Natural Gas: The Way to Break Our Oil Addiction?by Bill Chameides | October 8th, 2008
posted by Wendy Graber (Researcher)
We’ve been told that we are addicted to foreign oil. Many Americans agree that this is an addiction we must break – not only to stop the flow of dollars overseas to countries that are often hostile to America, but also to lower our emissions of greenhouse gas pollution. The question is how? Some suggest that compressed natural gas (CNG) is the answer.
Like petroleum, natural gas is a hydrocarbon. That means it is composed of carbon and hydrogen atoms and when you burn it, it combines with atmospheric oxygen to form carbon dioxide and water and releases heat energy. An internal combustion engine is designed to use some of that heat energy to drive a motor that can, in turn, drive your car.
Unlike gasoline or diesel fuel, natural gas (obviously) is a gas. To make it practical for use in an automobile, natural gas must be compressed and then pumped under pressure into a metal container to retain it’s compressed state. Compressed natural gas (or CNG) is the form of the fuel typically used for transportation, although some heavy-duty vehicles use liquefied natural gas as well.
The amount of carbon dioxide emitted from using hydrocarbon fuels (such as, gasoline, diesel, natural gas) is largely determined by the ratio of carbon (C) to hydrogen (H) in the fuel. While natural gas has a lower ratio than other petroleum fuels (and therefore emits less carbon dioxide), it is also primarily composed of methane, which in of itself is a very powerful greenhouse gas. Leakage of methane at any point in its life-cycle – from its extraction from the earth to its being pumped into your car – will offset the global warming benefit of its lower C-to-H ratio. Bearing this in mind, when all is said and done it is estimated that using CNG to fuel our cars would lower greenhouse gas emissions by about 30% when compared to petroleum.
CNG as Bridge to Future
Clearly CNG is an improvement over petroleum, but since it still emits greenhouse gases, it is not the ultimate answer. Still, as has been suggested by some (think TV commercials), CNG could be a great, low-carbon bridge while we wait for the development of viable carbon-free ways to propel our automobiles and trucks. Indeed more and more of our city buses and government cars and even some privately owned cars run on CNG.
So what are we waiting for? Let’s go CNG whole hog, right now. But wait, it may not be that easy.
Hassle-Factor – Refueling
Because CNG is a gas, it is less dense than petroleum. As a result, you need a much bigger fuel tank in a car run on CNG than one powered by gasoline. And that means less room in the trunk and/or back seats. The advantage of this larger fuel tank is that it allows someone driving a CNG vehicle to travel about as far on a single tank of gas as someone driving a petroleum-powered car. For example, a Department of Energy website indicates that Honda’s natural gas Civic, the Civic GX, can go up to 220 miles without refueling while it’s gas-powered sister can go approximately 350 miles without refueling.
The bigger problem with CNG vehicles may be where to refuel. Currently there are about 1,300 gas stations with CNG fuel. You can find one here.
This is not a reason to shun CNG. And if your trips are mostly short commutes, it would probably not be a significant issue. But it is something you need to know before you make the switch.
Conversion Not Trivial
However, converting our entire transportation system from one based on petroleum to one based on natural gas is not trivial; it will take time, and it will take significant investments.
Americans currently drive about 235 million cars and light trucks. Over the past ten years, an average of about 16.4 million new cars and light trucks were bought each year. If we assume that this rate continues, and that every new car goes to replacing a petroleum car with a CNG car, it would take about 14 years to make the conversion. With an aggressive retrofitting program this time frame could be significantly shortened.
By far the bigger issue with converting the fleet has to do with infrastructure. We can’t drive CNG cars if we can’t get CNG at our gas stations. One option is a home filling station, but that will clearly not work for an entire fleet. We will need a new distribution system capable of delivering sufficient natural gas to stations all around the nation and require installation of new pumps at the gas stations that can compress the gas and allow it to be safely transferred to our cars tanks – because CNG is a highly flammable, greenhouse gas– there can’t be any leakage.
I have not seen any assessment of the costs of putting such a distribution system in place. I suspect it is significant. Let me know if you’ve done or are aware of such a study.
Is There Enough Natural Gas?
Ultimately, using natural gas to break our dependence on foreign oil requires that we have enough of it domestically to meet our needs. Do we?
The answer is a qualified yes. According to the Energy Information Administration, U.S. natural gas proved reserves are approximately 80 percent larger than our domestic proved reserves of crude oil on an energy equivalent basis. The U.S. holds an even larger potential natural gas resource —the so-called undiscovered technically recoverable resource. So, if the undiscovered resource proves to be real and recoverable, there does seem to be enough for a home-grown bridge to get us to a new technology which will allow us to drive our cars and trucks without foreign oil and without greenhouse pollution.
But it is also clear that natural gas is not a permanent solution nor is it going to happen overnight or without significant investments. And there’s another potential problem – replacing the natural gas currently used to generate electricity (a topic for a future post).
The need to conserve, drive more fuel efficient cars, and reconfigure the marketplace to encourage investment in new technologies as well as CNG conversion remains paramount.filed under: faculty, natural gas, transportation
and: alternative fuel, traffic