Home to 200,000 people, Aarhus in Denmark has become the first city in the world to power its water needs from energy generated from a wastewater plant. The Marselisborg Wastewater Treatment Plant has recently undergone upgrades that have helped it generate more than 150% of the electricity needed to run the plant – meaning that the surplus energy can be used to pump clean drinking water across the city.
In order to generate energy, wastewater treatment plants create biogas from wastewater and sewage by pumping the materials into heated digesters. Often this results in methane which is then burned to create electricity and heat. While the technology for this process isn’t new, what Aarhus has achieved stands a part for its ability to make the whole water consumption-waste-treatment process circular. This comes as a result of several policies and regulations the city has undertaken to reduce waste and tailor infrastructure to recover energy from water processing.
“We are about to be the first energy neutral catchment area,” says Mads Warming of Danfoss Power Electronics, which provides the technology for Aarhus Water, the municipal water utility, in an interview with New Scientist. Though the upgrades that have made energy-neutrality possible cost €3 million, the city expects that to be recouped in only five years as excess energy from the whole process can be sold back to the grid, while surplus heat can rerouted to the district heating system.
Earlier this year, Danfoss made more headlines by piloting another circular energy project in Als, Denmark. The Scandinavian technology giants calculated that they could power 16 standard homes annually by funneling excess heat created by refrigerator units in a single supermarket to the district heating system. Meanwhile, the supermarkets themselves set to benefit from reduced heating costs when the same energy is transferred within the building, as well as a reduced CO2 footprint. “The local supermarket close to the Danfoss’ headquarters in the south of Denmark now saves more than 31,000 USD annually on gas for heating. CO2 emissions are reduced by 34% by using the surplus heat from the refrigeration system to heat the supermarket and neighboring buildings,” writes Niels B. Christiansen, Danfoss’ President and CEO.