It is not unusual for visionaries to be impassioned, if not fanatical, and Willem van Eelen was no exception. Before he died in February at age 91, van Eelen looked back on his extraordinary life. He was born in Indonesia when it was under Dutch control, the son of a doctor who ran a leper colony. As a teenager, he fought the Japanese in World War II and spent several years in prisoner-of-war camps. The Japanese guards used prisoners as slave labor and starved them. “If one of the stray dogs was stupid enough to go over the wire, the prisoners would jump on it, tear it apart and eat it raw,” van Eelen recalled in a 2011 interview. “If you looked at my stomach then, you saw my spine. I was already dead.” The experience triggered a lifelong obsession with nutrition and the science of survival.

One obsession led to another. After the Allies liberated Indonesia, van Eelen studied medicine at the University of Amsterdam. A professor showed the students how he had been able to get a piece of muscle tissue to grow in the laboratory. This demonstration inspired van Eelen to consider the possibility of growing edible meat without having to raise or slaughter animals. Imagine, he thought, protein-rich food that could be grown like crops, no matter what the climate or other environmental conditions, without killing any living creatures.

If anything, the idea is more potent now. The world population was a little more than two billion in 1940, and global warming was not a concern. Today the planet is home to three times as many people. According to a 2013 report by the United Nations Food and Agriculture Organization, the livestock business accounts for about 14.5 percent of all anthropogenic greenhouse gas emissions—an even larger contribution than the global transportation sector [see “The Greenhouse Hamburger”]. The organization has projected that worldwide meat consumption will grow by 73 percent between 2010 and 2050.

Meat grown in bioreactors—instead of raised on farms—could help alleviate planetary stress. In 2010 Hanna Tuomisto, then at the University of Oxford, co-authored a study of the potential environmental impacts of cultured meat. The study found that such production, if scientists grew the muscle cells in a culture of cyanobacteria hydrolysate (a bacterium cultivated in ponds), would involve “approximately 35 to 60 percent lower energy use, 80 to 95 percent lower greenhouse gas emissions and 98 percent lower land use compared to conventionally produced meat products in Europe.”

As it is, 30 percent of the earth's ice-free land is used for grazing livestock and growing animal feed. If cultured meat were to become viable and widely consumed, much of that land could be used for other purposes, including new forests that would pull carbon out of the air. Meat would no longer have to be shipped around the globe, because production sites could be located close to consumers. Some proponents imagine small urban meat labs selling their products at street markets that cater to locavores.

The only choice left
Even winston churchill thought in vitro meat was a good idea. “Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing by growing these parts separately under suitable medium,” he predicted in a 1932 book, Thoughts and Adventures. For most of the 20th century, however, few took the idea seriously.

Van Eelen did not let it go. He worked all kinds of jobs—selling newspapers, driving a taxi, making dollhouses. He established an organization to help underprivileged kids and owned art galleries and cafes. He wrote proposals for in vitro meat production and eventually plowed much of his earnings into applying for patents. Together with two partners, he won a Dutch patent in 1999, then other European patents and, eventually, two U.S. patents.

In 2005 van Eelen and others finally convinced the Dutch Ministry of Economic Affairs to pledge €2 million ($2.5 million) to support in vitro meat research in the Netherlands—the largest government grant for such research to date.

By that time, an American scientist had already succeeded in growing a piece of fish filet in a lab. Using a small grant from nasa, which was interested in developing food sources for deep-space voyages, Morris Benjaminson removed skeletal muscle from a common goldfish and grew it outside the fish's body. Then an associate briefly marinated the explants in olive oil, chopped garlic, lemon and pepper, covered them in bread crumbs and deep-fried them. “A panel of female colleagues gave it a visual and sniff test,” says Benjaminson, now an emeritus professor at Touro College in Bay Shore, N.Y. “It looked and smelled pretty much the same as any fish you could buy at the supermarket.” But nasa, apparently convinced there were easier ways to provide protein to astronauts on long deep-space voyages, halted funding for Benjaminson's research.

In the Netherlands, van Eelen and Henk P. Haagsman, a scientist at Utrecht University, used their grant to fund a consortium to try to make meat from stem cells, which are able to generate a wide range of tissue types. They aimed to culture stem cells isolated from farm animals and then induce the cells to form skeletal muscle tissue. The team included a representative from meat company Meester Stegeman BV, then part of Sara Lee Corporation in Europe, as well as top scientists at three Dutch universities. Each university studied different aspects of in vitro meat production. Scientists at the University of Amsterdam focused on producing efficient growth media; a group at Utrecht worked on isolating stem cells, making them proliferate and coaxing them into muscle cells; and those at Eindhoven University of Technology attempted to “train” the muscle cells to grow larger.

