The global voluntary market for carbon credits roughly doubled in 2008, according to a report by
Ecosystem Marketplace and
New Carbon Finance. For the year, 123.4 million metric tons of carbon dioxide equivalent (MtCO2e) were transacted valued at $705 million USD, compared with 65 million tons of credits valued at $331 million in 2007. The report estimates U.S.-originating 2008 offset volume at 31.4 MtCO2e.
The average price for voluntary credits in 2008 was $7.34/tCO2e, an increase of 20% from $6.10 in 2007 and 79% from $4.10 in 2006, according to the report. A carbon credit, also known as an offset, is a tradable commodity representing a unit of carbon dioxide emissions reduction or avoidance. Typically, one credit/offset represents a reduction or avoidance of one metric ton of carbon dioxide or carbon dioxide equivalent (CO2e).
Renewable energy projects were the most common sources of carbon offsets, supplying more than 50% of the total volume of credits transacted in 2008. Landfill gas (methane) capture projects were the second most popular type, responsible for 16% of the market, mostly owing to activity in the United States. More than 96% of offset credits were verified to a third-party standard in 2008. The top four verification standards, responsible for 79% of the over-the-counter market, were:
Voluntary Carbon Standard,
Gold Standard,
Climate Action Reserve, and the
American Carbon Registry. Data for the report,
Fortifying the Foundation: State of the Voluntary Carbon Markets ... 
