Six of these buses will appear late next year or early in 2009 in the Jiading District where the city's first hydrogen refueling station has already been built.

More buses powered by hydrogen-based fuel cells are being planned for the city over the next few years as more refueling stations are built downtown.

"We hope to have a lot of hydrogen-powered buses on Shanghai streets," Yu Zhuoping, dean of the automotive engineering college of the city-based Tongji University, said at an international symposium of hydrogen energy yesterday.

The Shanghai project will ask overseas companies to submit tenders for the buses next month.

Yu's college has been working with the Shanghai Automotive Industry Corporation Group to develop a hydrogen-based fuel cell car with a "Shanghai brand," a possible alternative propulsion system for the buses.

It is one of the country's two pilot hydrogen-based vehicle projects funded from a grant of 300 million yuan (US$40 million) provided by the city government, the Ministry of Science and Technology and the United Nations.

For the other project, three hydrogen-based fuel cell buses have been working in Beijing's public transport for more than a year.

Yu said the UN has been promoting clean energy transport in developing countries including Egypt, Brazil, India and Mexico.

He said the developing countries, as seen by UN, have more urgency than developed countries to develop clean energy vehicles because they have a larger potential car market.

In the United States there are about 700 cars on average for every 1,000 people - a figure that precludes the development of new cars - but in China there are only 20 cars for every 1,000 people.

Zhang Zhihong, deputy chief of the Hi-tech and industrialization department of the Ministry of Science and Technology, said: "We will use zero-emission vehicles within the site of World Expo 2010 and the fuel cell-powered buses will play a key role."

Fuel cell is an electro-chemical system which converts a chemical reaction directly into electricity. It is a renewable energy and does not produce harmful emissions.