2.14

 In 1970 the Environmental Protection Agency (EPA) was established  Required to set and enforce air quality standards  Air quality standard – max amount of pollutant allowed  2 kinds – emissions and ambient air  Emissions – gases and particles entering the air from smokestacks, chimneys, and exhaust pipes  Emission standard – max amount of an emission allowed to enter the atmosphere

 Ambient air – outdoor air  National Ambient Air Quality Standards (NAAQS)  Sulfur dioxide (SO 2 )  Nitrogen dioxide (NO 2 )  Ground-level ozone (O 3 )  Carbon monoxide (CO)  Particulate matter (PM)  Lead (Pb)  EPA reports national estimates of emissions for the principal pollutants each year

 EPA must set standards based on:  Best available scientific evidence of effects caused by pollutant  Public opinion  Standards must protect human health and prevent damage to the environment  EPA’s job to weigh risks of pollution against the benefits of the product

 First attempt to control pollution was the use of tall stacks  Tallest stack is in Ontario – 1,300 feet  CAA made tall stacks illegal, but law was not enforced  Citizens can take industries and/or government agencies (i.e., EPA) to civil court if they allow pollutants to exceed EPA standards

 A grandfather clause in the 1977 CAA amendments protected existing power plants from the expense of costly pollution controls  1990 CAAA requires older plants to clean up their emissions  Power companies choose most cost-effective way to meet the standard  Energy conservation  Renewable energy  Switch to lower-sulfur fuels  Pollution control technology

 1990 CAAA established a emissions cap – max amount of sulfur dioxide that can be released into the atmosphere from all electrical power plants  Some plants are allowed to pollute more than others, but the total is limited to 8.9 million tons  One allowance permits a power plant to emit 1 ton of sulfur dioxide  Power companies may buy, sell, trade, or hold allowances  Fines are imposed for missions that exceed allowances  CAIR places permanent cap on emissions of SO 2 and NO 2 in eastern U.S.

 Soft coal – contains % sulfur  Hard coal – contains % sulfur  Limited supply  Most coal is used in eastern U.S., and most coal there is soft coal  Oil contains less sulfur than coal, and natural gas contains far less sulfur  But soft coal is widely available and less expensive

 Coal washing decreases maintenance and increases efficiency of combustion  Scientists are investigating ways to break chemical bonds in organic sulfur  Biochemists are trying to develop bacteria that will eat sulfur compounds

 Wet scrubber – pollution control device where emissions are passed through a spray of water, which has been mixed w/ finely pulverized limestone  90% removal  Costly to install and operate  Disposal of scrubber sludge is problem

 Pressurized fluidized bed combustion (PFBC) – boiler that can burn low-grade fuels (i.e., high- sulfur coal)w/o producing large amounts of SO 2 or NO 2  Can also burn other fuels such as wood waste, sewage sludge, municipal waste, tires, etc.  Advantages include:  Fuel is burned at lower temperatures, reducing amount of NOx formed  Scrubber is not required  Less expensive to operate  Produces less solid waste  More compact

 Cyclone – flue gases are forced through a vertical tube in which a whirlwind throws larger particles against the sides of the tube  Only removes larger particles  Electrostatic precipitator – gives particles a strong electrical charge; the charged particles are attracted to metal plates w/ opposite charge  99.9% removal efficiency  Expensive to install, cheaper to operate  Fabric filter (baghouse) – holds series of fabric bags that filter emissions  Comparable to precipitators in cost and efficiency