(Bloomberg) -- OMV AG formed a geothermal joint venture with one of its biggest natural gas customers — the city of Vienna — to help heat homes and buildings in the Austrian capital and dial down the company’s fossil fuel business.

The so-called Deeep venture between OMV and Vienna’s municipal utility, Wien Energie GmbH, plans to begin drilling next year to tap boiling-hot reservoirs as much as 5 kilometers (3.1 miles) underground. It’s part of the city’s €20 billion ($21.5 billion) effort to eliminate the need for gas to heat homes and businesses over the next decade-and-a-half. 

“We’re accepting this risk as a company in order to help Vienna de-carbonize,” OMV Chief Executive Officer Alfred Stern said Monday. 

Geothermal energy has been an underfunded and marginalized technology in the European Union’s effort to stall global warming. While the bloc pours billions of euros into wind, solar and hydrogen, it’s committed just a fraction of that to exploit underground reservoirs of hot water. Geothermal’s up front capital costs, complex technology and risk of failure have converged to mute investor interest. 

Read more: Tuscan Geysers That Inspired Dante Can Fix Europe’s Energy Bind

As part of its strategy to end its fossil fuel production by mid-century, OMV has been investing in alternative energies to recycle fuel. It bought a €34 million stake in Eavor Technologies Inc. in June that’s intended to bring the Canadian company’s geothermal drilling techniques to Europe. Initial cost estimates to open Vienna’s first 20-megawatt geothermal plant by 2027 are about €20 million. 

“The set-up costs are higher than with gas,” said Stern. “But whereas we’re now spending resources internationally to bring fuel into Austria, this investment will remain within the country.”

This initial project will provide emissions-free heat to 20,000 homes, OMV said in a statement. It gave no details about the volume of emissions reductions.

The oil and gas company’s long history exploring the Vienna basin for oil, as well as recently updated three-dimensional geological assessments, will help mitigate drilling risks, Stern added. Hot water will be extracted from the drill holes, with heat channeled in Vienna’s district heating network before the liquid is re-injected into underground reservoirs. 

“It’s an ambitious plan,” said Peter Weinelt, a director at the Viennese holding company investing in the project. “Vienna already has one of Europe’s biggest district heating networks. But in the future, rather than heat generated through burning trash, we’ll extract it from the Earth’s warmth.”

©2023 Bloomberg L.P.