قالب وردپرس درنا توس
Home / Business / BBC – Future – Could wood buildings be a solution to climate change?

BBC – Future – Could wood buildings be a solution to climate change?



I am standing on a seemingly ordinary construction site of an inconspicuous office building in East London. The seven-storey building is about two-thirds finished – the basic structure and the stairs are present, with the plastering and the wiring is just beginning. But as I walk around, something else slowly reveals itself. The construction site is quiet and clean – it even smells good. And there is a lot of wood. On construction sites, wood is usually used as a mold to pour in the concrete. But here is the wood the concrete.

"Because a wooden building weighs 20% of a concrete building, gravity is greatly reduced," says architect Andrew Waugh, who leads me around. "That means we only need minimal foundations, we do not need large amounts of concrete in the ground. We have a wooden core, wooden walls and wooden floor panels ̵

1; this is how we reduce the amount of steel to a minimum. "Steel is commonly used in most large modern buildings to form the main inner columns or reinforce concrete. In this wooden building, however, there are relatively few steel profiles. The remaining parts are bolted together like a Meccano set and can be easily disassembled at the end of (or during) the life of the building. "If you wanted to build a staircase here," says Waugh, pointing to the ceiling, "unscrew the beam [steel] there, take a chainsaw, and cut a hole in the wood [floor]."

Every year, enough concrete is poured to cover all of England.

Our dependence on concrete and steel for the construction of buildings to sports stadiums is associated with significant environmental costs. Concrete accounts for 4-8% of global carbon dioxide (CO2) emissions. After water, it is the most abundant substance on Earth, accounting for about 85% of the total mining and is associated with an alarming depletion of the world's sand. Every year, enough concrete is poured worldwide to cover all of England.

You may also like

• The outrageous plans to transport icebergs to Africa
• The poisons released by the melting of the ice
• Like lightened clouds Combating climate change

Some architects, such as Waugh, argue for a return to wood as a primary building material and enforce it. Wood from managed forestry stores carbon instead of emitting it: as trees grow, they absorb CO2 from the atmosphere. As a rule of thumb, one cubic meter of wood contains about one tonne of CO2 (about 350 liters of gasoline, depending on the tree species).

Wood not only removes more CO2 The atmosphere added by manufacturing is doubled by replacing carbon intensive materials like concrete or steel to reduce CO2 emissions. A recent advisory report to the UK Government on the use of "biomass in a low-carbon economy" found that "the largest quantities of [biomass] reduction currently occur when wood is used as building material … to store carbon and displace carbon-rich Cement, brick and steel. "

Between 15% and 28% of UK-built new-builds use timber frame structures, capturing more than one million tonnes of CO2 annually. Increased use of wood in construction could triple that amount, the report said. "The use of new wood-based material systems such as cross-laminated timber enables savings of a similar magnitude also in the commercial and industrial sectors."

Cross laminated timber or CLT is the main material on the construction site Andrew Waugh leads me around East London. Since it is a "wood material", I expect something similar to chipboard or plywood. But CLT looks like ordinary 3m long 1 "thick wooden boards with lots of knotholes and splinters. The ingenuity is that the planks are made stronger by gluing in three layers, each layer being perpendicular to the other. This means that the CLT "does not bend or bend, but has integral strength in two directions," says Waugh. "[A CLT] Wall supports the ground above it, with a horizontal thickness to carry a load over it that looks like a long beam." This, he says, changes the architecture.

Having built CLT for a decade, Waugh believes it can achieve anything a concrete and steel building can do, and beyond. It was invented in the 1990s, partly in response to the "death of the furniture and paper industry," says Waugh. "60 percent of Austria is forest and they had to find a new outlet. So you have developed cross laminated timber. "

Other wood-based materials such as plywood and MDF consist of about 10% adhesive (glue), often urea-formaldehyde, which can produce hazardous chemicals when recycled or incinerated. However, CLT contains less than 1% adhesive and typically uses a bio-based polyurethane. The planks are bonded together under heat and pressure to fuse this small amount of adhesive using the moisture of the wood. Look, smell and touch, it is as pure as a tree house for children – branches and so on.

