I am standing by a newly built road intersection in Guangzhou in southern mainland China. The roads are thronged with traffic. Somewhere nearby, my guidebook says, there is a bar. But it is nowhere to be found, even though the guide was published recently. The city is changing too rapidly for any book to keep up with. Guangzhou acts as a microcosm for China in 2007, where a spectacular pattern of rapid, dramatic and polluting urban change is occurring.

Along with rapid economic growth, China is also undergoing an unprecedented urbanisation. In the last decade, many hundreds of millions of people have moved from the countryside to the city, and over the next few decades an estimated 300m will do the same. In order to cope, hundreds of new cities are being built. Among them is one that is rather unusual: it is called Dongtan, and it is claimed that it will be an eco-city – the world’s first. Dongtan, which will be situated on the island of Chongming near Shanghai, is to be ecologically friendly, carbon neutral and self-sufficient in water and energy.

Self-sustaining city
The city will be designed on behalf of the Shanghai Industrial Investment Corporation by a British global design and consulting firm Arup. So far, full details of how it qualifies as an eco-city have not been revealed publicly. However, a number of things are already clear – it is not just an eco-city because it involves a few solar panels and wind turbines. It is designed from the ground up to be a self-sustaining city, environmentally, culturally and economically. Many clever ideas, such as energy production and farming, have been carefully integrated.

On the technology side, there are plenty of ways of greening a new city. Dongtan will generate its own electricity and heat from renewable sources such as wind turbines, biogas from municipal waste and sewage, and biofuels from agricultural waste. A combined heat and power plant will run on rice husks that were previously thrown away.

Energy producers will purchase the husks from farmers, says Malcolm Smith, head of Arup’s urban design team. This is one of the ways that the designers hope to create a green economy.

Recycling will be a key feature in the eco-city – with waste being treated as a resource rather than a problem. Buildings will be made using local materials where possible, to reduce the energy costs associated with transport of building materials.

A combination of traditional and innovative technologies (yet to be disclosed) will reduce the energy requirements of buildings by 70%.

Transport will also be green. As the city is being built from scratch, it is a great opportunity to reduce the energy required for transport by tinkering with the population density and distribution. In Dongtan, people will never be far from places of work, recreation, leisure and public transport. In addition, the city is designed around cycle paths, pedestrian routes and man-made canals, the latter being most efficient in terms of energy and weight relationships, says Smith. Cars will not be allowed, and visitors to the city will have to leave them at the city limits.

Tinkering with the population density of Dongtan is important for another aspect of its greenery. Smith says that an eco-city must also be a self-sustaining system. It must sustain itself economically, socially and environmentally.  In other words, it must generate its own jobs and culture as well as electricity and food. It can’t be a sleepy, low-rise commuter town for workers in nearby Shanghai. To make this possible, Dongtan must contain enough people to generate the critical mass needed for, say, hospitals, schools, jobs and community groups. But keeping energy for transportation down to a minimum also means that the city must be compact and high density. In the city centre, the intention is to have around 160 people per hectare (about four times lower than nearby Shanghai’s central districts).

Open space for residents
A high population density does not mean people are packed like sardines into every single available centimetre. The city will have plenty of open space for its residents: 30 square metres per person. In London the figure is 20.5, and in Los Angeles it is 6.6. Dongtan will also be very sensitively integrated with a local wetland, which is a nature reserve of international significance.

Work will begin on Dongtan in early 2007 and by 2010 the first phase will be complete – a 100-hectare (1 square km) area will accommodate 10,000 people. By 2020, Dongtan will be home to a further 80,000. The total site is 86 square kilometres and ultimately could support half a million people.

Can it succeed?
The big question, of course, is will it work? Its agenda, to demonstrate an alternative to the kind of development happening elsewhere in China, will quite possibly succeed. But whether it will truly become an eco-city, and achieve its ambitious goals such as carbon neutrality is not yet clear – many parts of the city’s design are being tested for the first time. For some of those involved, this is a research project.

When the city is officially shown at the 2010 World Expo in Shanghai, it will no doubt make an international splash. And three other eco-cities are already planned.

Not much will change in other parts of the world, though, for two reasons. The first is that in most places there is a limited ability to make radical changes in the urban environment. For one thing, some parts of Dongtan cannot simply be transplanted. Its climate, environment, local economics and its social context are unique. For example, Dongtan’s economy will rely partly on tourism and its transportation on canals. This won’t be possible everywhere. Yet how a city is financed and supported will be location specific. This issue, says Smith, is “possibly the key question when we talk about sustainability”.

The second problem for the notion of green cities is that half the world’s population lives in cities that are already built – it is not possible to design them from scratch to be eco-friendly.

How would one turn London or New Delhi into an eco-city? More depressingly, still, in most other parts of the world countries are completely failing to provide cities for similar mass migrations of people, let alone cleverly designed green cities.

Although an eco-city seems long overdue, it begs the question of why such an innovative project is happening for the first time in China – which is still a developing country – and whether green cities are only possible in places where the government exerts a heavy hand. However, if Dongtan and other eco-cities prove viable in China, it also sends another message. If the Chinese system can facilitate an ecotopia and sustainable development, then there will be a blueprint for other nations across the globe to use to develop their own self-sufficient cities.

Natasha Loder is the science and technology correspondent at The Economist