decarbonizing the energy mix. Biomethane, obtained by upgrading biogas, simultaneously allows the local production of clean energy, waste valorization, and greenhouse gas emissions mitigation. Among various upgrading technologies, the use of activated carbons in adsorption-based separation systems has attracted significant attention due to their versatility, cost-effectiveness, and sustainability potential. The present review offers a comprehensive analysis of the factors that influence the efficiency of activated carbons on carbon dioxide adsorption and separation for biogas upgrading. The influence of activation methods, activation conditions, and precursors on the biogas adsorption performance of activated carbons is revised. Additionally, the role of adsorbent textural and chemical properties on gas adsorption behavior is highlighted. By synthesizing current knowledge and perspectives, this work provides guidance for future research that could help in developing more efficient, cost-effective, and sustainable adsorbents for biogas upgrading.