“The energy embodied in the materials for new buildings around the world — mostly steel and concrete — accounts for 11 percent of global carbon emissions.” That’s according to an opinion piece in the New York Times written jointly by Frank Lowenstein, the chief conservation officer of the New England Forestry Foundation; Brian Donahue, an associate professor of environmental studies at Brandeis University; and David Foster, a director of Harvard Forest and the president of the Highstead Foundation. With consciousness of carbon emissions from the utility industry on the rise, the contribution to the world’s carbon emissions problem by other sectors such as construction and shipping often gets overlooked.
The Case For High Rise Wooden Buildings
Lowenstein, Donahue, and Foster argue that “expanding wood construction while limiting global harvesting to no more than the annual growth could produce a combination of emissions reduction and carbon sequestration equivalent to eliminating construction emissions altogether. This could take a big bite out of the carbon problem, roughly equivalent to the present contribution from all types of renewable energy.”
A study conducted by researchers at the University of British Columbia found that constructing a 5-story office building with wood had less than a third of the global warming impact of a comparable steel and concrete building. The university has an 18-story dormitory made from cross laminated timber — a form of wood construction that is similar to plywood but on a much larger scale. Wooden buildings not only reduce the carbon emissions from construction, they keep atmospheric carbon locked up for the life of the building — or longer if components are reused.
“Forest ecosystems and wood buildings can be our most important climate allies. We should minimize the conversion of forests, enable more wood construction and incentivize private landowners to improve their stewardship,” the three authors say. “By tying together the city and the forest, this effort could unite rural and urban citizens toward shared goals — a livable climate, a viable economy and a vibrant, living landscape.”
Wooden buildings may sound counterintuitive. Doesn’t wood burn? Well, yes, actually it does. That’s how we make S’mores and such. But cross laminated timber — known as CLT — is about as fire resistant as concrete. And structurally it is as strong as steel. Recent US wood buildings include the 7-story 3T building in Minneapolis, the 8-story Carbon 12 building in Portland, Oregon, and a 6-story dormitory for the Rhode Island School of Design. Around the world, wooden buildings are dotting the skyline in Canada, Norway, Sweden, England, Australia, and Norway.
Zero Emissions Cement
Making cement requires lots of energy and very high temperatures — up to 2,500º F — and accounts for about 8% of global emissions. Now researchers at MIT say there is a way to make zero emissions cement using cheap electricity from renewable sources such as wind turbines to split water into oxygen and hydrogen. In a paper published in the Proceedings of the National Academy of Sciences, they say if the electricity costs less than 2 cents per kilowatt and the carbon dioxide created as the end result of the process can be captured and sold, their plan is economically viable.
Portland cement is the most frequently used cement today. It comes from combining calcium oxide with silica in a kiln at very higher temperatures. Calcium oxide comes from heating limestone to around 900º C, according to ArsTechnica. Electrolyzing water in the presence of limestone produces calcium hydroxide which can be converted to calcium oxide fairly easily. Not only that, the hydrogen and oxygen created by electrolysis can be used to heat the furnace needed to make the Portland cement.
According to Dezeen, the researchers wanted to come up with a process that would be a relatively small change in the way Portland cement is made today. In order for industry to adopt the new technology, it is important that they not start by throwing away all the equipment they currently use. Small scale changes could be implemented fairly quickly.
Decarbonizing the manufacture of cement is vital because the number of buildings worldwide is expected to double by 2060, producing the equivalent of one new New York City every 30 days. Using conventional methods, that means a lot of carbon dioxide will get released into the atmosphere in conventional building techniques are used. “How do you penetrate an industry like that and get a foot in the door?” asks Leah Ellis, a postdoctoral researcher and lead author on a paper about the project which argues for change “in a stepwise fashion.”
Wood Vs. Concrete
At the Architecture of Emergency climate summit in London last month, several leading architects and engineers said there wasn’t time to redesign concrete. Instead they urged architects to stop using concrete and start using wood. “If we invented concrete today, nobody would think it was a good idea,” said Michael Ramage, an architectural engineer and University of Cambridge academic.
The MIT proposal offers a way for cement and concrete to continue as a staple of the building industry without polluting the atmosphere with more and more carbon dioxide. Maybe the MIT proposal and using more structural wood components could combine to help the Earth breathe a little easier.
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