Gas Technology: Doors opening for NGV trucking

Natural gas vehicle (NGV) trucking's benefits are becoming more apparent as consumers realize its potential in reducing emissions and overall fuel costs.


Rapid refueling, whether LNG or CNG is a requirement for a successful OTR natural gas site. More of these facilities are being installed across the U.S. and Canada. Many offer a choice between CNG and LNG. Courtesy: U.S. Department of EnergyIt has long been recognized that over-the-road (OTR) trucking represents a major opportunity to replace petroleum fuels with natural gas. This market segment also has great potential for reduced emissions and lower fuel costs. A decade ago the obstacles were large and included a severe lack of fueling points, unavailability of heavy-duty natural gas vehicles (NGV) powered road tractors, and long payback times for adopters of the natural gas option. Today, many of those obstacles have been overcome, and the benefits are more obvious than ever.

Getting the process started

In some ways it has been a chicken-and-egg dilemma. Operators were reluctant to switch to NGV road tractors because of the lack of refueling infrastructure.  Fuel providers were reluctant to build NGV fueling points suitable for OTR truckers because of the limited demand for this service. But change was coming. OEM truck manufacturers first began offering NGV engines in sizes suitable for refuse trucks, ready-mix concrete trucks, delivery vans and transit buses. In many cases these were intended more for customers who had time-refueling systems on their own premises. But these introductions jump-started truck manufacturers and began demonstrating to others the many benefits of NGV fueling.

Several companies have supported this transition for NGV trucking. Questar Fueling, a subsidiary of Questar Corporation in Utah, has initiated an extensive program of building OTR truck fueling stations in Utah and stretching out into Kansas, Oklahoma, Colorado and Texas. Currently the company has five of these dedicated NG truck fueling stations operating, and three more near opening. Many more are in the planning or construction stages.

Another important provider is Clean Energy Fuels Corp., headquartered in Newport Beach, California and has developed more than 500 public and private fueling points across the United States and Canada. Of these, nearly 250 are suitable for fueling tractor-trailer units and many are along major Interstate Highway routes. Other regional and national fuel providers continue to build fueling stations that close the gaps in the North American “natural gas highway.”

Large engines now available

Another important force has been Cummins-Westport, a joint venture between Cummins Engines and Westport Innovations, a company specializing in technology for NGV engines. This Cummins Westport team has delivered over 50,000 NGV engines worldwide. An important milestone was Cummins Westport’s introduction of an 8.9 liter truck engine in 2007 and more recently a 12.0 liter model in 2012. These two engines are now offered as options by major truck manufacturers such as Kenworth, Peterbilt, Mack, Navistar, Freightliner and Volvo.

In particular, the availability of the 12.0 liter engine has been an important spur for NGV trucking growth. This engine can provide adequate power for large OTR units. NGV engines have spark ignition systems rather than compression ignition as in diesel units, and require a completely different engine design. Of great interest is the fact that natural gas is a very clean engine fuel, so many of the complexities involved in emission reduction with diesel fuel are not required. The Cummins Westport engine employs a Three-Way Catalyst (TWC) technology that allows the engines to meet strict EPA 2010 emissions standards. The TWC device is installed in the engine muffler and requires no maintenance.

A suitable fueling site for OTR truckers requires adequate space for vehicles. Often such facilities are co-located with other truck stop amenities such as restaurants, showers, convenience stores, and other outlets. Courtesy: Questar Fueling12 liter engine important development

According to Judd Cook, Director of Business Development for Questar Fueling, the availability of the 12 liter engine has done much to make OTR trucking with natural gas feasible. Cook notes, “For many OTR applications, the 8.9 liter engine was not powerful enough. The 12 liter has caught a lot of people’s attention. And from what I’ve heard, it has been trouble-free and reliable.”

