|مقاله در مورد "چگونه شهری سبز بسازیم"|
|ساعت ۱۱:٥٥ ب.ظ روز ۱۳۸٧/٥/٦ کلمات کلیدی: مقالات ،اموزشی ،تحقیقاتی|
how to build a green city
For the next three years, much of the world’s attention will be directed toward China and its two biggest cities, Beijing, home to the 2008 Olympics, and Shanghai, site of a World Expo in 2010. For now though, these cities are often known for something else: pollution.
No visitor returns without remarking on it. “The sky was a yellow haze the whole time,” is a typical comment, or “It looked like rain every day, but it was just the pollution.” Noon can be indistinguishable from dusk. Car headlights gleam through the smog, disclosing the very traffic that causes much of it. The blog “Mad About Shanghai” maintains an “Oriental Pearl Tower Visibility Index,” named for the shapely television tower on the city’s skyline, the third-tallest man-made structure in the world. The index is a scale of one to five, where five represents, in the blogger’s words, “What Tower—I can’t see a freakin’ thing!” By April of this year, the government had twice issued its most severe Air Pollution Index rating, which advises, “The aged and patients should stay indoors.”
Pre-Olympic concern about the effects of pollution on the upcoming games has been so great that Beijing city officials agreed to shift the metropolis’s power plants from coal to natural gas and to relocate a giant downtown steel mill to a site hundreds of miles away. In Shanghai, too, the government has been moving factories out of the city for more than a decade. For the country as a whole, however, that’s a zero-sum game, shuffling sources of pollution around like pieces on a chessboard.
So China has embarked on a bold, expensive experiment to see whether pollution and waste—of all forms, not just the kind that taints the air—can be drastically reduced or even eliminated. In March it broke ground on what it calls the world’s first eco-city. Designed by the London-based global consulting firm Arup Group, Dongtan (as the new city will be called) is to be built on an island that is just a ferry ride away from central Shanghai. The government expects that by the time of the Expo this new enclave will be a showcase city of 8000 and that it will have half a million residents by 2050.
Dongtan will ban all polluting cars, even the most advanced hybrids. It will dig canals for waterways. On its streets, people will get around using electric cars, bicycles, or just their legs. “Cities today are built around the automobile,” says Malcolm Smith, an urban-design team leader at Arup. “You build a very different type of city if you know the automobile isn’t the central form of transportation.”
The city will recycle as much as possible, including all its wastewater; grow food on its own environmentally sensitive farms; and create all its own energy in nonpolluting ways—wind, solar, and the burning of human and animal wastes. It will encourage, and in some cases require, the use of local labor and novel building materials, such as a concretelike substance that can be made from ash and used cooking oil.
Most of these technologies are not new, and many are commonly used in Western Europe, if not in Asia or the United States. What will make Dongtan unique are the integration of environmentally friendly practices and the strict exclusion of older, polluting ones. Dong Shanfeng, a senior architect at Arup and the company’s local team manager for the Dongtan project, says, “What we’re trying to do with Dongtan is not about technology innovation; it’s the combination of technologies. It’s not a technical experiment. It’s an experiment of how people can develop a new city in the right way.”
In November 2005, Arup, which has offices in 37 countries, signed a broad contract with Dongtan’s developer, Shanghai Industrial Investment (Holdings) Co. (SIIC). That agreement expanded Arup’s responsibilities for Dongtan and started the company working on designs for two other developments, with one to be near Beijing. The high-profile ceremony took place at 10 Downing Street and was attended by Chinese President Hu Jintao and British Prime Minister Tony Blair.
If it’s unusual for a business deal to be witnessed by the heads of two of the world’s most powerful nations, so too is the idea of creating from scratch an eco-city as large as Manhattan and more populous than Edinburgh or Atlanta. But building cities virtually overnight is nothing new for the Chinese. In 1980, the central government created a special economic zone for Shenzhen, at the time a small fishing village about an hour from Hong Kong. These days, it’s a sprawling metropolis of 9 million.
In 1990 the Chinese established another special economic zone east of central Shanghai in Pudong New Area, the territory between the Huangpu River and the East China Sea [see the map in “City, Heal Thyself”]. At the time, downtown Shanghai had 13 million people, and Pudong was a sleepy stretch of farmland, countryside, and shipping warehouses. Today, Pudong is the most overcrowded district in an overcrowded city—at least 1.5 million people packed into block after block of high-rises and stunning skyscrapers.
Shanghai, which now has 14.5 million people, grew rapidly, but it did not grow well, at least from the point of view of sustainability. Although hundreds of its apartment and office towers are less than two decades old, a 2002 study found that compared with people living in other major world cities the average Shanghai resident had only half the living space and yet consumed twice the amount of power.
