In 1990, the U.S. Congress passed legislation that amended the Clean Air Act to create a new program to mitigate the effects of acid deposition in the U.S. through emission reductions of sulfur dioxide (SO2) and nitrogen oxides (NOx) at electric utility plants across the country. The SO2 reductions, totalling a 40% reduction nationally from 1980 levels or a 10 million ton reduction annually, are achieved largely through an emission trading system, the largest program of its kind designed to date. This trading system has the potential to save up to half of the compliance costs associated with more traditional source-by-source emission limit programs.
This paper briefly discusses background on the acid rain issue in the United States, and the principal features of the program, including: a permanent cap on utility emissions of SO2 beginning in 2010, decision to grant up-front allocation of emission credits to reduce individual approvals of trades, the use of continuous emission monitors and automatic penalties to ensure compliance, and integration of the Acid Rain program requirements with other Clean Air Act programs. The paper also discusses the development of the allowance trading market to date, including the types of compliance options chosen and quantity and type of emissions trading being conducted.