DUTCH STARTUP LOOP runs a factory in the city of Delft that’s unlike any other you may have visited. For one thing, as soon as you enter, the scent of mushrooms fills your nostrils like the smell of a forest after rain. If you follow your nose, you’ll arrive at a damp former vehicle repair workshop, filled with industrial-size fridges, heaters, fans, and two greenhouses. White lab coats and glassware are dotted around, and in one corner sit 25 yellowish-white caskets the color of a poorly maintained incisor, racked up and ready to go. Each is around the size and width of a fully grown man, and subtly different in color and texture, like Styrofoam with a soft, velvety outer coating. This is the production line for a living box in which to bury dead people.
On any other given work day, there would have been a dozen staff members busily bustling around the place, but the factory was closed on the cold October afternoon I visited, so Loop’s founder, Bob Hendrikx, a 27-year-old with a long, boyish face and wavy dark brown hair, showed me around. “The weather conditions outside make a lot of difference,” Hendrikx says, explaining the manufacturing process. “One degree off and you have a different product.”
Loop is a design company conceived around the simple idea of solving everyday problems by harnessing the unique attributes of living organisms. Its first product, the Living Cocoon, is a funeral casket made from mycelium, the tangle of microscopic filaments that exists underneath a mushroom. If the mushroom is the fruiting body (think apples or oranges), the mycelium is the rest of the tree: roots, branches, and all.
When mushrooms reproduce, they release airborne spores that, when they land on a substrate in a suitable environment, produce cylindrical white filaments known as hyphae. As these grow and branch they create webs of hyphae called mycelium. The mushroom you see above ground is only a tiny part of the organism; the rest extends rootlike below ground, spreading out in every direction. Given time, resources, and optimal conditions, mycelium can become vast. The largest on record, a specimen of Armillaria ostoyae discovered in Oregon in 1998, covers a total of 2,384 acres, making it the largest living organism in the world.
Mycelium is nature’s great recycler. As they feed, hyphae release enzymes that are able to convert organic compounds like wood and leaves, but also human-made pollutants—including pesticides, hydrocarbons, and chlorinated compounds—into soluble nutrients. As such, mycelia have been deployed to clean up oil spills and chemical contaminants. Myco-remediation, as the method is called, has been used by the US military to clear up neurotoxins, and to clean asbestos and Japanese knotweed found in London’s Queen Elizabeth Olympic Park before the 2012 games.
Given the right substrate, such as wood chips, mycelium fibers will digest and bind the material together to form a dense and spongy mass; to the naked eye, it looks like a slimy white rubber. But despite this initially unappealing appearance, many designers, including Hendrikx, have been exploring the potential of mycelium composites as an environmentally friendly building material. Mycelium composites have many advantages. Growing them doesn’t require any external energy, heat, or even light. Once dehydrated, the material becomes lightweight, durable, and hydrophobic. And packing a mix of mycelium and organic matter into a mold and then leaving it to grow makes it possible to form structures such as packaging, furniture, clothing—and even caskets. “It’s like baking a cake,” Hendrikx told me. “The mycelium does all the work.”
My visit came at the busiest time in the designer’s career. Two days after my arrival, Hendrikx was due to present the latest iteration of the Living Cocoon at Dutch Design Week in Eindhoven, where he was nominated for two awards, including the 2021 Young Designer award. There was a lot to prepare.
The design world has been embracing mycelium since 2007, when the New York-based company Ecovative first demonstrated home insulation grown with a patented mushroom-based material. Other companies, including Italy-based Mogu and the UK’s Biohm, have also used mycelium as an insulation material. Mycelium composites are being sold as sustainable replacements for uses as diverse as alternative leather and vegan bacon.
Its uses in construction have also grown. In 2014, New York design studio The Living built a cluster of circular towers using 10,000 biodegradable blocks made from mycelium and crop waste. In 2017, a group of architects in Southwest India inserted spores into a triangulated timber framework to build the roof of an architectural pavilion. That same year, a group of architects went one step further with the MycoTree, a tree-like structure that was capable of supporting its own weight, demonstrating that mycelium composite materials might even be used to provide a structural framework for buildings.
