SHENZHEN - The city of Shenzhen, in south China's Guangdong province, launched a carbon trading scheme on Tuesday, the country's first market for compulsory carbon trading.

The scheme covers 635 industrial companies and some public buildings that account for about 40 percent of the city's carbon emissions, the Shenzhen carbon trade exchange said in a statement.

Under the trading program, those which emit below their quotas could sell their excess limits to other emitters and even investors for profit.

The carbon intensity, or the amount of carbon produced per unit of gross domestic product, of the 635 industrial companies in 2015, will slump 32 percent from levels in 2010, the statement said.

Eight deals, or 21,112-ton carbon quotas, were traded Tuesday at prices ranging from 28 to 32 yuan ($5.2) per ton.

China's National Development and Reform Commission, the top economic planning agency, also approved pilot carbon emission trading schemes in six other areas: Beijing, Tianjin, Shanghai, Chongqing, Hubei and Guangdong.

Experts and government officials hailed the pilot schemes as a landmark step for China in building a nationwide carbon emission trading market.

The country has pledged to reduce carbon dioxide emissions 40 to 45 percent per unit of GDP by 2020, in comparison with 2005.