The scientists made some progress. They were able to grow small, thin strips of muscle tissue in the lab—stuff that looked like bits of scallop and had the chewy texture of calamari—but several obstacles remained to commercial-scale production. “We gained knowledge, we knew a lot more, but we still didn't have [something that tasted like] a T-bone steak that came from a petri dish,” says Peter Verstrate, who represented Meester Stegeman in the consortium and now works as a consultant. In time, the Dutch money ran out.

Van Eelen fumed in 2011 that one scientist involved was “stupid” and others just milked him and the Dutch government for money. “I don't know what they did in four years—talking, talking, talking—every year taking more of the money,” he said.

The scientists respond that van Eelen never understood the scale of the challenge. “He had a naive idea that you could put muscle cells in a petri dish and they would just grow, and if you put money into a project, you'd have meat in a couple of years,” says Bernard Roelen, a cell biologist who worked on the project at Utrecht.

Van Eelen was not the only one who imagined a revolution. In 2005 researchers published the first peer-reviewed article on cultured meat in the journal Tissue Engineering. The authors included Jason G. Matheny, co-founder of the lab-produced meat advocacy group New Harvest. He has no illusions that the path will be easy. “Tissue engineering is really hard and extremely expensive right now,” he says. “To enjoy market adoption, we mainly need to solve the technical problems that increase the cost of engineered meat.” That will take money, he notes, and few governments or organizations have been willing to commit necessary funding.

To the researchers involved, that failure seems shortsighted. “I think [in vitro meat] will be the only choice left,” says Mark J. Post, head of the physiology department at Maastricht University. “I'm very bold about this. I don't see any way you could still rely on old-fashioned livestock in the coming decades.” In 2011 Post continued van Eelen's project by launching an ambitious attempt to culture enough beef to make a hamburger.

Assembly required
In theory, an in vitro meat factory would work something like this: First, technicians would isolate embryonic or adult stem cells from a pig, cow, chicken or other animal. Then they would grow those cells in bioreactors, using a culture derived from plants. The stem cells would divide and redivide for months on end. Technicians would next instruct the cells to differentiate into muscle (rather than, say, bone or brain cells). Finally, the muscle cells would need to be “bulked up” in a fashion similar to the way in which animals build their strength by exercising.

But tissue engineers have come up against multiple problems. When stem cell lines proliferate for long periods, many cells suddenly decide on their own to differentiate. And of those cells that do wait for the external signal to differentiate, many do not turn into muscle as instructed. “If 10 cells differentiate, you want at least seven or eight to turn into muscle cells, not three or four,” Roelen says. By 2011 only about half of the stem cells were turning to muscle on command.

The Utrecht scientists tried to extract and develop embryonic stem cell lines from pigs. Such cells would, in normal conditions, be able to duplicate every day for long periods, meaning 10 cells could grow into a staggering amount of potential meat in just two months: over 50,000 metric tons. “Culturing embryonic stem cells would be ideal for this purpose since these cells have an (almost) infinite self-renewal capacity,” according to a 2009 report by the Utrecht team. “In theory, one such cell line would be sufficient to literally feed the world.”

Such cell lines have been developed from mice, rats, rhesus monkeys and humans. But embryonic cells from farm animals have a tendency to differentiate quickly—and of their own accord—into specialized cells. The Utrecht team's porcine cells often veered toward “a neural lineage”—brains, not bacon.

Post chose to work with adult stem cells called muscle satellite cells, which exist within skeletal muscle and are largely preprogrammed to replace muscle fibers when they are injured or die off. Satellite cells do not proliferate as readily as embryonic cells do, but they form muscle more reliably.

Cost poses another barrier. The culture used to grow stem cells of any kind is very expensive. In 2011 Roelen estimated that cultured meat cost $50,000 a pound—and it was not acceptable to vegetarians, because the nutrient baths were derived from fetal calf or horse serum taken from slaughtered animals. But scientists have since developed recipes for “chemically defined media” that include no animal products. They have also been able to genetically engineer plant cells to produce animal proteins that could be used to grow the meat. Both these types of media remain prohibitively expensive.

An algae-based medium may eventually work best because algae can produce the proteins and amino acids necessary to sustain cell life. But that, too, is costly—at least for now. Post has optimistically estimated that large-scale production of in vitro meat could lower the price to about $10 a pound and that coming advances in the technology will reduce costs further.

Once researchers are able to produce a big supply of muscle cells, they will need to keep the cells alive and bulk them up. It is possible now to assemble cells into a thin strip of tissue, but when the layer gets more than a few cell layers thick, parts of it start to die off. The cells need a constant flow of fresh nutrients to stay alive. In the body, these nutrients are delivered by the bloodstream, which also removes waste. Post is trying to develop a three-dimensional system that delivers such nutrients.