If we can use mycelium composites to build structures that change how we live on this planet, Hendrikx began to think we could also change how we leave it. Traditional means of disposing of the dead—burial in wood and metal caskets, or cremation—leave an indelible mark on the planet, polluting the soil or the air. A mycelium casket, Hendrikx thought, would in theory allow the dead to enrich the soil, turning polluted cemeteries into flourishing forests.
The Living Cocoon is more than a casket. For Hendrikx, it is the first step in establishing a mutualistic relationship between humanity and nature. Alongside the mycelium caskets, he is working on growing pods that he believes could one day be scaled up for humanity to inhabit. In theory, these rooms, buildings—or eventually, even entire settlements—could be turned into compost after their useful life, returning their nutrients and disappearing without a trace as quickly as they’ve been grown.
“We are missing out on a lot of opportunities by killing intelligent organisms and turning them into a bench. This thousand-year-old species, we turned it into a piece of wood; that’s what we’re good at,” Hendrikx told me as we packed a fully grown Living Cocoon into the back of his van. “Nature has been here for billions of years, and we have been here for just a few thousand. So why do we insist on working against it?”
Hendrikx’s appreciation for design began with his father, Paul, who runs his own construction company and spent Hendrikx’s childhood extending and expanding their family home in central Eindhoven. As a child, Hendrikx was enamored with New York skyscrapers, and he later set out to become an architect, eventually studying at the Delft University of Technology.
As a postgraduate student, Hendrikx became interested in the impact of traditional construction materials. Construction is responsible for around one-tenth of global CO2 emissions, more than shipping and aviation combined; cement production alone is thought to produce 4-8 percent of human-made carbon emissions. If nature has been growing things for billions of years, Hendrikx thought, why can’t it also grow our homes?
For his thesis, Hendrikx researched “living architecture”: organisms such as coral and algae, or materials like silk, with which you could theoretically grow a house. But the standout was mycelium, which is cheap, abundant, and grows quickly. Mycelium-composite structures also have tremendous sound and heat insulation.
According to Dirk Hebel, one of the architects behind the design of the MycoTree, mycelium composites might one day directly replace concrete in some construction projects. With the correct substrate, growing conditions, and post-production, Hebel’s team at the Karlsruhe Faculty of Architecture has grown mycelium-composite bricks with a compressive strength similar to that of a baked clay brick. “Around 80 percent of our buildings worldwide are just one or two stories, so the majority don’t need super-high-strength materials,” Hebel says.
NASA is also exploring how mycelium composites could “revolutionize space architecture,” says professor Lynn Rothschild. Since 2017, Rothschild, leading a team funded under the NASA Innovative Advanced Concepts (NIAC) program, has been testing how such material might react to Martian and lunar conditions. “Any time you can lower your up-mass—the mass that you’re having to launch against Earth’s gravity—you save enormously on the mission costs,” Rothschild says. “If we can save 80 percent of what we were planning to take for a big steel structure, that’s huge.”
Rothschild envisions pop-up structures that operate as a lightweight scaffolding on which mycelium could grow. The structure would be coated in a nutrient solution because there is no organic substrate available on Mars or the Moon, and cyanobacteria, which would produce the oxygen the mycelium needs. Once the structure has grown, Rothschild suspects you could use sunlight to “cook” the organism, and she believes mycelium composites could eventually be used for landing strips, garages to protect rovers from wind and dust, and even full settlements. “You don’t need to worry about joints, you don’t need to worry about size, you don’t need to worry about planning every detail in advance,” she says.
TYPICALLY, MYCELIUM COMPOSITES are heated and killed after forming, which turns the structure rigid. Hendrikx also intended to kill the mycelium, but he grew to appreciate it as a conscious being, rather than a product, and so uses it alive. Building with living mycelium composites is a challenge, however. The organism needs a steady food source; if the substrate runs out, the structure loses its integrity and cannibalizes itself. When the mycelium is alive, these composites also feel more like slimy, wet cardboard than hardboard—and there’s the possibility it will sprout mushrooms whose spores can cause respiratory problems.
