Parked under an awning of trees in Camas, Washington, Doug Knippel’s converted semitruck trailer smells like strong, sour beer. It’s the scent of hundreds of pounds of barley, leftover from a local microbrewery, being devoured by young Hermetia illucens: black soldier fly larvae. Knippel dips his hand into a tray and comes back with a palmful of rice-sized organisms writhing through his fingers. “I’ve been composting since I was a kid. I love turning waste into something that’s usable,” he says. “I’m taking waste and I’m creating food from it instead of just soil.”
Knippel is one of a growing number of bug breeders rearing black soldier flies to help simultaneously tackle three of the biggest environmental issues in the United States: greenhouse gas emissions, irresponsible land use, and food waste. Black soldier fly larvae convert waste into a popular garden fertilizer: their poop, which is called frass. Chickens go wild for the later stages of larvae, which are fat with protein and oil and can be processed and sold as animal feed. Projections estimate the black soldier fly industry to be worth $2.57 billion by 2030, and as companies scale up, they could provide a pressure relief valve for the United States’ food waste issues and the greenhouse gases that come with it. If implementation around the world is any indication, the flies may become a large-scale trash solution for our waste-burdened world.
The U.S. Department of Agriculture (USDA) estimates that 30% to 40% of American food is thrown away every year. Much of that food ends up in landfills, where it makes up 22% of municipal waste annually. Unable to reach soil, food decomposes and releases methane gas, which is at least 25 times worse for the climate than carbon dioxide. Garbage dumps produce nearly a fifth of U.S. methane emissions.
Trash-diversion tactics like composting have grown in the last decade to address the issue, but we’re still landfilling more food than we were 10 years ago. Meanwhile, American agriculture raises animals on resource-heavy protein such as soy and fishmeal. Demand for soy is leading to widespread deforestation in South America, while 20 million tons of wild seafood fit for humans is used as fishmeal every year, even for fish like tilapia that were traditionally bottom-feeding vegetarians.
“I’m taking waste and I’m creating food from it instead of just soil.”
Enter the black soldier fly. Adult flies have a thin, dark body, don’t bite or sting, and only live for a week. Unlike houseflies, black soldier flies aren’t attracted to human habitation, they don’t transmit diseases, and they’re already endemic in many places around the globe. A single female lays around 500 eggs that hatch into larvae after four days. These maggots have a taste for everything that rots, from vegetable scraps to meat chunks, and they eat twice their weight in scraps every day. Once they plump up, a week or so after hatching, they’ve reached their most valuable state as kernels of protein and fat.
Knippel harvests small and medium-sized larvae by pouring them over a screen that filters out any leftover waste and larger larvae. While young larvae are tawny, the later stages turn black and are either fed to his farm’s chickens (if they’re shipped, they’ll pupate before arriving) or collected to mature into breeding flies. This late stage of larvae instinctually crawl away from their wet waste-filled homes and toward drier material. Producers exploit this instinct, placing small ladders in the waste bins that the larvae can climb up, allowing them to “self-harvest.”
The fact that these grubs are stuffed with protein matters. A hectare of land can produce about a ton of soy a year, depleting and eroding soil over time. One estimate suggests the same space could produce 150 tons of insect protein, constantly rechargeable by adding more garbage. A 2019 study published in Waste Management measuring an Indonesian facility found that black soldier flies reduced carbon dioxide emissions to nearly half of what’s produced by composting — and composting already reduces greenhouse gas emissions when compared to landfills.
The chunky wrigglers have been a pet reptile delicacy for years, but thanks to regulatory changes by the Association of American Feed Control officials in 2017, black soldier flies are now an approved food source for chickens and some fish. Chickens happily eat the grubs whole, which is how Knippel’s backyard operation sells his larvae. Larger companies like Enviroflight, however, squeeze the oil out and grind the leftover protein to sell wholesale. Separating the two allows feed manufacturers to blend the exact macronutrients necessary for the animal they’re feeding.
Like Knippel, the soldier fly industry aims to transform trash into treasure. So far, most companies, including Enviroflight, have focused their energy on pre-consumer waste. Enviroflight uses grains from bourbon distilleries, for example, and Knippel uses leftover barley — both of which would otherwise end up in landfills. But that doesn’t begin to tap into the potential of kitchen debris.
