Washington, D.C.- Improved drilling techniques have unlocked vast new reserves of shale gas, a resource that could be large enough to displace significant amounts of coal, and an energy source that emits less than half the carbon dioxide. But growing shale gas development has raised both environmental questions and public controversy. A new independent assessment by the Worldwatch Institute concludes that improved adherence to drilling best practice and better regulatory oversight are essential to assure environmental and public protection as shale gas production continues to expand.