SHANGHAI, Aug. 21 -- Shanghai is promoting a method of recycling waste concrete which not only saves material but also protects the environment, city officials said yesterday.

The city's first such recycling center has been set up at Baosteel Group, and its first batch of recycled concrete is suitable for construction use, they said.

"We will promote this recycling method as soon as possible and as widely as we can," Zhang Yunjie, deputy director of the Shanghai Engineering Administrative Bureau, said yesterday.

Recycled concrete is now being used to renovate the 28-kilometer-long Hutai Road. It will account for about a third of the project's concrete needs, saving 100,000 tons of natural gravel and stone.

Technicians of the Baosteel Group explained there is a three-step process to recycle concrete: grinding the waste concrete in a huge machine, cleaning and selecting it, and mixing it with conventional concrete at a ratio of three to seven.

Sun Jiaying, an engineer of Shanghai Engineering Planning and Design Institute, said: "The technology is of vital importance for Shanghai as the city doesn't produce raw material for concrete."

According to the engineering bureau, which supervises the city's infrastructure construction, Shanghai's demand for concrete will increase over the next three years, mainly due to Metro construction and projects related to the 2010 World Expo.

Some 200 new Metro stations are being built, while dozens of nearby roads and elevated roads are being renovated.

It's estimated that the city will use 40 million tons of concrete this year while producing around five million tons of waste concrete.

Last year, the city produced 4.5 million tons of waste concrete. If all of it was recycled, it could pave roads the size of 4,465 basketball courts, officials said.

Weng Lida, an expert in protecting water resources, said earlier that over-mining of natural gravel and stone could pollute water and reduce plants. It could also lead to natural disasters such as mud slides.