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How to Build a Black Soldier Fly Compost Bin

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By Jonathan Olivier | Feb 15, 2021

 

By creating a black soldier fly farm, you’ll have direct access to protein and fat sources for your chickens to snack on. And with low input in its production, it’s also an affordable way to keep your fowl fed. Once the larvae hatch, they’ll actually help keep pest flies away from the food source.
Photo by Adobe Stock/Max

I’m constantly looking for ways to feed my livestock — chickens, rabbits, and pigs — at a minimal cost. Keeping overhead expenses down on the farm means I make fewer trips to the feed store, and I can pocket more money at the farmers market. But, for me, it’s more than that. It’s about closing the loop by keeping inputs within my farm and reducing waste.

I’ve found several ways to achieve a cost-free, closed-loop system to feed my farm animals. Using local spent brewery grains and picking up older produce from a nearby organic grocery store have lowered my feed costs. I also grow my own duckweed, which is high in protein, as a feed supplement.

Although, I think one of my favorite methods has been taking my kitchen scraps to build compost, which I use to grow black soldier fly larvae. During warmer months, these protein-packed grubs are a constant supply of food for my laying hens that free-range around the farm.

What Are Black Soldier Flies?

Black soldier flies aren’t your typical housefly; they aren’t vectors of disease, and they certainly aren’t pests. That’s because adult black soldier flies don’t have mouthparts to feed on waste, whereas houseflies are attracted to food and can spread illness as they flit between food sources. Instead, the soldier flies, which are more similar to mud daubers in appearance, are attracted to food that’s already beginning to decompose so they can lay eggs on it.

The insects lay their eggs on decomposing organic matter, such as kitchen waste, and the larvae soon emerge to feed. You’ve likely seen these whitish grubs before in your compost pile and maybe considered them repulsive maggots. However, the larvae are harmless, functioning much like earthworms in that they decompose organic matter quickly and efficiently. In fact, as the larvae feed on waste, they create an environment that’s inhospitable to pest flies seeking to lay eggs, which reduces their numbers, according to an article by the Texas Master Gardener Association.

In his essay “Black Soldier Fly & Red Worm Bioconversion,” Paul Olivier of the nonprofit Empowering the Poor through Waste Transformation writes that the larvae “can effect as much as a 20-fold reduction in the weight and volume of food waste in a period of less than 24 hours.” Olivier goes on to note that the larvae can eat as much as 40 grams of food waste per day in a square meter.