Released Sept. 10, 2007
TWIN FALLS, Idaho — Waste not, want not, the saying goes. That’s something Mother Nature doesn’t need to be told. When she breaks down a waste product from one organism, she meets the needs of other organisms in the food chain.
In the Magic Valley, scientists from the University of Idaho and Idaho State University are benefiting from Mother Nature’s good nature by raising black soldier flies on manure from Idaho’s dairy farms. The immature fly larvae reduce the manure piles by half while turning themselves into nutritious fish feed. Better still, they harvest themselves in the process.
No wonder the innovative project is being funded by USDA Sustainable Agriculture Research and Education: it could help sustain two of Idaho’s agricultural industries at once.
Principal investigator Sophie St. Hilaire, an aquatic species veterinarian at Idaho State University, first hit upon the notion of pairing black soldier flies with dairy manure after a former employer suggested that flies might make good substitutes for pricey fish meal in trout diets. Although they thrive in manure, black soldier flies—native to warmer climates—can’t survive Idaho winters and don’t feed during the two brief weeks that they’re winged adults, thereby alleviating scientists’ concerns that they’ll become pests.
St. Hilaire soon invited University of Idaho waste management engineer Ron Sheffield and fish nutritionist Wendy Sealey to help her explore the feasibility of the idea. Initial results proved encouraging, and Sheffield is now hammering out the on-farm logistics while Sealey evaluates the manure-fed larvae’s nutritional value to rainbow trout. After enhancing the dairy manure with fish wastes rich in fish oil, the trio noted that the larvae responded by “bioaccumulating” dense concentrations of heart-healthy omega-3 and omega-6 fatty acids—nutrients that a health-conscious public values in the fish it eats.
Sheffield hopes the research will eventually lead to a small niche-market industry for Idaho dairymen. “The goal isn’t to reduce the volume of dairy manure in Idaho but to use a waste product of one industry to develop an alternative protein source for another,” he says. “Dairymen could take manure solids that they would typically land-apply as a fertilizer and instead develop a value-added product that supports another major industry in the state.”
The trout industry needs that support because the costs of fish meal and fish oil—key components of trout diets that are becoming scarcer worldwide—are reaching $1,400 a ton. “We have to identify additional sources of protein and lipids for fish feeds,” Sealey says. “If we can capitalize on waste products, it’s a benefit to everyone involved.”
The next step: take their small-scale research to a local dairy to see if the concept plays out economically in the real world. At Buhl, cooperating dairyman Dean Swager is looking forward to the scientists’—and the flies’—activity. “If something helps the dairy industry, I’m always a party to that,” he says. “We have only one income on our dairy and that’s milk. If we can diversify and have another income, that would be wonderful.”
In preparation for next spring’s rollout on the Swager dairy, Sheffield is designing and building a two-piece, 8-foot-diameter fiberglass globe. He’s including “very small ramps” that the black soldier flies will use to wriggle up out of the manure when it’s time—after two months—to turn into flies. Unbeknownst to them, however, Sheffield is also including a hole at the top of each ramp through which the black soldier fly larvae will fall—straight into harvest buckets. “They’ll take their own long walk to their own demise,” he says. If he can add a heater to the inside of the fiberglass globe, Sheffield will be able to extend the flies’ beneficial behavior to a second generation—altogether about six months between April and November.
According to Sheffield, Vietnamese restaurant owners use a much simpler and smaller container to let black soldier flies gobble down their table scraps. “I must be from Texas,” he says, “because I have to make it bigger and better.”
After the well-fed larvae land in the harvest buckets, Sealey will wash and freeze-grind them and serve them to rainbow trout at the Hagerman Fish Culture Experiment Station. A commercial fish food processor might instead extrude them into pellets at high temperatures and pressure.
“It’s not that odd if you think about what trout eat in the wild,” Sealey says. “At numerous points in their life cycle, they are eating aquatic insects. So it’s not that much of a stretch to think that these things might also have nutrient value for them.”
University of Idaho agricultural research offers critical expertise and assistance to the state’s farm industry. For more information on research in waste management and aquaculture, visit http://www.kimberly.uidaho.edu/AgWaste/index.htm and http://www.webs.uidaho.edu/aquaculture/hagerman_research.asp.
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Contacts: Ron Sheffield, (208) 736-3600, rons@uidaho.edu
Wendy Sealey, (208) 837-9096, wsealey@uidaho.edu
Sophie St. Hilaire, (208) 282-5416, sthisoph@isu.edu
Marlene Fritz, (208) 364-6165, mfritz@uidaho.edu
