WENATCHEE VALLEY, Wash. — Katherine Sizov crouched down and gently placed one of her sensors in a corner of a cavernous warehouse room that was packed to the ceiling with crates of apples.

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Climate Visionaries highlights brilliant people around the world who are working to find climate solutions.

Forklifts carrying crates sped through the passageway outside. Trucks rumbled up to the warehouse, piled high with Ambrosias, Cosmic Crisps, Enterprises and all the bounty of Washington state’s densely planted orchards. A powerful fragrance hung in the air, mixing with the chill of the refrigerated rooms.

For the next eight months, the device she built — about half the size of a shoe box — was going to keep watch over the 5 million pieces of fruit jammed into that single room, making sure they didn’t overripen during their long stay in suspended animation. As a junior in college, Sizov started a company, Strella Biotechnology, to try to reduce waste in the U.S. food system — a problem that by some estimates creates as much emissions as 33 million passenger vehicles. Now, three years later, Sizov had talked her way into the warehouses of most of the country’s biggest apple producers, and her devices monitor about 15 percent of the entire U.S. crop.

Every fall, apple growers gather billions of apples, rush them into storage, seal the airtight doors and wait until harvest is a distant memory to reopen them. But every spring and summer, there are bad surprises when they slide open their massive warehouse doors only to discover that temperamental Honeycrisps have turned to mush.

Already, agriculture contributes more to greenhouse gas emissions than the total of all the cars, planes, trains and trucks in the world. The pressure to grow more food is leading to deforestation in the Amazon, the drying up of rivers and a greater demand for fossil fuel-based fertilizer. Anything that can be done to reduce waste and increase the productivity of existing agricultural land is a big win for the climate.

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Sizov, 24, wants to eliminate food waste one fruit at a time. In central Washington, it was an effort that required almost as much quick footwork as the épée squad she captained as a championship fencer in college. One moment, she was trying to beam the sensor’s WiFi signal through the reception black hole of millions of apples, which cause transmission issues because of their high water content. The next, she was sitting down with laconic apple growers with orchards planted generations ago, trying to convince them she could help them avoid wasted fruit. By day’s end, she might be folding her 6-foot frame into the passenger seat of a rental car, balancing her laptop on her knees and trying to win over Silicon Valley investors on Zoom calls using skills she had picked up partly by watching YouTube tutorials.

“These people wouldn’t normally sit in a room with each other,” Sizov said. “But they all agree that we shouldn’t be throwing away apples.”

When Sizov was growing up near Boston and, later, Alexandria, Va., she’d spend every summer at her grandparents’ dacha outside Moscow. Her parents had emigrated in the waning days of the Soviet Union in search of better medical treatment for her older sister, who had leukemia. Katherine was their first U.S.-born child. They sent her back each year so she’d know where she came from.

She could play along then-rutted roads near Sergiev Posad, an ancient monastery town about 40 miles outside Moscow. The church bells pealed over the winding streets below. From the stove came the sizzling of her grandmother’s doily-like blini, the sour cream-filled pancakes that Russian grandmothers cook as a testament of love for their grandchildren. They’d eat squash and cucumbers from their garden, while apples came from the neighbors’ trees next door. There wasn’t any food to waste because they ate everything that grew.

In the United States, she noticed, there was less of a direct relationship between the food on the tree and the food on the table.

In college, Sizov said, “I kind of realized, I don’t know where most of the food I eat comes from. I thought it came from the grocery store.”

But as she surfed the Internet, searching for topics for the PhD in neurogenetics she expected she would do, Sizov chanced upon a website that described the climate impact of food waste — up to 4 percent of U.S. greenhouse gas emissions, according to analyses from ReFed, a nonprofit organization that works to reduce food waste.

She was captivated. The problem will only intensify as the global population grows, experts say. By 2050, the United Nations expects there will be another 2 billion mouths to feed around the world, an increase of more than 25 percent in just three decades. And as countries such as China and India grow richer, their populations are gradually changing their eating habits: more meat, more eggs — and a bigger carbon footprint tied to raising all of those animals and clearing off land to grow more food.

“If you reduce food loss and waste by 50 percent, you can save a lot of production emissions, but you can also avoid a heck of a lot of deforestation,” said Tim Searchinger, a senior research scholar at Princeton University’s Center for Policy Research on Energy and the Environment. Searchinger explained that after accounting for the fact that an acre of farmland could otherwise be an acre of forest, the carbon footprint of food skyrockets as trees soak up so much carbon dioxide.

Eliminating waste also happens to be a way to help farmers and grocery stores earn more money, since the more efficiently food makes it to consumers, the more cash ends up with the people who’ve done the selling.

That’s Sizov’s sweet spot, she said: If she can convince her clients that eliminating food waste is profitable, the effort will spread far more quickly than if she is simply asking them to be greener out of the kindness of their hearts.

“The pulls of reducing food waste are good for everybody,” she said. “There’s a direct alignment of a sustainable goal with a profitability incentive.”

Like humans, apples breathe in oxygen and exhale carbon dioxide. Putting harvested fruit in special oxygen-starved rooms sends them into a deep slumber that slows their aging. The practice keeps Granny Smiths on grocery store shelves even in June, when the previous year’s harvest is long gone and the new year’s crop is still sweetening on the branch.

But it is hard to keep watch over the fruit while it is slumbering, since opening up the storage rooms would send in a rush of oxygen and speed the apples’ aging. And it’s hard to get the mix of oxygen just right: Too little oxygen and the fruit starts to decompose.

“It’s like being a fruit anesthesiologist. You want to keep it knocked out, but you don’t want to kill it,” said Glade Brosi, a handlebar-mustached tree fruit agronomist at agricultural technology firm Wilbur-Ellis, who was walking through an apple orchard with Sizov on a recent crisp morning.

They weren’t far from the warehouses where she had been setting up her sensors. The fruit growing on the trees was full of promise. The fruit rotting on the ground was emblematic of the problem.

Barren desert mountains towered above. Down a long slope, the Columbia River guttered below. The orchard didn’t look like the old-fashioned pick-your-own places parents take their kids on fall weekends. A generation ago, apple trees in commercial orchards were tree-shaped. Now they grow on trellises, in dense formations that create a “fruiting wall” — a flat surface of dense fruit that receives uniform sunlight and is easier to harvest.

The shift in techniques makes it possible to grow a lot more apples. And it’s possible to keep them fresh for longer, too, with a spray of 1-methylcyclopropene, slowing their ripening for months. If you’ve bought a conventionally grown apple in July at an American grocery store in the past decade or two, chances are it’s been treated with the stuff.

Sizov reached up to a tree and plucked off an apple. It was fat and red, blushing into pink. It looked delicious. She bit into it — and made a face. It was still heavy on starch, far from being ripe.

“This one needs a few months,” she said. It would be perfect next summer, after a long stretch of slow ripening inside the warehouse.