Disused for more than 30 years, a Dutch mine that once yielded polluting coal has been revived as a source of greener energy -- heating household radiators using warm water flooding its abandoned shafts.

Claimed by its originators to be the world's first such energy generator, the "Mine Water Project" in the south-western Limburg province went into operation last month, heating some 350 homes and businesses in a newly built neighbourhood in Heerlen.

It emits 55 percent less polluting carbon dioxide than other water heating systems.

"The global energy question can no longer be solved with fossil fuels," Christion Cornips, executive of the residential company Weller that initiated the project, told AFP.

"Energy shortages have to be addressed at a local level, and mine water is an example of that."

The project saw five new wells being drilled into the ground at five different locations. The wells reach depths of 700 metres (2,300 feet), from which are pumped nearly 80 cubic metres (2,800 cubic feet) of water per hour.

"The water temperature measures 32 degrees C (89 degrees F) at the bottom (of the well) and 28 degrees when it arrives at the surface," explains Jan-Jaap van Bergermeer, who supervises the project.

At the heart of the Gen Coel neighbourhood of Heerlen, one finds a towering glass building accommodating a cultural centre and library whose modernity symbolises the rebirth of an area that formerly comprised mostly small mine worker houses.

Underneath the building, heated with water from the mine project, Van Bergermeer opens a discreet door in the car park to reveal a network of arteries that directs the pumped water to machines that extract heat from it.

-- 'There is much promise' --

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"It is not the water from the mine that arrives in the heaters and taps," explained Van Bergermeer.

The extracted heat is used to warm household water supplies before being pumped back to a depth of 450 metres to reheat and be used again.

In the coldest of winter periods, users may require the help of traditional methods for extra heating.

Planners say water extracted from a shallower and cooler depth of 250 metres may in the future also be used as part of the new climate control system in summer.

Cornips said about 70 percent of any client's invoice was for subscription and 30 percent for actual consumption.

And while the cost to the consumer was similar to that for conventional heating methods, the price of the latter was more unstable for being closely linked to variations in energy prices.

Cornips said "several obstacles had had to be overcome" before the project could get off the ground.

Because it had no precedent, it started off as a legal headache with uncertainty about its status, and received a hostile reaction from energy companies who feared competition.

It was also challenging from an engineering point of view as new heating devices had to be invented and installed side-by-side with a conventional ones in case of a breakdown at the mine water project, said to Van Bergermeer.

"We developed everything from scratch."

After the discovery of natural gas in the north of the country in the late 1950s and with the advent of cheaper coal production facilities in other countries, the city of Heerlen was among several towns that saw its mines close and its communities shrink as thousands of jobs were lost.

Having been the reason behind Heerlen's transformation from a collection of agrarian villages to a key Dutch city, the coal mines are again at the forefront of energy technology.

"There is much promise," enthused van Bergermeer. "Imagine the heat in the mines of Lorraine in the north-east of France, which are more than two kilometres deep!"