The most advanced green buildings don’t just consume fewer resources. Some are made from materials that are taken quite literally out of thin air—forged from carbon dioxide and methane that would otherwise pollute the atmosphere. Everything from walls and furniture to the roofs above our heads can be made from greenhouse gases.
Removing atmospheric CO2 and putting it into something useful or storing it somewhere safely is called carbon sequestration. Carbon can be sequestered by scrubbing CO2 out of the exhaust stream in power plant smokestacks and pumping it deep underground, although this process still remains largely untested and prohibitively expensive. Another promising new technology transforms greenhouse gases into the fuel methanol.
There are even artificial “trees” developed by researchers at Columbia University which use sodium carbonate-impregnated “leaves” to capture carbon in a chemical reaction, producing sodium bicarbonate, also known as baking soda. The baking soda can later be heated to release pure, sequestration-ready CO2. But the problem with these ambitious new technologies is that few consumers have been willing to pay for them.
Trapping carbon in building materials, on the other hand, is a lot cheaper. The products that do this are generally cost-competitive with less sustainable options, and we don’t have to wait for big corporations or governments to act. We can choose to use these green alternatives in our own homes.
Granted, these materials are unlikely to make a big dent in our current climate crisis unless we combine their use with wasting a lot less energy. In 2014, the average U.S. residential utility customer consumed 10,932 kilowatt-hours of electricity, resulting in the emission of over seven tons of carbon into the atmosphere.
We already know some good ways to clean up our act. Insulating better and purchasing the latest energy-efficient appliances are two places to start lowering the carbon footprint of our homes. But to fully earn the Green Housekeeping Seal of Approval, you’ll also need to get smarter about what your house is made of. Fortunately, there is a growing number of cleaner and greener options to choose from.
Cement is the most widely used material in the world—and that is a problem. Making cement is a notoriously dirty business, consuming lots of energy in its heat-intensive manufacture and creating chemical reactions during production that account for 5 percent of our global CO2 emissions.
But not all cements are created equal. The sustainable cement maker Solidia Technologies has slashed its carbon output by tweaking the basic recipe, using less limestone and lower roasting temperatures. The cement further reacts with CO2 during the curing process (when it hardens), trapping the carbon permanently in the concrete matrix.
The company tells Smithsonian.com that their manufacturing process spews up to 70 percent less carbon into the atmosphere than conventionally produced cement. That amounts to over a thousand pounds less CO2 created for every ton of cement produced—not bad for one of the highest-emission industries on Earth.
Follow the Green Brick Road
You may soon be able to slather low-carbon cement onto bricks composed of power plant exhaust. The University of Newcastle in Australia has partnered with the chemical and mining giant Orica and the carbon innovation company GreenMag Group to pioneer a process called mineral carbonation, which turns CO2 from a gas to a solid.
“One of our aims is to use this material in products like brick, pavers and even plasterboard,” says Orica’s senior scientist Geoff Brent.
A metamorphic rock called serpentine is heated to release water and react with compressed CO2 from power plant exhaust to form magnesium carbonate—a powdery substance similar to baking soda—and silica sand, which in turn is molded into assorted building materials.
This carbonation process mimics natural geology, which creates carbonates through the slow weathering of minerals. Geologists believe that over millions of years this process reduced the excessive CO2 in the prehistoric atmosphere to levels that enable life to thrive today.
The world’s first pilot mineral carbonation plant will be opened on the grounds of the University of Newcastle in March. If this venture is successful, Orica hopes eventually to scale up to commercial production.
A New Meaning to "Green Roof"
Carbon can be trapped in our roofs as well using another mineral trick that nature has got up its sleeve—namely, olivine.
This literally green mineral, pictured above in its gem form, peridot, is one of the most abundant rocks in Earth’s mantle. It weathers quickly when it is exposed to CO2 in the air, sponging up the offending gas and converting the mixture into silicon dioxide and magnesite, which renders the greenhouse gas chemically inert.
The multinational company Derbigum has devised a roofing system that, when hit by rain, binds with CO2. Olivine in a roof can capture 1.25 times its weight in CO2 during the course of its lifetime. And when the olivine roofing membrane has done its job (it takes about 30 years for the mineral to stop reacting with CO2) then you can roll out a new roof and start all over again.
Separately, the same olivine that captures CO2 in roofs can be used to pave pathways and roads or be added to sandboxes and beaches. It is already being marketed as a soil amendment by the Dutch Company greenSand, which sells it to home gardeners who want to revitalize their soil and raise its pH Level to grow healthier carbon-sequestering trees and flowers.
But the company has even bigger agricultural ambitions. “If this catches on,” says greenSand spokesman Bas Zeën, “large areas of farmland will be turned into CO2 cleaners.”
Walk the Green Walk
Bamboo grows like a weed, matures in three years, regrows on its own without the need for replanting, and does not require a lot of fertilizer or pesticides to thrive. This tough material has greater compressive strength than concrete, making it ideal for many building applications like flooring, paneling, screens and stairs. Bamboo also sequesters a lot more carbon per acre per year than most other wood products.
Despite these impressive green credentials, though, not all bamboo is sustainably produced. Buyers should check out their suppliers first to make sure that the bamboo that they are purchasing is grown and harvested in an eco-friendly way.
Much of what is inside our houses is made of plastic. Plastics are produced in factories, which consume about 270 million tons of fossil fuels every year. But here too, there are some exciting new products to green up our act.
California-based Newlight Technologies has come up with a way to turn waste methane—a greenhouse gas 20 times as heat-trapping as CO2—produced on livestock farms into biodegradable plastic, a material that the company has named AirCarbon.
Producing plastic from pollution was not cost-effective until Newlight discovered a novel catalyst that allowed it to create the material at a lower unit cost than oil-based plastic of similar quality. The company is currently working with over 60 Fortune 500 companies on plans to use AirCarbon in a variety of products from cell phone cases to plastic bags and furniture, like the chairs pictured above in a rendering by the company KI.
Geoffrey Coates, a chemistry professor at Cornell University who developed a similar method of turning CO2 into the building blocks of plastics, says that we are on the threshold of a revolution where manufacturing can start taking carbon out of the atmosphere instead of putting it in. But he cautions that there will be no silver bullets.
“Experts on CO2 utilization recognize that there will not be one ‘cure-all’ for the CO2 problem,” Coates says. “It will take many technologies, each dealing with some portion of the excess CO2 being released, to make an impact.”