Black Soldier Flies as Recyclers of Waste
By Harvey Black
If black soldier fly larvae could enter competitive eating contests, they would excel, especially when it comes to eating nasty stuff that we don’t want around or wouldn’t think of eating ourselves. Then, after the larvae had eaten, they could be recycled as feed for livestock, although the U.S. Food and Drug Administration currently prohibits that.
“FDA does not believe the use of insect protein ingredients can meet the standard for being GRAS (Generally Recognized as Safe),” wrote an FDA representative in an email. “As a result, such ingredients would appear to require food additive approval to be legally used as an ingredient in animal food. At this time, no food additive approvals have been issued for use of any type of insect material as an ingredient for any purpose in animal foods.” The European Union has similar restrictions.
However, if the regulations were to change, black soldier flies (Hermetia illucens) could be used on a large scale to dispose of organic wastes such as manure or offal, according to an article in Environmental Entomology called “Ability of Black Soldier Fly (Diptera: Stratiomyidae) Larvae to Recycle Food Waste.”
The article is timely, as it was published around the same time that an article in PLOS ONE found that the ability of crickets to convert plant matter into protein may be overestimated.
During research at the University of Windsor, the larvae waxed fat on diets of pig liver, pig manure, kitchen waste, and fish offal. The researchers housed larvae in small containers with six grams of each type of waste. Each day the remaining amount of food was weighed and another six grams were added. The feeding stopped when the larvae began to enter what is known as “the wandering stage,” signaling that they were getting ready to pupate.
As a control, the larvae were also fed a diet of nice, clean poultry feed, and the researchers compared the results with those of the of the organic-waste diets. They found that the larvae chowed down most on the food-waste and fish-offal diets.
“Larvae fed on fruit and vegetable waste consumed almost double the amount than those fed on standard poultry feed,” they wrote.
In fact, even the larvae that were fed a diet of pig manure ate more than those which received poultry feed.
“The total amount of manure waste reduction was 44% greater than that determined for the standard poultry feed,” they wrote.
“The study was the first to show that the insects can thrive on food waste,” said Dr. Jeffery Tomberlin of Texas A&M, one of the co-authors. “Insects are no different from most other animals. They need a balanced diet. What we found was food waste and fish offal probably contained the right amount of protein and carbohydrates to allow them successfully to develop.”
The study is an example of the surging interest in using black soldier fly larvae to recycle waste. According to Louis Sorkin, an entomologist at the American Museum of Natural History, the larvae are very efficient, and the droppings from the larvae can used as plant fertilizer.
DipTerra LLC, a firm based in Lake Oswego, OR, sells black soldier fly larvae for recycling organic waste. The firm’s head, Dr. Terry Green, claims that homeowners can easily use the larvae to degrade organic waste such as food scraps. He sees the value of the larvae in dollars and in environmental terms.
“The issue is, where can the black soldier fly be used most beneficially in both the environment and from an economic point of view?” he said.
In 2005, a team of scientists from the University of Georgia and North Carolina State University issued a report which studied how black soldier fly larvae might be used in recycling pig manure. They found that “Manure mass was reduced 56% while the concentrations of most elements and nutrients were reduced 40 to 55%. Nutrient analyses and feeding studies indicate that dried black soldier fly prepupae grown on swine manure solids have value as a feedstuff, particularly for aquaculture.”
Since that report was published, attempts have been made to use black soldier fly larvae to produce fish feed from organic waste, as this Scientific American video featuring Louis Sorkin shows.
Dr. Tomberlin noted that the larvae would not actually be fed directly to livestock. Instead, “a process would be used to pull the protein out.”
While there may be optimism for the use of black soldier fly larvae as a source of animal feed, Tomberlin points to some questions that have to be dealt with, in addition to the FDA’s stance on the matter. For one thing, the larvae would only be one part of a healthy diet for livestock.
“The insects need to be developed as part of a feed ingredient,” he said. “Chickens may need one thing, swine may need another, and the black soldier fly is not going to be the cornucopia of nutrients.”
Beyond the issue of nutrition, there are other questions that must be answered concerning the use of the larvae in animal feed. One is the safety of the product. Tomberlin said that feed products must not carry harmful microbes, and that no heavy metals — which can be harmful — should be fed to livestock.
Tomberlin emphasized that there are no data yet to show that the larvae can be turned into safe feed for livestock in the U.S. However, work is being done in China, where they are industrializing the process.
“I’ve seen facilities in China where they’re producing 20 tons of larvae a week,” he said. “It works. It’s amazing they’ve been able to industrialize it more than anyone else in the world. They use it for animal feed, they use it for aquaculture.”
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Harvey Black is a freelance science writer. A long-time resident of Madison, Wisconsin, he has written for numerous publications including Environmental Health Perspectives, Scientific American Mind, New Scientist, The Scientist, and the Milwaukee Journal Sentinel.