The global voluntary carbon market has grown from 3 million to 5 million tonnes of CO2 credits traded in 2004 to 20 million to 50 million tons in 2006, and is expected to reach 100 million tons or more next year, according to The Climate Group, a London-based nonprofit organization.

The voluntary trade the Bank of New York registry targets is separate from the mandatory trade under the UN's Kyoto pact, such as the European Union's Emissions Trading Scheme.

The registry will seek to reduce the reams of certificates and legal contracts normally associated with voluntary emissions trading by homogenizing all such credits with a standard called Voluntary Carbon Units.

Clients may include car and airline companies whose emissions are unregulated in the first phase of the Kyoto pact, said another Bank of New York source.

Other big companies from the United States, the world's top carbon emitter but which has dropped out of the Kyoto pact, are expected to join. Many US companies, such as Alcoa Inc. and DuPont Co., have cut emissions voluntarily.

Ideally, companies that want to reduce emissions, whether to prepare for any future carbon regulations, or to improve their green image, could buy emissions credits on the registry from projects like wind farms, or companies that have cut emissions.

The bank also expects carbon credit speculators looking to buy low and sell high will use the registry. "It allows really anybody to trade them (carbon credits) and allows them to avoid all the paperwork that is associated with trading these credits," the second Bank of New York source said.

Unlike similar plans, such as California's Climate Action Registry, carbon credits on the Bank of New York will be verified by third parties that also validate carbon offset projects in the Kyoto protocol.

That should eliminate much of the uncertainty that has so far hampered voluntary carbon trade, said Alexander Rau, a founding partner at Climate Wedge, which manages a voluntary carbon fund with Cheyne Capital.

He said that when voluntary emissions credits are not verified there's nothing to stop owners of emissions-reducing projects from double-selling credits to unsuspecting buyers

"For the integrity of the whole voluntary carbon market the Bank of New York registry is a really crucial thing," said Rau. Currently in voluntary markets emissions credits "are sort of sloshed around physically," he said.

Carbon credits on the EU's market were selling for about US$19 a tonne on Friday and at about US$4 a tonne on the Chicago Climate Exchange.