Vehicle emissions control


Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines. The primary emissions studied include hydrocarbons, volatile organic compounds, carbon monoxide, carbon dioxide, nitrogen oxides, particulate matter, and sulfur oxides. Starting in the 1950s and 1960s, various regulatory agencies were formed with a primary focus on studying the vehicle emissions and their effects on human health and the environment. As the world's understanding of vehicle emissions improved, so did the devices used to mitigate their impacts. In the United States, the regulatory requirements of the Clean Air Act, which was amended many times, greatly restricted acceptable vehicle emissions. With the restrictions, vehicles started being designed more efficiently by utilizing various emission control systems and devices which became more common in vehicles over time.

Types of emissions

Emissions of many air pollutants have been shown to have variety of negative effects on public health and the natural environment. Emissions that are principal pollutants of concern include:
  • Hydrocarbons – A class of burned or partially burned fuel, hydrocarbons are toxins. Hydrocarbons are a major contributor to smog, which can be a major problem in urban areas. Prolonged exposure to hydrocarbons contributes to asthma, liver disease, lung disease, and cancer. Regulations governing hydrocarbons vary according to type of engine and jurisdiction; in some cases, "non-methane hydrocarbons" are regulated, while in other cases, "total hydrocarbons" are regulated. Technology for one application may not be suitable for use in an application that has to meet a total hydrocarbon standard. Methane is not directly toxic, but is more difficult to break down in fuel vent lines and a charcoal canister is meant to collect and contain fuel vapors and route them either back to the fuel tank or, after the engine is started and warmed up, into the air intake to be burned in the engine.
  • Volatile organic compounds – Organic compounds which typically have a boiling point less than or equal to 250 °C; for example chlorofluorocarbons and formaldehyde.
  • Carbon monoxide – A product of incomplete combustion, inhaled carbon monoxide reduces the blood's ability to carry oxygen; overexposure may be fatal.
  • Nitrogen oxides – Generated when nitrogen in the air reacts with oxygen at the high temperature and pressure inside the engine. NOx is a precursor to smog and acid rain. NOx includes NO and NO2. NO2 is extremely reactive. NOx production is increased when an engine runs at its most efficient operating point, so there tends to be a natural tradeoff between efficiency and control of NOx emissions. It is expected to be reduced drastically by use of emulsion fuels.
  • Particulate matter – Soot or smoke made up of particles in the micrometre size range: Particulate matter causes negative health effects, including but not limited to respiratory disease and cancer. Very fine particulate matter has been linked to cardiovascular disease.
  • Sulfur oxide – A general term for oxides of sulfur, which are emitted from motor vehicles burning fuel containing sulfur. Reducing the level of fuel sulfur reduces the level of sulfur oxides emitted from the tailpipe.

