Wired

Students in Maine have won the rights to pollute the environment with nine tons of sulfur dioxide at an auction sponsored by the US Environmental Protection Agency. They have now retired those rights, effectively keeping that sulfur dioxide from falling on Maine, or anywhere else, in the form of acid rain.

The SO2 Allowance Auctions, which derive their name from the chemical shorthand for sulfur dioxide, were set up in 1993 by the EPA to encourage energy companies to reduce emissions. The auctions let power companies, brokers and even private citizens bid for the allowances, or permits, to release a certain amount of sulfur dioxide into the air each year.

Power companies that release more SO2 than their permits allow must attempt to buy more allowances at the auctions, or purchase them at a premium from companies that have allowances to spare. Those that can’t gather enough allowances or that go beyond certain emissions limits in a given year face strict fines from the EPA. In this way, the system encourages companies to reduce their own emissions.

But when word of the auctions spread to environmentally concerned academics, a handful saw a way to stop specific quantities of SO2 from ever being created.