Barcelona is advancing urban mobility sustainability by powering its public transport fleet with biomethane produced from wastewater. This initiative is part 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.
These technologies convert surplus renewable energy into hydrogen, which is then synthesized into biomethane. The process, developed at the Baix Llobregat Wastewater Treatment Plant managed by Aigües de Barcelona, now fuels the NIMBUS pilot bus operated by Transports Metropolitans de Barcelona (TMB). This bus travels over 14,000 kilometers annually, cutting an estimated 28 tons of CO2 emissions each year and reducing its carbon footprint by over 80%.
Alessandro Solimeno, the project coordinator and a researcher at Cetaqua–Water Technology Centre, highlighted the project's success in sustainably producing high-quality biomethane from digested sludge. This aligns with Spain's national Biogas Roadmap, approved in 2022, which aims to quadruple national biogas production by 2030. Spain's broader energy strategy also includes ambitious renewable energy targets, with a draft plan aiming for 20 TWh of biogas production by 2030.
The LIFE NIMBUS project, co-financed by the European LIFE program and coordinated by Cetaqua, involved key partners including Aigües de Barcelona, TMB, and the Autonomous University of Barcelona (UAB). This collaboration is a crucial starting point for exploring larger-scale biomethane production at wastewater treatment facilities. Joana Tobella, Director of Innovation at Aigües de Barcelona, emphasized the necessity of such innovation projects to build stakeholder confidence and garner support for widespread implementation.
Beyond Barcelona, other cities are also exploring biomethane for public transport. Bristol in the UK, for instance, operates biomethane-powered buses that achieve significant reductions in carbon and nitrogen oxide emissions. The initiative exemplifies the potential of the circular economy in transforming urban transport and sets a precedent for metropolitan decarbonization efforts, aligning with Spain's commitment to increasing the share of renewable fuels in transport to over 30% by 2030.