    History

Throughout the 1950s and 1960s, various federal, state and local governments in the United States conducted studies into the numerous sources of air pollution. These studies ultimately attributed a significant portion of air pollution to the automobile, and concluded air pollution is not bounded by local political boundaries. At that time, such minimal emission control regulations as existed in the U.S. were promulgated at the municipal or, occasionally, the state level. The ineffective local regulations were gradually supplanted by more comprehensive state and federal regulations. By 1967 the State of California created the California Air Resources Board, and in 1970, the federal United States Environmental Protection Agency was established. Both agencies, as well as other state agencies, now create and enforce emission regulations for automobiles in the United States. Similar agencies and regulations were contemporaneously developed and implemented in Canada, Western Europe, Australia, and Japan.
The first effort at controlling pollution from automobiles was the PCV system. This draws crankcase fumes heavy in unburned hydrocarbons – a precursor to photochemical smog – into the engine's intake tract so they are burned rather than released unburned from the crankcase into the atmosphere. Positive crankcase ventilation was first installed on a widespread basis by law on all new 1961-model cars first sold in California. The following year, New York required it. By 1964, most new cars sold in the U.S. were so equipped, and PCV quickly became standard equipment on all vehicles worldwide.
The first legislated exhaust emission standards were promulgated by the State of California for 1966 model year for cars sold in that state, followed by the United States as a whole in model year 1968. Also in 1966, the first emission test cycle was enacted in the State of California measuring tailpipe emissions in PPM. The standards were progressively tightened year by year, as mandated by the EPA.
By the 1974 model year, the United States emission standards had tightened such that the de-tuning techniques used to meet them were seriously reducing engine efficiency and thus increasing fuel usage. The new emission standards for 1975 model year, as well as the increase in fuel usage, forced the invention of the catalytic converter for after-treatment of the exhaust gas. This was not possible with existing leaded gasoline, because the lead residue contaminated the platinum catalyst. In 1972, General Motors proposed to the American Petroleum Institute the elimination of leaded fuels for 1975 and later model year cars. The production and distribution of unleaded fuel was a major challenge, but it was completed successfully in time for the 1975 model year cars. All modern cars are now equipped with catalytic converters to further reduce vehicle emissions.
Leading up to the 1981 model year in the United States, passenger vehicle manufactures were faced with the challenges in its history of meeting new emissions regulations, how to meet the much more restrictive requirements of the Clean Air Act per the 1977 amendment. For example: to meet this challenge, General Motors created a new "Emissions Control Systems Project Center" first located at the AC Spark Plug Engineering Building in Flint, Michigan. Its purpose was to "Have overall responsibility for the design and development of the carborated and fuel injected closed loop 3-way catalyst system including related electronic controls, fuel metering, spark control, idle speed control, EGR, etc. currently planned through 1981."
In 1990, the Clean Air Act was amended to help further regulate harmful vehicle emissions. In the amendment, vehicle fuel regulations became more stringent by limiting how much sulfur was allowed in diesel fuel. The amendments also required a procedural change for the creation of gasoline to ensure there are less emissions of hydrocarbons, carbon monoxide, nitrogen oxides, particulate matter, and volatile organic compounds. Changes made to the CAA also required the use of oxygenated gasoline to reduce CO emissions.
Throughout the years, the Environmental Protection Agency continued to implement new regulations to reduce harmful emissions for vehicles. Some of the more important update standards are as follows.
  • 1983: For areas with big pollution problems, Inspection and Maintenance programs were created, meaning vehicles would need to get tested for emissions.
  • 1985: Changed the allowable amount of gasoline to 0.1 grams per gallon.
  • 1991: Lowered the allowable emissions of HC and for vehicle tailpipes.
  • 1993: Began developing new vehicle technology to help triple the fuel economy in family sedans, thus reducing harmful emissions.
  • 1996: Lead in gasoline officially banned. New regulations created with intentions of innovating vehicle design to be cleaner for the environment and improving engine performance.
  • 1998: Diesel engine standards further increased in efforts to reduce ozone and PM emissions for various vehicles including industrial equipment.
  • 1999: Tailpipe emission standards are finalized, sulfur contents in gasoline are reduced, and various boats/other marine vehicles using diesel had reduced emission limits for and PM.

    History of lead in gasoline

In 1922, lead was added to gasoline as an antiknock agent. It was not until 1969, nearly five decades later, that research began to show the negative health affects related to lead as a pollutant. Despite the plethora of negative health impacts discovered, no regulatory requirements were implemented to reduce lead levels in gasoline until 1983. Slowly, countries began banning use of lead in gasoline entirely from the years of 1986 to 2021. Japan was first to ban lead in gasoline in 1986, with North and South America following with nearly every country in the two continents banning lead by 1998. Africa was the latest to ban lead in gasoline with most countries banning in 2004 and 2005 and the last, Algeria, which didn't ban it until 2021.

Regulatory agencies

The agencies charged with implementing exhaust emission standards vary from jurisdiction to jurisdiction, even in the same country. For example, in the United States, overall responsibility belongs to the EPA, but due to special requirements of the State of California, emissions in California are regulated by the Air Resources Board. In Texas, the Texas Railroad Commission is responsible for regulating emissions from LPG-fueled rich burn engines.