Companies are attracted to pre-consumer waste because black soldier flies contain more or less protein, fat, and key nutrients depending on their diet. There are also concerns about the larvae and by-products being contaminated and fed to livestock, and more research is needed on how bugs perform on postconsumer diets, which is why black soldier flies are mandated for use only on pre-consumer waste in many countries outside of the United States.
“It smells almost fruity. Like strawberries mixed in with gross other things.”
But others are experimenting with the wasted food thrown out by households and institutions. Twice a week, Devon Brits, a research assistant at Louisiana State University, loads airtight 30-gallon buckets full of food rubbish from the campus’s dining halls into the back of a pickup truck. He drives 15 miles out of the city to an insect farm in West Baton Rouge Parish, where half-eaten burgers, pizza, and bread are ground into a pinkish-brown slush and fed to the larvae. “It smells almost fruity,” Brits says. “Like strawberries mixed in with gross other things.” The project, which processes about two tons of cafeteria scraps a week, is a partnership between the university and reptile-food producers Fluker Farms.
Brits, who first worked with black soldier flies in his native South Africa, says he hasn’t seen any difference in the quality of larvae fed postconsumer waste. The consistency of the menu helps — cafeteria food doesn’t change a whole lot week to week. Still, they test for contaminants like salmonella, E. coli, listeria, and other major pathogens on a weekly basis. Some of the larvae are sold, while others are funneled back into the farm for breeding.
Getting a system like this to work on a municipal scale hasn’t been fully realized yet. Several international companies are turning waste into protein privately, such as AgriProtein in South Africa, whose legislation allows for postconsumer waste. The company is currently trialing a pre-consumer waste facility in California. One of the largest black solider fly companies globally, Enterra, opened a 170,000-square-foot plant near Calgary, Canada. France, Chile, Ireland, Malaysia, Spain, and the Netherlands all have operating black soldier fly businesses, primarily focused on making protein rather than zapping trash.
The hardest part of the process, and perhaps the most expensive, is breeding. Knippel’s trailer is a testament to that — it originally belonged to a larvae supplier, who built the structure but could never get the flies to mate. The flies are notoriously precious about temperature change, barometric pressure, and humidity, which can affect how many eggs they lay, according to Knippel. After a year and a half of working on the project, the would-be supplier handed Knippel the keys. Knippel cleaned the breeding area, added food to attract the flies (adults don’t eat, but do want to lay eggs near a food source), and started monitoring the space daily. Within two weeks, his flies were laying eggs.
The economics of larvae rearing are also challenging. Spring Yang founded Symton, a larvae company in Texas, before moving to China to help build black soldier fly settlements to process restaurant waste. He says that for the numbers to work, larvae managers have to sell the grubs for protein — they can’t just process waste. He believes that in order to scale, the industry would need to split into fly breeders, waste eaters, and feed makers, each supporting the other.
“I just love the fact they can consume so much so fast.”
But waste-diversion projects are being imagined. Charlotte, North Carolina, has plans for a pilot program to divert postconsumer waste from landfills and provide a feed source for farmers. A 12,000 square-meter factory in the Baiyun District of Guangzhou of China can gobble up to 50 tons of chow. Even if producers stay limited to pre-consumer waste in the U.S., there’s still plenty for the bugs to eat.
Of course, projects don’t have to be citywide to be impactful. University studies mapping the bug’s appetite have popped up around the country. A Texas company uses the flies to process restaurant leftovers in Austin and farmers are experimenting with creating their own closed-loop system, breeding larvae to feed their poultry.
Knippel’s 10-acre farm at Northwest Redworms receives 10,000 pounds of food waste from food banks, Imperfect Foods, and other vendors every week. Most of the food is processed worms, which demolish the produce and turn them into valuable castings. But while Knippel’s red wigglers and European nightcrawlers work hard, he maintains the black soldier flies are even more impressive. Worms take a minimum of two to six months to produce castings that gardeners covet — even longer for Knippel, who uses a special process for his worm beds — while his larvae demolish 100 pounds of barley on a lazy day. They can process “10 times that,” he says, easy.
The next step beyond his fly trailer would be a 40-by-40-foot structure with several rooms for breeding rather than the single room he has now. According to his estimates, it would cost him $200,000. But with a facility that size, he could make 10 times what he’s making now. Add an extra $100,000 in equipment and he thinks he could process all the waste for his city of nearly 24,000 people.
“I just love the fact they can consume so much so fast,” Knippel says. “I love the worms, but I put a lot more work into the worms than the larvae. I get a lot more back from the larvae.”