So Hendrikx approached Bob Ursem, the scientific director of the Botanical Garden at Delft University of Technology. A convivial 64-year-old with gray hair and round Harry Potter-like glasses, Ursem suggested the mycelium be placed in a state of dormancy: alive but not growing. Drying the fungus with a low heat renders it inactive; the material becomes stiff but remains adaptable, and it doesn’t decay as easily. (There’s also no sprouting.) To bring it back to life, one need only reintroduce the mycelium to a suitably humid environment.
“A fungus can grow and stop,” Ursem says. “It deactivates, forming a hard shield or a cocoon, until it has the environment and the food for it to grow again.”
Dormant mycelia pave the way for new kinds of architectural geometries and spatial organizations. Instead of seeing construction as an assembly of components, Hendrikx began to envision a world in which we could cultivate entire buildings or even settlements in one go. Inhabitants could grow extra rooms by triggering the mycelium’s capacity to reanimate. According to Ursem, buildings might one day be able to self-assemble on site. “What you get is flexible housing,” he says.
Because live mycelium networks are capable of transferring electrical signals like a brain, and these signals respond to mechanical, optical, and chemical stimulation, such intelligent buildings could theoretically respond to their environment. According to Andrew Adamatzky, a professor and head of the Unconventional Computing Laboratory at UWE Bristol, homes could turn on a light when it goes dark or open the window if CO2 levels are too high. Fungi react to stimuli; one could also imagine living homes that detect illnesses in their inhabitants based on the air they exhale. “In principle, fungi react to all stimuli that dogs react to, so if dogs can be trained to detect something, then fungi can do the same,” Adamatzky says.
However, dormant mycelium is unstable; such homes could potentially reactivate at any time—even from a change in the weather. Rogue fungi might colonize other building materials, such as wood flooring, explains Mitchell Jones, a research scientist in the Institute of Material Chemistry and Research at the University of Vienna.
To overcome this, Hendrikx hopes to construct walls with two layers of dead mycelium enclosing a layer of living mycelium, much like the bark on a tree. This would shut water out from the inner layer, he told me, keeping the fungus there dormant. He also wants to implant sensors within the mycelium to monitor its temperature, moisture levels, and the amount of remaining substrate. Based on that data, he said inhabitants could decide to grow the home by adding substrate, shrink it by starving it, or maintain it by applying an algae-based solution filled with nutrients. All this, in Hendrikx’ mind, could be controlled through an app.
“As with [any] home, you need to nurture it to extend your stay,” Hendrikx told me. “If we don’t take care of our environment, then the home won’t care for us.”
AS SOON AS Felix Lindholm was diagnosed with prostate cancer in early 2020, he began to wonder what to do with his body after his death. (Felix’s name has been changed to protect his family’s privacy.) A retired director of an art school in a town close to Belgium’s border, he loved nature and wished to tread lightly on the planet as he left it. He bought a plot at a “natural burial” ground, where graves are dug by hand and synthetic fabrics are banned.
Lindholm researched caskets made of biodegradable materials like recycled paper, cardboard, wicker, willow, and banana leaf; he even considered a simple, organic cotton shroud. Then he discovered the Living Cocoon. In September 2021, he became a Loop customer.
Death has a more deleterious impact on the environment than many realize. According to one estimate, cemeteries in the US take up around 1.4 million acres, while around 13,000 tons of steel and 1.5 million tons of concrete are used for burial vaults annually. If every burial used wooden caskets, they would need 150 million board feet of hardwood each year. Metal coffins, popular because they’re better at preserving the body, corrode in the soil or oxidize in underground vaults.
