Yale Environment 360: The U.S. satellite TV provider DISH Network Corporation has announced it will introduce 200 propane-fueled vans to its fleet in 2013, another sign that propane, like natural gas, is offering an increasingly cost-effective transportation fuel alternative to gasoline and diesel. While there are already more than 13 million propane-fueled vehicles worldwide, propane historically has been considered a niche fuel because of high production costs. But driven by the surge in domestic shale oil and gas production,...