The LIFE NIMBUS project opens a biomethane production plant using waste sludge

Investigadors del projecte NimBus davant de l'autobús

The initiative, led by the Cetaqua Water Technology Centre, aims to foster a circular economy and represent a green energy and transport model for the metropolitan area of Barcelona by powering buses with biomethane obtained from sewage sludge. The GENOCOV research group at the UAB has worked together on this project with Aigües de Barcelona (Agbar) and Transports Metropolitans de Barcelona (TMB).


The consortium of the European LIFE NIMBUS project recently celebrated the start-up of the biomethane production plant from sewage sludge, which will power a public bus in the metropolitan area of Barcelona. This bus, part of the Transports Metropolitans de Barcelona (TMB) fleet, will be the first to run on biomethane obtained from sewage sludge and will reduce its carbon footprint by more than 85% thanks to the use of a high quality fuel of renewable origin, neutral in emissions.

In Europe, the transport sector consumes around 30% of total energy. However, only less than 10% of the fuels used for transport are renewable. In view of this situation, the European Union aims to raise this figure to over 30% by 2030. LIFE NIMBUS, a research project co-funded by the European Commission under the LIFE Programme, aims to promote more sustainable transport through a circular economy. This initiative is aligned with the Biogas Roadmap, approved in Spain in 2022, which identifies the challenges and opportunities for the development of this gas of renewable origin and plans to quadruple its national production by 2030.

During the opening ceremony, the importance of research and collaboration between the public and private sectors to provide solutions to decarbonise transport was highlighted. In this sense, the general manager of Aigües de Barcelona, Rubén Ruiz, insisted on the "need to promote innovation through alliances and public-private collaborations in order to respond to the main challenges arising from the climate emergency". "Waste recovery projects to promote sustainable mobility in cities are necessary to achieve an ecological transformation of our environment and are a clear example of our commitment to a model that respects the environment, based on the circular economy and sustainable development," he added.

General manager of Cetaqua, Carlos Montero, insisted on the "importance of involving the end user in the project starting in the ideation phase and ensuring their monitoring and involvement in its development". Thanks to this, Carlos Montero pointed out that "we are able to make the transfer of results more agile".

The rector of the Universitat Autònoma de Barcelona, Javier Lafuente, stressed that the start-up of the plant is a "good example of transferring the knowledge generated in the laboratories for the improvement of society, one of the missions of the University. The UAB is involved in the production of biomethane from hydrogen using biological systems, which are much more sustainable than conventional ones. In addition, the project demonstrates for the first time the bioelectrochemical production of hydrogen on a pilot scale from wastewater, with very encouraging laboratory results. This technology fits perfectly into the current paradigm shift in which water treatment must become an opportunity to recover resources, both material and energy-wise".

The CEO of TMB, Gerardo Lertxundi, thanked the entire TMB team that has made this project a reality and stressed that "it is a sustainable circular economy project to which TMB is fully committed" and pointed out that "it is a strategic project for TMB and we hope it will be continued in order to be able to use biomethane on a massive scale".

A boost to ecofactories to promote a circular economy

LIFE NIMBUS has enabled the design and construction of a biological methanation demonstration plant at the Baix Llobregat ecofactory, managed by Aigües de Barcelona (Agbar). This initiative is another example of Agbar's commitment to innovation and sustainability, which promotes the ecofactory concept as a solution to promote a circular economy and reduce environmental impact.

The ecofactory converts the traditional wastewater treatment plant into a facility that generates valuable resources. In this case, sludge from the wastewater treatment plant will be used as fuel to drive green transport in the Barcelona metropolitan area, thereby encouraging the city to move closer to the proposed climate neutrality by 2050.

"This initiative tests various technologies, focusing on the production of biomethane, a high-quality, renewable fuel. In addition, LIFE NIMBUS promotes electricity-to-gas technology for storing surplus renewables. The project has only envisaged the operation of a biomethane-fueled bus, but, depending on the results obtained, the operations can be scaled up to a larger volume," says Oriol Casal, LIFE NIMBUS project manager at Cetaqua.

Public-private collaboration for more sustainable urban transport

This project, whose acronym stands for Non-IMpact BUS and which proposes a green energy and transport model in Barcelona, is led by Cetaqua Water Technology Centre, with the participation of Aigües de Barcelona, manager of the Baix Llobregat WWTP; Transports Metropolitans de Barcelona (TMB), which has provided a bus from its fleet with a daily route of 100 km, and the GENOCOV research group of the Universitat Autònoma de Barcelona (UAB), responsible for the design, construction and development of the bioelectrochemical technology (BES), which allows an more efficient production of hydrogen by using less electricity. The project is also supported by the Metropolitan Area of Barcelona.

More information:

This information is related to the following SDG

  • Industry, innovation and infrastructure
  • Affordable and clean energy
  • Sustainable cities and communities
  • Partnerships for the goals
  • Clean water and sanitation
  • Climate action