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?
Cleaner at the Tail Pipe
The short answer is that yes, natural gas is a cleaner alternative if the only other option is petroleum. With CNG, many key emissions are significantly reduced. According to EPA tests, carbon monoxide emissions are reduced by 90 to 97 percent, carbon dioxide emissions reduced by 25 percent, and nitrogen oxide emissions reduced by 35 to 60 percent.
In summary, the EPA found that there are "fewer toxic and carcinogenic emissions from natural gas vehicles, and virtually no particulate emission."
Considering the Whole Lifecycle
When the entire lifecycle of natural gas is considered, however, it is impossible to call it "clean." Sourcing natural gas, like petroleum, is becoming increasingly difficult. To increase yields and tap into areas not suitable for conventional extraction techniques, operations have turned to hydraulic fracturing, commonly known as "fracking."
Fracking has been shown to be extremely harmful to local environments. The nature of the process -- which consists of releasing gas from rock or shale with high-powered blasts of water -- is inherently difficult to control. This has led to groundwater contamination and earthquakes, to name just two of the many consequences.
Furthermore, there is some evidence that the emissions of gas extracted through fracking are actually higher than estimated.
The Truly Clean Alternative
There is one other option that fits the same applications CNG does, but without the dirty trail. That option is electric vehicles.
Like CNG, electric vehicles would fit very well into municipal and industrial applications -- where vehicles return to a central station each day for refueling. The electricity for these vehicles could, of course, come from coal, oil, or gas but building the recharging and fleet infrastructures means that a door is open to a future powered by solar, wind, and other renewable energy sources.
In the end, CNG vehicles may be "cleaner" than conventional gas vehicles, but they are a short-term -- and possibly short-sighted -- alternative that excludes much more responsible solutions.