ABSTRACT An analytical plant design model was developed to describe the quasi‐stationary state of vacuum pressure swing adsorption (VPSA) process for upgrading biogas (CO 2 and CH 4 ) to biomethane (CH 4 ). A reduced VPSA cycle comprising the steps adsorption, depressurization, and evacuation was considered, using a model biogas with 50% CO 2 in 50% CH 4 . The mass balance for the gas phase was formulated using a simplified advection‐reaction approach and for the solid phase using the Linear Driving Force (LDF) model. The steady‐state model serves as a basis for process design and optimization, allowing the determination of the required bed height as a function of the target product purity.