WASHINGTON (AP) — Energy Secretary Rick Perry's keynote speech at the World Gas Conference in June opened with a marching band and ended with an exhibition by the Harlem Globetrotters. It was a spectacle befitting the industry symposium. "We're sharing our energy bounty with the world," Perry gushed from a stage at the Washington Convention Center.

Long undervalued, natural gas was once burned off indiscriminately as an unwanted byproduct of oil drilling. But the fuel's fortunes have changed. Cooled to minus 162 degrees Celsius, natural gas condenses into a liquid marketed as a clean alternati...