Hieroglyph (44 page)

This futuristic city might not look very different from cities today. The one noticeable change would be how energy and food are generated in nearby farms and factories. Though the actual buildings would be recognizable to anyone from the twenty-first century, they're made from very different kinds of materials. Roads, paints, windows, and even toilet paper are made using substances and processes that don't exist yet. Still, all these innovations could grow out of technologies we're developing today to create solar fuel generators.

The metabolic city is an unintended consequence of research into solar power technologies.

Today, researchers at the Joint Center for Artificial Photosynthesis (JCAP) at UC Berkeley and Caltech are working on solar fuel generators that will convert water, sunlight, and carbon into liquid fuel. To do it, they've had to invent a new, high-throughput method for testing possible materials that could be used to absorb light and create fuel.

Solar fuel generators have to act as light antennas, drawing in as many wavelengths as possible, but also as catalysts to split water and carbon into oxygen and hydrocarbon fuel. They have to be rugged and able to function in salt water, and they have to be cost-effective. We don't yet have materials that can be all these things—and work together.

Ian Sharp, a physicist who works with semiconductor materials at JCAP, is trying to figure out how to layer different materials on top of each other to create a device that can absorb light as well as transform water and carbon into fuel. Often, this means guiding electrons through ultrathin layers of material. “It's kind of like brewing coffee,” Sharp says. “You want the coffee to make it into your cup, but you also want the grounds to stay where they're supposed to be. Except, with our device, the holes of the coffee filter are smaller than a few nanometers. And that means the system can become unstable, and you end up with a cup of coffee grounds.”

In his analogy, the electrons are your coffee, and the water that contains those electrons are the grounds—you want to get your electrons to pass through into the semiconductor, but prevent water from coming in and corroding everything. The filter is designed to filter electrons out of water and keep the semiconductor nice and dry.

Ten years ago, scientists like Sharp would have had to mix and test new materials for their filters or light absorbers over months, exposing them to different levels of heat and corrosives to see how well they worked. JCAP scientists have retrofitted an ink jet printer to synthesize and print out tiny dots of metal mixed up from different amounts or types of elements. The result is a long, scrolling paper like what you'd get out of an old dot-matrix printer. Except each dot on it is a novel material that can be tested in parallel. Up to one million of these new materials can be produced in a single day.

Consider that this high-throughput synthesis of materials is being used in many other labs too. Though JCAP will eventually settle on a particular stack of materials for its light absorbers and catalysts, it will have created millions of other materials with novel properties in the process. It plans to make information about all those materials available for free online. Other scientists working on different problems in materials synthesis can consult JCAP's database.

This is a classic example of how taking on a big scientific project can lead to other forms of innovation on the way to a long-term goal. JCAP scientists want to generate solar fuel from carbon dioxide and water. Along the way, however, they'll make it possible for engineers in many other fields to discover new materials that could lead to what we saw in the biomimetic city: spray-on, high-performance windows, foam roads, sophisticated 3-D printers, superdurable environmental sensors, and extremely efficient water recycling systems.

It will also lead to actual solar fuel generators, another reason this futuristic city looks a lot like San Francisco today. Unlike current solar energy, which is intermittent and terrifically difficult to store, solar fuel can be packaged up in drums just like oil and gasoline.

We'd fill our gas tanks with solar fuel and use pipes to bring it into the city from the nearby generator fields. We'd retrofit a lot of our current infrastructure to work with this new, carbon-neutral fuel. The fact that we won't have to reinvent the way we deal with fuel could help us transform our cities sustainably, and slowly. Instead of tearing cities down, we'll recycle them and patch them up with new materials. Our cities will evolve to be more like biological organisms that are self-restoring.

On the road to developing efficient solar fuel generators, we could create cities whose technologies behave like components in an environmental system. As Sharp put it to me, “It's not a future that looks totally different, but the subtle differences are important. The result is very realistic.”

Life in the Ruins: What Would Make This Scenario Possible?

Unlike the biomimetic city, the Mound city is actually biological. Everything from its water filtration systems to its solar energy production is done using biological organisms. Its structures aren't “smart” like iPhones—they are smart because they are teeming with bacterial colonies that respond dynamically to the environment. This city is the result of advances in synthetic biology that allowed engineers to use the photosynthetic process in cyanobacteria to convert water and light into hydrogen fuel.

Modeled on St. Louis, the Mound city looks dramatically different from cities of today—though, as our narrator explained, its architecture does resemble the styles favored by the Meso-American peoples who built Cahokia on the eastern side of the Mississippi River in the 600s CE. Historians believe that one reason Cahokia may have been abandoned in the 1200s is that the centuries-old city became polluted with waste and ruined by unsustainable agricultural practices. (There's evidence that the locals diverted rivers multiple times for irrigation.) Many of the problems that plagued people of that era are also issues for St. Louis's inhabitants today. The coal industry won't last forever, and droughts in the Midwest wreak havoc on the food supply.

