Will the skyscrapers of the future be made out of wood?

Wood products that are nearly as strong as steel are going into more high-rises, locking up carbon. But can we grow enough trees to keep pace?

Wednesday, January 15, 2020,
By Saul Elbein
This apartment building in Joensuu  is, according to its designers, the tallest all-wood building in ...
This apartment building in Joensuu is, according to its designers, the tallest all-wood building in the world.
Photograph by Antti Asikainen, Natural Resources Institute Finland
The Heinrich Boll Foundation and the Pulitzer Center provided grant support for this story.

Until about your grandparents’ childhood—or maybe your great-grandparents'—the world was made of wood. Everything from weapons and wheels, barrels and houses, tools for cooking and industry, was at least in part derived from materials taken from the bodies of trees. People were born in oak beds and rocked in poplar cradles and killed by walnut-stock rifles and buried in pine coffins.

Now a growing industry wants to bring back the golden age of wood starting with skyscrapers. “Look at this,” Antti Asikainen, an austere, affable Finnish forestry professor, says admiringly, pointing to a rectangular hole cut in the sheetrock of a 12-story apartment building, exposing the skeleton below.

The frame inside is made of mass timber, a high-density wood product that is one of the new range of high-tech products the global economy relies upon forests to fill. Mass timber has a particular utopian appeal among a certain set of architects and designers, and its supporters predict that the cities of the future will be all-wood high-rises like the one Asikainen and I are standing in above the eastern Finland university town of Joensuu, which spreads like a carpet along the canals of the Pielisjoki River.

Below us, the landscape bears the fruits of a style of forestry calibrated to reliably turn out the most trees possible. Piles of mostly spruce stacked in the rail yard stretch to the horizon. The day before, Asikainen says, the river and canals had been full of an enormous float of spruce logs on their way down from North Karelia or the Russian boreal forests, bound for markets beyond the Baltic Sea.

If all new-model wood products have their acolytes, proponents of mass timber speak of it with a particularly evangelical zeal, because they see it as not only a chance to decarbonise the construction sector, but also a significant technical upgrade in its own right. (See what cities of the future could look like.)

All of those products, from the paper fluff in nappies to the bones of skyscrapers, rest on a possible irresolvable contradiction: They all rely on the steady, controlled growth of trees, with harvests generally planned out decades in advance. For the past hundred years, that system of so-called scientific forestry, which grew up to counter the seemingly unstoppable deforestation of late 19th and early 20th-century Europe, has provided the wood products that a growing population requires.

That system, however, depends on something that is disappearing: a steady climate and forests that remain where they’ve been, a paradigm threatened by the very climate crisis that makes carbon-sucking buildings seem appealing.

Tall buildings, made of wood

The Jonesuu apartment building is a case in point. Virtually anywhere else in the world, that exposed skeleton would be concrete reinforced with steel. Here in Finland it’s wood: In fact, save for a two-inch concrete slab between each floor, the whole building is made of wood. Specifically, one of the high-tech, engineered materials collectively called mass timber or structural timber.

That makes this building, according to Asikainen, the executive vice president of the Forest Research Institute at the University of Eastern Finland, the tallest all-wood building in the world.

“Oh, they have one in Oslo that is 13 stories,” he says with the ghost of a grin, “but their first floor is concrete. Ours is all wood.”

The Forest Research Institute, like counterparts in Sweden and Norway, designed and built the apartment building as a test project in its constant search for new products to make from their nation’s forests. This is a project that carries, in Finland, shades of a national religion. After its disastrous World War II invasion of the Soviet Union—Finland carries the dubious distinction of having been Hitler’s only democratic ally—the country paid its onerous reparations bill with the wood it produced by converting its thick boreal forests into a highly managed landscape.

These forests, like those of so-called production forests or working forests around the world, from Karelia to the Scotland, form the base of an enormous industrial pyramid, the foundation of a staggering array of consumer products of which mass timber is only the latest. Forests are now asked to produce a long list of things that, in an era of growing concern over fossil fuels, is increasing in turn.