As a corpse decomposes, it releases around 40 liters of liquid, including water, ammoniacal nitrogen, organic matter, and salts. Bodies may contain metals like silver, platinum, and cobalt from orthopedic implants and mercury from dental fillings. If the deceased has had chemotherapy, the liquid may leach out; then there’s embalming fluid, a potent chemical cocktail that contains formaldehyde, a carcinogen. The 18 million liters of embalming fluid that leach into US soil annually could fill six Olympic-size swimming pools.
When buried without a coffin, in ordinary soil, an unembalmed adult normally takes eight to 12 years to decompose to a skeleton. Placed in a coffin, the body can take decades longer. As a result, a quarter of England’s cemeteries are expected to be full by 2023.
Cremation is no better. Globally, the industry is estimated to produce 6.8 million tons of CO2 annually, as well as carbon monoxide and sulfur dioxide.
Natural burials have grown in popularity, as has resomation, where bodies are dissolved in water and potassium hydroxide. And then there’s human composting. The first large-scale facility opened in Seattle in January 2021.
Hendrikx was encouraged to pursue the idea of the Living Cocoon by a passer-by at Dutch Design Week 2019, where he was presenting “Mollie,” a home constructed out of blocks of living mycelium cultivated from mushroom spores from Japan. Hendrikx believed a mycelium casket could make death “restorative” by cleansing the soil.
Each Living Cocoon is grown using mycelium Ganoderma lucidum, a fungus that’s venerated across East Asia for its healing powers. In China it’s known as lingzhi, which translates to “mushroom of immortality,” while the Japanese refer to it as reishi, meaning “soul mushroom.” Hendrikx chose Ganoderma because it’s a fast colonizer, but also because it can consume a wide range of substrates, leading to better growth and stronger, more penetrative bonds. The better the growth, the tougher the mycelium composite; the last thing you want is for the coffin to collapse before it’s in the ground.
The moment the casket is lowered into the soil, “a party begins,” Hendrikx told me. The humidity reactivates the fungus, so it begins hunting for food. Its enzymes first break down the wood chips, then any toxins that exist in the soil. Fungi are able to break down most environmental toxins, except heavy metals—they absorb and hyperaccumulate those in their fruiting bodies, which can then be removed.
Once there’s no food left, the fungus starves, dies, and becomes food for other microorganisms in the soil, which go on to colonize the corpse. According to Hendrikx’s early testing, the Living Cocoon is absorbed into the earth in around 60 days, and while he doesn’t have data to prove it, he believes a body inside a Living Cocoon will decompose in just two to three years.
A FEW DAYS after my tour of the Loop factory, I joined Susanne Duijvestein, a “green” funeral director, for a tour of Zorgvlied, one of the Netherlands’ largest cemeteries, a short cycle ride outside of Amsterdam, where peacocks roamed freely among the shadows of sycamore and oak trees.
For Duijvestein, a 35-year-old former banker with a tangle of long, blonde hair, marble headstones are symbolic of a society that still doesn’t know how to deal with death. As she showed me the natural burial section, an area of flat ground bereft of markers, statues, and even floral arrangements, she said that there is no silver bullet when it comes to disposing of the dead—but if there was, it wouldn’t be the Living Cocoon. “We need a lot of systemic change,” she tells me, “not a single coffin that costs a lot of money.” (Each Living Cocoon costs €1,495, about $1,530.)
Duijvestein, for one, doubts Loop’s promises. There is still no evidence, she says, that the mycelium reactivates when buried, where there’s little to no oxygen. Any oxygen in the coffin and in gaps in the soil would be consumed by microbes. Myco-remediation is an aerobic process, so it would be like trying to light a fire underground.
“Before [Hendrikx] went viral, he hadn’t actually buried a human body before. So his claims aren’t proven yet,” Duijvestein said. “I do know that among many other species, fungi definitely help with decomposition in natural circumstances on top of the ground. But I am not convinced that they also work six feet under with the typical poor cemetery-soil conditions.”
