17%: Portion of global electricity use that goes to refrigeration.Illustration: Jan Siemen
Back in 2001, a middle-aged man made a video of his car and sent it around to a few friends. So far, so predictable—but this video featured a dilapidated Vauxhall Nova whizzing around a junk-strewn yard in a cloud of fog. At the wheel was Peter Dearman, a rumpled-looking autodidact who had spent the better part of four decades imagining a way to build engineering's ultimate vaporware: a motor powered only by air.
Born in 1951 on an egg farm north of London, Dearman would seem an unlikely candidate to have solved the problem. He left school at age 15 and worked in the family business for a while, then took a job at a local sheet-metal factory. He spent his evenings as many Englishmen do—out in the garage or the garden shed, tinkering. But Dearman's aptitude and ambition set him apart from other hobbyists. Over the years he filed patents for an improved adjustable wrench, a solar hot-water system, and a portable resuscitator that is still used in ambulances today. His most impressive achievement, however, was the Nova, whose engine he cobbled together from string, a used beer keg, a red plastic trash bin, and a coffee can's worth of liquid nitrogen.
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The idea behind Dearman's project dated back to at least 1899, when a Danish inventor named Hans Knudsen claimed to have designed an automobile that could run on “clear, bluish” fuel—liquefied air, to be sold at a penny a gallon. Rather than spewing out a toxic mix of pollutants and greenhouse gases, it would leave a harmless trail of condensation in its wake, wafting by at the stately speed of 12 mph. Knudsen received admiring media coverage at the time, but his company went belly-up in a matter of years. Modern cynics suspect he was engaged in a Theranos-style fraud, in part because no one could figure out how he'd done it. For years, a working liquid-air engine seemed about as fanciful as a perpetual motion machine.
Still, the underlying principle was sound. Most engines rely on heat differentials. In the case of, say, a gasoline-powered car, the fuel is mixed with air, crammed into a piston chamber, and set alight, causing it to jump more than 1,000 degrees in temperature. The gas rapidly expands, propelling the piston and, in turn, the wheels. Take the same process, slide it way down the Fahrenheit scale, and you've got a liquid air engine. The nitrogen fuel starts out at 320 degrees below zero. When it enters the (much warmer) piston chamber, it boils off into gas. The change in temperature is smaller than with gasoline, so the pistons move with a little less oomph—but it's enough to get the wheels going. The real problem comes later: All that frigid fuel coursing through the engine quickly freezes it, effectively wiping out the heat differential. The air stops expanding, and the car runs out of puff.
The roadblock was clear, Dearman told me recently. He'd been pondering how to get around it since he was a teen. In a car that runs on heat, you need something to keep it cool—a radiator. In a car that runs on cold, you need the opposite. “I had an idea in my head for how to make it work, but I knew I wasn't going to get anywhere until I had some research to go on,” he said.
The breakthrough came in 1999. Dearman was watching an episode of the BBC's dearly departed flagship science program, Tomorrow's World, in which the presenter visited the University of Washington to report on a rather clunky-looking converted mail truck. It had trouble with hills, and its top speed was 22 mph, but it ran on liquid nitrogen (a profligate 5 gallons per mile). Invented by Abe Hertzberg, an eccentric professor who had previously come up with a laser-powered airplane, the truck boasted one major innovation. Before the freezing-cold fuel reached the engine, it ran through a heat exchanger, a series of concentric tubes that circulated outside air around the fuel line. John Williams, who worked on the truck as a graduate student, explained that the exchanger ensured “the whole thing didn't turn into a giant ball of ice.” But it didn't tackle the fundamental problem—that the liquid nitrogen still rapidly cooled the engine, throttling its own expansion into a gas. “Our project was a proof of concept,” Williams explained. “We were reconciled to a certain degree of terribleness.”
From his sofa in the historic market town of Bishop's Stortford, Dearman immediately saw both the logic of Hertzberg's design and a way of improving on it. The answer to making sure the nitrogen continued expanding? Antifreeze. “It's obvious, but it's only obvious once you've seen it,” Dearman said. He went out into his garage, grabbed a blue plastic jug from the shelf, and started playing around with his lawn mower, hacking its engine to squirt a mixture of antifreeze and water into the piston chambers on each stroke. This brought ambient heat directly to the place it was needed most—and the engine's efficiency skyrocketed. The same trick worked on the battered Nova, bought as a guinea pig.
