TMB will begin testing biomethane as fuel starting in June

At the Aigües de Barcelona wastewater treatment plant (WWTP) in El Prat de Llobregat, a small plant is being finalized that will serve to convert its sludge into biomethane. This renewable gas will be used as fuel for Transports Metropolitans de Barcelona (TMB) buses, as explained by its CEO, Gerardo Lertxundi, in an interview with The New Barcelona Post. Biomethane has a similar composition to natural gas and, therefore, can power a vehicle. After starting to test hydrogen as fuel, the public transport operator is focusing on this other renewable gas, which can help it reduce its carbon footprint by 80%.

Life Nimbus, the project that aims to test biomethane in TMB, is led by the Water Technology Center (Cetaqua) and involves the participation of TMB, Aigües de Barcelona, and the Universitat Autònoma de Barcelona (UAB). The Barcelona Metropolitan Area (AMB) also supports them. Its main objective is to analyze the possibility of converting treatment plants into ecofactories, that is, facilities that generate new resources from wastewater, in this case, energy in the form of gas.

According to the project manager, Oriol Casal, the plant, with an area of less than 300 square meters, is expected to start operating this June, after the final tests are carried out in May. Currently, civil works are underway to install the necessary equipment to operate the plant in the next two months. This initiative has European funding of almost two million euros and will end in November 2023.

With Life Nimbus, it is expected to be able to fuel a single vehicle, which will travel daily from the TMB depots in the Zona Franca to the Baix Llobregat WWTP to refuel in about five minutes ---the same time it takes to do so with natural gas--- and start the route, still to be decided. Sources from the public transport operator indicate that, in addition to participating in Life Nimbus, they are looking for other suppliers of this renewable gas. They also point out that 35% of their fleet is already powered by gas, such as liquefied natural gas (LNG).

Beyond testing biomethane as a sustainable fuel, the initiative will allow studying a new technology to obtain this renewable gas, which until now has only been tested on a small scale, in laboratories. Biomethane comes from biogas, which is obtained from waste such as slurry, excrement, sewage sludge or slaughterhouse waste. To convert it into biomethane, it has to be cleaned to eliminate the carbon dioxide it contains and be able to be used energetically.

In Europe there are around 700 plants dedicated to producing biomethane, with a special presence in countries like Germany, France or the United Kingdom, and almost none in Spain, with only two. In these facilities, biomethane is obtained by separating the CO2 and methane found in biogas. Life Nimbus wants to see how efficient it is to obtain biomethane from methanogenesis. This technique consists of chemically reacting CO2 with hydrogen, which must have a green origin, and converting it into methane.

In Europe there are around 700 plants dedicated to producing biomethane, with a special presence in countries like Germany, France or the United Kingdom, and almost none in Spain, with only two

If Life Nimbus obtains positive results, building a larger plant will be studied. However, a challenge opened by this pilot test is the need to find a source of clean hydrogen, as well as to find a mechanism to generate enough electricity to make methanogenesis possible. The EDAR Baix Llobregat will allocate only 1% of the biogas it generates to this test, allowing a bus to operate, but, if its full capacity were used, a fleet of more than a hundred vehicles could be covered.