Even at that, offices and homes are cold in the winter and uncomfortably warm in the summer, observes Saskia Sassen, an urban sociologist who teaches at the University of Chicago and the London School of Economics. “Shanghai missed a major opportunity by not building energy-efficient homes and offices during its construction boom,” she says.
One of those high-rises is at 98 Huai Hai Zhong Road, where Arup has a crowded set of offices on the 12th floor. The building is so new that the lobby remains dark and unfinished, and you can hear the wind whistling through the elevator shafts. Dong, the youthful team manager, who studied urban design and social science in London, offered a welcome cup of hot tea during an hour-long January interview in his drafty office.
Buildings in Dongtan will be only three to eight stories tall, Dong says. It’s the optimal height for delivering services such as water and heat. For example, the best way to regulate the temperature of a building in a temperate climate like Shanghai’s is to have double-pane windows with louvered shades that automatically open and close to provide sunlight in winter and shade in summer. But the powerful winds encountered high up on a skyscraper would cause such louvers to break before long. Moreover, rooftop solar panels can heat most of the water required for a low-rise, but they would satisfy only a small fraction of a high-rise’s needs. So by limiting heights, both these strategies can be applied, which will allow Dongtan’s buildings to use only one-third the energy of comparable floor space on the mainland.
Work on Dongtan’s basic infrastructure—power generation plants, major roads, the water supply, canals, and sewers—has just begun, and office construction won’t commence until next year. But you can get an idea of what the city will be like by visiting Pujiang Intelligence Valley (PIV), a large office park being built 15 kilometers south of downtown Shanghai on the mainland by Shanghai Pengchen United Industry Co., a real estate developer committed to sustainability.
PIV will ultimately encompass 20 buildings. Two opened last fall, one with four stories, the other with five. Steven Liu, the project’s general manager, claims these structures met an ambitious goal of operating with 75 percent less energy than what offices in Shanghai use. They are almost certainly the most energy-efficient buildings in China.
Construction costs were 25 percent higher than they otherwise would have been, an investment that Liu says will pay for itself in five or six years from the energy savings. He points to 10 different technologies being deployed, including those high-tech window louvers, which are set into walls that are a foot thick and contain two layers of insulation. Some conservation strategies are decidedly low-tech, such as collecting rainwater and planting grass on rooftops. Fresh air is cycled through a series of filters, and the humidity is strictly regulated.
The centerpiece of PIV’s energy efficiency, however, is a system of geothermal pipes. A 13-centimeter-diameter water main runs 100 meters underground, where the earth is, compared with air temperatures, cool in summer and warm in winter. Water—some of which is collected rainwater—is pumped down and then up into sets of smaller pipes that run through each floor and wall. The system was developed in Germany and Switzerland, and most of the materials were purchased from European companies.
Though it uses some energy, the geothermal pump needs to operate only one day out of three, even in winter, such as the chilly January day I visited PIV. The temperature stayed between 18 ºC and 20 ºC, and I was comfortable enough to take off my sweater. I wasn’t there long enough to detect a difference in the quality of the air, but the workers with whom I spoke said it was the most pleasant office they had ever worked in.
Liu says that the ideal PIV tenants will be high-tech companies that are as concerned about the quality of life as about the additional space they will earn by locating themselves outside the central city. PIV’s design places the office buildings around a 1.3-hectare man-made lake with schools of fish swimming about and birds pecking the surface for insects, an unusual scene for an office park.
PIV’S goal to be “a harmonious business park with R&D, commercial life, and leisure” is, unsurprisingly, also central to Dongtan’s design, as envisioned by Arup and the developer, SIIC. Dong says that harmony with nature is a principal concern. “It will not be the people here, and nature there,” he says. “It will be a city, but with walkways and waterways and parks. Nature will be in the city.”
Gao Guihua, a vice president of Shanghai Chongming Dongtan Investment & Development Co., a subsidiary of the larger SIIC holding company, notes that Dongtan will eventually have one‑third the residential population of Manhattan in about the same area and, presumably, fewer commuters and tourists.
The city will use only about 150 liters of water per person per day, Gao says, about the same as Singapore, which is among the world’s most advanced cities. More important though, Dongtan’s circulatory system will be based on reuse. Water from offices and homes will be captured by recycling plants that will distinguish so-called gray water from black water. Black water contains human wastes; gray water, everything else. Some gray water will go directly into wetlands, but much of it will be purified and then piped back into homes or sent north to irrigate farmland. Black water will be treated as an opportunity instead of as a pollution problem. The toilet wastes will be isolated by a steaming process, and the resultant biomass will be used to generate energy—being either dried and burned or used to produce methane. Animal wastes on the ecofarms will also be used as a source of energy when they aren’t needed as fertilizer.
