Municipal biowaste management is at the core of the transition towards a circular bioeconomy in the EU. However, most urban systems are still far from being aligned with these principles. This paper addresses the case of the Metropolitan Area of Barcelona. The current system of biowaste management is compared with a more sustainable alternative scenario. Regulatory and non-regulatory drivers and barriers for the transition from the current state to the alternative scenario are identified and later transformed into policy recommendations using a multi-stakeholder approach. This paper focuses on the separate collection of biowaste and the production of biomethane. Increasing the quantity and quality of separate biowaste collection is a prerequisite for the market-relevant production of biogas from anaerobic digestion that can be converted into biomethane. The results show that more efficient collection systems such as door-to-door or smart bins together with tax incentives such as the pay-as-you-throw principle are key to increasing the amount of collected biowaste, while targeted communication combined with controls and penalties are key to minimizing impurities. In addition to financial incentives for the construction of new anaerobic digestion plants, financial incentive systems are also required for the biomethane sector to ensure competitiveness with fossil fuels.