Because of the growing number of NGV engines being used in commercial vehicles of all kinds, the price premium for the technology is steadily reducing. According to Chad Lindholm, the head of the trucking group at Clean Energy Fuels, several years ago a trucker would pay a premium of nearly $100,000 for a natural gas-powered road tractor. Today that premium is down to $30,000 to $45,000. He expects it will continue to go down as the volume of sales of these tractors increases.

CNG and LNG advantages and disadvantage

At fueling points, natural gas may be dispensed as compressed natural gas (CNG) or liquid natural gas. Lindholm indicates that there are advantages for each fuel type. CNG is a pressurized fuel and requires heavier tanks and has a lower energy density than LNG, thus more frequent refills are sometimes required. However for trucks that return to base daily, it may be the best choice, particularly if the base has a slow-fill or fast-fill refueling station on site. Long-term storage in the vehicle tank is possible with no loss of fuel.

LNG may be a better choice if the vehicle is operated over the road for longer distances and in some cases the refueling time is shorter, thus operators spend less time refueling. LNG is held at a temperature of -260°F and if the tank is not emptied, it begins venting to the atmosphere in about five days, so there is an energy loss. Vehicle LNG fuel tanks are lighter than those for CNG for the same capacity. Generally LNG is most advantageous for long-distance truckers that don’t frequently return to base.

A fraction of the price of diesel

CNG is usually compressed at the delivery site from pipeline-delivered natural gas, while LNG is more commonly delivered by tanker to the refueling point.  Delivered cost of either natural gas fuel is typically one-half to two-thirds the price of the equivalent gallons of diesel fuel. Fuel costs are generally cited as gallons-of-diesel-equivalent (GDE). Because it need to be trucked to the dispensing site, and because of the energy cost of the liquefaction process, LNG is typically somewhat more expensive than CNG. Estimates of the cost differential range from 25 cents to as much as 75 cents GDE.

Payback for the higher cost of a natural gas tractor can range from one to three years, depending on local fuel costs and miles driven.  If, as Lindholm projects, natural gas vehicle costs continue to decline proportionate to diesel vehicles, the paybacks could be even shorter. Currently the price of diesel fuel is somewhat depressed because of lower crude oil prices. How long this will continue is debatable. Judd Cook from Questar Fueling indicates that the fuel price differential is a major driver in the decision to switch to natural gas, and some truckers are watching trends. At the current time, he feels the typical paybacks are 18 to 24 months, which is enough to continue to stimulate interest.

Environmental benefits as well

In addition to fuel and dollar savings with OTR vehicles fueled by natural gas, there are environmental benefits as well. According to the California Air Resources Board, CNG-powered vehicle emit 20% to 29% fewer greenhouse gas emissions. It is estimated that new natural gas vehicles offer a 40% reduction in NOX emissions compared to new diesel vehicles, and a 95% reduction compared to the current entire fleet of gasoline and diesel vehicles. Particulate emissions are reduced 98% compared to the current fleet.

A recent example of the transition to natural gas vehicles is the announcement by Fred Meyer Stores, a division of the Kroger Company, that they were replacing 40 diesel road tractors with LNG-fueled tractors to be based out of their distribution center in Clackamas, Oregon. As an integral part of this project they worked with Clean Energy Fuels to build a private fueling station on the site. The trucks will be part of the fleet that delivers product to 123 multi-department stores in the Northwest. As part of this project, the company received a $490,000 grant from the Federal Highway Administration through the Oregon Department of Transportation.

Owners testing NGV

Many other national and regional truckers are placing their first orders for natural gas vehicles for the purpose of watching trends and observing the operation of these units first-hand. Many believe we are in the opening years of a major transition to natural gas-fueled highway trucking.  More infrastructure is needed, and the vehicle numbers are still relatively small, though growing rapidly. But the chicken-egg dilemma has been largely resolved and growth is underway.

More information

Clean Energy Fuels Corp.


Natural Gas Vehicles for America

Questar Fueling

This article originally appeared on Gas Technology Spring 2015 issue.

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