. . . Natural Gas Powered Trucks
For decades, natural gas has provided clean power to thousands of households and businesses nationwide. Today, more than 1,000 vehicles traveling U.S. roads are powered by natural gas that is cooled to a liquid — liquefied natural gas (LNG). LNG results when natural gas is cooled to temperatures of 260 degrees below zero, thus producing a viable vehicle fuel used mainly in heavy-duty trucks and buses.
LNG is odorless, colorless, non-corrosive, and non-toxic. When extracted from underground reserves, natural gas is composed of approximately 90% methane. During the liquefaction process, oxygen, carbon dioxide, sulfur compounds, and water are removed, purifying the fuel and increasing its methane content to almost 100%. As a result, LNG-fueled vehicles can offer significant emissions benefits compared with older diesel-powered vehicles, and can significantly reduce carbon monoxide and particulate emissions as well as nitrogen oxide emissions.
Availability of Natural Gas
To date, LNG vehicles have primarily been used by fleet managers. Therefore, most LNG refueling stations are located at heavy-duty vehicle fleet operations not open to the public. This is due in part to the various safety issues.
In
conjunction with plans to expand LNG
use in long-haul trucking in the West,
efforts are under way to improve access to
LNG fueling stations in that region. For
example, California expects to fund the development of public-access facilities.
Such a program is aimed at helping heavy duty
trucks switch to natural gas.
LNG’s complex onboard storage system
does not make it a viable fuel for light-duty vehicles. It is, however, replacing
diesel in many heavy-duty trucks
and buses and many new gas-fueled
locomotives. For example, some trash
trucks in San Diego and some long haul
trucks in Los Angeles and Sacramento
use LNG fuel. In addition,
the number of LNG-fueled transit
buses is expanding rapidly as many
cities try to reduce air pollution levels.
Bus fleets in Orange County,
California, and Phoenix, Arizona, are
fueled entirely by LNG.
Affordability of Natural Gas
Depending on the quantity of vehicles purchased and the equipment used, LNG heavy-duty trucks or buses can cost an additional $30,000 to $50,000. Industry experts expect these costs to drop as market development and vehicle production rises. Fuel dispensing and fuel storage required for LNG typically costs $15,000 to $22,000 per vehicle.
In addition, LNG's price is highly dependent on geographic location, purity of feedstock, transportation costs, and quantity of fuel purchased, but LNG's cost per mile is generally less than or equal to the price of diesel.
Performance of Natural Gas
There are no discernible differences in LNG vehicle performance, operation, and utility when compared with diesel. The high ignition quality of LNG is similar to that of diesel, providing for similar durability and engine life overall.
Safety of Natural Gas
A LNG vehicle parked indoors and unmoved for a week or more will vent a flammable gas mixture that could catch fire in the vicinity of an ignition source. To address this safety issue, LNG use should be restricted to frequently driven fleet vehicles or to vehicles stored outdoors. Only trained personnel should service the vehicles. In addition, refueling vehicles with LNG requires training because of the fuel’s ultra low temperature. It can cause frostbite if it contacts skin. Since LNG is almost 100% methane -- a greenhouse gas -- it can also contribute to global climate change if accidentally released into the air. Methane is slightly soluble in water and, under certain environmental conditions (anaerobic), it does not bio-degrade. If excess amounts accumulate, the gas can bubble from the water, possibly creating a risk of fire or explosion.
Maintenance of Natural Gas Vehicles
LNG’s cleaner burning characteristics can result in longer engine life and reduced maintenance costs. Using LNG eliminates the need for periodic tank inspections. In addition, some maintenance savings are anticipated for vehicles using LNG when compared with gasoline powered vehicles because of the reduced frequency of oil changes. Because of the fuel’s below freezing temperatures, only trained personnel should maintain LNG vehicles.
Emissions Characteristics
Actual emissions will vary with engine design; these numbers reflect the potential reductions offered by LNG relative to diesel.
Production of half particulate matter
of average diesel vehicles can significantly reduce carbon
monoxide emissions.
Reductions of nitrogen oxide and
volatile organic hydrocarbon emissions
by 50% or more.
Potential reductions in carbon
dioxide emissions of 25%
depending on the source of the natural
gas.
Drastic reductions in toxic and carcinogenic
pollutants.
Increase in methane emissions.
* Estimates are based on theLNG's inherently "cleaner" chemical properties with an engine that takes full advantage of these fuel properties.