That's why physicist Himadri Pakrasi has created an interdisciplinary initiative at Washington University in St. Louis called the International Center for Advanced Renewable Energy and Sustainability (I-CARES). The cornerstone of the initiative is a series of projects devoted to alternative energy, with Pakrasi focusing on genetically modified cyanobacteria.

A few years ago, Pakrasi made headlines when his lab created a strain of cyano that could produce far more hydrogen than average. If we could capture and use that hydrogen, he speculated, we'd have the beginnings of a new kind of sustainable fuel. Instead of drawing carbon from stores deep beneath the earth, this cyano would draw carbon that's already free-floating in the environment as part of its natural life cycle. This is the very definition of a carbon-neutral fuel.

When I visited Pakrasi in St. Louis to talk about how he imagined I-CARES would change the future, he suggested that one day his city would draw its energy from both algae and ultra-high-efficiency solar cells. His colleague Richard Axelbaum, an environmental engineer, gave me a tour of a model power plant facility at the university that the group thinks could represent a transitional phase between coal energy and algae energy. The plant is designed for “clean coal” burning, a process where the harmful by-products of coal burning are reduced and, in some cases, recycled. Carbon is siphoned off during combustion and fed to huge tanks of algae that will ultimately produce fuel. Tailings, instead of being stored in toxic ponds, are used in the production of asphalt.

This kind of energy plant, where coal burning feeds into the production of biofuel, is a reminder that we can't change over from one kind of energy production to another overnight. We have to move through transitional stages while corporations and the public adjust to the new carbon economy. To transition to the Mound city, however, we need more than hybrid fuel production facilities. The public must become accustomed to the idea that their city will run on genetically modified organisms.

Sustainable fuel from cyano could be the GMO that sets off a synthetic biology gold rush. After a generation grows up using GMOs for fuel, GMO panic might seem like an antiquated superstition. Today, we are already seeing the development of “smart” materials in labs—including bacteria-based, self-healing cement—but many people fear the idea of building with biology. It's possible that Pakrasi's strain of cyano, or something similar, could convert that fear into familiarity.

The result might be a place like the Mound city, where people use modified cyano for everything from air filtration to fuel. They also build with smart, self-healing materials, treating microorganisms the way we treat microprocessors today. Their Mounds are covered in vines and grasses that are an integral part of the city infrastructure.

However, Mound city isn't just the consequence of scientific advancement. If science were all that mattered for building a city, we could have a Mound city in fifty years. Cities are fundamentally social and economic structures. We'd need a social transformation that allowed for things like carbon taxes.

People living in the Mound city would also have dramatically different expectations about how they would live. Our narrator's home is in a densely populated building where her neighbors' cyano affects the functioning of hers—much the way a plumbing problem in one apartment can become a leak in another. She also doesn't own a car, nor does she expect to live in a place that is clean in the way most urbanites today would want. Dirt and plants are everywhere. And energy comes where you can get it. Most of the time, she powers up her computer by walking on a treadmill made with viruses that convert kinetic energy into electricity. For city dwellers of today, this might sound like a dirty, crowded, difficult existence.

To modern eyes, the Mound city would look like a ruin, with crumbling, scarred buildings that have been overrun with plants. But to people of the future, it would represent the apex of technology. Or rather, biology. Instead of building against the environment, Mound citizens would be building with the environment. They'd be using Earth's greatest source of energy: solar. It would be hard to know where the city stopped and the natural world began. It wouldn't be the sterile, orderly future of
Star Trek
that many of us were promised. It would just be Earth.

The biomimetic city and the Mound city are both imaginative products of a long-term scientific search for new kinds of solar energy. They remind us that every great innovation spawns more inventions than we intended.

As we move forward, new technologies and new social ideas may make the future as strange to us as a new city is to visitors from out of town. But if we choose our scientific projects wisely, we can harbor a rational hope that there will be friendly tour guides in centuries to come, willing to show our descendants around.

file404/Shutterstock, Inc.

FORUM DISCUSSION
—
Urban Sustainability

Vandana Singh, James Cambias, and other Hieroglyph community members debate sustainable cities, community gardens, and the “zoopolis” at hieroglyph.asu.edu/solar-city.

A HOTEL IN ANTARCTICA

Geoffrey A. Landis

© 2013, Nina Miller / ASU

MAYBE IT STARTED THE
day his laser company failed, the day his best friend, Saladin, drove off into the sunrise on his motor scooter, taking along the girl that Izak Cerny had always planned would be his girlfriend, and he stood on the curb waiting for lawyers and police cars to take everything he'd worked for, watching the sun rise, wondering what to do next.

Zak had stayed at a hotel that night. His credit cards were no good, but the banks hadn't yet flagged them for fraud. The hotel bill would just add a few more meaningless numbers to an epic bankruptcy. In a few days he would be thirty years old.