A Cleaner Breath
Pollution has cast its ominous shadow across the world. Two of the pollutants that are emitted by automobiles are hydrocarbons (unburned fuel) and nitric oxide. When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which the NO is converted to nitrogen dioxide (NO2). NO2 is a brown gas and at sufficiently high levels can contribute to urban haze, hence the smog that laypeople in big cities complain about.
However, a more serious problem is that NO2 can absorb sunlight and break apart to produce oxygen atoms that combine with the O2 in the air to produce ozone (O3). Ozone is a powerful oxidizing agent, and a toxic gas. In North America elevated levels of tropospheric ozone cause several billion dollars per year damage to crops (45 million/per year in Ontario), structures, forests, and human health. It is believed that the natural level of ozone in the clean troposphere is 10 to 15 parts-per-billion. Due to the increasing concentrations of hydrocarbons and NO2 in the atmosphere, scientists have found that ozone levels in "clean air" are now approximately 30 parts-per-billion (Atmospheric Chemistry). Even if the sky above you seems to be clear and blue, smog is everywhere. “It is a choking sensation every time one ventures out into the streets” (Smog).
What we typically call smog is primarily made up of ground-level ozone. Ozone can be good or bad depending on where it is located. Ozone in the stratosphere high above the Earth protects human health and the environment, but ground-level ozone is the main harmful ingredient in smog. Ground-level ozone is produced by the combination of pollutants from many sources, including smokestacks, cars, paints, and solvents. For example, when a car burns gasoline, this process releases exhaust fumes and these smog-forming pollutants rise into the sky. When fossil fuels (e.g., gasoline) are burned, a variety of pollutants are emitted into the earth's troposphere, the region of the atmosphere in which we live.
Weather and geography determine where smog goes and how bad it is. When temperature inversions occur, warm air stays near the ground instead of rising. If winds are calm, smog may stay in place for days at a time. As traffic and other sources add more pollutants to the air, the smog gets worse. Often, wind blows smog-forming pollutants away from their sources. The smog-forming reactions take place while the pollutants are being blown through the air by the wind. This explains why smog is often more severe miles away from the source of the smog-forming pollutants than it is at the source. The smog-forming pollutants literally cook in the sky, and if it's hot and sunny, smog forms more easily. Just as it takes time to bake a cake, it takes time to cook up smog. It takes several hours from the time the pollutants enter into the air until the smog becomes harmful.
Since smog is blind, nothing stops smog and air pollutants from crossing county and state lines. When a metropolitan area covers more than one state (for instance, the New York metropolitan area includes parts of New Jersey and Connecticut), their governments and air pollution control agencies must cooperate to solve their problem. Governments on the East Coast from Maine to Washington, D.C. are working together in an interstate effort to reduce the area's smog problem.
In 1990, the Clean Air Act was passed in an effort to clean up our planet. Here's how the Clean Air Act reduces pollution from criteria air pollutants, including smog: First, The Environmental Protection Agency, or EPA, and state governors cooperated to identify “nonattainment” areas for each criteria air pollutant. These are areas where the air pollutants usually exceed the national standards. Then, the EPA classified the nonattainment areas according to how badly polluted the areas are. There are five classes of nonattainment areas for smog, ranging from marginal, relatively easy to clean up quickly, to extreme, in which a large amount of work and a time are needed to clean up (Cleaner Emissions). The Clean Air Act uses this new classification system to tailor clean-up requirements to the severity of the pollution and set realistic deadlines for reaching clean-up goals. If deadlines are missed, the law allows more time to clean up, but usually a nonattainment area that has missed a clean-up deadline will have to meet the stricter clean-up requirements set for more polluted areas. Not only must nonattainment areas meet deadlines, states with nonattainment areas must show the EPA that they are making moves to clean up the air before the deadline, making reasonable further progress. States will usually do most of the planning for cleaning up criteria air pollutants, using the permit system to make sure power plants, factories and other pollution sources meet their clean-up goals. The comprehensive approach to reducing criteria air pollutants taken by the 1990 Act covers many different sources and a variety of clean-up methods. Many of the smog clean-up requirements involve motor vehicles (cars, trucks, buses). Also, as the pollution gets worse, pollution controls are required for smaller sources. However the EPA recently reviewed the current air quality standards for ground-level ozone, or smog, and particulate matter (or PM). Based on new scientific evidence, revisions have been made to both standards. At the same time, EPA is developing a new program to control regional haze, which is largely caused by particulate matter. Under the Clean Air Act, the EPA is required to study whether and how to reduce hazardous air pollutants from small neighbourhood polluters such as auto paint shops, print shops, etc. The agency will also have to look at air pollution after the first round of regulations to see whether the remaining health hazards require further regulatory action.
