Leather, Grown in a Lab Without Cows

Modern Meadow’s factory will crank out leather via yeast fermentation.

A square of white raw hide and a square of black dyed hide
A rawhide made from collagen grown in yeast (left) and semifinished, dyed hide (right)  (Modern Meadow)

To make leather, first you have to raise a cow.

Or another animal, though you really do need the whole animal because since pretty much the beginning of time, it has not been possible to grow skin for leather without the attendant flesh and bone and blood and guts.

But now a company called Modern Meadow says it can “biofabricate” leather without the rest of the cow. It does not quite grow cow skin, either; it grows a strain of yeast engineered to produce collagen, the protein in skin that gives leather its strength and stretch. Traditionally, making leather amounts to removing almost everything from skin (fat, hair, etc.) that isn’t collagen. Modern Meadow is basically skipping ahead. Once purified, pressed into sheets, and tanned, their vat-grown collagen becomes, essentially, leather.

No dead cows. No scars or nicks. And none of the petrochemicals used to make pleather or vegan leather.

It’s a radical new way of making leather, reliant on genetic engineering and decoupled from the processes of traditional agriculture. Engineered yeasts have long been used in the production of drugs like insulin, but recently—and perhaps surprisingly given the debate over genetic engineering—they’re entering the world of luxury goods: spider silk, perfume, and now leather.

When Modern Meadow publicly unveils its leather in the next month—in the form of a “reimagined” graphic T-shirt—it will not be at a store but at a fashion exhibit at New York’s Museum of Modern Art. The company employs a chief creative officer as well as a professional tanner, and it’s been carefully cultivating its mystique. Modern Meadow doesn’t just want to imitate leather, the company keeps reiterating; it wants to reimagine leather, transcending the physical limits of a cow.

The T-shirt “will change the way you think about leather,” promised David Williamson, the company’s chief technology officer, though he could not yet reveal to me how.

* * *

Modern Meadow was not always so interested in fashion. Its founders—CEO Andras Forgacs and his father and chief scientific officer Gabor Forgacs—had previously started the company Organovo to grow human tissue for medical and pharmaceutical research. Going from engineering human tissue to animal tissue, says Andras Forgacs, seemed like a logical next step. In 2011, they started Modern Meadow with the goal of growing leather and eventually meat in tissue culture.

But they quickly ran into a problem of economics. Organovo only had to make tiny quantities of tissue for medical purposes, which it could then sell at high prices. “The value of that is super high when you’re dealing with life and death,” says Forgacs. A steak requires growing many thousands of times more cow tissue, at a much lower price per ounce. The economics of leather are slightly better.

Forgacs tells me now that he had always planned to focus on leather first. But the idea of the lab-grown meat fits into an established narrative of what biotechnology is for, and meat’s ethical and environmental problems are more ubiquitous than leather’s. The meat angle got quite a bit of early press attention. As late as 2015, Modern Meadow was giving journalists a taste of cultured “steak chips.” Today, its website no longer has any mention of cultured meat.

A sheet of collagen produced by Modern Meadow (Modern Meadow)

Modern Meadow initially tried to grow cow skin cells for leather much like how it grew cow muscle cells for meat. Mammalian cells are finicky, however, and they require specific and nutrient-rich medium. The problems were twofold: One, the medium required to grow the cells includes serum extracted from unborn calves, thus negating any animal-free promises; and two, all kinds of unwanted bacteria and yeast will grow in a nutrient-rich medium, requiring expensive equipment to maintain sterility.

Williamson walked into these problems when he joined Modern Meadow from DuPont in 2015, and he eventually decided the mammalian cells had to go. Modern Meadow was going to get into hardy, fast-growing yeast. “Yeasts are the things you worry about contaminating your mammalian tissues,” says Williamson. And since yeast is already widely used to manufacture molecules of interest—alcohol for beer and wine, for example—there is plenty of ready-made industrial-scale equipment tailored to yeast fermentation.

The challenge, then, is getting yeast to make bovine collagen. It’s easy enough to splice genes from another species into the microscopic creatures. Scientists have been doing this for decades, and it’s how pharmaceutical companies use vats of yeast to make human insulin. But yeasts do not spit out collagen that automatically assembles into sheets of leather. Williamson’s team had to add two other genes for enzymes that help modify the collagen’s molecular structure, and then—using another process he declined to detail—Modern Meadow forms it into sheets of rawhide. The rawhide can be tanned just like the stuff that comes from cows.

Williamson calls traditional leather making a top-down process. You start with a cow skin, strip off the fat and hair, cut out imperfections, and work around parts of the skin that are thinner or weaker than others. At Modern Meadow, he says, “we’re doing bottom-up assembly.” By tweaking the collagen network, the team can make leather whose size is unlimited by the physical size of cattle, or more tear resistant, or impossibly thin. It could even tinker with the molecular structure of collagen—optimizing it for one property or another.

As part of its entry into the world of fashion, Modern Meadow is quick to tout its design credentials. Williamson notes that his scientists work hand in hand with the company’s designers, led by chief creative officer Suzanne Lee, who has experimented with making clothing from kombucha. Forgacs says the company is also partnering with several brands, though he could not yet name them.

The leather industry is watching too, curiously but with reservations. Steven Lange, director of the Leather Research Laboratory at the University of Cincinnati, told me to keep the bigger picture in mind: “You don’t want to lose sight of the fact we’re dealing with a waste byproduct of the food industry.” In other words, it’s demand for meat and milk that drives the supply of leather.

Modern Meadow was in fact onto something with its initial if overambitious twin goals of meat and leather. (Other companies like Memphis Meats have since taken up the challenge of culturing muscle cells in a lab.) The production of the meat and leather have been connected for millennia for good reason. Collagen-making yeasts allow Modern Meadow to build a new leather supply chain from scratch, but it still must exist in a world where animal agriculture has created vast, entangled supply chains.

It may now be possible to make leather without a cow. The problem that remains is people still want the rest of the cow