And there things might have ended if Dearman's brother, a contractor, hadn't mentioned the Nova to a wealthy client, who put up funding for a patent application. In 2004, the client also introduced Dearman to Toby Peters, a former war photographer turned business strategist who had been working on corporate social-responsibility initiatives. Peters was skeptical, so he took the engine to the University of Leeds for a full workup. The science checked out. The Dearman engine was about as efficient as its gas- and diesel-powered counterparts; roughly a third of the energy in the fuel was actually put to work, and the rest went to waste. But no amount of antifreeze would solve the underlying issue: Gallon for gallon, liquid air contained far less energy than fossil fuels. It would never supply as much torque and horsepower as car buyers demanded.
Then, in 2011, Peters had an epiphany of his own. Thinking of the Dearman engine purely as a source of locomotive power missed its unique selling point. Where a typical engine lets off waste as heat, Dearman's vented it as cold. And cold, Peters told me, is “immensely valuable.” What the newly formed Dearman Company was trying to sell, in other words, was not so much an engine as a mobile cooling unit. That meant it had plenty of prospective customers waiting behind the wheels of refrigerated trucks.
The sales pitch wrote itself: Rather than relying on diesel-powered units, which warm the world with greenhouse gases and clog pedestrians' airways with asthma-inducing particulate matter, customers could upgrade to a Dearman, which would emit only nitrogen. What's more, it would cost the same to operate as a conventional system, while being quieter to run, quicker to refuel, and faster to cool down. Yes, making the liquid nitrogen would consume energy—but even when you factored that in, the Dearman engine would result in an emissions savings of about 40 percent over diesel. If the grid powering the fuel plant was running on renewable energy, the figure rose to 95 percent.
The logic was impeccable, but would winning the argument be enough? History is full of examples of clever new technologies that never found their market, either because the timing was wrong or the branding was bad or a company with deeper pockets flooded the playing field with a rival product. Capitalist economies are generally imagined to operate according to the laws of natural selection: The fittest survive, and the rest go the way of the Betamax. In practice, though, the outcome is rarely so meritocratic. At the dawn of the age of domestic refrigerators, for instance, there were two competing designs—one powered by electricity, the other by gas. Even though gas fridges were quieter and less expensive to operate, electricity won out. Big companies threw their prodigious ad budgets behind it, and consumers did as they were told. If Dearman and Peters were going to remake the cold chain, the temperature-controlled network through which food travels around the globe, they'd need more than a really good idea.
The journey from garage prototype to commercial appliance was a long one. Peters focused on fundraising and business development; Dearman worked alongside his son and a growing team of engineers to refine his original design and make it increasingly efficient, compact, lightweight, and dependable. By 2015 a truck equipped with a Dearman refrigeration unit was racking up miles around Warwickshire, undergoing testing to make sure that what worked in the controlled conditions of the lab held together on the rain-slicked, potholed roads of the real world.
A year later, Sainsbury's, the UK's second-largest grocery chain, borrowed a Dearman unit for a three-month trial, shuttling goods from its depot in Essex to London-area supermarkets. A year after that, a Dearman-cooled truck spent six months delivering pints of Ben & Jerry's across the Netherlands for Unilever, without losing a single load.
There were 3 million refrigerated trucks on the road worldwide, and the fleet was expected to grow to 17 million by 2025. Peter Dearman's invention seemed like a shoo-in replacement for diesel. Before too long, even the Royal Society, Britain's most esteemed scientific body, was inviting him to pop round for dinner.
To the modern eater, it can be difficult to grasp just how much, and how quickly, mechanical cooling has transformed both the human diet and the global climate. The technology made its commercial debut only after the Civil War; its earliest adopters were German-born brewers in the Midwest, looking to keep their lager caves chilled in the steamy summer months. But it wasn't long before other industries realized that refrigeration could be used to manage one of humankind's oldest anxieties: food spoilage.
For millennia, people and microbes have been engaged in a form of interspecies warfare. Bacteria and fungi attempt to colonize our food, and we, in response, attempt to delay their advance using an arsenal of preservation techniques. In what was likely a long and slow process, pursued through trial and error, different communities developed different methods for stopping the rot. Some proved quite delicious—stinky cheese, smoked salmon, salami, miso, marmalade, membrillo. Even the gelatinous pleasures of Scandinavian lutefisk or Chinese century eggs have their devotees.