Dongtan’s ecofarms will lie directly next to the central city. Solid and liquid wastes can thus be easily used on the farms, because they won’t have to be moved long distances. Likewise, the transportation of food from farm to table—a waste of energy necessitated by urban life—is minimized.
The urban part of Dongtan and the farms will occupy a slice of land that lies near the eastern end of Chongming Island [see photo, “Old and New”]. At 86 square kilometers, Dongtan will cover about 7 percent of the island. Agricultural researchers from a number of Chinese and European universities have already set up greenhouses to learn which crops will grow best in Chongming Island’s soil and how best to grow them.
Italian scientists have been particularly active, under the auspices of an organization called the Sino-Italian Cooperation Program for Environmental Protection, itself sponsored by the Italian Trade Commission and by the Italian Ministry for Environment, Land, and Sea. The organization began in 2000 and is active in a number of Chinese cities, including Beijing, Xian, and Tianjin. According to Silvia Massimi, the program manager for the Shanghai office, her organization started working with the city in 2004 and within a year began efforts to foster sustainable agriculture for Dongtan.
A three-year project aims “to start production of organic food on the island and to teach local people how to do agriculture without pesticides and with advanced techniques for saving water,” Massimi says. “They’re doing experimental trials using biological products instead of chemicals and pesticides.” The main problem is the salinity of the soil, caused by the surrounding East China Sea. “They are testing nonchemical, nonpolluting techniques to cultivate vegetables on the island,” she says. There’s a lot to study.
As an alluvial island—the world’s largest—there’s nothing to Chongming Island but compacted silt, and the island’s 1300‑year history has been determined by the vagaries of the sedimentary activity of the Yangtze River. Chongming was formed north of its current location by a large flood in A.D. 619. By the 13th century, it had at least 12 000 residents. The islanders credit themselves with inventing the junk, a type of sailing ship that for many centuries was key to China’s trading prowess.
Chongming’s edges continually washed away but were replenished by the Yangtze, which just as quickly washed the silt of its 6000-km riverbed into the sea. Like most rivers, though, it changed course over time and the island essentially disappeared at some point, only to reappear when the river’s mouth reformed in its present location. Peasants from Jiangsu province to the north resettled the island, and by 1896 regular ferry service was started from Shanghai.
Like a child hitting adolescence, in 1950 Chongming began a growth spurt, doubling its size over the course of the next 50 years, from 600 to 1229 km2 in 2001. One cause was deforestation at the upper reaches of the Yangtze’s watershed and the resulting soil erosion. A second cause was improved funding on the island for dams and other breastworks against the sea, which were a priority for the new government of Mao Zedong.
Chongming’s territorial expansion has all but stopped, because the Three Gorges Dam, a thousand kilometers upstream, now blocks most silt from going any farther downstream. Still, the island grows about 150 linear meters each year at its eastern end, the site of the third and final geographical component to Dongtan’s development.
To the east of the eco-city and the ecofarms, the Chinese Central Government is creating a national park. Besides being a draw for tourists, the Chongming Dongtan Nature Reserve will satisfy part of China’s obligations under the Ramsar Convention on Wetlands, an international treaty that has been in place for more than three decades and that, among other things, protects traditional migration routes for birds and fish. The Chinese government has imposed on SIIC a 3.5-km buffer between Dongtan and the reserve.
Although the plans are indeed grand, at the moment an observer at the site of the future city sees nothing to reveal what lies ahead. Hardly a spadeful of earth has been turned over for the eco-city of Dongtan, and work on both the ecofarms and the nature reserve has been preliminary. There are exactly two legacy buildings on the site of the city. One contains SIIC’s local offices; the other is a dormitory and cafeteria for its 200 workers, many of whom come over by ferry on Monday and return to Shanghai for the weekend. When the city is built, commuting in the other direction will presumably be more common, though both Arup and SIIC say that a key part of sustainability is that people work in the city in which they live.
To stand on the marshland that will be part of the nature reserve, you would similarly have no idea of its importance—that it is on a migratory path for birds that stretches from Australia to Canada and that it borders waterways that are the only habitat of young Chinese sturgeon. On the cold January day I was there, a lone seagull pecked away at something unseen between two large rocks. The wind blew stiffly and the air smelled of salt and seaweed. Nearby, construction workers dug into hard, sandy soil, working on a two-lane road that will run through the buffer zone. Turning away from the sea and looking past the roadcut, into a new-growth forest, I couldn’t picture a city.
In the 1980s, when China was planning the new special economic zone within Shanghai, the decision was between Chongming Island or Pudong. It chose Pudong. Although that decision created a skyline as breathtaking as New York’s, it is breath its residents can ill afford, given Shanghai’s smog. The city, in short, cannot afford another Pudong. Today, with Dongtan, Shanghai hopes to forge a new urban form using the best sustainability practices available. For the sake of all the world’s megacities, let us wish it luck.