That means you will find trees in all sorts of unexpected products, beyond the whole trees that go into toilet tissue and paper towels. There is the factory just outside Joensuu that renders spruce pulp into fibres that can be woven like cotton, which is a pesticide- and water-intensive crop that competes with food for land. There is the tampon and nappy fluff made from young yellow pine in the U.S. Southeast, and a small but rapidly growing market in compressed wood pellets from countries in the Baltic States sold to European power plants as an ecologically friendly replacement for coal.

Add to that the surging cardboard market driven by Alibaba and Amazon’s insatiable demand for packaging, says Forest Research Institute professor Lauri Sikanen, and planting soft pulpwoods “is like planting money.”

“It’s a win-win-win,” says John Klein, an architect and designer at the Massachusetts Institute of Technology who is developing a line of pre-fab mass timber office and apartment buildings in preparation for 2021, when reforms to U.S. building codes will permit all-wooden high rises up to 18 stories tall

Eight-story Carbon12, in Portland, Oregon, is the tallest all-wood building in the United States.
Photograph by Kaiser + Path

“When Boston talks about carbon neutrality in buildings,” Klein says, “they only ever talk about operational energy. No one ever talks materials.”

Like many mass-timber designers, Klein was first attracted to the medium for ecological reasons. Concrete and steel—each of which requires several rounds of breaking, grinding, and (in the case of steel) melting rocks—cost of a great deal of energy and therefore carbon dioxide emissions. Approximately 8 percent of the world’s total carbon emissions come from cement and concrete production, which releases about half a tonne of the dangerous greenhouse gas carbon dioxide (CO2) for every tonne produced. The manufacture of steel, which accounts for around 5 percent of all emissions, releases nearly twice its weight in CO2.

Mass timber, by contrast, promises to replace a material that releases huge amounts of carbon—if cement and concrete production were a country, it would be the world’s third largest carbon emitter, behind the U.S. and China—with one that could store it. The spruce logs below Joensuu, like the overstocked production forests of Oregon and North Carolina, were largely made of carbon the trees had pulled from the atmosphere. That means that mass timber, in theory, could store that carbon long-term in the walls of buildings. On the plantation forests they’d come from, new trees would go up in their place.

But over time, in addition to the carbon savings, Klein came to think wood was simply a better material for many purposes, one that would allow a new generation of light, strong structures resistant to fire and explosion. While mass timber isn’t as strong as steel, it also doesn’t collapse under direct heat as quickly. Mass timber advocates say it is far denser and more fireproof then the kinds of wood used to create structures like Notre Dame, built from 1,300-year-old trees that burned effortlessly when the cathedral caught fire in April 2019. (Read about the threats facing Notre Dame and other World Heritage sites.)

“You get a mass timber beam [burning], and it gets a nice, predictable char,” Klein says.

A few weeks before, he had done a workshop where he and a group of architecture students built a mass timber platform, and then roasted a pig on it. The wood blackened but was not consumed.

Cities of the future

Back in the lobby of the Forest Research Institute, a breathtaking, mass-timber structure that looks like a cross between an ark, a bird’s nest, and an enormous, cosy pine cone, Asikainen shows me an array of wood composites of the sort that might fill Klein’s buildings. There is cross-laminated timber (CLT), which looks like inch-thick strips of heartwood arranged like a Jenga set to produce a block that is pretty much the definition of the word solid. Or glu-lam, used to make structural beams that are like extremely strong plywood, and LVL—laminated veneer lumber—which makes excellent heavy beams and had formed the skeleton of the apartment building.

To a designer like Klein, those blocks don’t just use less carbon than concrete or steel, they lend themselves better to modern architecture. “We’re basically computer scientists now,” he says, and wood is simply a better, more plastic material for the design programs he uses to simulate building layouts based on his customers’ needs, which are always changing.

