BRUSSELS, Belgium — It's been more than 20 years since the last coal was dug out of the ground by the once-thriving mining communities of Belgium's Campine region.
Now there's hope of new riches beneath the area's sandy heathland.
The Campine is one of dozens of regions across Europe believed to be sitting on significant reserves of shale gas — the underground fuel that has revolutionized energy supply in the United States over the past decade.
"The potential in Europe could be huge," says Professor Richard Davies, a specialist at Britain's Durham University and advisor to the industry. "We've got all the right sort of rocks."
Shale gas now accounts for more than 20 percent of US natural gas production, up from barely 1 percent in 2000. By the 2030s, it's share is expected to be over 50 percent.
The United States is on course to become self-reliant in gas. Its heating bills are already four times lower than European levels.
Now prospectors are sharpening their drills in Europe and some governments are hoping for a US-style shale bonanza.
There are estimates that Britain could be sitting on enough reserves to meet its gas needs up to the end of the century.
While Poland has significantly downgraded its estimated shale deposits, it could still have enough to keep it gas independent for more than 60 years and break its reliance on Russian energy imports.
Shell signed a $10 billion deal to develop shale gas in Ukraine in January. Oil companies in Spain are planning to spend up to $1.3 billion to search for unconventional gas reserves estimated at over $900 billion — a handy sum for a country struggling with the euro-zone debt crisis.
There is a catch of course.
Environmentalist say the "fracking" process that uses a high-pressure cocktail of water, sand and chemicals to releases shale gas from the rock has the potential to trigger earthquakes as well as releasing a toxic mix into the water supply and surrounding countryside.
Incidents of air and water contamination in the United States should serve as an example for Europe, where risks are even higher due to the need to drill deeper and in more densely populated areas, says Antoine Simon, shale gas campaigner for Friends of the Earth Europe.
"The risks are way too high to be repeated in Europe," Simon said in a telephone interview. "It would be simple madness to go ahead considering all the impacts that have already been observed in the US over the last two decades."
In addition, ecologists claim, a new gas boom will undermine efforts to tackle global warming and undermine Europe's commitment to renewable energy.
Mindful of the environmental concerns France — which some believe has Europe's biggest shale gas deposits — has introduced a five year ban on fracking.
The Netherlands, Bulgaria, Luxembourg and the Czech Republic have imposed moratoriums on drilling for shale gas. For others, however, the economic potential outweighs the risks. In December, Britain lifted an 18-month ban on fracking.
"It may be that this gas revolution is really quite transformative and there is going to be a lot more gas and the price won't be as expensive," Prime Minister David Cameron told parliament. "It would be a big risk just to ignore what is happening in the gas market."
Romania's government also lifted a year-long moratorium in March. Shale gas deposits shared with neighboring Bulgaria and Hungary are estimated to be more than 538 billion cubic meters — enough to meet the country's gas needs for 40 years.
That's quite an incentive for the EU's poorest country, which now depends on imports from Russia for a quarter of its gas needs.
However thousands have taken to the streets to protest the government decision to grant Chevron more than a million acres of land to drill for shale deposits. "Frack off Chevron," has become a popular slogan with the Romanian protesters.
Supporters argue shale gas is too big an opportunity for Europe to ignore.
The European Union's dependence on imported gas is already at 60 percent, and mounting demand and declining domestic supplies of gas from conventional supplies will see that ratio rise to 80 percent unless shale reserves are developed, says Monica Cristina, advisor to the industry platform Shale Gas Europe.
Many countries in eastern Europe see fracking key to end their dependence on energy imports from Russia, which has been accused of turning off the tap on oil and gas pipelines as a means of exerting political pressure.
Cristina says the economic stakes are even greater, with the competitiveness of European industry on the line.
"It's basic economics, if you have more gas supply there will be pressure for the price to go down, and cheaper gas means a more competitive European industry," Cristina said. "If you look across the ocean, we see a manufacturing revival in the US. Europe will be the loser if no action is taken on reducing energy costs."
However, even shale gas supporters acknowledge that there are doubts about the extent and potential impact of Europe's shale gas.
Poland, which has invested most in developing shale reserves, last year announced its expected reserves were estimated at a maximum of 768 billion cubic meters, down from an earlier estimate of 5.3 trillion. Exxon Mobil gave up searching for shale gas there in June after failing to find viable qualities with it's two exploratory wells.
Even if gas is found in sufficient quantities, European officials have cautioned against expectations of a shale gas El Dorado.
"We should not fool ourselves that shale gas would not be the game-changer that it has been in the US," Connie Hedegaard, the EU's commissioner for climate action told Britain's Guardian newspaper last month.
"This is not going to be as cheap as in the US. We have different geology that makes it more tricky (to extract shale gas). We don't have the same wide open spaces. We pay more attention to what local people think."