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FYI
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A test conducted by the EPA on a propane-fueled car revealed that net carbon
monoxide emissions were 93 percent less, hydrocarbons 73 percent less, and nitrogen oxides 53 percent less than federal emission standards for gasoline.
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(Source: Information provided by Texas Railroad Commission,
Alternative Fuels Research and Education Division, Austin.)
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A third way to reduce pollution from cars is to change to cleaner-burning
fuels. Alternative fuels have two advantages over conventional fuels: price and cleanliness. One disadvantage is that most alternative-fuel vehicles cannot
travel as far without refueling. For example, a gasoline-fueled vehicle able to travel 100 miles would travel only 85 miles on propane and 31 miles on
compressed natural gas (CNG) because the alternative fuels have lower energy content.* However, improvements in automobile manufacturing
technologies are increasing gas mileage for propane, methanol, and natural gas vehicles.
There are currently three different ways of powering cars: conventional
combustion engines, which can use a variety of fuels; electricity through charged batteries; and fuel cells, which use hydrogen electrons to power a battery.
A fuel cell is a foot-long tablet no thicker than a computer disk made up of two plates separated by a membrane. Either
hydrogen gas or hydrogen-rich fuels like methanol or gasoline flows through one plate, where electrons are stripped off
the hydrogen atoms with a catalyst, while air flows through the other. The hydrogen electrons flow through an
electrical circuit that powers the engine, while the hydrogen atoms themselves seep through the membrane, where they combine with the oxygen molecules in the air to form water.
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COMPARISON OF EMISSIONS FROM VEHICLES
USING DIFFERENT FUELS
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SO2
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NOX
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CO
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Fuel Cell Engines
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|
|
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Hydrogen Gas
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0
|
0
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0
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Natural Gas
|
2
|
52
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11
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Methanol
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2
|
39
|
8
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Combustion Engine
|
|
|
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Gasoline
|
48
|
205
|
700
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Diesel
|
48
|
350
|
870
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Battery-powered Electric Motor (emissions from generation of power to charge
battery)
|
145
|
143
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40
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Source: Anthony DePalma, "The Great Green Hope: Are Fuel Cells the
Key to Cleaner Energy?" The New York Times (October 8, 1997), C6.
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Note: All emissions in milligrams per mile.
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Fuel cell vehicles are cleaner because they produce much less heat and waste than do
conventional combustion engines. Instead, they produce water and only some heat.* Most of the major car companies have
invested in fuel cell technology.* Fuel cell technology does present challenges. Storing hydrogen gas is difficult, and is dangerous
should a leak occur. Using methanol is easier, but it takes up more room, is more costly, and produces more emissions.
Combustion engines can use a variety of fuels, including natural gas, propane,
methanol, gasoline, and diesel fuels. Vehicles powered by compressed natural gas or liquefied petroleum gas -- also known as propane -- are cleaner because they use a
closed-loop system: there is no evaporation or escape of uncombusted gas before it reaches the tailpipe. Propane-powered
vehicles emit even less nitrogen oxides than vehicles using natural gas. Another significant advantage of both
compressed natural gas and propane use is that both fuels eliminate the need for underground storage tanks. Texas
has had more than 15,000 reported cases of leaks from underground petroleum-storage tanks, leaks that often contaminate soil and water.*
A number of companies, including Honda and Toyota, now have cars on the market which are "hybrid" vehicles. These
vehicles use electricity during certain times, such as to start up the vehicle, and gasoline for highway driving. The miles
to the gallon that these vehicles offer are currently the best commercially available in the U.S.
The conversion of vehicles to alternative fuels might be beneficial to the state's economy, since Texas sits atop 27.5
percent of known natural gas reserves in the continental United States.* Propane is the most widely used alternative
fuel in Texas, the United States, and the world, and Texas produces more propane than any other state. More than 60
percent of propane comes from natural gas production; the remainder is derived from crude oil during the refining
process. Farmers and ranchers in Texas have long relied on propane to fuel agricultural vehicles, and rural Texans have used it for heating and cooking for over fifty years.*
At present, the major obstacles to the use of alternative fuels are: (1) the lack of an infrastructure for distributing them
to consumers, and (2) the range limitation, especially considering the distances between towns in West Texas and the
Panhandle. Unlike regular gasoline or diesel fuels, compressed natural gas is not available at refueling stations on every corner.
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FYI
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A diesel-fueled bus emits as much particulate matter as 500 gasoline-powered
automobiles
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(Source: GLO, Putting Together the Pieces: The Recapitalization of
the Texas Economy [January 1989], 25.)
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Another obstacle to the use of alternative fuels is the cost of converting an old
vehicle to run on an alternative fuel. The price tag for converting an average car to propane, which includes replacement of the fuel system and installation of new
electronics, is about $2,000.* Conversions to natural gas use is even a little more
expensive. Despite these costs, converting vehicles may be economical for some fleets in the long run because propane and natural gas are cheaper than gasoline
and because maintenance costs are generally lower over a three- to five-year period.
The Texas legislature created its own plan for alternative fuels by passing legislation in 1989 and 1991.* The legislation required state agencies, school districts with more than 50 buses, and all mass transit authorities in major urban areas
to purchase only those new vehicles capable of running on alternative fuels. Nonetheless, in 1995, the legislature
changed direction and replaced fuel standards with emission standards, allowing mass transit authorities and state
agencies to use any combination of fuel -- whether natural gas, liquid petroleum gas (propane), methanol, ethanol,
electricity, or low-sulfur diesel and reformulated gasoline -- with any kind of vehicle providing they met the LEV standards.* In addition, school districts were exempted altogether and only the four nonattainment areas were covered
under the Health and Safety Code, enforceable by the TCEQ. Other areas in the state are covered by the Texas Transportation Code.
Finally, in 1997, the legislature acted further, exempting mass transit authorities in 'moderate" nonattainment areas
such as the Beaumont-Port Arthur and Dallas-Fort Worth regions.* However, the decision by the EPA to switch
Dallas-Fort Worth to a serious nonattainment area makes the Texas Clean Fuels Program applicable to this region as well.
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