Klein envisions a future urbanisation boom like the one he saw in China in the early 2010s, when he worked at breakneck speed designing high-rises as cities like Shanghai filled in to accommodate the millions moving there. Mass timber, he says, is much easier to customise and prefabricate than concrete or steel: it allows designers to send plans directly to the factory to be built to spec in a practice he calls “file to factory.” That translates to faster construction, lower costs for labour, and less disruption for existing cities.

“Right now, every building is prototype,” he says—built to spec, never repeated.

If that weren’t true, Klein thinks, his firm could offer the teeming cities of the 2020s a line of standardised, customisable, mid-rise apartments and office buildings, largely made of modular mass timber, that developers could order to spec like IKEA sofas—which are, of course, themselves a new-model wood product, built as they are out of medium-density fibreboard (MDF) or compressed wood chips.

Controlled forests

But for all the hype around mass timber, only a few U.S. firms east of the Mississippi are making it. Which means, for now, that if you want to build a CLT building, you have to order the materials from Europe, from factories like Binderholz in the stunning Zillertal Valley in the Austrian Alps.

There, Natalie Binder pilots her Mercedes Benz at high speed through the massive wood lot of her family’s sawmill, careering around piles of spruce logs 30 feet high and oncoming forklifts. Around us, the valley slopes seem to touch the sky, covered in the Alpine forests where Hans Binder, the family patriarch and Natalie’s grandfather, had worked as a cowherd and logger to earn the money to buy the family sawmill.

Now it is an empire, transformed by the decision of subsequent generations of Binders to commit the family to mass timber, which today it makes into a dizzying array of products in its 13 factories, from glulam to load-bearing solid-wood panels.

Binder, who grew up in the family factories—“When I was eight, if I wanted a new saddle for my jumping horse; I had to spend a hundred hours of filing or answering phones,” she says—moves through the sawmills at a confident and relentless near-run, watching entire spruce logs neatly debarked to fuel the generators that run the mill, then shot through grids of blades that rapidly vivisect them to spec, creating the thick boards that would be glued and heat-pressed to make the custom structural timber products ordered by clients like Klein.

Perhaps it seems odd that architects in the U.S. have to import mass timber from Europe, when there is currently such a glut of building-quality pine that Southeastern landowners are selling off their young trees to make tissue paper or nappy fluff, rather than letting them mature.

In part, that’s because Binderholz has what no firm in the U.S. does: a mature CLT supply chain that stretches hundreds of miles down rail lines and 50 miles down truck routes into the surrounding spruce forests. Yet for all the company’s huge supply, Binder says, the factory’s supply is deceptively fraught. The sawmill never has more than 10 days’ supply on hand; it relies, like all wood product companies, on the fragile base of a ready supply of trees that can take decades to grow, and that come from landscapes being asked for ever more output.

This means, first, competition. “Everyone who is doing new green tech—biofuels, bio-plastics—thinks they’re going to get the forests for their thing,” says Mary Booth, who runs the Massachusetts-based Partnership for Policy Integrity. “It’s not like there's vast amounts of unused land lying around waiting for us to cultivate something great on it.”

Second, all of this, from the quickest-used toilet paper to the longest-lasting mass-timber beam, is coaxed from the land by the sort of meticulous control of forests that may no longer be desirable—or even possible.

A history of planning

Just across the German border from Binderholz, 82-year-old Bavarian forester Albrecht Von Bodelschwingh walks through a German production forest to show me how they had ensured the supply of wood without denuding the landscape.

His profession rests on a paradox that arose in the 17th century, as Central Europe’s growing industrial towns started to run out of wood. It’s easy to forget that before the fossil fuel era, wood was a necessary ingredient in everything from silver smelting to building to baking, and early forest managers like the 17th century-Hans Carl von Carlowitz—the first to publish on the concept of sustainability—had to figure out how to guarantee the steady supply of a crop that takes hours to burn but entire human lifetimes to grow.