Having worked in the funeral industry for five years, Duijvestein told me how she’s seen many supposedly green funeral products that don’t perform as claimed. One of the most memorable was the Infinity Burial Suit, made from organic cotton embedded with material from specially cultivated mushrooms. Developed by Coeio, a California-based “green” burial company, it made headlines in 2019 when former Beverly Hills 90210 star Luke Perry was buried in one. Like the Living Cocoon, it claims to use mycelium to cleanse the body of toxins and return nutrients to the soil, but some have questioned this premise.
One of the suit’s loudest critics is Billy Campbell, a cofounder of the first conservation burial ground in the US. According to Campbell, Coeio’s technology is not grounded in science, because the fungi would almost certainly die as soon as they’re buried in the earth. The fungi the Infinity Suit uses, the gray oyster, would also be unable to digest the harsh toxins the body excretes. Loop’s Living Cocoon, Campbell says, would fall at the same hurdle: The Ganoderma lucidum, another species that feeds predominantly on cellulose-rich organic matter, would be unable to deal with the toxins coming from the human body. Because Ganoderma are most effective in an acidic environment, he says, they’re also unlikely to survive the alkaline environment of ammonium seeping out of a corpse.
“You can’t just put a bunch of fungal stuff that you’ve grown on cellulose or some other cultural medium deep into the ground,” Campbell explains. “It isn’t going to survive long enough for remediation to be possible.”
That’s not to say the Living Cocoon isn’t a more sustainable solution than a wood or metal casket; but Campbell worries that Hendrikx’s claims are overblown. “I think it is incumbent on them to demonstrate that [the mycelium] is reactivated in a meaningful way,” Campbell says. “For now, I see this as one more product, and not a bad one, but not a breakthrough.”
THE MORNING AFTER my meeting with Duijvestein, I took the train to the Hendrikx family home in Eindhoven. Overlooking a peaceful garden setting through the panoramic windows in the living room, I listened as Hendrikx took a new order for four Living Cocoons—his largest yet—and fielded calls from enthusiastic investors and journalists eager to report on his exhibition.
Over lunch, he batted away my questions about whether the Living Cocoon would indeed activate in the soil because Ursem had told him that it would. “At the beginning, our first assumption was that there was no oxygen, but then we learned there was. The answer is just simply ‘Yes.’ We can talk for a long time about it, but …” Instead, he explained how he intends to incorporate bioluminescent fungus, which can be triggered to glow in the dark, to replace the candles people sometimes place on a grave. In the future, he wants to grow gene-edited light-emitting trees that he believes could one day line idyllic city streets. “Instead of street lamps, we’d just have a nice tree,” he told me.
That afternoon, we transported some bushes from the family’s garden to the Microlab, a concrete behemoth of a building that hosts Dutch Design Week. In one corner of the exhibition space lay the latest iteration of the Living Cocoon. Light brown and with more curvature than a regular casket, it’s supposed to make death feel more human. Hendrikx had surrounded it with an assortment of trees and flowers, to make it look as aesthetically pleasing as possible. Even then, it still looked otherworldly, out of place.
It wasn’t until the following week that I heard from Hendrikx again: “We won,” he texted, with a photo of the “Public Award” trophy. After the award, he was invited to speak about the coffin on national television in the Netherlands and on CNN and to give a lecture at the Stedelijk Museum.
It was a landmark moment for Loop. But to Hendrikx it was just one piece of a larger puzzle. The goal of the casket is to “prove that we can collaborate with living organisms,” he says, which will pave the way for his more radical living products. “It’s unrealistic right now, but for me it’s the only way forward.”
THE NEXT STEP is to develop a portfolio of live mycelium funeral products for humans and animals, and then to move into above-ground composting and luminous trees. One day, Hendrikx wants to bioluminate entire cities and then, at some point, to build those cities out of mycelium. “We are pioneering, but this is a movement we will see in the coming decades,” Hendrikx says. “Before this, people were seeing nature as a source for inspiration. The next stage is using it for collaboration.”
This article was originally published in the May/June 2022 issue of WIRED UK magazine.
