The lie was delicious.

For years, Americans consumed their frothy, full-dairy cappuccinos, marbled meat and flaky fried chicken without worry. The food was cheap. The drive-throughs, abundant. And the supply seemed infinite — until it wasn’t.

Over the last few decades, a steady drumbeat of documentaries, books and escalating disasters has made it clear that America’s current food system, filled with factories and feedlots, can’t be sustained without making the planet and its people sick. Industrial agriculture, responsible for one-third of all greenhouse gas emissions around the world, is destroying ecosystems.

“If we want to have an American type of food consumption, we need three to five planets,” Dr. Ferdinand von Meyenn, a Swiss food scientist, said in a phone interview. “We don’t have that.”

So scientists have been searching for solutions, ones that will make protein-rich food cheap, accessible and far more sustainable. The good news? They already have answers. The problem, they say, is scaling them.

The protein problem

People need protein for balanced, healthy diets. But that’s become a problem for the planet.

“We get most of our protein-rich and fat-rich foods from animal farming,” George Monbiot, an ecologist and journalist, said in a phone interview this week. “And animal farming is arguably the most destructive of all industries on Earth.”

He added that the industry as a whole is “the primary cause of habitat destruction, wildlife loss, extinction, land use, soil degradation, water use and one of the major causes of climate breakdown.”

In an effort to address this problem and limit animal cruelty, food entrepreneurs and scientists have spent decades working to develop high-protein meat alternatives from plants. But until just a few years ago, these products were a novelty, eaten by a small group of committed vegans and vegetarians.

But even if protein is available in other forms, Americans aren’t converted. In a 2018 Gallup poll, only 5 percent said they were vegetarians. The majority of the country has high fidelity to meat and dairy products — a taste that has long been difficult to replicate with plants.

“To put it simply, plants are crunchy, and meat is chewy. This is why veggie burgers can often feel crumbly or mushy in texture, without the bite and springiness of animal protein,” the chef J. Kenji López-Alt wrote for The Times. He added that “animal fat, which provides mouth-coating richness and juiciness,” is also difficult to replicate with plant-based fats.

But researchers have been working on a solution — one that can replicate those nutrients, tastes and textures without using animals.

A fermented future?

Fermentation, essential for making sourdough bread, beer and cheese, has been around for centuries. But advances in the science of fermentation are helping researchers decouple animals from the proteins they produce.

Specifically, “precision fermentation” is helping food scientists grow ingredients found in animal products without the need for a traditional farm. Instead, the scientists isolate the specific ingredients, then multiply their cells in brewery-style tanks. The result? Animal-free eggs, milk and meat that are biologically similar to animal products.

“It’s a new way of producing protein-rich and fat-rich foods, which can greatly reduce the amount of land we require and the amount of water,” Mr. Monbiot said.

“It’s a tool in the tool kit to get these plant-based products over those next few hurdles, from a sensory perspective and from a cost-reduction perspective,” she added. “This is very, very different than what was happening in the protein space, say, five years ago.”

These products, alongside lab-cultivated meat, could appeal to flexitarians or to occasional consumers of plant-based products who haven’t been sold on the taste so far, enabling more consumption of meat alternatives.

And that little bit could make all the difference, scientists say.

A recent study in Nature found that replacing just 20 percent of global beef consumption and other grazing livestock with “microbial proteins,” or those made from fermentation, could cut annual deforestation in half by 2050. (Whether the plant-based foods, many of which are highly processed, are healthier is subject to debate.)

“Replacing the milk, meat and, one day, even the eggs that we eat would massively take pressure off the planet,” Mr. Monbiot said. “It could also develop a whole new cuisine that we can’t even imagine at the moment. Just as the first farmers to capture a wild cow weren’t thinking about Camembert.”

Scaling up

Enthusiasm for this innovation abounds. (“Precision fermentation is the most important environmental technology humanity has ever developed,” Mr. Monbiot said. “We would be idiots to turn our back on it.”)

But the question remains: How quickly and effectively can the companies working in this space scale their work — and bring products in development to market?

Still, start-ups working on innovating fermented foods are navigating “inherent inefficiencies,” Dr. Specht said. To succeed, and deliver a return for investors, they need to build new infrastructure and nurture talent in a food industry trained to support animal farming.

“They’re on a knife’s edge of profitability,” Dr. Specht added, while the companies also try to deliver products at a “price point within reach of most consumers.”

She argues that it’s a critical moment for governments to invest in “research and development and provide incentivizes for building out the industry’s infrastructure,” as many nations have invested in the renewable energy sector in recent years.

Without regulation and support, some worry the industry could one day be dominated by major agriculture companies, like Tyson, Smithfield, Perdue and Hormel, which have all rolled out meat alternatives in recent years.

“Monopoly and intellectual property is a genuine worry,” Mr. Monbiot said. “Ninety percent of the world’s grain passes through the hands of four corporations.”

“We don’t want to replicate that problem. We want to confront that dominance,” he added.

Have you ever been on a date in a bizarre or unexpected location? Maybe you crossed the Atlantic Ocean on a cargo ship for your 10th date. Or perhaps you wound up on the side of a mountain. Or at a restaurant after hours.