China's first carbon neutrality-themed expo, the Shanghai International Carbon Neutrality Expo, has attracted nearly 600 enterprises worldwide. The expo runs from June 11 till 14, and covers six key fields. China's Emissions Trading Scheme, or ETS, has now replaced the EU's as the world's biggest emissions trading system, according to the country's Ministry of Ecology and Environment. CGTN's Zheng Chunying explains how carbon trading works.