Chongqing launched its carbon trading market on Thursday, marking the operation of all seven approved pilot trading schemes in the country.

China began piloting carbon trading in 2011 and approved seven trading schemes in Beijing, Tianjin, Shanghai, Chongqing, Shenzhen, Guangdong and Hubei.

Chongqing is the last to start the carbon trading scheme among the seven pilot provinces and cities.

Under the schemes, enterprises which produce more than their share of emissions are allowed to buy unused quotas on the market from those that cause less pollution.

Xie Zhenhua, deputy head of the National Development and Reform Commission, said Chinese enterprises had traded over 3.85 million tonnes of carbon emission quotas as of May 23.

These quotas were sold for 125 million yuan, making China a major carbon trader, second only to the European Union.