A scientific study in Poland has found that shale gas extraction at one site produced some toxic refuse but that the waste was reused and didn't harm the environment.
The report was presented Friday by the Polish Geological Institute, which carried out its study last year when a company, Canadian Lane Energy, began test drilling near Lebien, in northern Poland.
Poland has some deposits of shale gas and is hoping to exploit them to cut its dependence on Russian natural gas. It hopes to repeat what has happened in the United States, where large shale gas discoveries in the past 10 years have given the country independence in the gas sector.
It is still unclear, however, how much shale gas there is in Poland, and the process of extracting it has come under fire by environmentalists.
In hydraulic fracturing, or fracking, a technology developed in the United States, large quantities of pressurized water and some chemicals are used to break underground rocks and release gas trapped in them. Most of the water remains underground, but some returns to the surface and is toxic.
"Cases of leakage and water contamination in the U.S. show that this is not a safe technology," Katarzyna Guzek of Greenpeace told The Associated Press.
The report said the procedure at the site it studied produced some highly toxic liquid and some solid refuse, but that it was all either reused or utilized. Laboratory studies found no pollution to surface or ground water, soil or air, it said.
"Soil, air, water _ the studies show that all these elements of the environment are safe if exploration of shale gas is conducted in accordance with legal regulations," the study said.
Guzek said the study was carried out at the start of exploration in Poland and does not reflect dangers from a long-term activity.
Lane Energy is among more than a dozen international companies that have obtained licenses to explore for shale gas in northern and eastern Poland.