Many CLT factories in Austria are even using renewable biomass, using scraps, branches and twigs. Some factories produce enough electricity to power the surrounding communities.

Although CLT was invented in Austria, Waugh Thistleton, a London-based architectural firm, was the first to construct a multi-story building. Murray Grove, an otherwise ordinary nine-story residential building with a gray disguise, caused "shock and horror in Austria" during construction in 2009, says Waugh. So far, CLT has been used only for "beautiful and simple two-story homes", whereas everything that was larger has been used on concrete and steel. At Murray Grove, the entire structure above the first-floor slab consists of CLT panels, with all the walls, floor slabs and elevator cores made of wood like a honeycomb block.

The project has since inspired hundreds of architects to build tall with CLT, from the 55m high Brock Commons Tallwood House in Vancouver, Canada, to the 84m high, 24-story "HoHo Tower", currently in Vienna, Austria , is built.

Since 2001, Canada's forests have emitted more CO2 than it absorbs

Recently, it has been required to plant trees on a colossal scale in order to capture CO2 and mitigate climate change. Although young trees are efficient and effective carbon sinks, this does not apply to old trees. The earth maintains a balanced carbon cycle – trees (along with all other plants and animals) grow with carbon, they fall and die and release that carbon. This balance was out of balance when humans discovered ancient carbon and oil carbon pools that had been trapped in previous carbon cycles and started to burn, releasing the resulting CO2 into our atmosphere much faster than the current cycle with.

Many pines in managed forests, such as the European spruce, take about 80 years to mature, as they net net carbon during these growth years – but once mature, they lose about as much carbon through the decomposition of Needles and fallen branches as they absorb. As in Austria in the 1990s, there was a decline in demand for paper and wood in Austria, in which huge parts of the managed forests were no longer used worldwide. Instead of returning to the original wilderness, these monocrops cover the forest floor with sour pine needles and dead branches. For example, Canada's large forests have emitted more carbon since 2001 than they absorb, as old trees are no longer actively felled.

The best form of carbon sequestration is probably to cut down trees: to restore our sustainable, managed forests and use the resulting wood as building material. Managed forests certified by the Forest Stewardship Council (FSC) usually plant two to three trees per felled tree. The more wood demand is, the greater the growth of both the forest cover and the CO2-hungry young trees.

and the protection of primeval forests is essential. But unmanaged monocrops do not help anyone, and soils of dry pine needles are also the main cause of forest fires – something that North America and many parts of the world now experience annually. Targeted harvesting significantly reduces this risk.

These benefits have not escaped the US authorities. Melissa Jenkins of the US Federal Forest Service recently stated at a meeting of the Environmental and Energy Study Institute (EESI): "We have a situation of overcrowded forests: when a wildfire burns down, these fires burn hotter, they burn faster and they make much more effort To prevent … If we can build markets for these wood products, landowners are more likely to farm or thin their land sustainably. "She stresses that CLT has the potential, in particular, to reduce forest fires risk [and] supports the economic development of rural areas and job creation. "

The market seems to agree. Less than five years after his arrival on the shores of the US, CLT projects are currently underway in almost all US states. More importantly, unlike the UK, which currently imports all CLT products, the US invests in domestic CLT production. The factories are located in Montana and Oregon, others in Maine, Utah, Illinoi, Texas, Washington, Alabama and Arkansas. Amazon's new "Tech Hub" in Minneapolis is made of plywood (like CLT, but not with glue, but with nails). The Wood Innovation Act of 2018 also included provisions for the research and development of wood pulp.

