Advantages and DisadvantagesThe biggest advantage of NGVs is that they reduce environmentally harmful emissions. natural-gas vehicles can achieve up to a 93 percent reduction in carbon monoxide emissions, 33 percent reduction in emissions of various oxides of nitrogen and a 50 percent reduction in reactive hydrocarbons when compared to gasoline vehicles. NGVs also rate higher in particulate matter 10 (PM10) emissions. PM10 particles transport and deposit toxic materials through the air. NGVs that operate in diesel applications can reduce PM10 emissions by a factor of 10.
Natural-gas vehicles also offer these benefits:
- NGVs are safer. The fuel storage tanks on an NGV are thicker and stronger than gasoline or diesel tanks. There has not been an NGV fuel-tank rupture in more than two years in the United States.
- Natural gas costs are lower than gasoline. On average, natural gas costs one-third less than gasoline at the pump.
- Natural gas is convenient and abundant. A well-established pipeline infrastructure exists in the United States to deliver natural gas to almost every urban area and most suburban areas. There are more than 1,300 NGV fueling stations in the United States, and more are being added every day.
- Natural gas prices have exhibited significant stability compared to oil prices. Historically, natural gas prices have exhibited significant price stability compared to the prices of petroleum-based fuels. This stability makes it easier to plan accurately for long-term costs.
- NGVs have lower maintenance costs. Because natural gas burns so cleanly, it results in less wear and tear on the engine and extends the time between tune-ups and oil changes.
One of the biggest complaints about NGVs is that they aren't as roomy as gasoline cars. This is because NGVs have to give up precious cargo and trunk space to accommodate the fuel storage cylinders. Not only that, these cylinders can be expensive to design and build -- a contributing factor to the higher overall costs of a natural-gas vehicle compared to a gasoline-powered car.
Photo courtesy Johns Hopkins University Applied Physics Laboratory
Rear undercarriage showing fuel cylinders
Another drawback is the limited driving range of NGVs, which is typically about half that of a gasoline-powered vehicle. For example, Honda's natural gas Civic, the Civic GX, can go up to 220 miles without refueling. A typical gasoline-powered Civic can go approximately 350 miles without refueling. If a dedicated NGV ran out of fuel on the road, it would have to be towed to the owner's home or to a local natural gas refueling station, which might be harder to find than a "regular" gas station.
Finally, it should be noted that natural gas, like gasoline, is a fossil fuel and cannot be considered a renewable resource. While natural gas reserves in the United States are still considerable, they are not inexhaustible. Some predict that there are enough natural gas reserves remaining to last another 67.1 years, assuming that the 2003 level of production continues.
Despite some of the advantages offered by NGVs, they are still relatively uncommon. According to the Natural Gas Coalition, there are currently 130,000 NGVs on the road in the United States today and more than 2.5 million worldwide. To put this into perspective, consider that there were 142.5 million registered vehicles in 2001 -- which means gas-powered vehicles outnumber NGVs almost 1,100 to one in the United States. And yet more than 40 different manufacturers, including Ford, General Motors, Toyota and Volvo, currently produce NGVs.
Photo courtesy Honda
The Phill Home Refueling Appliance
While vehicles such as the Civic GX and the E 200 NGT are only available in very limited markets (the former in certain western states, the latter in Europe), NGVs are expected to become more widely available to consumers in the next two decades, especially as the price of oil continues to rise. When that happens, being green will be a little bit easier.
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Many long-haul trucks and buses run on a different form of natural gas called liquefied natural gas, or LNG. LNG is made by refrigerating natural gas to -260°F, condensing it into a liquid. The liquid form is much more dense and thus has more potential energy for the amount of space it takes up. That means more energy can be stored in the same amount of space on a car or truck.