More urban buildings in Beijing, including some Olympic Games venues, are expected to use environment-friendly geothermal energy by the year 2010, according to senior municipal officials.

Official with the city's development and reform commission Chen Huaiwei estimates that 20 million square meters of buildings will be using geothermal energy by then.

The municipal government is drafting preferential policies to encourage more real estate developers to use this kind of clean energy, he said.

It is planning to give developers easier access to bank loans or may give them subsidies if they adopt the technology in new buildings, Chen said.

The technology is also expected to be adopted in some Olympic Games facilities, according to Sun Ji, chief engineer of the Ever Source Science & Technology Development Co Ltd, a major developer of the technology.

"The National Aquatics Centre has shown interest in the technology and negotiations are ongoing," he said.

Geothermal energy is the heat stored in the Earth's crust. In Beijing, most of it will come from shallower ground, according to Sun.

The top 100 meters of the Earth's surface maintain average temperatures of below 25 C and pumps can get it out and use it to heat or cool, according to Sun.

"Like a cave, this temperature is warmer than the air above it in the winter and cooler than the air above in the summer," he said.

"The biggest advantage is that consumption does not have any impact on the environment."

So far, 3 million square meters of buildings have adopted the technology in Beijing, and its use is expected to replace 112,500 tons of coal or 75 million cubic meters of natural gas in winter alone, said Sun.

"There will be emissions of 280,000 tons less of carbon dioxide and 2,640 tons less of sulphur dioxide," Sun said.

"The use of such energy is good for saving energy, which is extremely important for China, a country bottlenecked by a severe lack of energy," said Yu Jun, deputy director of the government of Haidian District in Beijing.

A group of enterprises established an industry union on Tuesday in Beijing to promote the use of geothermal energy.