How Vienna uses its wastewater to heat homes without Russian gas

How Vienna uses its wastewater to heat homes without Russian gas
How Vienna uses its wastewater to heat homes without Russian gas

56,000 Viennese homes are heated using wastewater using three huge heat pumps.

Brand new pipes transport wastewater through three huge heat pumps in the most powerful installation of its type in Europe, which heats up to 56,000 Viennese homes, a new low-carbon solution to reduce dependence on Russian gas. No more old boiler: here, the polluting fossil fuel is replaced by a resource from the nearby wastewater treatment plant and valorized thanks to the neighboring hydroelectric plant.

“100% local and renewable,” project manager Linda Kirchberger, who works for Wien Energie, the main energy supplier in the Austrian capital, which has nearly 2 million inhabitants, told AFP. “We take six degrees of wastewater with the pumps and we re-inject it” into the 1,300 kilometers of heating pipes which run through the city’s basements, one of the largest networks on the continent, explains Linda Kirchberger. during a visit to the site, orange helmet on his head.

And Vienna wins on all fronts: it reduces its still very significant dependence on hydrocarbons purchased from Russia at war against Ukraine, while diversifying its sources of supply. More than 40% of final energy consumption for heating and hot water in Vienna is still covered by natural gas, according to official figures communicated by the town hall on its website.

By 2027, a total of 112,000 homes must be connected to the new system operational since December, the tailor-made installations of which were provided by a factory installed in France of the American company Johnson Controls.

Wastewater, the new black gold?

Although domestic heat pumps are better known (using in particular the heat contained in the air) and are subsidized in certain countries such as Germany and France, these pumps can very well be installed on a larger scale. Other European metropolises are also eyeing this innovation based on “a new Source of energy, which we find in abundance under our feet in every urban area”, notes expert Florian Kretschmer, from the University of Natural Resources. and Life Sciences Vienna (BOKU).

So wastewater, the new black gold? In any case, their recovery is already commonplace in northern Europe, as well as in Switzerland, the water released into the river after having been relieved by a few degrees also becoming an advantage, against a backdrop of global warming. . In the background of this initial investment of 70 million euros in Vienna, decided four years ago, is the recognition in 2018 by the European Union – of which Austria is a member – of wastewater as a Source of renewable energy.

“Europe has made notable progress in sustainable heating solutions”, key in the fight against climate change, underlines Lars Nitter Havro, analyst at Rystad Energy.

But “the recovery of heat from wastewater for collective heating is still in its infancy”, while to be profitable, this technology must be exploited for thousands of homes, he notes. . This analyst recalls that almost half of EU households run on fossil fuels, with heating today generating some 4 billion tonnes of CO2, around 8% of global emissions.

“It is clear that we must review our energy system to achieve independence,” notes Linda Kirchberger, echoing the efforts of EU states which have reduced their demand for gas, particularly Russian, in the face of the shock of the conflict in Ukraine.

With this new installation, Vienna is therefore taking a first step towards “a secure supply, also guaranteeing price stability” which is appreciable in view of the recent outbreak which shook Europe.

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