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Urban Outfitters - How engineers hope to transform congested cities into sustainable homes for half of humanity. + BY THOMAS K. GROSE

In 1925, Dar es Salaam was a leafy colonial port with 30,000 residents. As recently as 1972, Tanzania’s largest city was home to a mere 396,000 people. Today, the population has swollen to 3 million and a once short drive from downtown to the affluent residential neighborhood now takes two hours. If the head count doubles every 12 years, as the World Health Organization (WHO) projects, Dar es Salaam could join the congested ranks of “megacities” with 10 million or more inhabitants by 2034. The pressure on its already strained infrastructure — electricity is rationed and food supply lines barely keep up with demand — almost certainly will be acute.

Dar es Salaam is just one of many cities experiencing the unprecedented growth —and growing pains — that characterize the world’s first Urban Century. Roughly half the planet’s 6.6 billion people currently live in cities, consuming the bulk of all cars and food produced and spewing 70 percent of global carbon emissions. A million more people move to cities each week. By 2030, an estimated six in 10 humans will dwell in major metropolitan areas, including 29 megacities. (Today, there are 19, up from just two 50 years ago.) While much of this surge is created by desperate refugees from economically depressed rural regions of Africa and south Asia, many cities in wealthy nations are growing fast, too. New York’s population is expected to jump from 8.2 million to 9.1 million by 2030; London’s could skyrocket by 14 percent, to 9 million, within seven years.

Dar es Salaam, Tanzania
Dar es Salaam, Tanzania
Photograph by Muhammad Mahdi Karim

For engineers, this flood of humanity presents a host of complex design challenges and opportunities to innovate. Chief among them: how to find workable, cost-effective ways to relieve stresses on vital transportation, energy, and water systems. “If we don’t have good engineering and planning, these cities will come under enormous strain and will not be nice places to live, and they will be disastrous for the environment,” says Mathieu Lefevre, executive director of the New Cities Foundation, a Geneva-based think tank geared toward sustainable metropolises. “The role of the engineer is essential to making sure we can act on the opportunities presented by urban demographics.”

Starting Over vs. Retrofitting

Countries with enough space and deep pockets have a blank canvas to plan their urban futures. China, for instance, intends to spend $1.6 trillion within the next 10 years creating new cities from scratch. Saudi Arabia is building King Abdullah Economic City, with a port and an industrial zone, to house a projected 2 million residents. Even Ghana and Kenya have broken ground on ambitious satellite developments outside their capitals. But the “main show” for engineers will be retrofitting older, struggling cities, like Karachi, Kinshasa, and Manila, “that were not built on solid foundations,” says Lefevre. In some ways, advancing technology allows the developing world’s megacities to “leapfrog ahead” of the costly infrastructure industrialized nations had to develop. For instance, cellphones eliminate the need to string costly landlines; in many African countries, telecommunications networks are already primarily cellular.

Key to making cities work better is knowing how cities work. Engineers “have to be more systems-oriented, and understand all the interactions of a city,” says Jean-Pierre Bardet, engineering dean at the University of Texas, Arlington, and the former head of the Center on Megacities at the University of Southern California. Bardet favors a system-of-systems approach. “When we talk of megacities, it is not just a question of size, but a question of complexity,” he says. The easiest way to grasp that concept, explains Loring F. Nies, a civil engineering professor at Purdue University, is to consider the connections between water, energy, and food, and then overlay such things as transportation, healthcare, finance, and telecommunications. “If one stops working, it impacts the others.”

Whether in a newly built metropolis or centuries-old capital, traffic is every city’s “No.1 problem,” says New Cities Foundation’s Lefevre, who holds degrees in public policy and economics. Clogged transportation arteries not only frustrate commuters and hamper food delivery and commerce; they waste energy. A 2011 study by the Texas A & M Transportation Institute found that congestion caused drivers in America’s 439 metropolitan areas to spend 4.8 billion more hours on the road and to purchase an extra 1.9 billion gallons of gas, for a cost of $101 billion. City traffic is a health issue, too, killing 1.3 million people annually and injuring an additional 50 million, according to the WHO.

Repairing or replacing existing systems is hugely expensive. The American Society of Civil Engineers has put the cost of modernizing bridges, solid waste systems, and other infrastructure in the United States at $2.2 trillion. But technology that improves the use of what we already have pays dividends. London, Singapore, Stockholm, and Milan, for example, have instituted congestion zones in central areas that use CCTV cameras and license-plate recognition systems to charge tolls on vehicles entering the zones. Washington, D.C., Los Angeles, and San Francisco are testing sensor-guided smart parking systems.