Cars, trucks, buses and other mobile sources release large amounts of hazardous air pollutants like formaldehyde and benzene. Cleaner fuels and engines and making sure that pollution control devices work should reduce hazardous air pollutants from mobile sources.
Many provisions and changes have been added to the Clean Air Act. For instance, the Bhopal tragedy inspired the 1990 Clean Air Act requirement that factories and other businesses develop plans to prevent accidental releases of highly toxic chemicals. The Act establishes the Chemical Safety Board to investigate and report on accidental releases of hazardous air pollutants from industrial plants. The Chemical Safety Board will operate like the National Transportation Safety Board (NTSB), which investigates plane and train crashes (Clean Air Act).
In addition to clean up efforts, alternative power sources are being examined, and many have already gone into effect. One such alternate source for the fuelling of automobiles is electricity. Electricity is unique among the alternative fuels in that mechanical power is derived directly from it, whereas the other alternative fuels release stored chemical energy through combustion to provide mechanical power. Batteries commonly provide electricity used to power vehicles, but fuel cells are also being explored. Batteries are energy storage devices, but unlike batteries, fuel cells convert chemical energy to electricity. A large number of various types of batteries are being tested for use. Some of the technologies being used or evaluated include lead-acid, nickel cadmium, nickel iron, nickel zinc, nickel metal hydride, sodium nickel chloride, zinc bromine, sodium sulphur, lithium, zinc air, and aluminium air. The first benefit of using electric fuel is that you are not polluting the environment. Although, some people argue that there are some emissions that can be attributed to EVs, or the emissions that are generated in the electricity production process at the power (How Fuel Cell Works).
Another way alternative forms of energy are being used is in the use of a biodiesel fuel. Biodiesel (mono alkyl esters) is a cleaner-burning diesel fuel made from natural, renewable sources such as vegetable oils. Just like petroleum diesel, biodiesel operates in combustion-ignition engines. The use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter. It also decreases the solid carbon fraction of particulate matter (since the oxygen in biodiesel enables more complete combustion to CO2), eliminates the sulphate fraction, as there is no sulphur in the fuel, while the soluble, or hydrocarbon, fraction stays the same or is increased. Therefore, biodiesel works well with new technologies such as catalysts, which reduce the soluble fraction of diesel particulate but not the solid carbon fraction, particulate traps, and exhaust gas recirculation, or a potentially longer engine life due to less carbon (Biodiesel Fuel).
Another alternate fuel is petroleum, but there is a growing concern that there is too limited a supply to serve as a cure to the world’s problems. However, liquefied petroleum gas (LPG) consists mainly of propane, propylene, butane, and butylenes in various mixtures. It is produced as a by-product of natural gas processing and petroleum refining (Alternative Fuels). Propane is also a popular, cleaner fuel resource. With propane’s simple molecular composition, propane-fuelled vehicles emit significantly lower levels of carbon monoxide, hydrocarbons and nitrogen oxides than gasoline-fuelled vehicles. The level of air-toxic emissions from propane-fuelled vehicles is also low. According to the National Propane Gas Association, U.S.A., spark plugs from a propane vehicle last from 80,000 to 100,000 miles and propane engines can last two to three times longer than gasoline or diesel engines (Alternative Fuels).
