Natural gas, or CNG (Compressed Natural Gas), is an alternative fuel in the USA. But that's not the case everywhere else. In Thailand, Argentina or Italy, it's a very popular fuel, not far from being mainstream, with hundreds of thousands of drivers using it everyday. CNG is also on the rise in Germany, Switzerland and Malaysia.
Should the United States follow these examples? Before giving an answer, we have to weigh the pros and cons of natural gas as a fuel.
The first advantage is that natural gas is readily available everywhere in the world, and that reserves are plentiful. Everybody's talking about peak oil, but who has ever heard about peak gas? There's also a strategic issue here, as oil is often imported from unfriendly countries, whereas natural gas can be pumped from the heartland of America. It's less of a point in Europe, as the choice between oil from the Middle-East and natural gas from Russia is not an easy one.
Second, natural gas is cleaner burning than gasoline or diesel. There's much less toxic emissions, and that's why the EPA rates CNG cars so highly. If air quality is a concern, CNG is the top choice, and nobody can argue against that. Natural gas is also better than regular fuels when it comes to greenhouse gases emissions. We can give a few numbers here. A gross estimate would be that when a gasoline engine is converted to natural gas, with that new fuel, oxides of nitrogen (NOx) emissions are down by around two-thirds, and CO2 emissions are reduced by close to a fifth. These are substantial improvements!
Third, about any gasoline car can be converted to CNG. All that is required are new injectors, new fuel lines going to a new gas container, and new software for the engine electronics controls. Some professionals advertise that they can convert just about any car in one single day of work.
Fourth, there's a cost advantage as about nearly everywhere in the world, natural gas is less taxed than gasoline. Filling the tank is cheaper, and cost per mile is down. But the downsides are never far, with the first one being that you have to refill more often. This is a problematic issue: natural gas a very low energy density. That's why it's compressed. CNG tanks holds gas at a 200 or 350-bar pressure (5000-psi), but even at 350-bar, a CNG container has to be 3-times as big as a gasoline tank to hold the same energy.
Most often, it's not the case. So cars running on natural gas have a shorter range than their gasoline counterparts, and a much reduced trunk because the CNG container has to be somewhere. It adds weight too, as it must withstand the pressure, meaning it has to built from heavy steel. In the future, it's likely that CNG tanks will be made with composite materials, which are very tough but light, but these are very expensive.
Handling of natural gas is also less friendly at the pump. You have to make sure the connection is leak proof, and the flow is slower than gasoline. You refill in 5-minutes instead of 3. Another problem comes when you start the car. If you happen to have a bivalent vehicle, or dual-fuel with the ability to run either on gasoline or CNG, you will notice immediately that power is down with the gaseous fuel. The difference can be as high as 25%!
If your car is slow running on gasoline, don't ever think of having it converted to CNG. Last but not the least problem, alternative fuel stations are few and far between. Unless you live in a big city, there might not be a station selling natural gas anywhere close to you. You may have natural gas at your home, but house outlets would be way too small to fill the container of a car. Unless you don't mind 12-hour long refills, that is not an option.
All this leads us to the conclusion that CNG might not be the great solution its partisans would like us to believe. But there could a way to unite the advantages of natural gas with those of regular gasoline. It's not rocket science, it's something that the oil industry knows how to do, we have to convert natural gas into a liquid fuel. That's called GTL (Gas-To-Liquid).
Shell is already doing it in their huge Pearl project in Qatar. No car needs to be modified, as the new fuel has the same qualities of regular gasoline, and the formerly gaseous fuel can be sold at any normal pump, in every gas station in the country. All the investment needed is at the refinery. The good points of CNG are retained, it's a greener fuel than normal gasoline, and as easy to handle as normal gasoline.
So now, we can see who are the people who wants Americans to convert their cars to CNG. They are the people who wants the basic drivers to make investments, but who don't want to make any investment themselves, in producing a fuel drivers would be ready to use immediately.
