China's national carbon market is likely to regulate 3-4 billion tonnes of carbon dioxide by 2020 and be worth up to 400 billion yuan ($72 billion), a government official said on Thursday, which would make it twice as big as the EU market, currently the world's biggest.

The National Development and Reform Commission (NDRC), China's top economic planner, and the Asian Development Bank held a conference in Tianjin on Thursday, outlining initial plans for a nationwide market to slow down the rapid growth of greenhouse gas emissions in China.

Promethean task: reducing China's carbon footprint.

A senior climate official said last month China planned to start a national market in 2016.

Over the first five years of the scheme, the NDRC plans to bring emitters accounting for 3-4 billion tonnes of CO2 annually into the scheme, around 4per centnt of China's total emissions, according to a presentation delivered by Jiang Zhaoli, director of domestic policy and compliance in the NDRC climate change department.