Welcome to the age of wood
April 27, 2019
Wood has long been part of the material mix, used in buildings, tools and for energy. But in the not-too-distant future, it may be the dominant material. Everything that is made from fossil-based materials today can be made from a tree tomorrow.
But not wood as you know it. Sure, raw wood has many useful properties: it is strong, yet light and flexible. It is beautiful and economical. It literally grows on trees. But it also has some serious disadvantages that caused it to be overtaken by other materials. Its properties are unpredictable. It burns, cracks and rots. It is bulky and non-transparent.
But the same can be said of other raw materials. Crude oil, iron ore and the basic ingredients for concrete are of little use as they are. To unlock their potential, they have to be processed. The same is true of wood – we just have to discover how, and then build the infrastructure to do it. When we have cracked that, we will enter the Wood Age.
The first place where wood is likely to replace unsustainable materials is in buildings. It already has a long history as a construction material, but its disadvantages mean that new buildings are mostly made from steel and concrete. These are great for construction but appalling for the environment.
Steel production accounts for about 3 per cent of the world's greenhouse gas emissions and concrete about 5 per cent. That is not sustainable. According to the recent report from the Intergovernmental Panel on Climate Change on keeping warming below 1.5°C, the drastic emissions cuts required mean building construction has to be carbon neutral by 2020.
That almost certainly means radically cutting down on steel and concrete. Luckily, this is already starting to happen thanks to a wood-based material called cross laminated timber (CLT), which can replace both. CLT is made by gluing sheets of wood together- usually from Norway spruce or beech trees - to create large, flat slabs. These can be stacked to make buildings like giant Lego blocks.
CLT was invented in the 1990’s, but is growing in popularity thanks to an ongoing race to build the world's tallest wooden skyscraper. The current leader is an 18-storey student residence in Vancouver, Canada, which was finished in 2017. This year it will be overtaken by a block in Brumunddal, Norway.
And more are on the drawing board, including an 80-storey, 300-metre tower planted right In the middle of London's Barbican Centre. The skyscrapers are raising awareness, but the real action is in mid-rise buildings. An eight-storey wooden building can be prefabricated off-site and put together in a few days.
The raw material can be grown in sustainably managed forests and given how many of those there are, the wood for a single apartment takes just 7 seconds to grow.
And while CLT costs a bit more than steel and concrete, it makes construction quicker. Rather than spewing carbon dioxide, it locks carbon away for the lifetime of the building, typically 60 to 70 years. This carbon storage can be a small but useful brake on climate change.
According to a 2017 report on greenhouse gas removal by the Royal Society and the UK Royal Academy of Engineering, switching to timber in construction could instantly wipe a billion tonnes off the world's annual carbon emissions. That is 2.3 per cent of the total - not a huge amount, but in a world where we have to do everything, immediately, it isn't to be sniffed at.
And as cities grow, the potential of CLT does too. Around 65 per cent of the urban infrastructure that will be needed in 2030 has yet to be built. If it is constructed with concrete
and steel, we have little chance of keeping temperatures down.
CLT does not eliminate the old materials completely but reduces them by up to 80 per cent. We still use concrete for foundations, but a wood building is about a third of the weight of a steel and concrete building. That means we require a lot less foundations, so it reduces the amount tremendously.
Extract from an article written by Graham Lawton in 'New Scientist', March 2019