Structures made of wood-based materials can generally be built faster and easier, thus reducing labor costs, fuel consumption and energy consumption on site. Alison Wring, director of the infrastructure company Aecom, cites a CLT apartment block with around 200 apartments, which "only took 16 weeks [to build] … while traditional construction with a concrete frame would have taken at least 26 weeks. Similarly, Waugh, a recently refurbished 16,000-square-foot CLT building, would have required around 1,000 cement truck deliveries for the frame alone. To deliver the entire CLT, we only needed 92 deliveries. "

Other countries are also turning to wood. Monika Lebeničnik, sales engineer at Ledinek Engineering, an Austrian-Slovenian company that manufactures presses for CLT factories, sent me her order form from 2013. It starts with a flood of orders from Austria and Scandinavia. But from 2017, there will be a sudden boom from Japan, France, Australia, Latvia and Canada. "The annual capacity of such lines ranges from 25,000 to 50,000 cubic meters [of CLT]," explains Lebeničnik. The data suggest that 1,000 cubic meters of CLT correspond to about 500 harvested trees. Factories that process 50,000 cubic meters incorporate the bound carbon of 25,000 trees per year.

There are even advantages that make the material particularly attractive for countries such as Japan, as earthquake testing has shown good performance. A joint Italian-Japanese research team built a seven-story CLT building and tested it on a "shake table" (a cool, but uncanny video of it is available on Youtube). They found that it was able to withstand the shocks of the 1995 earthquake in Kobe, Japan, which destroyed more than 50,000 buildings. With random timing, says Waugh, "Americans have planted many trees in Japan as part of the Marshall Plan – that was over 60 years ago, and they are now reaching maturity." It is designed to withstand temperatures of up to 270 ° C before it begins to carbonize – the charring on the outside then acts as a protective layer for the structural density of the underlying wood. In contrast, concrete can flake and crack at similar temperatures, and steel loses strength.

Not everyone believes, however, that the future is CLT. When I ask Chris Cheeseman, Professor of Materials Resource Engineering at Imperial College London, if wood could use concrete as our primary building material, his answer is blunt. This will not happen, it can happen with some small programs on the ground, but you have to appreciate the massive use of concrete and the massive importance of concrete for the infrastructure and society, which is exceptionally good because of its functionality and robustness Material. "

There is also the question of the" end of life. "Carbon only remains trapped in the wood as long as the building stands or is reused in another building, and if it rots or burns to produce energy, the whole becomes Doug King, a civil engineering graduate and consultant on sustainability issues, told me, "If we do not care about the disposal of wood materials at the end of their life, there is no guarantee that the overall cycle will benefit them Society brings. "Previous research by Arup estimated in 2014 that d Half of the timber ends up in landfills, 36% recycled and the remaining 14% burned for biomass.

Despite these problems, Waugh remains ambitious. The average lifespan of a building is 50-60 years – that's more than enough time for architects and engineers to sort out reuse and recycling issues. The conversion into biochar could be a possibility. Waugh's buildings should be easy to disassemble for future generations.

Basically, along with a growing group of international architects, he is convinced that the mass introduction of CLT is an important weapon in the fight against climate change. "It's neither a fad nor a fad," he tells me as we finish his tour of its East London construction, and I take my last, inappropriate breath through the forest air. "The largest commercial developer in the UK has just bought this building. For me, this is the place where you want to be. I want this to be mainstream. Everyone should build with it.

I return to my original question: Can we realistically return to wood as our primary building material? "It's not just realistic, it's essential," argues Waugh. "It has to happen. In architecture, one always resorts to the sketch: The sketch is climate change.

Tim Smedley is a UK-based sustainability writer. His first book is Clearing the Air: The Beginning and End of Air Pollution. Join more than a million Future Fans by clicking on Facebook or Twitter or Instagram

may like this story, sign up for the weekly bbc.com newsletter titled "The Essential List". A handpicked selection of BBC Future, Culture, Capital and Travel stories delivered to your inbox every Friday.


Source link