One problem that is plaguing today’s air quality is automobile emissions. Emissions from a single car is not that great, but with the number of cars in the United States as high as it is, and increasing at the rate it is, the personal automobile is the single most polluter in cities across America. “Driving a private car is probably a typical citizen’s most polluting daily activity.”
Burning fuel in an engine produces the power needed to get a car moving. Pollution from cars is formed by the by-products of the combustion process, known as exhaust, and from the evaporation of fuel itself. The gasoline and diesel fuels that are used to supply power to the engine are mixtures of hydrocarbons. Hydrocarbons are compounds made up of carbon and hydrogen atoms.
In a “perfect” combustion process, the oxygen in the air would convert all the hydrogen in the fuel to water and all the carbons to carbon dioxide. The nitrogen in the air would remain unaffected.
Ideal Combustion:
Fuel (hydrocarbons) + Air (oxygen and nitrogen) –> Carbon Dioxide (CO2) + Water (H2O) + unaffected nitrogen
But in reality, the combustion process isn’t “perfect” and does not convert all the hydrocarbons to water and carbon dioxide. The automobile engines emit several types of pollutants.
Actual Combustion:
Fuel + Air –> unburned hydrocarbons + Nitrogen Oxides (NOX) + Carbon Monoxide (CO) + CO2 + H2O
When unburned hydrocarbons react with nitrogen oxides and sunlight, ground-level ozone is formed, which is a major component of smog. Although ozone (O3) in the upper atmosphere is natural and protects life on earth by filtering out ultraviolet radiation, at ground level, ozone is a health problem. “It irritates the eyes, damages the lungs, and aggravates respiratory problems.” Ozone is also the most widespread urban air pollution problem.
Nitrogen oxides are formed under the high pressure and temperature conditions in the engine. Nitrogen oxides help form ozone and contribute to the formation of acid rain. Carbon monoxide occurs when carbon in the fuel is “partially oxidized, rather than fully oxidized to carbon dioxide.” This is an example of the incomplete combustion.
Carbon monoxide is a colorless, odorless, and poisonous gas. It has been long recognized as a serious problem to one’s health. Lawmakers have attempted to remedy this issue.
Another way emissions are extracted into the air is by way of fuel evaporation (see diagram). With the advances of controls of automobile emissions, fuel evaporation is rising as the majority of pollution. There are four ways in which fuel evaporation occurs: diurnal, running losses, hot soak, and refueling.
Gasoline evaporation increases as the temperature increases with the day, heating the fuel tank and venting gasoline vapors. This is called diurnal evaporation. Running losses occur as the car is running. The hot engine and exhaust system can allow for gasoline vapor release. Hot soak evaporation occurs as the car is cooling down. After the engine is shut off, the engine remains hot enough to release gasoline vapors. The gasoline tank is always filled with gasoline vapor. When the attendant refuels the gas tank, these vapors can exit and enter the atmosphere. This is refueling evaporation.
The EPA, the Environmental Protection Agency, recognized automobile emissions were going to be a problem in 1970, when the government passed the Clean Air Act of 1970 into law. This gave the EPA authority to regulate motor vehicle pollution. The EPA, since 1970, has progresses to become stingier as the years went on. EPA standards dictate how much pollution automobiles may emit, but the automakers are the ones who decide how to achieve such standards.
In the early 1970’s, automakers installed a catalytic converter that was designed to convert carbon monoxide to carbon dioxide. These converters reduce carbon monoxide emissions by as much as eighty percent.
In the past decade, the federal government required gasoline to be less volatile in the summer, for the reason vapors would not escape into the air and create ground-level ozone. To promote better fuel combustion, oxygen-containing compounds may be added to gasoline. This practice is implemented where carbon monoxide is known to be a serious problem. Other changes in the composition of gasoline, such as reducing benzene, toluene, and xylene, reduce ozone-forming pollutants.
As the EPA looks to the future with the automobile emissions problem, they foresee a switch to fuels that are cleaner than today’s gasoline. There are several choices including alcohols, natural gas, propane and electricity. These fuels are cleaner due to the fact that they do not contain toxics, e.g. benzene, and because their simple compounds do not yield complex combustion by-products.
I feel a move to ethanol based fuel would create a better situation for the world. Although the ideal scenario would be to drop oil as our main fuel for such things as automobiles, it would create economic stress on many countries that depend upon their sale of oil. Another option I would conclude with implementing would be to add yet another catalyst to the engine that would completely combust the hydrocarbons and leave the nitrogen unobstructed. This, I feel, would abolish the problem that occurs when the nitrogen forms nitrogen oxides, and allows oil to still be used as a major financial backbone in the world. That is, until oil runs out…