Ethanol has also been explored as a cleaner form of fuel. Ethanol (ethyl alcohol, grain alcohol, ETOH) is a clear, colourless liquid with a characteristic, agreeable odour. Two higher blends of ethanol, E-85 and E-95 are being explored as alternative fuels in demonstration programs. Ethanol is also made into ether, ethyl tertiary-butyl ether (ETBE) that has properties of interest for oxygenated gasoline and reformulated fuels. The environmental benefits of ethanol include: 1. 10% ethanol blends reduce carbon monoxide better than any other reformulated gasoline blend. 2. Ethanol is a safe replacement for toxic octane enhancers in gasoline such as benzene, toluene and xylene. 3. ETBE lowers gasoline volatility and is, thus, particularly effective in reducing VOC emissions from automobiles (Alternative Fuels).
Also, Methanol is widely used as a cleaner fuel source. Methanol (CH3OH) is an alcohol fuel. As engine fuels, ethanol and methanol have similar chemical and physical characteristics. Methanol is methane with one hydrogen molecule replaced by a hydroxyl radical. It is produced from natural gas in production plants with 60% total energy efficiency. Methanol can be made with any renewable resource containing carbon such as seaweed, waste wood and garbage. This is a promising alternative, with a diversity of fuel applications with proven environmental, economic and consumer benefits. It is widely used today to produce the oxygenate MTBE added to cleaner burning gasoline. Cars, trucks and buses running millions of miles on methanol have proven its use as a total replacement for gasoline and diesel fuels in conventional engines. Methanol offers the greatest hope for early and broad introduction of fuel cells that will make the widespread use of electric vehicles practical within the next few years. Whether reformed to provide hydrogen for conventional fuel cells or used directly in the latest liquid fed cells, methanol will overcome the greatest remaining obstacle to commercialisation, by offering the only economical way to transport and store the hydrogen needed for fuel cells. Methanol fuel cells will greatly reduce carbon dioxide emissions for vehicles and virtually eliminate smog and particulate pollution (Alternative Fuels).
Gasoline No. 2 Diesel Biodiesel (B20) Electricity Ethanol (E85) Hydrogen Liquified Petroleum Gas (LPG) Methanol (M85)
Chemical Structure C4 to C 12 C10 to C 20 Methyl esters of C16 to C 18 fatty acids N/A CH3CH2OH H2 C3H8 CH3OH
Octane Number 86 to 94 8 to 15 ~25 N/A 100 130+ 104 100
Main Fuel Source Crude Oil Crude Oil Soy bean oil, waste cooking oil, animal fats, and rapeseed oil Coal; however, nuclear, natural gas, hydroelctric, and renewable resources can also be used. Corn, Grains, or agricultural waste Natural Gas, Methanol, and other energy sources. A by-product of petroleum refining or natural gas processing Natural gas, coal, or, woody biomass
Energy Ratio Compared to Gasoline 1.1 to 1 or 90% (relative to diesel) 1.42 to 1 or 70% 1.36 to 1 or 74% 1.75 to 1 or 57%
Physical State Liquid Liquid Liquid Electricity Liquid Compressed Gas or Liquid Liquid Liquid
Environmental Impacts of Burning Fuel Produces harmful emissions; however, gasoline and gasoline vehicles are rapidly improving and emissions are being reduced. Produces harmful emissions; however, diesel and diesel vehicles are rapidly improving and emissions are being reducedespecially with after-treatment devices. Reduces particulate matter and global warming gas emissions compared to conventional diesel; however, NOx emissions may be increased. EVs have zero tailpipe emissions; however, some amount of emissions can be contributed to power generation. E-85 vehicles can demonstrate a 25% reduction in ozone-forming emissions compared to reformulated gasoline. Zero regulated emissions for fuel cell-powered vehicles, and only NOx emissions possible for internal combustion engines operating on hydrogen. LPG vehicles can demonstrate a 60% reduction in ozone-forming emissions compared to reformulated gasoline. M-85 vehicles can demonstrate a 40% reduction in ozone-forming emissions compared to reformulated gasoline.
Source: US Department of Energy
The Quality of the air we breathe, unfortunately, now depends on the human populous. We know the problems that exist and how they are caused. Regulatory steps have been taken, however, it is believed that stronger measures must be taken with the ever-growing industry and mobilization (more automobiles) of the world. It is up to the people to take responsibility to keep the world’s air clean enough to breathe. Cleaner emissions, reduction of automobiles on the roads, and cleaner burning fuels are important factors that we the inhabitants of the world must strive for so that our Earth will be a liveable place.
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