Germany’s answer to that question gave the world, for better or worse, the heavily managed style of forestry production that later spread to countries like Finland and the United States. In the 19th century, Heinrich Cotta instituted a rigorous system of strict volumetric analyses, so that landowners—and the state—would always know how much timber was on hand. 

Landowners had to submit outlooks to the state every year for their forests, detailing their plans 10 years out. This was necessary because of what haunted Cotta’s work: the spectre of decline, of a world starved of construction materials and fuel. The spruce forest von Bodelschwingh walked through had been a peat bog before local families, in times of wood shortage, dug up and dried the peat to heat their houses and stoves.

The U.S. Forest Service started in a one-room forestry school—America’s first—in the mountains of Pisgah Forest, North Carolina, seen here.
Photograph by Education Images, Universal Images Group/Getty Images

Now the peat was gone and the wetland forest that had once grown from it had been converted to dryland. This dance with collapse, Cotta wrote in his seminal 1817 Preface, was at the core of the profession of forester, who he compared to a doctor managing a patient in long and chronic decline: “’The good physician lets people die; the poor one kills them. With the same right one can say the good forester allows the most perfect forests to become less so; the poor one spoils them.”

Cotta’s ideas of rigorous management and stand-by-stand planning became, through a late 19th-century diaspora of German foresters, state of the art throughout the world, introducing new techniques like row-planting of trees as cash crops and the first industrial-scale clear-cuts followed by planted rows of saplings. In the early 1900s, German forester Carl Schenck trained much of the first generation of the U.S. Forest Service from a one-room forestry school—America’s first—in the mountains of Pisgah Forest, North Carolina.

Despite his love for the forests of Appalachia, and his regret at the wild coves of massive old-growth chestnuts and tulip poplars he cleared for his boss, George Vanderbilt, Schenck and emissaries like him helped instill a system that has slowly crowded out the wild forests in favour of a system of forest management that treats “forest health” as inseparable from a woodland’s ability to supply the planned production of board feet of lumber or fibre for industrial use.

Judged exclusively by the reliable production of lumber, that system has been an extraordinary success.

There are trees being cut in Bavaria today that were planted for that specific purpose before the American Revolution. Meanwhile, in the United States, timber “inventories” are so high that the U.S. Forest Service, like the Finnish Forest Research Institute, is throwing research money at potential markets like mass timber construction. In 2019, they awarded nearly $9 million in grants to wood innovation projects. (2020 proposals are open now.)

And yet in the American South, which loggers and tree farmers boast is “the wood basket to the world,” behind the growth in inventory lies a greater decrease. (Industry advocates like to say that forests are increasing, which is true, provided you take ‘forest’ simply to mean an area that isn’t zoned for anything else, regardless of what kind of trees, if any, it has on it at the moment. A clear-cut, according to the USDA, is still a forest.)

Since 1952, when the first plantation forests came to the region, those highly managed forests, fed on herbicides and pesticides and with minimal biodiversity, have spread loblolly pine monocultures over an estimated 14 million hectares—an area slightly larger than Florida—much of it former natural forest. Worldwide, there were 296 million hectares of planted forest as of 2015—an area roughly that of India, that spreads, inexorably, about one percent a year.

Useless plans

In the past decades, German forestry has retreated from clearcutting to a practice that resembles horticulture on an extremely long time scale, a landscape, one German sawmill owner told me proudly, “where you wouldn’t know they were logging.”

But those planted, planned systems—as Asikainen, the Finnish researcher, told me—rest on two shaky foundations. They require land, for which they compete with wildlands and cropland. And they require that conditions remain predictable over decades or even centuries, which makes them vulnerable to the current age of growing climate flux.

Now, Bavarian forester von Bodelschwingh says, “We can’t plan anymore. We make our schemes, but they’re useless.”

