Natural Gas Vehicles

Comparison of:

Passenger vehicles running on compressed natural gas (CNG) with

Gasoline and hybrid electric models, and

Heavy-duty trucks running on liquefied natural gas (LNG) with their diesel counterparts.

High costs, reduced cargo space, and range issues— along with stiff competition from other alternative fuels—are likely to make switching to natural gas a tough sell for passenger vehicles. Tractor trailer semi-trucks running on LNG can be a good deal for reducing oil use, conventional pollutant emissions, and costs, but significant uncertainty surrounds the size of their carbon footprints.

Natural Gas Vehicles at a Glance

There are 110,000 natural gas vehicles in the United States.  There are 840 compressed natural gas and 39 liquefied natural gas fueling stations in the United States (compared with 4,000 diesel truck stops). Sources: Bryce 2011; Natural & Bio Gas Vehicle Association 2011.

Passenger Vehicles: Comparing the Options

The light-duty vehicle market currently has one natural gas entrant: the Civic Natural Gas (formerly the GX) by Honda. Chrysler, Ford, and Hong Kong–based Hybrid Kinetic Motors are also gearing up to produce passenger vehicles that run, at least in part, on natural gas.

Without a subsidy, the natural gas Civic costs $26,240—modestly more expensive than the $24,700 hybrid but substantially more expensive than the $19,905 gasoline version. Its maintenance and repair costs are also considerably more expensive.

The fuel economy for the natural gas Civic is about the same as that of the gasoline alternative. But fuel tanks for compressed natural gas are large and heavy, decreasing cargo space by a dramatic 50 percent compared with the gasoline version. Also, its range is lowered to only 218 miles, compared with 383 miles for the comparable gasoline vehicle and 504 miles for the hybrid.

The Economics of LNG-Fueled Heavy-Duty Trucks

Natural gas is more likely to fuel large trucks, particularly tractor trailers, and fleet vehicles, including buses. In addition to the cost and range issues, it would be costly to build the infrastructure to service passenger vehicles throughout the nation’s extensive road system.

Current estimates suggest natural gas trucks have very high up-front costs—around $70,000 more than comparable diesel trucks. Maintenance costs for natural gas trucks are also difficult to calculate: they have been found to be as much as 29 percent greater than their diesel counterparts at one facility, and 6 percent at another, but these estimates are dated.

Yet natural gas historically has cost less than diesel as a fuel, and currently is much cheaper at a gasoline equivalent of $2.50 per gallon. As a result, natural gas trucks can still make economic sense under plausible, albeit optimistic, scenarios—by providing payback periods that might be acceptable to truck buyers, for example.

Solving the Chicken-or-Egg Problem

The biggest stumbling block to the introduction of a new fuel is generally the lack of infrastructure for refueling. Those who would build the infrastructure want to see many vehicles needing the fuel, but those who would buy the vehicles want to see the infrastructure in place first. For natural gas, it has been huge enough to have kept the general public out of the market. Between the compressors for the gas and the cooling units for the LNG, not to mention fuel storage and refueling, only fleet vehicles fueled at centralized facilities could make a go of it.

All this has been changing with the plunging price of natural gas. Companies with large holdings of natural gas wells and high production goals, like Chesapeake Energy, have been looking for outlets for selling their gas, and even to create new markets, with the increase in demand raising prices and increasing profits. Accordingly, some companies have been making plans to invest in infrastructure. Chesapeake Energy’s plans are the most impressive: they are building 150 LNG/CNG stations on interstates across the country, using Pilot J truck filling station land. Other companies are partnering to build and operate LNG “corridors” between some major cities to support heavy-duty truck traffic. Thus, this segment of the market could experience significant growth.

The Last Hurdle: Uncertain Environmental Benefits

With costs and infrastructure in their favor, LNG trucks face one more hurdle—their carbon footprint. Compared to diesel fuel’s lifecycle carbon emissions, those of LNG from conventional gas wells or from shale gas wells are smaller. But if the natural gas itself—methane—is not burned, it becomes a greenhouse gas 25 times more powerful than carbon dioxide over a 100-year period in the atmosphere. Calculating just how methane emissions compare with their carbon dioxide counterparts is tricky, though. Because methane lasts for far less time in the atmosphere, some researchers use a much higher factor in converting methane to its carbon dioxide equivalent. In addition, the amount of methane that escapes—is “fugitive,” in industry parlance—from gas wells is uncertain. According to the latest studies, putting together the short lifetime of methane and a high estimate for fugitive methane emissions can result in lifecycle emissions for LNG vehicles exceeding those of diesel. Until this issue is settled, the environmental benefits of natural gas vehicles are uncertain. (Resources For The Future, Alan J. Krupnick)