North America's first auction of greenhouse gas emissions permits last week raised nearly $38.6 million that will go toward energy efficiency and renewable energy projects in six Northeastern and Mid-Atlantic states.

The Regional Greenhouse Gas Initiative (RGGI) sold nearly 12.6 million carbon dioxide emissions (CO2) allowances Friday to 59 participants at a clearing price of $3.07 each. The floor was set at $1.86 per allowance, each of which allows electricity generators to emit up to a ton of carbon dioxide.

"The first RGGI auction has successfully used market forces to set a price on carbon, and this will send a clear signal to support the investment in clean energy technologies," Pete Grannis, RGGI chair and commissioner of the New York State Dept. of Environmental Conservation, said in a statement Monday.

RGGI is North America's first mandatory greenhouse gas cap-and-trade program and spans 10 states: Connecticut, Maine, Maryland, Massachusetts, Rhode Island, Vermont, New York, New Jersey, New Hampshire and Delaware.

New York, New Jersey, New Hampshire and Delaware, which represent 55 percent of the allowances to be traded under RGGI, didn't offer the permits in the inaugural auction because of regulatory delays.

The smaller supply of allowances had promised to foster demand for buyers, which include electricity generators, investors and environmental groups. All 10 states will offer allowances in the next auction Dec. 17. The quarterly auctions will take place through 2011.

RGGI only covers electricity generators. Two three-year compliance periods, meant to stabilize emissions, run between 2009 and 2014. The cap, now set at 188 million tons of CO2 per year, will ratchet down 2.5 percent annually between 2015 and 2018 for a 10 percent total reduction. Critics have said the cap is set too high to yield significant emissions reductions.

RGGI futures on the Chicago Climate Futures Exchange opened Monday at $3.25 a ton, finishing at $3.76.