The forested German landscape is in the grips of traumatic change, from the brightly flowered Asian ornamentals bursting among the river cane to the dying conifer spending its last energies in a final burst of cones. In von Bodenschwingh’s yard the trees are growing quickly in the heat of a record European heatwave, becoming fat on CO2 and nitrogen, speeding upward like teenagers in an uncontrolled spurt, outpacing their own root beds so that heavy snow or high winds could bring them down easily.

He points at a stand of young spruce growing atop the old peat bog, the offspring of the older spruce stand that surrounds them. They had grown in a cavity ripped in the woods in the 1990s by Vivian and Viebke, a pair of winter tornadoes that ravaged the German timber industry.

Those storms, says Esther von Roehm, a timber procurer who worked for the local magnate that owned the spruce, were traumatic. Now they were so common that she and von Bodelschwingh struggle to remember the names of any recent ones.

In addition to this, the two foresters cite other assaults: the beetle colonies that waited out the newly mild winters in the dead wood left by the high winds, and which sallied forth aggressively this year to attack new stands. The root rot that spread from infected stumps underground through the fungal networks that connect the trees. The fungi that rotted out the insides of hardwood trees, so that finally the newly powerful winds took them down.

“Five years from now,” von Bodelschwingh says, pointing at a tree with a balding crown, “there won’t be any more ash trees on this land. And that’s something everyone in Germany will have to face, because it’s dying everywhere.”

This is something, he says, “you can’t find in books. You can’t find it in history. Our teachers can’t tell us anything. Now our 10-year plans are useless. Even a one-year [plan] sometimes is.”

Out in the Bavarian forest, we’re surrounded by the signs of a kind of subtle decompensation, bits of fraying in the rural economy. Deadfall covers the ground—as much as might be harvested in 10 normal years of proper management, von Roehm says—so much that prices of spruce logs had plummeted, removing the incentive for forest managers to clear their plots and leaving room for destructive beetles to move in.

Marc Castellnou, a fire expert from Catalonia, believes the heavily populated forests of Central Europe may soon face a new era of wildfire like that which has struck the Mediterranean, if warming, forest disease, and rural abandonment continue to spread. “And that,” Castellnou says, “is the nightmare scenario.”

Adapt and diversify

The solution, inasmuch as there is one, says Finnish scientist Asikainen, favours adaptation over planning and diversity over monoculture. A reversal, that is, of the trends of the last two centuries. Back at the Wood Research Institute in Finland, he boots up his computer to show me a heat map: the predicted risk of losses from winds on given plots, stretched across a lake in eastern Finland where he has a cottage.

The paradigm of the future will be “risk management,” he thinks, rather than the rigorous, and rigid, planning of before: using remote sensing and predictive analytics to help landowners take into account future losses from root rot, fungi, insects, fire, or windstorms.

“People will shorten their cutting cycles,” he says, meaning plantation forests will store, on average, less carbon.

It also means an urgent need to retool the current system seen as necessary to consistently produce the consumer goods, durable and disposable, that Western-style consumer society has come to rely on. Now the dependence on such a system looks more like a liability, Asikainen said: The old era of industrial monoculture forests now standard across the world have left the wood products industry terribly exposed to any new pest or change in the environment.

“A strategy built around more biodiversity may be more resilient to risk than monocultures,” he says. “We have to regenerate the forest to meet changing growth conditions. We need to regenerate the forest and favour resilient tree species.”

One answer, drawing on the 19th-century works of Cotta, may be a greater acceptance of one of the most taboo subjects in the modern West: decline. “Just as the good physician cannot hinder that men die because that is the course of nature, so the best forester cannot hinder that the forests, which came to us from past times, become less now they are being utilised,” Cotta wrote in the Preface.

On the heat map on Asikainen’s computer, one region, near his cabin, glows a refreshing blue: low risk. That’s because that area, Asikainen sighs, was itself a monoculture: The owner had sold off his spruce and replanted it with new seedlings. Now the saplings stood in neat rows, about as wild as a corn crop, as sinewy and fibrous as cotton, their young bodies bending easily in the winds of whatever change may come.

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