A study of Boston and San Francisco traffic led by Marta González, an assistant professor of civil and environmental engineering at the Massachusetts Institute of Technology, found that efforts to encourage the use of mass transit, telecommuting, or car pools aren’t terribly effective. But if just 1 percent of commuters from a few key neighborhoods avoided rush-hour driving, they could cut travel time for all commuters by up to 18 percent. Moreover, that percentage “is very conservative” and scalable, says González, whose team determined which neighborhoods to target by using cellphone data to figure out drivers’ regular routes. “It’s based on routine behavior, and this happens in cities all over the world,” says González. The next step is more difficult, she admits: “How do you provide incentives to get enough people [in the right areas] to adopt” an alternative to rush-hour driving?

If such persuasion fails, clogged city streets are likely soon to become easier to navigate with tiny, highly maneuverable networked electric cars that share information with each other and drive within fast-moving packs. Indeed, at last month’s Consumer Electronics Show, Toyota showed off a prototype of just such a car crammed with high-definition cameras, radar, infrared sensors, and satellite connections, while Audi announced it is testing a self-driving car.

One of the lowest-cost forms of mass transit – buses – can become more convenient through improved planning. In Curitiba, a city of 2.2 million in Brazil, municipal buses travel in special lanes free of other vehicles and stop lights. Passengers pay as they enter the bus stop—many of which have high-tech, tubular designs and are comfortable—so boarding stops last no more than 19 seconds. As a result, 70 percent of Curitiba’s 1.3 million daily commuters use the buses, cutting fuel use to 30 percent below that of similar-size Brazilian cities and producing one of the country’s lowest pollution rates. Meanwhile, international design company frog has been promoting the concept of aerial gondolas as a low-cost means of urban transportation. The firm estimates a mile-long connection would cost between $3 million and $12 million to construct, compared with around $400 million per mile for a subway.

Smart Infrastructure

Sensors, wireless technology, and fiber optics make new or existing bridges, roads, buildings, and tunnels safer and more efficient. “The construction industry has lagged behind others in terms of innovation,” says Robert Mair, a professor of geotechnical engineering at Cambridge University and principal investigator of the school’s Center for Smart Infrastructure and Construction. But that’s clearly changing. His team is developing wireless sensors, powered by energy harvested from the wind and vibrations of passing vehicles that can predict stresses and strains, and thus extend the design life of older infrastructure. Smart infrastructure, says Lucio Soibelman, chair of the department of civil and environmental engineering at the University of Southern California and an expert on smart facilities and intelligent water grids, is the only affordable way urban America can address what he calls its biggest problem: aging, deteriorating buildings. Fiber optics, for example, can be used to determine how well the deep concrete piles used to anchor skyscrapers are performing; those data can be used to design and construct piles using much less concrete. Currently, civil engineers almost certainly overestimate how much cement is needed for piles because they err on the side of caution for safety reasons. “We have to make assumptions that are very conservative,” Mair says, and that’s wasteful. Reducing the use of concrete, the world’s most popular building material, would also help cut carbon emissions. Cement accounts for 5 percent of human-produced carbon emissions because the materials are baked in superhot kilns.

“Green” cement offers another potential energy-saving construction option. Alex Moseson, a mechanical engineer at Drexel University, has developed an alkali-activated cement that requires no heating and is composed of 68 percent limestone, a common and low-carbon material. Also in the mix are the industrial byproducts slag and fly ash, along with a commercial alkali, which together take the place of the kiln-produced clinker needed to manufacture traditional portland cement. The resulting “green” cement—similar to that made by the ancient Romans—cuts energy use and carbon emissions by 98 percent compared with its conventional counterpart. “That’s a very strong draw for the developed world,” Moseson says. “I would call this a disruptive technology.” Though bringing his product to industrial commercial scale is proving difficult, he believes it is “highly likely” that alkali cement eventually will be widely used.


New “green” construction materials include an alkali-activated cement developed by Drexel University mechanical engineer Alex Moseson. He calls it “disruptive technology.”
Photograph by Steve Marsel

Water Works

As cities expand, many are draining their water sources dry. “Over-extraction is an ongoing problem,” says Sarah Bell, a senior lecturer in environmental engineering at University College London whose research focuses on water management. Many cities opt to pump water great distances to ensure supplies, but that requires a lot of energy and pipelines. Ultimately, Bell says, cities must use the same technology as desalination to recycle wastewater, forcing it through ultrafine membranes under high pressure to remove micropollutants. A number of cities around the world, including San Diego, have safely and successfully recycled wastewater. Though energy intensive, desalination technology has made great strides over the past five years and eventually should spur demand and lower prices. “It’s gone crazy,” says Bell. “It’s still very expensive, but less expensive than 10 years ago.”

