It would be interesting to know the methane emissions of propane. It almost defies logic that they would do a study on CNG and not propane. It is apparent that if there were no gov subsidies that CNG would fall on its face and propane would be just fine. It is a very real possibility that federal subsidies will dry up in the near future. I've not heard anything but the current admin is aiming to trim wherever it can and these subsidies seem like low hanging fruit to me.