Between a desert and a dry place: Beijing's green projects drain scarce water resources

Smog-plagued Beijing is anxiously awaiting its first batch of synthetic natural gas - a material converted from coal and piped 300 kilometres from Heshigten Banner in northeastern Inner Mongolia.

The gas will power some of Beijing's central heating systems in the harsh winter months, replacing coal to cut harmful emissions of particulate pollutants.

When the pipes are fully pumping next year, Beijing will receive 4 billion cubic metres of synthetic gas a year - nearly half of last year's natural gas consumption - a step towards switching all the city's heating systems and industrial boilers from coal to gas.

But there is an ominous tinge to the seemingly green investment: environmental experts say the water-intensive conversion process could drain already scarce water resources in the country's drylands in the northwest, eroding land and causing more sandstorms.

"If water depletion continues … not only will the local people suffer, the environmental impact could be profound," Chinese Academy of Sciences ecology researcher Xie Yan says.

Nationwide, replacing dirty coal with cleaner natural gas is a key measure in reducing the choking smog that spreads over more than a quarter of the country and is inhaled by nearly 600 million people. Because of the country's limited conventional natural gas and abundant coal reserves, converting coal to natural gas seems a convenient choice.