Meanwhile he has demonstrated one way to add bulk to the muscle cells: exercise them. “If you take your cast off after a bone break, it scares you: the muscles are gone,” he says. “But within a couple of weeks they're back. We need to replicate that process.” Scientists have tried stimulating the tissue with electrical pulses. But that is costly and inefficient, bulking up the cells by only about 10 percent.

Post found some success with a different approach. He provides sticking points made of Velcro to which the developing tubules of muscle can attach. When anchored on either end, the fibers develop tension on their own and expand in size. But at this stage, he says, “we're not looking at Schwarzenegger muscle cells.”

Post has described another, more complex method that might work even better. The body naturally stimulates muscle growth with micropulses of acetylcholine and other chemicals—which are inexpensive to supply. “The trick is to do it in very, very short pulses,” Post says. The hurdles to that are technological, not scientific.

Breakthroughs in all these areas will take money, which so far has come in unpredictable bursts, mainly from private sources. In 2008 People for the Ethical Treatment of Animals (PETA) offered $1 million to anyone who could grow commercially viable chicken in a lab by 2012. The deadline was later extended to 2014, but the money still went unclaimed. More seriously, the European Union has funded studies on the social and moral questions related to in vitro meat, Google co-founder Sergey Brin gave Post's lab $325,000 to try to create a lab-grown hamburger, and a Brooklyn-based start-up called Modern Meadow recently raised $10 million in venture capital to fund its quest to make cultured leather and meat.

The ick factor
Some see social acceptance as the biggest barrier of all to producing in vitro meat on a commercial scale. “I've mentioned cultured meat to scientists, and they all think, ‘great idea,’” says Tuomisto, who now works for the European Commission. “When I talk to nonscientists, they are more afraid of it. It sounds scary. Yet it's basically the same stuff: muscle cells. It's just produced differently.”

Cor van der Weele of Wageningen University has been investigating the philosophical aspects of cultured meat (for example, is lab-grown meat a moral imperative or morally repugnant, or some combination of the two?). She has been intrigued by the emotional reactions that some people have toward the idea. “We call it the ‘yuck response,’” she says. “People initially think that it might be something contaminated or disgusting.”

But that perception can change quickly, van der Weele observes. She notes that people often associate cultured meat with two other ideas: genetically modified foods—which are often seen, particularly in Europe, as a dangerous corporate scheme to dominate or control the food supply—and negative perceptions of the meat industry in general, with its factory farms, disease and mistreatment of animals. Once people realize that cultured meat is not genetically modified and could be a clean, animal-friendly alternative to factory farms, she says, “the scared, very negative response is often very fleeting.”

Such observations are only anecdotal, of course. One of the European studies observed that many people initially reacted with revulsion at the notion of cultured meat but then developed more ambivalent feelings as they thought through the potential pros and cons both personally and to society at large. Further studies are under way to determine ways to frame the issue that might enhance consumer interest. Proponents imagine a day when governments will levy special environmental taxes on meat produced from livestock or when consumers will be able to opt for in vitro meat that is labeled “cruelty-free.”

“I don't think you want to know about the hygienic conditions in the majority of slaughterhouses in the U.S. or the efficiency of euthanasia,” Post says. Another outbreak of disease—like mad cow or bird flu—could make cultured meat seem all the more appetizing. “We are far from what we eat,” Roelen says. “When we're eating a hamburger, we don't think, ‘I'm eating a dead cow.’ And when people are already so far from what they eat, it's not too hard to see them accepting cultured meat.”

Post's bold scheme to create a hamburger in vitro culminated in a highly publicized demonstration in August 2013, when he, food scientist Hanni Rützler and food writer Josh Schonwald shared bites of the first cultured patty. The taste was bland but not disgusting, according to Schonwald. The lack of fat was noticeable, all agreed.

The fact that it took three months of effort and more than $300,000 to produce a single, mediocre-tasting patty—which consisted of roughly 10,000 short strips totaling 15 billion cells—suggests that cultured meat is not likely to turn up in supermarkets anytime soon.

“It's basically a stunt to generate more funds,” Post acknowledged even as the project was just starting. “We're trying to prove to the world we can make a product out of this.” But can cultured meat be made to taste like the conventional variety?

“I think so,” Roelen says. “Most of the taste in a chicken nugget or a sausage is artificially made. Salt and all kinds of other things are added to give it taste.”

Van Eelen, who regarded himself as “the godfather of in vitro meat,” was not a fan of such stunts. He was a diehard idealist and argued that it is important to launch the in vitro revolution with meat that looks, smells and tastes just like anything you would buy off the farm.

In recent years van Eelen also saw that time was running out to realize a dream that he had pursued nearly his entire life. “Every time you talk to him, he's speaking about someone else he's found who will be the top scientist who will solve his problems,” Roelen said in 2011. “I can understand his point of view. But I can't change the laws of the universe.”