Adapted from The Unnatural World: The Race to Remake Civilization in Earth’s Newest Age, by David Biello. Published by Scribner, a Division of Simon & Schuster, Inc. Copyright © 2016 by David Biello. Reprinted with permission.
The search is on for technologies that can pull carbon dioxide out of the air, thanks to a global push to limit such pollution and thus to limit global warming. The air we all breathe now boasts more than 400 parts per million of the colorless, odorless gas—more than at any point since Homo sapiens became a species.
To begin to slow or even reverse the rising concentration, new technology will be required, especially in a world in which entire governments continue to deny a global warming problem exists. There are a host of possibilities, from helping soils trap carbon to burying CO2 at sea, but a leading candidate to solve this carbon conundrum may be plastic.
Physicist Klaus Lackner at Arizona State University and his colleagues have stumbled upon a resin—typically used to purify water—that will greedily suck CO2 out of the air. When Lackner inserts a strip of plastic impregnated with particles of this resin, CO2 levels inside a test tank begin a steady march down.
A small prototype of an artificial tree that would use the resin to cleanse the sky sits atop a building on Arizona State campus in Phoenix. The plastic tree doesn’t look much like vegetation: Thin strips of beige, wavy plastic stacked one atop another in a clear box hidden from the desert sun by a piece of plywood covered in a black cloth. In fact, the photovoltaic panel on a tall tripod standing beside this ungainly apparatus looks more like a tree. But the box shares one big thing in common with photosynthetic organisms, from a microscopic plankton to a towering redwood—it can suck CO2 out of the air.
The plastic tree is just one of a new wave of devices aimed at helping people get a handle on this outsized trash problem. Another prototype, this one using liquid chemicals instead of plastic, busily scours the air near Squamish, British Columbia, and yet another may soon cleanse the seemingly pristine mountain air of Switzerland.
And those are just the machines. A brewery for ethanol in Illinois could end up burying CO2, turning the manufacture of biofuel into a way to draw carbon out of the sky. Similar CO2-sucking biofuels could be made from everything from algae to kelp. Or people could use minerals that react with air to remove the gas.
Today the sky is an open sewer for such pollution. Smokestacks billow filth, tailpipes belch fumes, and all the while CO2 invisibly accumulates, warming the world. Burning fossil fuels, clearing forests, and plowing up grasslands have changed the composition of the air we all breathe.
Concentrations of carbon dioxide—the same molecule each of us exhales with every breath—have climbed from around 0.03 percent of the air in the sky to 0.04 percent over the last few centuries. That may not seem like much but a shift of 100 parts-per-million has been enough to raise global average temperatures by one degree Celsius already, with much more warming in store. And if geologic time is any guide, such a seemingly minute shift has been enough to change the Earth’s climate from an ice age in which glaciers a mile thick cover the spot that presently hosts New York City, to the relatively balmy temperatures of today that allow a global capital to flourish seaside.
The ability of CO2 to trap heat has been known since the 19th century and rising levels of CO2 in the sky have been tracked since the 1950s. In 1992 the governments of the world agreed to do something about it but have spent the last several decades dithering and burning more and more fossil fuels rather than developing techniques and technologies to stop pollution and clean up the air.
As of now, civilization as a whole adds nearly 40 billion metric tons of CO2 to the air each year. Some of those molecules will still be in the air trapping heat more than 1,000 years from now—unless something is done to take them out.
Today, the ocean absorbs the bulk of the carbon liberated by people’s penchant for fossil fuel burning. At the same time, trees and other plants have grown greener as a result of all that extra CO2. But the planet’s plants may have peaked in their ability to absorb more CO2, and the more the oceans absorb the more acidic they get, which might be the worst impact of all that carbon trash.
Never one to think small, Lackner estimates that 10 million plastic trees could drop CO2 concentrations by 0.5 parts-per-million per year, putting the world on track to remove all the CO2 it has added over the course of the next few centuries. But to really think big and to counteract the 40 billion metric tons of CO2 dumped each year would require more like 100 million plastic trees. For comparison, people (and robots) make roughly 80 million cars per year presently.
Those 100 million plastic trees would also consume a lot of electricity and water, among other things, and that’s if the resin works as well as hoped. Then there’s the challenge of cost. An estimate from the American Physical Society suggests capturing CO2 from the air might cost roughly $600 per metric ton, which makes an artificial tree a luxury good if used to pull 1.5 trillion metric tons of greenhouse gas out of the atmosphere in order to reduce concentrations by 0.01 percent.
That deployment would just pick up the trash. All that carbon has to go somewhere. The best bet for disposal may be to bury it back underground just like all those fossil fuels. Or more energy can be applied to all that captured CO2 to transform it back into fuels like oil or ethanol—an opportunity to endlessly reuse and recycle the carbon if a cheap, abundant, clean energy source can be found and used.
The world needs people like Lackner to engineer through invention another Carboniferous period, a time hundreds of millions of years ago when swampy forests enabled vast amounts of carbon to be buried as the dirty black rock we now call coal. Our enterprising species dug up this coal—and oil and natural gas—and liberated the carbon inside by burning these fossil fuels. If this enterprising species doesn’t clean up the resulting mess with technologies like plastic trees to pull carbon out of the air, we may find ourselves in an unhealthy Anthropocene with a climate too weird, wild and hot to handle.