Over the past several years, the shale revolution has upended oil and gas markets in the United States and the world at large. At first, shale development was dismissed as unworkable, then it was minimized as unsustainable. Now, having helped drive a massive drop in the global price of oil, it is hailed as an economic and geopolitical game changer. But shale isn’t the only energy story of interest, nor even the only potentially revolutionary one.