This, some analysts say, makes them better than the widely traded European carbon emission permits, which are mainly given out for free under a cap-and-trade scheme intended to curb the heat-trapping gases largely blamed for global warming.

CERs offer an incentive to cut CO2 through projects to develop clean energy in developing countries where emission standards are often lower, making real cuts easier to achieve.

Nord Pool says it is the world's first standardised CER that can be traded over an exchange, covering the years 2008 and 2009. The Oslo-based exchange already offers a marketplace for European carbon emissions permits.

"The listing of CER contracts represents an important contribution to the development of a secondary market for this product," Nord Pool said in a statement.

The first trade was between Dutch utility Essent and Norway's Statoil, Nord Pool said.

Twenty-five December 2008 contracts changed hands at 16.22 euros per tonne of emissions, and 25 of the December 2009 at 16.48 euros.

HIGH HOPES

A CER is an emission credit obtained through the clean development mechanism (CDM) implemented by the United Nations.

The CDM is one of the Kyoto mechanisms and involves the transfer of capital and technology from industrial countries to developing nations to cut CO2 by investing in clean technology.

"I hope this will become a large market because by conviction I think that CERs should be a large part of the market -- they are the only ones that actually reduce emissions," Statoil's head of power and emission trading Jo Overaa told Reuters.

CER contracts enable companies to comply with the rules of the European Union's emission trading scheme and governments to fulfil their obligations under the Kyoto pact, Nord Pool said.

"In two or three years this could really take off and become an important market," Nord Pool's head Torger Lien told Reuters.

Lien said the CER market could grow as big as the European carbon allowance market but acknowledged there was still a lot of uncertainty involved. The European Union allowance (EUA) market was worth over US$24 billion last year.

"It will be interesting to see in the next six to eight weeks how it is welcomed by the trading community," Lien said, adding that other exchanges were also likely to list CERs.

Statoil's Overaa said: "The big advantage of what Nord Pool is doing is that it is cleared by the exchange so we do not have any counterparty risk and the product is standardised."

"It should be a good argument for increased liquidity that everyone knows what they are trading," Overaa said.