Tomorrow’s town planners could take a leaf from nature’s book with timber buildings. More than a leaf: the whole tree and all the cuttings as well.
Tim Radford is a founding editor of Climate News Network
Cross-posted from Climate News Network
European and US scientists have a root-and-branch answer to the challenge of tomorrow’s cities: switch to wood, construct timber buildings and reduce the risk of even more devastating global temperature rise.
Their reasoning is bold and simple: it takes energy to make steel and cement, which must be mined or quarried, a process that puts the remaining wilderness at risk.
Forests represent stored atmospheric carbon. If timber from the planet’s forests could be used to construct the houses and offices needed for the additional 2.3 billion urban dwellers expected by the year 2050, then that would mean that the great cities could become sinks or repositories of stored carbon.
And new trees could grow in the space left by the harvested timber to add to the world inventory of stored carbon. The new towns and cities could become a kind of bank vault in which to save up to 700 million tonnes of carbon a year that might otherwise have spilled into the atmosphere as the greenhouse gas carbon dioxide.
“Since the beginning of the industrial revolution we have been releasing into the atmosphere all of this carbon that had been stored in forests and in the ground,” said Galina Churkina, of the Potsdam Institute for Climate Impact Research, Germany.
“We wanted to show that there can be a vision for returning much of this carbon back into the land.”
Strong fire-resistance
Wood is a fuel. It burns well. Paradoxically tree trunks, and treated timber assembled from laminates, do not. Structural timbers may char in a fire, but this has been shown to make them more resistant to burning. Experiment and research has shown that buildings of engineered timber up to 18 stories in height can be resistant to fire.
In effect, atmospheric carbon, turned into high-strength wood fibre by photosynthesis, could be made as safe as reinforced concrete. But, according to a new study in the journal Nature Sustainability, in 2014 the making of cement spilled 1,320 million tonnes of carbon dioxide into the atmosphere and steel manufacture added another 1,740 million tonnes.
And between 2005 and 2015, mining in Brazil alone was responsible for 9% of the loss of all Amazon forest land during that decade: the act of prospecting for or extracting mineral commodities destroyed 12 times more than the areas stipulated in the mining leases.
The Potsdam scientists are not the first to suggest wood as an alternative to bricks and mortar, or bamboo as a replacement for cement, steel and glass. But their analysis may be the most detailed so far of a new way to confront the challenge of tomorrow’s climate-tested cities.
The researchers built a series of scenarios to test their hypothesis. New city structures must be built to accommodate an additional million or more humans every week for the next three decades. The proportion now expected to be fashioned from timber is half of 1%.
“Trees offer us a technology of unparalleled perfection. If we engineer the wood into modern building materials we humans can build ourselves a safe home on Earth”
A five-storey house made from laminated timber could store 180 kilos of carbon a square meter: that is three times the biomass above ground in natural forests. If construction from wood was stepped up to 10%, new construction could store 10 million tonnes of carbon a year; if the world switched to 90% this figure could rise to almost 700 million tonnes.
“Trees offer us a technology of unparalleled perfection,” said Hans Joachim Schellnhuber, a co-author of the study and a founder director of the Potsdam Institute.
“They take CO2 out of our atmosphere and smoothly transform it into oxygen for us to breathe and carbon in their trunks for us to use. There’s no safer way of storing carbon I can think of.
“Societies have made good use of wood for buildings for many centuries, yet now the challenge of climate stabilisation calls for a very serious upscaling. If we engineer the wood into modern building materials and smartly manage harvest and construction, we humans can build ourselves a safe home on Earth.”
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