Most of these preserved foods are incredibly long-lasting, as well as portable. What they are not, however, is the same as fresh: The chemical and physical transformations required to vanquish microbes inevitably also alter the food's original flavor, texture, and appearance. The introduction of widespread, on-demand refrigeration changed all of that, overturning thousands of years of dietary history.
The earliest mobile mechanical cooling units were patented in 1939 by Frederick McKinley Jones, the first African American to receive the National Medal of Technology. Like Dearman, he was a high school dropout and self-taught engineer. Prior to his invention, perishable foods such as meat, dairy, and produce had to be entombed beneath a thick layer of hand-shoveled ice for transportation. In the early decades of the 20th century, a railcar full of California-grown cantaloupes destined for New York City would be packed in 10,500 pounds of ice—and re-iced with another 7,500 pounds several times during its multiday journey. Even then, shipments experienced considerable shrink. Indeed, the impetus behind Jones' invention was the loss, by his boss' golfing buddy, of an entire cargo load of raw chicken. It had to be tossed when the truck carrying it broke down and the ice protecting it melted.
During World War II, the Defense Department quickly seized on Jones' diesel-powered devices, sold under the brand name Thermo King, to supply troops with everything from blood plasma to frosty Coke. In the years afterward, refrigerated trucks transformed the American foodscape. Regional distribution networks gave way to national ones. Slaughterhouses and processing facilities grew increasingly enormous and more remote, driving down the cost of meat and making it an everyday staple. Agriculture became concentrated in those places where a particular crop could be cultivated most cost-effectively, with the result that California now grows half of the fruits and vegetables eaten in the United States.
Today, in fact, more than three-quarters of everything on the average American plate is processed, packaged, shipped, stored, and sold under refrigeration. It is the reason orange juice, stockpiled in giant tank farms, tastes the same year-round, like soda. It is the reason many tomatoes, genetically tuned to maximize cold tolerance rather than flavor, taste like nothing at all. Refrigeration has made us taller and heavier; it has changed the composition of our gut microbes; it has reshaped our kitchens, ports, and cities; it has reconfigured global economics and politics. In 2012, six years before the Royal Society feted Dearman and his engine, the academy's distinguished members declared refrigeration the most important invention in the history of food and drink—more significant than the knife, the oven, the plow, and even the millennia of selective breeding that gave us the livestock, fruits, and vegetables we recognize today.
But as the cold chain has expanded, distributing artificial perpetual winter across the world, it has wreaked havoc on the natural cryosphere, the glaciers and icebergs and frozen swaths of tundra that help keep Earth's climate system in check. Refrigeration already accounts for about a sixth of humanity's electricity usage, and the demand is only expected to grow as countries such as China and India busily build US-style systems of their own. In the next seven years, analysts predict, the global refrigeration market will quadruple in size.
More cooling—of the conventional kind, at least—means more warming, and not just because of runaway power consumption. Refrigerant leaks are a problem too. Once released into the atmosphere, many of these chemicals contribute to climate change. The most up-to-date domestic refrigerators lose less than 1 percent of their refrigerant every year, but commercial refrigerated warehouses can leak up to 35 percent. Different systems use different refrigerants, some of which, like ammonia, have a negligible effect on the climate. But others, like hydrofluorocarbons (HFCs), are known as “super” greenhouse gases because they are thousands of times more warming, molecule for molecule, than CO2.
Although HFCs are gradually being phased out under the terms of a global agreement signed in 2016, their use is still on the rise in developing countries. That's partly why Project Drawdown, a climate change mitigation initiative founded by the environmentalist Paul Hawken, lists “refrigerant management” as the single most effective solution to global warming. (The category includes those chemicals used to chill people as well as food: Air-conditioning and refrigeration rely on the same technology, and their usage is rising in lockstep.)
And if we do nothing? Suddenly the slogan of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers begins to sound more like a threat than an assurance: “Shaping Tomorrow's Environment Today.” Preserving food for a planetary population of 9 billion using existing technology would deliver on that promise in the most disastrous manner. And yet, in the 81 years since Jones patented the Thermo King, there has been remarkably little innovation in the cold chain—or there wasn't, anyway, until Peter Dearman.
For a moment last year, it appeared that the curse of the liquid-air engine might not be broken after all. The Dearman units were working well, but the company had burned through its investment capital and was struggling to pay its bills. By early December, it had entered receivership. All was not lost, however: In January, a Denver-based angel investor named Thomas Keller swooped in and bailed the company out.
