It’s dirty, it stinks and it could make a major contribution to the green energy revolution in the future: sewage. With a few tricks, the devil’s brew in our wastewater treatment plants could be producing energy. Professor Michael Sievers at the Clausthal Institute of Environmental Technology (CUTEC) has developed a biofuel cell in cooperation with several other technical universities. The idea is that sewage treatment plants could be transformed from energy guzzlers into power generators—and wastewater into valuable raw materials.
In contrast to conventional fuel cells, Sievers’ biofuel cell is powered by carbon instead of hydrogen, and there is plenty of carbon in sewage. But to turn it into electricity, Sievers needs help in the form of tiny bacteria. They devour organic residues in the wastewater, decomposing plant materials, fecal matter and urine, thus also cleaning the water. This process also releases electrons and this released energy is then captured by the biofuel cell, generating electricity.
Towards the end of 2016, a pilot biofuel cell was tested in real life for the first time when it was integrated into a sewage treatment plant in Goslar. It cleaned around four thousand liters of wastewater daily for three years. “It gave us some useful information,” Sievers says. The team was able to identify suitable materials and find appropriate electrodes and catalysts. But there were floods and blockages whenever there was heavy rainfall. And the electricity generated wasn’t even enough to operate the plant, much less generate a surplus.
Sievers believes that the use of his biofuel cell could really pay off for treating highly polluted wastewater from industrial sources.
Despite this, Sievers sees great potential in his project. The treatment of wastewater in sewage plants is expensive for municipalities and accounts for about 10 percent of energy use. At the same time, there is four to five times as much energy lying dormant in the stinking sewage than is required to operate such a plant. Sievers believes that the use of his biofuel cell could really pay off for treating highly polluted wastewater from industrial sources. If the technology works perfectly, it could also reduce the amount of sewage sludge, which has to be removed and incinerated at great expense, by up to 80 percent.
The German Federal Ministry of Education and Research is also confident about the project’s potential and will be providing Sievers and his team almost 6 million euros over the next five years. By 2024, the researchers in Goslar hope to develop and build an independent wastewater facility, including biofuel cells, and test its operation. They are currently working on a new reactor concept that works only with its own self-generated energy. If everything goes according to plan, the tiny bacteria could be transforming our waste into electricity in the future, and not just in Goslar.
