Grand Canyon NPS/Creative Commons
Gasoline, everyone knows, is a polluting, volatile source for fuel. Still, the vast majority of vehicles around the world depend on it. Indeed, petroleum has proven to be persistent, dominating the "age of the automobile" since its inception.
In spite of this, growing unreliability both in market price and supply -- not to mention concerns over CO2 and other pollutants -- has forced many to look for alternatives. One that has gained favor -- especially in commercial applications -- is compressed natural gas (CNG). The question is: Can CNG be a clean alternative to petrol?