Barcelona's public transport system is advancing its sustainability goals by incorporating biomethane, produced from wastewater, as a fuel for its buses. This initiative is a key outcome of the European LIFE NIMBUS project, a five-year endeavor that has successfully demonstrated the production of biomethane from wastewater treatment plant sludge and advanced power-to-gas technologies.
The innovative process, developed at the Baix Llobregat Wastewater Treatment Plant managed by Aigües de Barcelona, has enabled the supply of biomethane for a pilot bus operated by Transports Metropolitans de Barcelona (TMB). This specific bus covers over 14,000 kilometers annually using biomethane, resulting in an annual reduction of 28 tons of CO2 emissions and an over 80% decrease in its carbon footprint.
The LIFE NIMBUS project, co-financed by the European LIFE program and coordinated by Cetaqua–Water Technology Centre, involved significant collaboration with partners including Aigües de Barcelona, TMB, and the Autonomous University of Barcelona (UAB). The project's conclusion was marked by a final event in Barcelona, highlighting its role as an effective circular solution for decarbonizing urban fleets.
Alessandro Solimeno, the project coordinator and a researcher at Cetaqua, emphasized the project's success in sustainably producing high-quality biomethane from digested sludge, presenting a viable circular economy model for urban transport. This initiative aligns with Spain's broader energy strategy, particularly its Biogas Roadmap approved in 2022, which aims to quadruple national biogas production by 2030.
Joana Tobella, Director of Innovation at Aigües de Barcelona, underscored the importance of such innovation projects in building stakeholder confidence and securing support for larger-scale implementations. Spain's Biogas Roadmap prioritizes waste, including sewage sludge, as key feedstocks, aiming to multiply national production by 3.8 by 2030. The LIFE NIMBUS project serves as a crucial precedent, demonstrating the potential of the circular economy to contribute to metropolitan decarbonization efforts, with potential applications extending to freight transport.