Chemistry’s fight against food waste

Two refrigerated trucks leave a warehouse near Nashville, Tennessee, at about 6:00 a.m. They stop at local grocery stores, picking up food that is about to hit its expiration date. The trucks, operated by the antihunger nonprofit One Generation Away, rescue food that would otherwise be thrown away and give it to people and groups that need it.

By noon, the trucks have half a dozen pallets loaded with food. In one truck, a large cardboard box is filled with baked goods: sliced bread, baguettes, pastries, and a crème brûlée with berries. The pallets hold jars of red curry paste, boxes of macaroni salad, and fresh cauliflower.

On Mondays, One Generation Away delivers part of its haul to the Nashville Food Project, which makes thousands of meals a week for community groups. This week, Julia Baynor, Nashville Food Project’s meal manager, picks up some lettuce, green beans, and lots of prechopped butternut squash. “That butternut squash, it’s got to get cooked tomorrow,” she says. “It’s on the edge.”

Even if the produce isn’t perfect, Baynor finds a way to use it. Bruised apples are mashed into applesauce. Old strawberries are blended into smoothies. Hardly anything goes to waste. But that is far from typical.

In the US, around a third of all available food is never eaten. The US Department of Agriculture estimates that 165 million kg of food goes to waste every day, more than the weight of a fully loaded aircraft carrier.

When that food goes to a landfill, the fuel, fertilizers, and pesticides that went into making it are also wasted, and as the food decays, it produces methane, a greenhouse gas.

According to the Food and Agriculture Organization of the United Nations, in 2011, food that went uneaten emitted more greenhouse gases than the country of India. Meanwhile, the UN’s World Food Programme estimates that 1 in 10 people doesn’t have enough food, and 50 million people face emergency levels of hunger.

A number of companies are employing chemistry to reduce food waste at multiple steps in the food supply chain. That chemistry is in products that preserve the quality of produce on the farm, kill pathogens that can spoil food after harvest, and increase food’s shelf life. If all that fails, other companies are turning food waste into valuable chemicals.

But chemistry alone won’t solve the food waste problem. An analysis from ReFED, a nonprofit fighting food waste, calls chemistry that increases shelf life an emerging technology that could be too expensive to be effective. It suggests that interventions designed to change consumer behavior—such as reducing portion sizes, selling premeasured ingredients in meal kits, and educating consumers—are the best ways to reduce emissions from food waste. “That’s a pretty tricky segment to address through chemistry,” ReFED executive director Dana Gunders says.

But given the scope of the problem, chemistry has an important role to play, says Ahmed Moody Soliman, CEO and cofounder of Ryp Labs, a company that aims to extend shelf life. “This is not going to be one solution,” he says. “You’re going to have to come at it from different angles.”

Growing food

It can take a year for an apple to get from an orchard to a consumer’s plate, and its journey demonstrates both food waste problems and some of the solutions.

In the US, the industry group USApple estimates that farmers grow about 5 billion kg of apples annually, mostly in the state of Washington. The USDA reports that about 4% of those apples never make it to a grocery store. The main problem is ethylene.

Apples, like many other fruits, emit ethylene as they mature. Ethylene binds with a protein in fruit cells and serves as a signal to begin the ripening process. If the process starts too early, apples can be overripe by the time they reach a store.

In 1994, North Carolina State University researchers Edward Sisler and Sylvia Blankenship discovered that a molecule called 1-methylcyclopropene (1-MCP) can slow that process by binding with ethylene receptors in the apple. The company AgroFresh acquired the technology and introduced it to the apple market shortly afterward. Today, the company claims that its 1-MCP products are used on over 90% of apples stored in the US and prevent 10 million kg of food waste every day.

Most often, 1-MCP is used to slow ripening during storage, but AgroFresh also sells a 1-MCP product that apple farmers can spray on their trees when they are nearly ready to harvest. Chief Technology Officer Duncan Aust says this approach buys farmers more time.

About 30% of fruit and vegetable loss happens on the farm, according to USDA researchers. That loss is largely due to a combination of high labor costs for harvesting fruits and vegetables and volatile prices. Some farmers abandon labor-intensive crops if prices suddenly drop.

“There are no really effective, automated machines out there for picking apples in the orchard. It’s still a very manual labor process,” Aust says. “If I can’t get the labor to pick all the apples when they’re ready . . . those apples stay on the tree and rot or drop off.”

Storage and shipping

Once apples are harvested, they’re placed into bins that can each hold 450 kg of the fruit. Thousands of bins are stacked inside large rooms. The oxygen is then sucked out, 1-MCP is often added, and the rooms are sealed.

For farmers, the goal is to keep the apples in storage as long as possible. Selling later in the season fetches a higher price, but it also increases the chance that the apples will go bad.

Farmers try to unseal storage rooms with the ripest apples first, but they don’t know whether they made the right bet until the end of the season. “Sometimes you open that door and it’s just applesauce,” says Katherine Sizov, CEO and founder of Strella Biotechnology.

Strella makes sensors that monitor the concentration of ethylene and carbon dioxide inside rooms storing fruit like apples and bananas. Measuring those chemicals can tell you how ripe the fruit is and how long it will last.

Strella’s sensors track ethylene concentration using the same receptor proteins found in fruit. The company is also trying to develop an electrochemical sensor, which would be cheaper and potentially more sensitive.

