The HES-SO Valais-Wallis University of Applied Sciences has developed the world's longest microbial fuel cell, a project that will produce electricity by purifying wastewater.

Up and running since the end of 2018 and developed with the support of the Swiss Federal Office of Energy and The Ark, in collaboration with HE-Arc in St-Imier, the microbial fuel cell produces enough electricity to power several lithium batteries but more importantly, it purifies the water of all its organic elements for free.

The project began in 2016 in Fabian Fischer's laboratory at the HES-SO Valais-Wallis University of Applied Sciences. The construction of the current system, a 14-meter long stack composed of 64 connected batteries, took a full year to complete and the project will be further fine-tuned over a two-year period. "Research is only still in its infancy. By improving the process and expanding the installation, we could save more than 600,000 Swiss francs a year in energy and cover the electricity needs of 250 households," he states.

A 25% return on investment

The improvement potential of the current system is substantial. "In theory, it is possible to achieve an effective yield of 25%. A wastewater treatment plant with a population of 100,000 could generate an annual income of CHF 1.75 million while in Switzerland, we could produce about 0.2 kilowatt-hours per person per day, with an annual potential of between 500 and 700 gigawatt-hours," explains Fabian Fischer. The energetic assessment will then be positive and wastewater treatment plants will become producers of clean energy: instead of paying for electricity, wastewater treatment plants could produce it.