Household heating could be fuelled by sewage if an invention that recently went before a panel of experts is taken on board.

Waste can be used to generate energy with the device, which was praised by the experts for its pioneering technique.

"The implementation of this device could save the use of many types of traditional energy, such as coal, to provide air conditioning and heating for buildings," said Sun Dexing, leading member of the device's research team and professor from the Environmental Science Department of the Harbin Institute of Technology (HIT).

"No one had hit on the idea of extracting energy directly from unprocessed waste water before," he said, "as the filthy water would quickly block the pipes flowing through."

Sun said his device uses electricity and a kind of septic tank to extract heat from the raw sewage before it is sent to be processed. The heat retained can be used to heat homes.

Some countries, such as Norway, have also developed similar technology.

"But they used processed water, while mine uses unprocessed, which is easily available and more practical," he said.

Calling his invention environmentally friendly, Sun said big cities have great advantages to adopt this technique as they produce so much sewage each day.

The device could be 20 per cent cheaper to run than traditional heating systems and central air conditioning systems, he said.

The device had been used in a hotel and plaza in Harbin with some success.

One of two experimental sites, the Wangjiang Hotel, has completely stopped coal for its winter heating, and the move has reduced its heating bill by half.

The Taigu Plaza, which was designed to use the device at the beginning of March, produces enough energy to heat and air condition itself.

In China, the energy consumption of buildings accounts for nearly 20 per cent of total energy consumption.

Sun hopes the device will be used in apartment complexes to save more traditional energy sources.

"Basically, the waste water produced by six or seven families can meet the needs of one family here in Harbin," he said.

"The device possesses huge social as well as economic benefits," said Jiang Yi, from the Chinese Academy of Engineering.

(China Daily July 7, 2005)