How Do You Compost With Black Soldier Fly Larvae?

Updated: Aug. 25, 2023

These little critters may look gross, but they're gardening superheroes.

Spring is officially upon us, which means now is the perfect time to ready the soil for your garden. For perfect potting soil, you’ll want an optimal blend of nutrient-rich soil, drainage-promoting natural matter and compost. And this year, home gardeners are turning to a new composting helper: black soldier fly larvae. Here’s everything you need to know about these efficient and generous garden helpers.

What Are Black Soldier Flies?

Black soldier flies are insects about the size of your thumbnail. They look ordinary enough—sort of like skinny, black wasps—but are exceptionally talented composters. The makers of the Compot, a ground-inset composting unit, and many other agricultural experts swear by them as the ideal critter for disposing of your food waste.

This is because black soldier flies have a unique ability to amend your soil. Basically, composted food scraps create an acidic fluid called leachate, which the black soldier flies process. In doing so, the pH of the leachate becomes more alkaline and its ammonia content is boosted. This results in amazingly fertile soil for your garden. Additionally, studies have shown that the levels of E. coli and salmonella are substantially reduced in soils amended by black soldier flies.

Where Can I Find Black Soldier Flies?

Earthworms found in a composting fertilizer binZummolo/Getty Images

Many gardeners find black soldier flies in their worm farms. This is, unfortunately, not an ideal place for them. They can block the drainage, create foul odors and starve or crowd out the worms. Moreover, if you try to kill them off, they will reappear nearly instantly. If you find them here, it is worth relocating them to your garden or compost pile. There, they can work their processing magic, and can also serve as a tasty snack for garden critters like lizards and birds. And if you find them in your garden already, leave them be!

Can I Buy Black Soldier Fly Larvae for Composting?

You definitely can! Black soldier fly larvae are typically sold as food for pet reptiles and chickens, or as fishing bait. Try to find them at your local feed store, or online at a bulk-feeding retailer such as Symton.

How Do I Use Black Soldier Fly Larvae for Composting?

Basically, all you need to do is bury the larvae into your compost pile. They thrive in moist, dark environments, but as they pupate, will make their way to the surface. The soldier fly larvae will eat twice their body weight daily, reducing your waste by up to 50%. Note that because they are such efficient composters, they may yield less compost by volume than you are used to. However, that compost will have a gorgeous mix of 43% protein and 35% fat, and will beautifully nourish your garden.