China will become the world's largest market for natural gas vehicles as the country moves away from diesel and gasoline to combat its growing air pollution problem, experts said.

Pu Chungan, secretary general of China Industrial Gases Industry Association, said that the country has already been on the fast track to develop natural gas-fueled vehicles and gas stations. As the world's largest carbon emitter, China has promised to ban older dirtier carbon-emitting vehicles from roads.

"There is a great potential of growth for natural gas, a cleaner alternative to diesel fuel and gasoline. The fuel is about 20 to 30 percent cheaper than its diesel equivalent," he said during the ceremony of the 6th ANGVA 2015, an international natural gas vehicle expo.

According to the National Gas Vehicle Engineering and Research Center, China has now about 3.3 million natural gas-powered trucks, buses, and cars on its roads, and is expected to add another million by 2015.

As of the second half of this year, there are about 3,700 compressed natural gas refueling stations and 1,620 liquefied natural gas stations.