LIFE NIMBUS contributes to the circular economy by generating biomethane, a power-to-gas technology that transforms the remaining 35-40% CO2 in the biogas into biomethane biologically, in a process called biological methanation.
Hydrogen is needed to fulfill this reaction and, with this technology implemented in the Baix Llobregat treatment plant. Part of this hydrogen will be provided by a bio-electrochemical system (BES) while saving up to 50% of energy than a conventional electrolyser and providing bio-H2 by carrying out oxidation-reduction reactions, using microorganisms as biocatalysts.
These systems are based on oxidation-reduction reactions, using microorganisms as biocatalysts. These microorganisms are known as exoelectrogens, or anode respiring bacteria (ARBs), and are characterized by their ability to interact electrically with an external electrode.
Therefore, using these technologies it is possible to generate, simultaneously with the purification of wastewater, a certain electrical potential in the case of microbial fuel cells (MFC), added-value organic compounds, in the case of microbial electrosynthesis (MES), or products of interest such as hydrogen in the case of microbial electrolysis cells (MEC).
The MEC reactor in this project will provide hydrogen with an energy consumption of 2 kWh/Nm3 H2, which UAB has deeply studied (Baeza et al. 2017).
The prototype has been installed in the treatment plant with only interconnections missing (assemble the wastewater, canoes to carry the water from the primary sedimenter and its subsequent evacuation and connect the plant electrically to the “general dismissal”).