<p>Biomass gasification is a promising route for renewable energy production and waste valorization; however, conventional biomass-to-biogas systems can suffer from low methane purity, limited carbon utilization, and integration challenges. Integrating carbon capture and utilization can improve product gas quality while reducing net CO₂ emissions through separation and downstream conversion. This study evaluates biomass-to-biogas systems by isolating the effect of downstream CO₂ management strategies on overall process performance. Three configurations were designed and compared under an identical gasification framework: (i) direct methanation, (ii) activated carbon adsorption followed by methanation, and (iii) amine absorption using methyldiethanolamine (MDEA) followed by methanation. The systems were modeled using Aspen Plus, Aspen Adsorption, and Aspen HYSYS, and a laboratory-scale fixed-bed adsorption unit using TiO₂-doped activated carbon was constructed to qualitatively assess CO₂ capture feasibility under controlled conditions. The results demonstrate trade-offs among capture effectiveness, methane yield, and system complexity across the three pathways. The objective of this work is to provide a consistent, downstream-focused comparison of CO₂ handling strategies in biomass-to-biogas systems and to support the adsorption-based pathway with experimental proof-of-concept evidence.</p>