A problem almost as burdensome as traffic and water is solid waste disposal. The answer all too often has been immense dumps outside major cities – and the slightly more civilized Western equivalent, the urban landfill – or belching incinerators. The resulting danger to groundwater and air quality has lately been compounded by disposal of electronic components containing lead. Recycling has proved, at best, a partial solution.

Waste-to-energy systems that capture gas from trash are becoming increasingly sophisticated, but their high start-up costs are impossible for much of the developing world to meet. A small U.S.-Pakistani pilot project could show a low-cost path forward. Co-led by a U.S. Department of Agriculture research engineer, William Orts, and Romana Tabassum, a 2007-8 postdoctoral researcher in biological systems engineering at Virginia Tech, it seeks to develop new technology for converting waste into renewable energy. The team is studying ways of producing biomethane gas and ethanol simultaneously from agricultural biomass, industrial waste – including office waste, newsprint, and packaging – and municipal solid waste. According to the team’s website, its hope ultimately is to transfer the technology developed to the private sector for commercialization. Elsewhere, aid groups are encouraging community-based micro-enterprises for waste separation and recycling, and household compost bins.

Building Downward

Amid a global race to erect ever taller skyscrapers, some cities are also burying less salubrious facilities underground to make room for more attractive properties aboveground. Hong Kong, for instance, is considering plans to build sewage plants, parking lots, and its civic center in bedrock. There is precedent: Norway and Finland have underground municipal water-treatment plants and heating/cooling plants. Oslo, Norway’s cavern-laced capital, has buried its National Archives and transformed old bomb shelters into a huge sports complex, while Montreal is latticed with 20 miles of shop-lined pedestrian tunnels. In Kansas City, Mo., engineers and architects have carved old limestone mines into what Progressive Engineer calls the world’s largest underground business complex. The subtropolis offers a naturally cool, secure environment for storing records, saving on construction costs. And because limestone is three times as strong as concrete per square inch, the vaults can accommodate extremely heavy items. Ventilation remains a concern, however, so engineers use steel doors and industrial fans to circulate air according to each tenant’s needs.

Carved from limestone mines in Kansas City, Mo., SubTropolis, the world’s largest underground business complex, offers low lease rates and utility costs,
constant temperature and humidity levels, and sustainability.
Photos courtesy of SubTropolis & Google

Despite their challenges, cities also offer efficiencies of scale. “Urbanization is a great thing,” contends Purdue’s Loring Nies, whose research areas include urban systems sustainability. Greater density, for example, cuts per-home infrastructure costs by making it easier to supply power and remove garbage. Residents in compact neighborhoods also rely less on cars, improving air quality. Many cities have created bike lanes on major thoroughfares – encouraging a healthy shift away from solo commuting by auto. Efficient systems can be installed or encouraged community wide, as Los Angeles and the District of Columbia are doing with energy-saving LED street lighting. Buildings topped in vegetation to improve heating and cooling, and to filter CO2 and pollutants — are becoming increasingly popular urban fixtures, including atop Chicago’s city hall.

Interdisciplinary thinking is essential in re-engineering cities, says Leidy Klotz, a Clemson University associate professor of civil engineering whose research focuses on sustainability in the built environment: “There are no textbooks to tell us how to fix these problems.” USC’s Soibelman agrees that input from social scientists is critical. He recalls designing a system based on sensor data that showed people how to cut their energy bills up to 25 percent by using their appliances more efficiently, but most folks couldn’t be bothered to employ it, despite the savings. After consulting with psychologists and sociologists, Soibelman’s team pitched the plan as a way to reduce a family’s carbon footprint. And it worked. “They would do it for energy, but not for money,” he says. “But how would an engineer figure that out?”

The interdisciplinary approach is unlikely to diminish the paramount role of engineers from a variety of fields. “For engineers, the 21st century will be the century of the cities,” reckons University of Texas, Arlington’s engineering dean Bardet, who plans to set up an urban research institute at his college. And while the vision and technological progress seen so far are undeniable, much more will be needed in the decades ahead. A number of megacities – New York, Lagos, and Karachi, to name just three – sit on coastlines vulnerable to rising sea levels and climate change-induced storm surges. So does emerging megacity Dar es Salaam.

Engineers have an additional incentive to help make urban areas sustainable and life-enhancing. They are likely to be living in one.


Thomas K. Grose is Prism’s chief correspondent, based in London.



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