Currently, Sizov says, many farmers decide which rooms to unseal by grabbing a handful of apples through a hatch in the door and testing their firmness and sugar content. That’s a tiny sample size for a room with millions of apples.

Other farmers use gut instinct. But as the climate changes and farmers experiment with new apple varieties, those hard-won instincts don’t always provide a full picture.

“They have that intuition that comes with decades of driving through the orchards,” Sizov says. “But the reality is, that’s really not translatable. And certainly not something we should be relying on to get food in our grocery stores.”

About a quarter of all the fresh apples grown in the US are exported, according to USApple. Keeping a piece of fruit at optimal ripeness as it travels in a storage container from Washington to Taiwan presents a new challenge.

The company Purfresh installs a device in shipping containers to convert oxygen from the air into ozone. The ozone reacts with ethylene and breaks it down into carbon dioxide and water, putting ripening fruit into a kind of cryogenic state during transoceanic voyages. Purfresh General Manager David Evans says the ozone molecules can also arrest mold and bacteria.

Breaking down ethylene means fruit arrives at its destination in better condition and can stay on the shelf longer, Evans says. That makes it easier to sell fruit all over the world at any time of year. “With an all-year-round supply of commodities and fruits, the seasons become obsolete,” he says.

At a recent USDA conference, Elise Golan, the department’s director for sustainable development, argued that the food system should move in the opposite direction to reduce waste. “The food system of the future needs to be more distributed and local,” she said. To that end, earlier this year the USDA announced hundreds of millions of dollars in funding to help food producers sell into local markets.

Retail and consumers

The USDA found that nearly two-thirds of food waste in the country occurs after a product has reached a grocery store. Consumers will reject produce for all kinds of reasons, according to Anthony Zografos, CEO and founder of the food-coating company Akorn Technology. “It’s too soft. It’s too mushy. It’s too hard,” he says. “The color might not be right.”

In early 2020, Zografos started working on an edible coating to make produce match consumers’ expectations. The coating has a wax that prevents moisture loss, an oil to preserve color, and a corn-derived protein that controls the fruit’s respiration rate. “You don’t want to overdo it,” he says. “If you don’t allow it to respire at all, basically it ferments.”

Several companies, including Apeel Sciences and AgroFresh, have or are developing similar coatings. A ReFED analysis says these coatings can be effective, but they can also be expensive and hard to integrate into the food supply chain.

Ryp’s Soliman says that’s why his company uses stickers to extend shelf life. “You want a solution that is easy to use that can be applied anywhere along the supply chain,” he says.

The stickers, which are in the pilot stage, slowly release natural antimicrobial compounds, such as lavender oil, to suppress mold and diseases that spoil food. The company is also developing bigger labels, sachets, and infused packaging materials to deliver the compounds.

Similarly, the start-up Hazel Technologies sells a pouch that slowly releases 1-MCP. The pouch can be placed in food packaging to slow ethylene production long after a piece of fruit leaves a controlled storage room. “It goes along for the ride,” chief technology officer and cofounder Adam Preslar says.

But consumers are paying attention to more than just the color and ripeness of their food. They’re also looking at expiration labels, and the language on them is inconsistent. ReFED estimates that confusion about the meaning of date labels is responsible for about 7% of all consumer food waste. Tweaking labels could divert more than 500,000 metric tons of food waste each year, the group says.

The start-up Mimica is developing date labels that it says are easier for consumers to understand. The labels—originally intended to help people with low vision read expiration dates—contain a blob of gel that feels solid when food is safe to eat. After the label has been exposed to a certain amount of heat, an activator chemical is released, turning the gel into a liquid and exposing plastic bumps that tell the consumer not to eat it.

Giorgia Raci, Mimica’s R&D team leader, says food companies usually date their products according to a worst-case scenario, so food is often good after the expiration date. She says Mimica’s label will reduce waste by giving consumers confidence that their food is still safe. “Most of the time, it’s still good,” Raci says. “Nothing bad is going to happen.”

Gunders, from ReFED, says many of these technologies show promise, but it’s hard to predict how they will change consumer behavior and whether they will ultimately reduce waste. “Behavior is hard to change for anything, but we have a very complicated relationship with food,” she says. “We really wrap a lot of our identity in food.”

The final destination

If food reaches the end of the supply chain, there is one final option to prevent it from going to waste completely. A number of researchers and companies are using food waste as a feedstock for valuable products.

At Iowa State University’s Polymer and Food Protection Consortium, researchers are trying to build a machine that can take, for example, a bag of moldy hamburger buns and automatically separate the waste from the plastic. The unwanted food can then be used to produce energy, and the packaging can be recycled. ChainCraft is using waste from the food and beverage industry to make medium-chain fatty acids for animal feed.

But Baynor, from the Nashville Food Project, sees food as something more than a commodity whose economic value needs to be salvaged with technology.

As she unloads the truck from One Generation Away, a pair of volunteers in the kitchen prepare bacon, lettuce, and tomato sandwiches for an after-school program. On the other side of the room, a staff member is using a trash can–sized skillet to cook ground beef for a massive lasagna that will be divided among a center for older adults, a YMCA, and a reentry program for people leaving prison.

“As opposed to being a food bank and doing emergency food, we do something that we call community food,” Baynor says.

She estimates that it costs her group about 65 cents to turn food that was going to be thrown out into a meal—a meal that gets people together and gives them a chance to connect.