In China, New Sustainable Cities Are Rising From Nothing
China is planning a building explosion of dense, sustainable suburbs, connected to its megacities by public transit. Can these “prototype cities” alter the course of the country’s unsustainable development?
Although Garden Cities never really caght on in the West, the Chicago-based Adrian Smith + Gordon Gill Architecture has resurrected the idea with Chinese characteristics: a “prototype city” twice as populous and 20 times as dense, with a tower taller than the Empire State Building at its core. Working with one of China’s largest real estate developers, the firm aims to build them by the score.
The first is slated for a patch of farmland roughly 10 miles from the core of Chengdu, China’s westernmost mega-city. Designed according to the specifications of Beijing Vantone Real Estate Co., the master plan calls for 80,000 residents to live and work within a half-square mile circle in which any point will be at most a 15-minute walk away.
To achieve that level of density—which is comparable to the Chicago Loop—“the average height of the buildings would have to be 18 stories,” says Adrian Smith. But to preserve a 480-acre greenbelt around the city, and to mollify officials anxious about developers chewing up so much farmland, the plans call for towers as high as 400 meters (1,312 feet), taller than anything in Chengdu itself. (At least until AS+GG complete their commission for a separate 450-meter tower downtown.)
Trains and mass transit will connect the satellite city to Chengdu’s core as part of the firm’s plans to restrict cars and dramatically reduce the city’s carbon footprint. With the help of infrastructure consultants Mott McDonald, the city will deploy a raft of tactics and technologies to holistically address waste, water, and energy in a manner designed cut landfill by 89%, wastewater by 58%, and energy by 48% compared to a typical Chinese city its size—which is good, because Vantone plans to sell at least one to every mega-city in China.
As Smith tells it, his partners at Vantone settled on the parameters of their neo-Garden City even before they found a site. “They were looking outside Beijing as well,” says Smith,” but the first [city] that said ‘let’s do this’ was Chengdu.”
“The old Ebenezer Howard satellite city concept never happened much in Europe, but with the growth and control that exists in China, it’s possible,” Smith adds. “It’s what, 80,000 people? That’s not huge. You’d need 12 to get to a million people.”
Vantone and AS+GG aren’t the first to propose a bright green protoype for China’s mega-urbanization. Not content to design entire cities-from-scratch, a raft of foreign architects, developers, and even sovereign governments are offering their projects as templates. Maybe the most famous is Songdo, the “city-in-a-box” designed by the architects Kohn Pedersen Fox on behalf of American developers Gale International. Plans to build as many as 20 sequels across China are on hold, although one is proceeding outside the provincial capital of Changsha without Gale’s involvement.
AS+GG’s Smith is looking even further abroad. “We think it makes sense not just for China, but for India as well,” he says. “Since India has no infrastructure to speak of,” or at least not enough to double the densities of its already mind-bendingly populous centers, “you have to build out from the city’s core.” Ebenezer Howard would be proud.
BEFORE we run out of fossil oil, we will thoroughly tap the sea floor, find and frack wells wherever they may be, and excavate and extract the most recalcitrant of oil shales. In so doing, we will fuel our lifestyle for a few more decades at the cost of releasing vast amounts of carbon dioxide, adding to global warming, melting ice caps, raising sea levels, acidifying oceans - and setting course for a future for which there are few optimistic scenarios.
In the face of all this, scientists are racing to find alternatives. Biofuels are my passion but they have had rather a bad press, from complaints about displacing food production to the inefficiency of soya beans and the carbon footprint of ethanol. Microalgae have a low profile but they deserve a much higher one, since the fossil oil we mine mostly comes from microalgae that lived in shallow seas millions of years ago - and they may be key to developing sustainable alternative fuels.
Algae are single-celled organisms that thrive globally in aqueous environments and convert CO2 into carbohydrates, protein and natural oils. For some species, as much as 70 per cent of their dry weight is made up of natural oils. Through transesterification (the process of adding three molecules of alcohol to one molecule of natural oil), the algae oils can be transformed into renewable fuels.
Microalgae hold great promise because some species are among the fastest growing plants alive and are therefore one of the best sources of biomass, while other species have been estimated to produce between 18,700 and 46,750 litres of oil per hectare per year, nearly a hundred times more than soya beans’ 468 litres per hectare per year.
But there are big unsolved problems at which governments should be throwing funds and brainpower as if we were involved in a Manhattan project. For example, since few species of microalgae have been domesticated, we don’t know how to grow them reproducibly or economically. At what scale will algae farming be efficient? To put this in perspective, US planes use 80 billion litres of fuel per year. To supply this fuel from microalgae at the lower end of the estimated production rate would take 4.2 million hectares - twice the area of Wales.
