<p>This study investigates the dynamic interactions between population, waste generation, and biogas demand in a circular economy, focusing on the Mikkeli region of Finland. This study fills a gap in the literature by examining the dynamic interactions between population behavior, waste generation, and biogas demand using an agent-based simulation model. Unlike previous studies, this research validates the simulation results using stakeholder data and an online biogas calculator, providing practical insights to enhance circularity in waste management and biogas production. The model aims to describe biogas production, provide insights into circularity, and identify potential solutions to improve it. Based on simulations, the biogas plant currently produces 488 tons of biomethane per year, which is enough to power all gas-powered passenger cars in the region, and this result was validated by stakeholder data and an online biogas calculator. The simulation shows that using wastewater sludge and municipal waste as feedstock can result in biomethane production ranging from 291 to 1504 tons annually, depending on the scenario. To increase production and circularity, waste management improvements and increased demand must be combined with biogas plant infrastructure upgrades. The simulation model is a valuable tool for estimating various scenarios and aiding decision-making in complex circular economy solutions. This study highlights biogas potential as a local energy source for transportation, as well as the importance of stakeholder participation in model development to address data and expertise challenges.</p>