The pros and cons of natural gas engines

Natural gas vehicles are changing the transportation industry, especially for fleet vehicles. Today there are more than 175,000 natural gas vehicles (NGVs) on the road and more than 23 million worldwide. A vast majority of these vehicles are heavy-duty, high mileage fleet vehicles designed for long-distance travel and hauling.

NGV vehicles have several advantages that make them attractive, especially as fleet vehicles. A few of these advantages include:

  • Natural gas fuel is more abundant and efficient: The US is the number one producer of natural gas in the world. We have over 90 years’ worth of supply, which gives natural gas greater price stability than gasoline or diesel. Natural gas is also more fuel-efficient than gasoline. It contains fewer hydrocarbons, and it has an octane rating of 130, which helps increase engine combustion and efficiency. It can be used in two forms in a natural gas engine: Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG).
  • NGV vehicles are better for the environment: Heavy-duty vehicles account for 50% of all smog emissions and 20% of all transportation-related greenhouse gases, despite only being 7% of the total traffic on the road. That’s a lot. Recent research from the University of California Riverside’s College of Engineering found that diesel engines emitted five times more NOx (nitrogen dioxide and nitric oxide) emissions than an NGV vehicle.
  • There are more NGV vehicles than you think. While it may be challenging to find a consumer NGV vehicle on the market, other industries have embraced NGV vehicles. Heavy-duty mileage trucks, transit vehicles, refuse trucks and school buses are some of the vehicles that now use natural gas engines. The heavy-duty trucking industry has especially embraced the NGV engines because of their lower fuel costs, improved fuel efficiency and reduced breakdowns. Fueling stations have expanded across the country, which makes it easier for large carriers to embrace the savings and efficiency of NGV vehicles. It’s also more accessible than ever to find the right NGV vehicles for your fleet. Fifty different US manufacturers are producing 100 different models of light, medium and heavy-duty vehicles.

The advantages of natural gas as a fuel source and vehicle speak for themselves. But what about the engines? How do natural gas engines produce such excellent fuel efficiency and savings? Here’s a quick breakdown of natural gas engines.

Natural gas engines operate very similarly to diesel and gasoline engines using a spark-ignited internal combustion engine. Fuel is stored in a tank, then injected into the engine where it is ignited by a spark plug system which causes the engine to run. There are also three different types of NGV engines:

  • Dedicated: Engines that run entirely on natural gas
  • Bi-fuel: Engines that can run on natural gas or gasoline with separate fuel systems
  • Dual-fuel: Engines that run on natural gas but use diesel fuel for ignition, usually found in heavy-duty vehicles

NGV engines that use CNG fuel tend to experience fewer breakdowns and lower maintenance costs over time. CNG fuel systems are sealed, so there is less chance of fuel loss or contamination. In the event of a spill, natural gas is less likely to ignite and mixes easily with air, so it disperses quickly in the environment. Combined with the fuel efficiency and savings that come with NGV engines, it’s no wonder that many fleet companies are beginning to embrace the technology.

However, like any new development, there are still drawbacks. Some of the issues still facing the widespread use of NGV vehicles include:

  • Fueling access: Compared to traditional fueling centers across the country, CNG and LNG fueling stations still have a long way to go. Currently, there are 1,680 CNG stations with another 50 planned, and 144 LNG stations with 38 planned. Here is an excellent map of the distribution of the stations, which clearly shows large areas where it may be difficult to fuel up.
  • Fuel storage: NGV vehicles require more space for storing fuel than gasoline or diesel-powered vehicles, especially when using CNG fuel. The cylinders to store the fuel may cut back on storage space in the vehicle. However, the fuel storage tanks are more durable to prevent spills and ruptures.
  • It is still an emerging technology. While NGV vehicles are increasing in popularity, especially in the heavy-duty transportation industry, they are still relatively unknown. Until there is widespread adoption, new engine developments and infrastructure to support NGV engines will take longer to accomplish.
  • Natural gas is not a renewable fuel. Despite the country’s abundant supply, and the reduced emissions that come with using natural gas, it is still a non-renewable fuel source. The US has over 90 years of natural gas reserves right now, assuming that consumption remains the same. If that number were to increase, the supply would dwindle faster, and prices may increase. The environmental impact of extracting natural gas is also high and can be a deterrent for increased adoption of natural gas as a fuel source.

NGV engines represent a significant change in the transportation industry. While NGV engines have not been heavily adopted at the consumer level, heavy-duty and high mileage transportation industries are excited about this technology and what it can do. The more we learn about NGV engines and develop the technology and infrastructure to support the industry, the bigger it will grow. Who knows how many vehicles will run on natural gas in the next few years? It’s certainly an exciting prospect that could help reduce emissions and protect our environment. As your fuel and lubricants supplier, we are here to help as new technology is continually developed to better meet your industry's needs.