In the last five months, the U.S. Food and Drug Administration has cleared two American producers of lab-grown meat to bring their products to market, finding "no questions" about the companies' claims the protein is safe for human consumption -- though critics still have concerns about the industry's financial viability relative to long-term output.
"That is a watershed moment because it's never happened before in the history of humanity," said Dr. Uma Valeti, founder and CEO of UPSIDE Foods, one of the approved producers.
Regulators from the U.S. Department of Agriculture are now deciding how to label cultivated meat for public sale and inspect facilities that produce it. The guidelines are expected sometime this year -- a final hurdle before the products can hit store shelves.
Americans were estimated to consume roughly 75 billion pounds of red meat and chicken last year, according to USDA data. That's nearly 225 pounds per American.
"I think of our cultivated meat as the one that can fill the delta between how much meat we eat now and how much we're going to have to produce for the next 30 years," Valeti said.
Cultivated, or cultured-cell, meat is grown in steel bioreactors from animal stem cells that are fed a mixture of vitamins, fats, sugars and oxygen. The process results in real meat tissue without having to raise or slaughter an animal.
Meat cultivating companies like UPSIDE and some environmentalists say the technique has the potential to dramatically curb greenhouse gas emissions from traditional animal farming, which also requires vast swaths of land and water as well as antibiotics for disease control.
ABC News was granted an inside look at the nation's first and largest cultivated chicken facility, run by UPSIDE Foods in an office park outside San Francisco.
"It takes two weeks to grow the equal to one chicken, a thousand chickens or 100,000 chickens," said Valeti, who is a cardiologist by training. What limits production is infrastructure.
UPSIDE says it can produce 50,000 pounds of cultivated chicken a year using current technology in its $50-million facility. Valeti said UPSIDE will need significant additional investment to scale up to 400,000 pounds a year -- but that's the goal.
"When we have the full force of humanity wanting to do something that is impossible, or perceived to be impossible, magical things can happen," Valeti said.
Animal rights advocates say "no kill" meat is also a way to reduce suffering and alleviate concerns about unethical treatment of animal populations on large commercial farms.
The concept has drawn billions of dollars in investment. UPSIDE has attracted high-profile financing from Bill Gates, Richard Branson and Whole Foods founder John Mackey.
President Joe Biden has also thrown support behind the effort, signing an executive order in September directing the Department of Agriculture to support "cultivating alternative food sources."
"Although the power of these technologies is most vivid at the moment in the context of human health, biotechnology and biomanufacturing can also be used to achieve our climate and energy goals," the order states.
Animal agriculture is responsible for at least 14.5% of greenhouse gas emissions worldwide, according to the U.N. Food and Agriculture Organization, nearly equivalent -- by some estimates -- to the share of emissions produced by cars, trucks, trains, airplanes and ships combined.
Most of those earth-warming gasses come from cows, which produce methane, scientists say.
While UPSIDE Foods and GOOD Meat, the second FDA-approved cultivated meat company, produce chicken, dozens of other start-up companies are preparing to produce and sell cultivated beef, lamb, pork and seafood from animal cells.
Critics contend that cultivating meat is an enticing prospect but remains little more than a novelty.
"The data's not there yet and the investment is known to be very expensive. How are you going to make an impact in the environment if you cannot scale this at a reasonable cost?" said Ricardo San Martin, director of the Alternative Meat Lab at the University of California at Berkeley.
"The narrative is very attractive. 'I don't need to kill chickens, and I can kind of just grow them in a vat and that's it' -- right? But those vats are very expensive and [have] very sophisticated people running them," said San Martin, who told ABC News research shows plant-based foods are most affordable and sustainable.
A study published in 2020 by the Johns Hopkins Center for a Livable Future concluded that cultivated meat produces roughly one-fifth of the greenhouse gas emissions of traditional beef but is still five to 21 times higher than plant proteins such as tofu or peas.
Bioreactors, like those used at UPSIDE Foods, are energy intensive, said researcher Raychel Santos.
There is also a debate over what to call a new competitor in the meat department. Trade groups representing American farmers and ranchers have been lobbying the USDA to clearly brand cultured-cell products as distinct from their own pasture-raised cuts.
"All I'm asking is that it be clearly identified because there's going to be a difference when that consumer eats that product," said Todd Wilkinson, president of the National Cattlemen's Beef Association. "And my product doesn't have to be genetically engineered."
Wilkinson wants the USDA to require products from UPSIDE and GOOD to bear the markers "cultured meat" or "lab grown."
"Something that just stands out and lets the consumer know what they're eating," he said.
UPSIDE's Valeti concedes customer education will be a big hurdle to clear.
"People are buying meat right now despite how it's made," Valeti said of what he calls the paradox of meat. "What if we can make the process more kinder, caring, healthier, nutritious? I believe everybody will get behind it."
He said he anticipates price-per-pound of UPSIDE chicken would start "slightly above organic," with a goal of competing on par with conventional chicken in five to 15 years.
Once USDA labeling is approved, UPSIDE chicken is expected to land first on fine-dining menus in a handful of California restaurants.
"Our goal is to be able to be available at Michelin star restaurants or at the backyard barbecue," Valeti said. "It's going to take some time to get to a point where we can be everywhere."