According to Keller, the firm's problems were “standard issue” for a technology startup. “Dearman had so many opportunities—so many inquiries, so many ideas for where the technology would be helpful—that it ran off in many different directions, all of which were costly,” he told me. His plan now is to simplify. He intends to focus entirely on finishing the next-generation engine. “It should be available for Unilever trucks this year,” he said.
Still, Keller seemed daunted by the challenges to come. Besides scaling up its manufacturing operation, a huge obstacle in itself, the company will have to hire a sales force, establish maintenance facilities, and develop a supply chain for spare parts. That entails either raising enough capital to build the infrastructure from scratch or partnering with the competition—an old-school refrigerated transportation company—in order to piggyback on its existing networks. “We're struggling a bit with that, frankly,” Keller said. “And so we're right back where Dearman was, with just a little pressure added.”
Toby Peters, who now works at the University of Birmingham, remains hopeful that the company will navigate past its latest financial roadblock. But he pointed out that, even if all 3 million of the world's refrigerated trucks were retrofitted with Dearman engines, that would not be nearly enough to save the world from refrigeration's catastrophic climate impact. “We are going to be deploying somewhere between 13 and 18 cooling devices per second for the next 30 years, and we're still not going to deliver cooling for all,” Peters said. Moreover, he added, “we simply can't green that volume of electricity.” Consider refrigeration's human analog: In 2017 and 2018, enough new room AC units were installed in the developing world that their combined energy demand exceeded the total amount of solar power generated globally.
Fortunately, the fix for the fossil-fueled fridge isn't limited to building a better fridge. There are other methods of food preservation waiting in the wings, some new, some old. In Santa Barbara, California, a company called Apeel has devised a high-tech edible coating that slows the metabolism, and thus the decay, of fruits and vegetables. Made from a waxy substance found in avocado pits, it extends produce life by nearly the same factor as refrigeration, while retaining more nutrients and flavor. In Australia, engineers recently announced an alternative to pasteurized milk, one of the most wasted foods in the United States. By using high-pressure processing—roughly 75,000 pounds per square inch, or the equivalent of stacking six elephants on a dime—they were able to make milk stay good for four times as long, without sacrificing taste. A Dutch designer named Floris Schoonderbeek, inspired by traditional root cellars, recently created the Groundfridge, a naturally cooled pod that can be buried in a backyard and filled with 20 refrigerators' worth of food. In Hokkaido, Japan's northernmost island, agricultural warehouses are cooled with last winter's snow. Chefs in Tokyo say the rice, asparagus, and beef that come from the region taste sweeter than their conventionally chilled counterparts.
All of these solutions offer improvements over mechanical refrigeration, not just in terms of climate impact but also in food quality and safety. But all of them are also piecemeal. A coating that keeps room-temperature blueberries plump and juicy for a month does nothing for milk. The ingenious snow-cooled meat lockers of Hokkaido wouldn't work in Santa Barbara, nor would a city dweller have anywhere to bury a Groundfridge. With conventional cooling, the answer to the question “Will it work?” is always a resounding yes. With these alternative methods, the reply becomes more wishy-washy: “It depends.”
And “it depends” is not usually the answer we're looking for. There's something reassuring about the one-shot solution, as opposed to the nuanced thinking required to apply local, circumstantial fixes. In some ways, mechanical refrigeration only became a problem because it became the answer to perishability. Once we had that particular hammer, everything looked like a nail. This hegemonic tendency—call it technological lock-in, confirmation bias, or just convenience—is understandable, but it's worth resisting. Given that single-solution thinking is what got us into trouble in the first place, we probably shouldn't replicate it in our prescriptions for the future.
It's likely too late for a refrigeration redo in the developed world, unless Peter Dearman can build a Nova capable of time travel. But our blueberries, eggs, milk, and carrots might yet stage an escape from the fridge, at least along part of their journey from farm to fork. In the meantime, we should work to ensure that those parts of the globe not yet bound by the cold chain approach food preservation as a problem with more than one solution. We can't—and shouldn't—pull the plug on refrigeration altogether, but it's not the only weapon in our age-old war on rot.
NICOLA TWILLEY (@nicolatwilley) is the cohost of Gastropod, a podcast that looks at food through the lens of science and history. She is at work on two books, one about refrigeration, the other about quarantine.
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