|A Natural Gas Vehicle of the
Natural gas has long been considered an alternative
fuel for the transportation sector. In fact, natural
gas has been used to fuel vehicles since the 1930's!
According to the Natural Gas Vehicle Coalition, there
are currently 150,000 Natural Gas Vehicles (NGVs) on
the road in the United States today, and more than 5
million NGVs worldwide. In fact, the transportation
sector accounts for 3 percent of all natural gas used
in the United States. In recent years, technology has
improved to allow for a proliferation of natural gas
vehicles, particularly for fuel intensive vehicle fleets,
such as taxicabs and public buses. However, virtually
all types of natural gas vehicles are either in production
today for sale to the public or in development, from
passenger cars, trucks, buses, vans, and even heavy-duty
utility vehicles. Despite these advances, a number of
disadvantages of NGVs prevent their mass-production.
Limited range, trunk space, higher initial cost, and
lack of refueling infrastructure pose impediments to
the future spread of natural gas vehicles.
Most natural gas vehicles operate using compressed
natural gas (CNG). This compressed gas is stored in
similar fashion to a car's gasoline tank, attached to
the rear, top, or undercarriage of the vehicle in a
tube shaped storage tank. A CNG tank can be filled in
a similar manner, and in a similar amount of time, to
a gasoline tank.
|Refueling an NGV
|Source: EREN - DOE
This natural gas fuels a combustion engine similar
to engines fueled by other sources. However, in a NGV,
several components require modification to allow the
engine to run efficiently on natural gas. In addition
to using CNG, some natural gas vehicles are fueled by
Liquefied Natural Gas (LNG). Some natural gas vehicles
that exist today are bi-fuel vehicles, meaning they
can use gasoline or natural gas, allowing for more flexibility
in fuel choice. Many of these vehicles, which were originally
gasoline only, have been converted to allow the vehicle
to run on either fuel. This conversion is costly, and
typically results in less efficient use of natural gas.
Why Natural Gas Vehicles?
There are many reasons why NGVs are increasing in abundance
and popularity. New, stringent federal and state emissions
laws require an improvement in vehicle emissions over
the foreseeable future. For example, the state of California
has some of the most stringent environmental standards,
many of which are currently unattainable with conventionally
fueled vehicles. Natural gas, being the cleanest burning
alternative transportation fuel available today, offers
an opportunity to meet these stringent environmental
In addition, natural gas is very safe. Being lighter
than air, in the event of an accident natural gas simply
dissipates into the air, instead of forming a dangerous
flammable pool on the ground like other liquid fuels.
This also prevents the pollution of ground water in
the event of a spill. Natural gas fuel storage tanks
on current NGVs are stronger and sturdier than gasoline
Natural gas is also an economic alternative to gasoline
and other transportation fuels. Traditionally, natural
gas vehicles have been around 30 percent cheaper than
gasoline vehicles to refuel, and in many cases the maintenance
costs for NGVs is lower than traditional gasoline vehicles.
In addition to being economic, many proponents of NGVs
argue that a transportation sector more reliant on domestically
abundant natural gas will decrease the U.S. dependence
on foreign oil - allowing for a more secure, safer energy
supply for the country.
|A 'Clean Air' Natural Gas Bus
|Source: Duke Energy
Gas Transmission Canada
The Environmental Benefits of NGVs
One of the primary reasons for pursuing alternative
fueled vehicle technology is to decrease environmentally
harmful emissions. It is estimated that vehicles on
the road account for 60 percent of carbon monoxide pollution,
29 percent of hydrocarbon emissions, and 31 percent
of nitrogen oxide (NOx) emissions in the United States.
All of these emissions released into the atmosphere
contribute to smog pollution, and increase the levels
of dangerous ground level ozone. Vehicles also account
for the emission of over half of all dangerous air pollutants,
and around 30 percent of total carbon emissions in the
U.S., contributing to the presence of 'greenhouse gases'
in the atmosphere. The environmental effects of NGVs
are much less detrimental than traditionally fueled
vehicles. More information on environmental standards is availbale at the Environmental Protection Agency (EPA).
Natural gas vehicles, when designed to run on natural
gas alone, are among the cleanest vehicles in the world.
In fact, the Honda Civic GX, released in 1997, has the
cleanest internal combustion engine ever commercially
produced. This natural gas powered automobile emits
so few pollutants that in some large cities the emissions
from the car are cleaner than the air surrounding it!
California, with some of the tightest clean air standards
anywhere in the United States, has recognized selected
natural gas vehicles as meeting and exceeding its most
stringent standards, including low-emission vehicle
(LEV), ultra-low emission vehicle (ULEV), and super-low
emission vehicle (SULEV) standards.
|Honda Civic GX - Super Clean
|Source: AFDC - DOE
Natural gas vehicles are much cleaner burning than traditionally
fueled vehicles due to the chemical composition of natural
gas. While natural gas is primarily methane, gasoline
and diesel fuels contain numerous other harmful compounds
that are released into the environment through vehicle
exhaust. While natural gas may emit small amounts of
ethane, propane, and butane when used as a vehicular
fuel, it does not emit many of the other, more harmful
substances emitted by the combustion of gasoline or
diesel. These compounds include volatile organic compounds,
sulfur dioxide, and nitrogen oxides (which combine in
the atmosphere to produce ground level ozone), benzene,
arsenic, nickel, and over 40 other substances classified
as toxic by the EPA.
Dedicated NGVs also produce, on average, 70 percent
less carbon monoxide, 87 percent less non-methane organic
gas, and 87 percent less NOx than traditional gasoline
For more information on the environmental benefits
of natural gas vehicles, visit the Natural
Gas Vehicle Coalition.
Who Uses Natural Gas Vehicles?
Natural gas vehicles as they exist today are best suited
for large fleets of vehicles that drive many miles a
day. Taxicabs, transit and school buses, airport shuttles,
construction vehicles, garbage trucks, delivery vehicles,
and public works vehicles are all well suited to natural
gas fueling. Because these vehicles are centrally maintained
and fueled, it is economical and beneficial to convert
to natural gas.
|Natural Gas Powered Public Transit
The primary impediments to the public proliferation
of NGVs include the high initial cost, limited refueling
infrastructure, and automobile performance characteristics.
NGVs, despite being cheaper to refuel and maintain,
are more expensive initially than their gasoline powered
counterparts. However, as the technology becomes more
advanced, the cost of manufacturing these vehicles should
drop, which may then be passed along to the consumers.
In terms of refueling infrastructure, there are currently
around 1,500 natural gas refueling stations in the U.S.,
over half of which are open to the public. Although
this is a small fraction of the number of gasoline fueling
stations in the country, as environmental standards
and government incentives for NGVs increase, supplying
natural gas as a vehicular fuel will become increasingly
While driving range, storage space, and initial cost
are currently preventing the mass production of dedicated
natural gas vehicles (which in turn is preventing the
expansion of public natural gas fueling stations), it
is expected that with improved technology, research,
and infrastructure, the use of NGVs in non-fleet settings
will increase in the future. Natural gas vehicles present
an exciting opportunity to reduce the damage of one
of our most polluting sectors.
|NGV of the Future?
For more information on Natural Gas Vehicles, please
visit these websites: