Thousands of meters below Germany’s Rhine river lies one of the world's biggest deposits of so-called ‘white gold’: lithium - a key ingredient for batteries needed to power the electric vehicle revolution and shift to a low carbon economy.
The lithium reserves are trapped in underground springs of boiling hot water across a 180-mile stretch of the Upper-Rhine Valley in southwestern Germany.
Geologists estimate it holds enough for more than 400 million electric cars, enough to wean Germany’s famed auto industry off lithium imports.
So far, the bulk of the world’s lithium has been sourced from remote Australia, which relies on energy-intensive processes for extraction, or the deserts of South America known as the lithium triangle.
Both wrack up a significant carbon footprint shipping lithium to Europe.
Horst Kreuter is the CEO of Vulcan Energy Resources, a German-Australian start-up looking to capitalize on the Rhine reserves and produce carbon-neutral lithium using geothermal energy.
"The method which we use to extract lithium is called 'direct lithium extraction'. This method has already been in use in South America for 20 years. Our thermal water here has a different composition and we need to adapt the procedure to our local situation. The conditions of the areas in the Upper-Rhine Valley are actually better as we have significantly fewer substances in the thermal water than in other places."
However even geothermal energy has detractors and extracting from such a densely-populated area could garner local opposition.
Lithium also has a chequered history when it comes to economics.
Projects have often fallen behind schedule and its price has been volatile, depending on supply bottlenecks and gluts.
Prices have soared this year as demand outstripped supply from the electric vehicle sector, seen as pivotal for the EU to meet its climate goals.
But some investors are doubtful over how quickly commercial scale extraction can be developed in Europe.