By Clytie Binder

Have you ever opened your compost bin during summer and been startled by these fat, wriggling maggots feasting on your food scraps?

It’s ok – these little creatures are Black Soldier Fly Larvae (BSFL) and they are a wonderful asset to have in your compost bin

I recently attended a Black Soldier Fly Larvae farming workshop run by LOCCAL member, Brian Donaldson (AKA The Worm Man) and I walked away full of admiration for these incredible insects. Far from being pests, BSFL are composting powerhouses.

What Are Black Soldier Fly Larvae?

The adult Black Soldier Fly is harmless – it doesn’t bite, sting or even eat. In fact, it doesn’t have a mouth! Its sole purpose in adulthood is to mate and lay eggs. The adults are attracted to the smell of rotting organic matter and will lay their eggs in cracks or crevices above decomposing material. Once hatched, the larvae drop into the waste and get to work.

The larvae are voracious eaters. They can consume up to 100 times their body weight in a single day. From a single gram of BSFL eggs, you can grow around 2 kilograms of protein – a, high-fat, high-protein food source suitable for chickens, pigs, fish, dogs and even humans.

BSFL complete their lifecycle in just 7 weeks, from egg to adult. As they prepare to pupate, they instinctively self-clean – leaving the compost pile in search of a dry place to transition to adulthood. This makes harvesting them for use as animal feed relatively easy.

Their waste, called frass, is a valuable by-product too. Richer than worm castings, BSFL frass can be used as a potent fertiliser, a compost activator, or even added to a worm farm.

While BSFL are definitely worth encouraging in the compost, they are not great in worm farms. They’ll outcompete worms for food, and the heat generated by their frass can kill off the worms. If you spot them moving in, take action:

• Remove BSFL by hand
• Reduce feed amounts
• Lower moisture levels
• Add more carbon (dry browns like shredded paper or leaves)

BFSL farming

Setting up a BSFL farm is simple. All you need is:

• Protection from rain
• Good drainage
• A space for egg-laying (e.g. cardboard crevices)
• A ramp or exit point for mature larvae to leave when they’re ready to pupate

The easiest DIY version is a bucket with drainage holes at the bottom, a slit cut down the side for larvae to escape, and a bundle of cardboard pieces above the food for egg-laying.

Best of all, BSFL eat nearly everything—fruit and veggie scraps, cooked food, meat, bones, dairy, coffee grounds, manure, and even garden clippings. They’ll slow down in cooler months, but will return when the weather heats up again

I also saw a great example of black soldier fly larvae farming when I visited the Sustainability in Prisons project in Washington USA a couple of years ago. Read more about that here

Do have any experience of farming black soldier fly larvae?