[redpoint5]

Given the facts that Dave presented, it seems CNG would be an excellent fuel to use with a turbo charged engine. Do CNG engines lend themselves to forced induction?

How does CNG compare in cost per mile (or $ per BTU) with gasoline?

Regarding the OP, no, it's not an environmentally responsible choice because it consumes mineral resources and emits so-called pollutants. The only environmentally responsible thing to do is commit suicide. Fortunately, we are not held responsible by the environment, but instead by other people. In my estimation, the benefit I provide to others by being a consumer of a product far outweighs the impossibly small and difficult-to-calculate cost of the "damage" done to the environment.