environmental facts
CONVERSION OF MOTOR VEHICLES
TO GASEOUS FUEL TO REDUCE AIR POLLUTION
Introduction
Further substantial reduction in air pollutant emissions
from new motor vehicles powered by gasoline engines is
expected by the mid-19 70's, but public demand for air quality
improvement in certain metropolitan areas has focused on the
possibility of converting vehicles already in use in such
areas to gaseous fuels.
Conclusions of the Environmental Protection Agency
EPA recommends conversion of existing vehicles for
fleet-operated vehicles in metropolitan areas in which
(a) logistical and economic considerations are favorable in
terms of availability of fuel and conversion equipment, and
(b) where major air pollution problems are attributable to
motor vehicle use.
What Gaseous Fuels Can Be Used for Automobiles?
Liquefied Petroleum Gas (LPG), a by-product in natural
gas processing and petroleum refining, has been used for
many years and is available in limited quantities in urban
areas. About 300,000 LPG vehicles are now in operation.
Natural gas also is used as a motor fuel and has
greater capabilities than LPG for reducing emissions.
It is used in two forms. Liquefied Natural Gas (LNG) and
Compressed Natural Gas (CNG). More than 4,000 natural gas-
fueled vehicles, most of them using CNG, are operated
experimentally in the United States.
Are Supplies of Gaseous Fuels Adequate?
It is likely that the demand for LPG will exceed the
available supply and boost prices. This, in turn could^
stimulate the refining industry to increase LPG production
at the expense of gasoline. Refinery-produced LPG is the
only gaseous fuel with a sufficiently adequate potential
source of supply to permit its use in conversion of a
TED S; ENVIRONMENTAL PROTECTION AGENCY • WASHINGTON. D.C. 2046(1
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large number of motor vehicles. Deducing lead levels in
gasoline could increase the supply of LPG as a by-product
under a modified refining process.
Severe shortages of natural gas exist in many marketing
areas. In considering conversion feasibility, each citizen
should assess his community's situation as to availability
of natural gas fuel.
It must be emphasized that if natural gas is diverted
from electric power generation to supply large numbers
of automobiles, increased power plant emissions of sulfur
oxides (SOx) from substitute fuels could more than offset
the benefits from reduced carbon monoxide (CO) emissions.
Also, conversion of space heating to natural gas could
produce important reductions in SOX, nitrogen oxides (NOX)
and particulate emissions, and thus be more effective in
improving overall air quality than would conversion of
fleet vehicles.
Availability of Adequate Engines and Fuel Systems for
Gaseous Fuels
Engines designed for gaseous fuel are not produced by
automobile manufacturers. But components are available for
converting auto engines to gaseous fuel. Some systems are
•more successful than others. While gaseous-gasoline, dual-
fuel systems greatly increase driving range and provide a
reserve fuel supply, they require compromises from perfor-
mance, fuel consumption and emission standpoints.
Reduction In Emissions From Automobiles Using Gaseous Fuels
There are inconsistencies in test data but here are
two examples:
1. Data from eight 1968-69 model gasoline vehicles
converted to LPG dual-fuel usage show the average emissions
reduction is 25 percent for hydrocarbons, 69 percent for
carbon monoxide and 13 percent for oxides of nitrogen.
Drivability impairment was noticeable but not critical.
2. Twenty 1970 model General Services Administration
vehicles, converted to full-time LPG operation, approached
1975 Federal emission standard levels for new automobiles.
The vehicles were tested before and after conversion.
Emission reductions were 81 percent for hydrocarbons,
86 percent for carbon monoxide and 64 percent for
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oxides of nitrogen. Drivability effects ranged from
barely noticeable to hazardous.
Some Operational, Handling and Safety^^robleins of Gaseous
Fuels
Vehicles converted to LPG have a range of 220 miles.
Those converted to LNG have a range of 240 miles. These
ranges compare favorably with gasoline-fueled passenger cars
Range of vehicles fueled with CNG is 70 to 100 miles.
A gaseous fuel tank occupies about one-third of a car's
trunk space.
Liquefied petroleum gas is available in most areas
from distributors who supply it for heating. Local
safety regulations, however, often confine distributors
to outlying areas so that refueling becomes inconvenient.
Both compressed and liquefied natural gases are avail-
able only at a limited number of locations. This is due
largely to the expense of liquiefaction at high-pressure
compressing plants.
Gasoline is a hazardous product but its distinctive
odor and usually visible evidence of leakage have held
accidents to a minimum considering its wide use. Gaseous
fuels are odorless, but odorants can and should be added
to both LPG and CNG. An odorant is being developed for
LNG.
Stringent local safety laws now in effect reflect
a general view that a safety problem exists with gaseous
fuels. But enough experience has now been accumulated with
gaseous-fueled vehicles to demonstrate that the fuels can
be used safely under closely-controlled fleet-operation.
Costs of Gaseous Fuels and Conversion
In the average market, cost of gaseous fuel per
operating mile is somewhat lower than the cost of gasoline,
but more expensive than diesel oil. Vehicle conversion
costs are about $300 for LPG and CNG kits and $700 for
LNG.
Many LPG vehicles have been converted on the basis
of economics alone. In fleet applications, however,
operating costs with natural gas can be competitive with
gasoline because of reduced maintenance costs.
July 1972
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ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PUBLIC AFFAIRS
Washington. D.C. 20460
POSTAGE AND FEES PAID
ENVIRONMENTAL PROTECTION AGENCY
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