Luckily, there may be a good way to cultivate this much algae while solving the ethical problem of producing biofuel without competing with agriculture. Freshwater algae can be grown in wastewater (effectively, water with fertiliser), or marine algae can be grown in a blend of seawater and wastewater. In both cases, wastewater provides a growth medium and the algae clean the wastewater by removing nutrients and pollutants from it. So there’s no competition for fresh water needed elsewhere, no reliance on synthetic fertiliser, and the environment benefits.
The UN estimates that the world produces around 1500 cubic kilometres of wastewater annually, of which more than 80 per cent is untreated. This means there is an ample supply of nutrient-rich water for the algae, while algae treatment is available to offset the environmental impact of wastewater.
There remains the question of how and where to grow the algae. A few species are cultivated commercially on a small scale, in shallow channels called raceways or in enclosures called photobioreactors (PBRs). Raceways are relatively inexpensive, but need flat land, have lower yields than PBRs and problems with contamination and water loss from evaporation. PBRs have no problems with contamination or evaporation, but algae need light, and where there is light, there is heat: a sealed PBR will cook, rather than grow, algae. And mixing, circulating and cleaning problems send costs sky high.
Assuming we can fix this, the question of siting remains. In order not to compete with agriculture, PBRs must use non-arable land reasonably close to a wastewater treatment plant. But in most cities, wastewater plants are surrounded by infrastructure, so installing PBRs on thousands of hectares around the plants would affect roads, buildings and bridges - again driving up costs prohibitively.
A solution occurred to me: for coastal cities, we should try a system I call OMEGA - Offshore Membrane Enclosures for Growing Algae. Some 40 to 60 per cent of Earth’s population lives near a coast, most of the biggest cities are near a coast, and nearly all coastal cities discharge wastewater offshore.
How does OMEGA work? It uses PBRs made from cheap, flexible plastic tubes floating offshore, and filled with wastewater, to grow freshwater, oil-producing algae. It would be easier to build the systems in protected bays, but breakwaters could also be constructed to control waves and strong currents. The water need not be deep or navigable, but a few things are crucial, including temperature, light, water clarity, frequency and severity of storms, boat traffic, nature and wildlife conservation.
Beyond solving the problem of proximity to wastewater plants, there are other advantages to being offshore. OMEGA uses buoyancy, which can be easily manipulated, to move the system up and down, influencing exposure to surface waves and adjusting light levels. And the overheating problem is eliminated by the heat capacity of the surrounding seawater.
The salt gradient between seawater and wastewater can also be exploited to drive forward osmosis. Using a semipermeable membrane, which allows water, but not salt, pollutants or algae to pass through, wastewater is drawn into the saltwater with no added energy. In the process, algae are concentrated in preparation for harvesting and the wastewater is cleaned, first by the algae, and then by forward osmosis. This produces water clean enough to release into the marine environment or recover for reuse.
If OMEGA’s freshwater algae are accidently released, they die in seawater, so no invasive species can escape into the ecosystem. In fact, OMEGA can improve conditions by providing a large surface for seaweed and invertebrates to colonise: part floating reef, part floating wetland. Then there are the extra possibilities of developing wind or wave power and aquaculture - growing food such as mussels.
OK, if it’s so good, where is it? For the past two years, backed by NASA and the California Energy Commission, and about $11 million, we have crawled over every aspect of OMEGA. In Santa Cruz, we built and tested small-scale PBRs in seawater tanks. We studied OMEGA processing wastewater in San Francisco, and we investigated biofouling and the impact on marine life at the Moss Landing Marine Laboratories in Monterey Bay.
I’m now pretty confident we can deal with the biological, engineering and environmental issues. So will it fly economically? Of the options we tested, the OMEGA system combined with renewable energy sources - wind, solar and wave technologies - and aquaculture looks most promising. Now with funds running out and NASA keen to spin off OMEGA, we need the right half-hectare site for a scaled-up demonstration. While there is enthusiasm and great potential sites in places ranging from Saudi Arabia to New Zealand, Australia to Norway, Guantanamo Bay to South Korea, as yet no one has committed to the first ocean deployment.
We could be on the threshold of a crucial transition in human history - from hunting and gathering our energy to growing it sustainably. But that means getting serious about every option, from alpha to OMEGA.
Jonathan Trent studied at Scripps Institution of Oceanography, University of California, San Diego, specialising in extremophiles. He is lead scientist on the OMEGA project at NASA’s Ames Research Center in California. This essay is based on a talk he gave at TEDGlobal 2012 and a paper in Biofuels
From issue 2879 of New Scientist magazine, page 30-31.