In the past, the primary origin of local air pollution has been emissions from stationary sources. These sites include power generating plants, oil refineries, chemical plants, steel factories, cement and glass manufacturing companies, space heating, and many other industries. Pollutants are emitted into the air from these plants through fossil fuel combustion, chemical processes, and the grinding or pulverizing of metals for cement, fertilizers, etc.
Under the Clean Air Act of 1970, the nation's 247 Air Quality Control Regions (AQCRs) were to be regulated by state implementation plans (SIPs). This procedure was enacted so that the states could demonstrate to the federal government their intentions of cleaning the air. Each state was to assess the air quality, then establish procedures, timetables, and standards (at least as strict as the national standards) for each major pollution source in the AQCR. Also, the plans needed to include a process for approving new sources and significant source modifications. After a state created its SIP, the Environmental Protection Agency (EPA) needed to approve it. If a state failed to generate a SIP, then the EPA had the power to control the programs for that state.
prevention of significant
In addition to cleaning the air in polluted areas, the Clean Air Act also required clean areas to maintain their level of air quality and prevent significant deterioration (PSD). Under this policy, areas with air quality better than the national standard were divided into categories:
class I: very little additional pollution is allowed
class II: moderate pollution is allowed
class III: pollution approaching but not bypassing NAAQS is allowed
Federal lands and parks were designated class I regions, and the states were to designate the remaining areas.
After the passage of the 1970 amendments, the federal government established National Ambient Air Quality Standards (NAAQS) for seven pollutants--paritculates, sulfur oxides, carbon monoxide, nitrogen oxides, ozone, hydrocarbons, and lead--without considering cost, technical feasibility, or the cost of compliance. These standards included the pollutant, teh concentration (grams of pollutant per cubic centimeter of air), the amount of time needed for compliance, and the number of times standards could exceed the allowed standard. The EPA needed to take into account both public health and welfare which it did by creating two standards for some pollutants. The primary standard was to promote human health with an adequate margin of safety to protect those most vulnerable, such as asthmatics, infants, and the elderly. The secondary standards, more strict than the primary, were to promote human welfare by increasing visibility, protecting buildings, improving crops, etc.
In a non-attainment area, an AQCR that has not yet achieved the NAAQS, existing sources must enact reasonably achievable control technology (RACT). They are to apply a control technology in order to achieve the lowest emissions it is capable of meeting considering technical and economic feasibility.
All new plants, or major additions to existing plants, regardless of size or location need to adhere to New Source Performance Standards (NSPSs). These are standards determined by the EPA considering cost, environmental effects, and state of the art technology. After the EPA sets the standards, it is the responsibility of the state to issue permits and enforce them. New sources in non-attainment areas are required to adhere to the lowest achievable emissions rate (LAER) which is the lowest emissions rate achieved by a similar source or the lowest rate for a similar source in a SIP anywhere in the country. A new source wishing to enter a PSD area needs to use the best achievable control technology (BACT) which is based on a maximum amount of achievable reductions once cost and technology are considered. These standards, LAER and BACT, need to be at least as strict as NSPS.
Emissions trading is a policy that makes use of credit from emissions reductions which, when enacted, demonstrated the flexibility of the EPA. For example, in order to prevent greater deterioration in an area, a new source would convince existing sources to cut back on emissions to compensate for those that the new source would be releasing into the atmosphere. Four different types of emissions trading exist: offset, bubble, banking, and netting.
The offset policy is one for new sources. Primarily, the source needs to satisfy LAER. Also, all of the existing sources in the area that are controlled by the owner of the new source need to be in compliance with emission standards. Lastly, the owner would need to urge existing sources to reduce enough emissions so that the new source would be an overall benefit to the area.
The bubble policy was the first principle of emissions trading. The EPA's definition of a source was each vent and each smokestack in each factory; however, the bubble policy proposes that the EPA consider the entire factory as a source. By placing an imaginary "bubble" around the factory and setting a standard for this entire source to comply with, industry can adjust the emissions of each individual smokestack (some can emit more than others) to what is economically feasible as long as the factory as a whole can comply.
By pooling together all of a factory's
emissions as one source, a company does not need to meet
standards for each stack, therefore, reducing costs.
Banking emissions is a way of reserving emission reduction credit. If a source retires and a new source is not introduced immediately, it can "bank" the emissions that are reduced by removing this source.
Netting allows plants that are being modified or extended to be exempt from NSPSs as long as the emissions increase plantwide is not significant.
After introducing many of these principles in the 1970s, the Emissions Trading Policy was enacted in 1982.
In the past, the primary origin of local air pollution has been emissions from stationary sources. These sites include power generating plants, oil refineries, chemical plants, steel factories, cement and glass manufacturing companies, space heating, and many other industries. Pollutants are emitted into the air from these plants through fossil fuel combustion, chemical processes, and the grinding or pulverizing of metals for cement, fertilizers, etc. These processes emit a number of harmful contaminants into the air. The most damaging being sulfur dioxide, nitrogen oxides, carbon dioxide, synthetic compounds, and particulate matter.
sulfur dioxide (SO2): This chemical is a colorless gas given off from the incomplete burning or heating of metals, and from the combustion of sulfurous coal or oil. The highest levels of sulfur dioxide occur during a sulfurous smog which can have serious health effects.
nitrogen oxides (NOx): These compounds pose problems, for the most part, in the forms of nitrogen oxide (NO) and nitrogen dioxide (NO2). They combine with hydrocarbons and other volatile organic compounds (VOCs) in the presence of ultraviolet sunlight to produce photochemical smog, mainly ozone (O3), which has adverse health effects.
carbon dioxide (CO2): This chemical, a byproduct of most fuel combustion, is a greenhouse gas and a major contributor to global warming.
synthetic compounds (i.e., CFCs): Until banned by new provisions of the Montreal Protocol, these compounds were produced and released by industries for air conditioning, insulation, cleaning fluids, etc. Some have been known to contribute to the destruction of stratospheric ozone.
particulate matter (PM10): These tiny particles are emitted in the form of soot and dust. They can decrease visibility as well as lead to health problems.
Scientists, industries, and governments have proposed many solutions to the stationary source emissions problem. Some are more realistic than others and some are more cost effective. The first attempt by industry was to increase the height of the smokestacks to minimize pollution in the local area. Soon, however, experts discovered that this only dispersed the pollutants over a wider area. They also found that by releasing SO2 and NO this high in the atmosphere, the chemicals combine with moisture to produce acid rain. In order to cut back on the pollution released from power companies, the switch to nuclear power was an option. These plants, however, began to create problems. For example, generators were unreliable, and new environmental consequences arose. Scrubbers were successfully introduced as a means of using wet limestone to remove a percentage of sulfur after combustion. Some companies refused these, however, because they were very costly, and they produced a sludge that was difficult to dispose of. Most federal authorities were in favor of removing sulfur before combustion. They wanted companies to use low-sulfur coal or even desulfurized coal and oil. This too put a financial burden on industry. Another option was the use of natural gas which emits some CO2 and NOx, but it almost completely lacks sulfur. This approach is again costly since natural gas is the least abundant fossil fuel. In an attempt to reduce their harmful emissions, most stationary sources have used one or a combination of some of these solutions. Overall, since the harmful effects were discovered, pollution has decreased considerably; however, there is still a long way to go before we have clean air.
top of page
sources for emissions mobile emissions clean air home