It's an eBay for carbon credits.

World Energy, which specializes in carbon and energy auctions, has officially opened its World Green Exchange, a website where companies can pick and choose what sort of carbon credits they want to buy.

The site lists carbon credits by various attributes – price, vintage (when the carbon saving activity took place), location, type of carbon saving activity, etc. – and then allows buyers to bid for them. The site has been up and running for beta customers but now it is open to all comers.

The idea is to make carbon credits more transparent. Now, in many carbon markets, buyers buy a blended carbon credit. As a result, buyers have been somewhat unclear on what they are purchasing, according to Kenneth Ivanic, vice president of environmental markets at World Energy. The business community has buzzed in recent months about "Rip-Offsets": these cost money but a fear lingers how much carbon and carbon-generating activity was actually reduced. The fear is that companies are just buying paper.

World Green Exchange attempts to go into detail about the activities behind the credit. On the site, for instance, a Brazilian company is auctioning off credits generated after the company switched to biomass rather than obtain wood from forests. It's a real credit that can be verified, he said. Selling it allows the Brazilian company to offset the cost and a polluter/buyer to reduce its own liability.

"The project would not have been developed without carbon credits," he said. "It's almost like a shopping mall."

Buyers can also go local. Companies in Ohio, for example, can buy carbon credits gathered from a project in that state. Why not buy to help local projects, Ivanic said.

"They [buyers and sellers] want to meet each other in a transparent way," he said.

World Energy charges a 1.5 percent fee to both the buyers and the sellers.

Worcester, Mass.-based World Energy provides technology and other services to the Regional Greenhouse Gas Initiative (RGGI), the carbon exchange that started last year in the Northeastern U.S. RGGI conducts a carbon auction every quarter and in the past three auctions (see Green Light post).

Last September, in the first carbon auctions conducted by RGGI Inc., the administrative body for RGGI, the auction yielded 12.6 million allowances for $3.07 per allowance, according to World Energy, which provides the underlying software and services for the auction. A second auction in December yielded 31.5 million allowances at $3.38 per allowance. At another auction on March 23, 31.5 million allowances were auctioned at $3.51 per allowance. The March auction also saw the sale of 2.2 million 2012 vintage allowances for $3.05 per allowance.

The Obama administration is expected to unveil a carbon cap-and-trade or carbon tax program sometime in the future, which will likely goose the market outside of the Northeast. Right now, companies in other regions buy carbon credits, but it's voluntary. Several other national governments are also looking at carbon plans (see Carbon Tax a Better Idea? and Carbon Tax Debuts in Canada).

Tax or cap-and-trade? It's an ongoing debate. A tax would essentially place a charge on carbon activities while a cap and trade system would provide allotments: If a company exceeds the allotment, it would have to buy credits on an open market. While many support a tax, there are a number of people in the Obama administration that favor cap-and-trade, including the President and Energy Secretary Steven Chu (see House Energy Bill Draft: Cap-and-Trade Included). 

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