An aerial drone photo shows the city view at sunset in Guangzhou, south China's Guangdong Province. (Photo/Xinhua)

Guangzhou - Carbon emissions allowances closed at 38.37 yuan (about 5.64 U.S. dollars) per tonne on Thursday, remained unchanged from last transaction day at Guangzhou Emissions Exchange.

A total of 100 tonnes of allowances were transacted on Thursday with a turnover of 3,820.84 yuan.

The allowances, officially known as Guangdong Emissions Allowances (GDEA), are carbon dioxide emissions caps assigned to companies. Firms whose emissions surpass their share must buy extra quotas from authorities or purchase unused quotas on the market from those that cause less pollution.

Since its opening in December 2013, the market has traded 234.26 million tonnes of GDEA, with a total turnover of 6.827 billion yuan.