China will expand its bans on coal burning to include suburban areas as well as city centers in efforts to tackle air pollution, the top energy agency said on Tuesday.

Detailing its clean coal action plan 2015-2020, the National Energy Administration (NEA) said it would promote centralized heating and power supply by natural gas and renewables, replacing scattered heat and power engines fueled by low quality coal.

The world’s biggest coal consumer will ban sale and burning of high-ash and high-sulphur coal in the worst affected regions including city clusters surrounding Beijing.

Beijing ordered a ban last year against coal burning in its six central districts from 2020.

Under the action plan, coal-fired industrial boilers will all shift to burn natural gas or clean coal by 2020 in the Beijing-Tianjin-Hebei city clusters, Pearl River delta and Yangtze River delta area, NEA said.

China has around 600,000 industrial boilers fueled by coal, most of them are in residential areas in northern China.

The government will offer subsidies for clean fuels, it said, without giving details.

In an earlier action plan released by the Ministry of Industry and Information Technology, China aimed to cut coal consumption by over 80 million tonnes by 2017 and more than 160 million tonnes by 2020.

China’s annual coal consumption, at about 3.7 billion tonnes, accounts for roughly 66 percent of its energy demand. Besides generating climate-warming greenhouse gases, it is a major cause of the hazardous smog that frequently shrouds cities such as Beijing and Shanghai.