While natural gas can be a viable short-term emissions-reducing strategy, especially for fleets, there are much better fuels available now, in terms of environmental impacts and personal convenience.
What is it?:
The same gas that heats two-thirds of American homes, lights stoves, and powers water heaters becomes a vehicle fuel when it is squeezed into cylinders as “compressed natural gas” (CNG) or chilled to form “liquified natural gas” (LNG). Natural gas is found underground and is mostly methane, with small amounts of other gases and water vapor. It is formed over centuries when animals and plants decompose while sealed off from oxygen.
- Natural gas is capable of burning more completely and cleanly than gasoline, emitting less particulate pollution. Greenhouse gas emissions are 25 percent lower than gasoline, and each fill-up is currently cheaper than gasoline.
- Drivers of cars that are equipped to take CNG can skip the gas station and refuel at home: A “Phill” unit, which can be purchased currently in 17 states for about $2,000 and mounts on a garage wall, allows customers to fuel their cars directly from the natural gas pipes that heat their homes. (Liquified natural gas, by contrast, is used almost exclusively for large industrial vehicles.) As for the safety of Phill units, the manufacturer, FuelMaker Corp. of Toronto, says they have safety mechanisms that will shut them down if they’re not connected properly or if the system senses a methane leak or other malfunction.
- Natural gas is a commodity extracted primarily here in North America, not imported from overseas. (Increased demand could change this.)
- For fleets of buses and trucks, natural gas historically was a much cleaner choice than diesel. Now, natural gas is losing its edge as cleaner diesel technologies close the gap between the two fuels, according to the Union of Concerned Scientists. Today, new ultra-low-sulfur diesel makes it possible to bring particulate matter pollution from diesel engines down to levels as low as natural gas engines, though older diesel vehicles require a retrofit filter for this improvement. For the next few years, natural gas engines still have lower emissions of nitrous oxides than diesel vehicles, though diesels are expected to reduce that pollutant to equal levels by 2010.
- Natural gas, like petroleum, is a finite, non-renewable resource.
- Natural gas stations aren’t easy to find—and there’s only one model of CNG car currently on the market.
- The CNG storage tank takes up about half of the traditional trunk space in a CNG passenger vehicle.
- Though a climate improvement over gas and a climate tie with ultra-low-sulfur diesel, it’s still not the best fuel available for reducing emissions.
The US Department of Energy estimates there is a 60-year supply of natural gas from conventional sources in the US, and more than a 200-year supply from advanced technologies and new discoveries.
The Honda Civic GX is the only current passenger car designed to run on CNG (a previous Ford model was discontinued). Some experiments are underway to use the methane that rises up from landfills, sewage, or manure as renewably generated “biogas.” This technique is used widely in developing countries, but is still experimental on a municipal level in the US.
Should You Make the Switch?:
No. You can get better mileage and lower emissions more with other fuels—and better convenience, too. Plus, if you’re looking to be part of a long-term environmental solution that’s renewable indefinitely, CNG isn’t it.
Natural gas might be a good intermediate emissions-reduction step for truck and bus fleets.
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