Composting with Black Soldier Flies

Composting with Black Soldier Flies

is way more efficient than many other methods of composting because you can feed them ALL kinds of biodegradable matter.

When I began composting with Black Soldier Flies inside the Compot back in 2009 there was very little information available online.   Most people in Australia had never heard of them.  Information is now readily available about composting with Black Soldier Flies.  Many companies now experiment with them for waste disposal and a protein-rich food source for animals.

Since launching the Compot in 2013, I have spent hundreds of hours speaking to people about using these special little critters as composters in a Compot.   Lots of people have found them in their worm farms.  Thinking they were house fly maggots they tried numerous methods of eradication only to find they’d reappear.

Once the Soldier Flies finds your worm farm it is difficult to eradicate them.  With a little effort and experimenting, you can find just the right spot in your garden where (for whatever reason) the Soldier Flies don’t go.  Some people are lucky but most aren’t.

Are they bad in a worm farm?

Composting with Black Soldier Flies in a worm farm is not ideal.   Using them above ground creates a foul odour.  And they will slowly crowd out your worms.  Or eat all the food leaving nothing for the worms.  Worms are self-regulating so will most likely eat each other at this point.

Plus the leachate the larvae produce is too acidic for the worms in the early stages of its decomposition.  The worms can’t escape from this is a worm farm.  In the ground, they will move away from the leachate until it is safe for them to consume it.

The Black Soldier Fly Larvae have been known to block the drain at the base of a worm farm causing worms to drown as the liquid can’t escape.   This requires a complete overhaul of your worm farm.  But don’t throw these little guys away.  Put them on your garden bed.  They will continue to decompose your waste or become food for garden critters.  Lizards, birds, chooks, and fish love them.  They make great bait for fishing enthusiasts.  This can be a smelly process.  Much easier to use a Compot.  But it does, of course, depend on your preferred method of waste disposal.

Black Soldier Flies are way more efficient at waste disposal than worms.  Try and find a way to make them work for you.

What does a Black Soldier Fly look like?

The mature fly is roughly the length of your thumbnail.   Long skinny and of course black.  In some countries, they can vary in colour.  Though they have no real mouth with which to eat food or bite you, they can suck up nectar or water to survive long enough to find a partner, mate and lay their eggs.   Unfortunately, they die after mating and egg laying. Such is the life of the Soldier Fly.

If you happen to find one in your house he has most likely lost his way.  Or you have something rotting in your kitchen that has attracted them.   They’re easy to catch and relocate outside the house.   It is best not to kill these little guys because they are so valuable for composting and waste disposal.   As there are so many of them it doesn’t really matter if one dies a little earlier than he should.  But better to just release them outside.

How do they lay their larvae?

The Black Soldier Fly has roughly 74 days to mate and lay their eggs.

After finding a mate the search begins for a suitable spot to lay their larvae. They don’t need to lay directly on the food source like house flies do.   They can lay anywhere near the food source and the larvae will find their way to the decomposing waste.

The picture above (captured by Mark) shows the Soldier Fly pushing his tail into the sugar cane mulch next to a Compot to lay its eggs.  Great shot Mark.

What do the Larvae look like?

Soldier Flies can lay anywhere from 400 to 800 baby larvae.   Incredible, coming from such a small creature.   Their larvae are so tiny they can get through the tiniest hole in your worm farm without you even noticing until it’s too late.

Unless you are lucky enough to catch them laying their larvae you are not likely to notice them till they are big fat juicy larvae inside your Compot.  They are super tiny white threads, smaller than a grain of rice .   As they grow one end tends to be tapered while the other end is blunt.   It is difficult to distinguish them from a blowfly maggot until they get larger when you can clearly see the ridges on their body.   Blowflies hatch in a day and at two days are roughly 4cm long whereas the Soldier Fly larvae are larvae as soon as they are laid.    From my experience, the Soldier Fly is fatter around the middle compared to the ordinary old fly larvae.  From my tests, it appears the blowfly larvae die when in a confined space with the Soldier Fly larvae.

In these early stages of the Soldier Flies life, when they are fat and white, they are good to feed to your chickens and fish.   I did try to feed them to some birds but they weren’t interested.   Mind you it could have been the fermented waste smell on them that deterred the birds even though I gave the larvae a rinse in water.

If you use wet bread to attract them (great if you are vegan) they remain nice and white and easier to collect to feed to chickens or fish as opposed to them sitting in a black slushy mess in side your Compot which is the usual way you will see then inside your Compot if you go digging.  If using the Compot inside your chicken pen you do not need to soak your scraps so the larvae will not smell fermented to the chickens.

How long to the larvae live?

The larvae last for roughly 22 days depending on the weather and food availability.   If it gets too cold they can hibernate in the soil for up to 9 months.   But they are fussy when it comes to light.   They prefer it to be dark so if you have them inside your Compot and you can’t see them they are most likely hiding under a layer of waste to protect themselves from the light.

In perfect conditions, you will see them inside your Compot very easily without having to go digging for them.   But you will still know they are there even if you can’t see them because your waste will keep dropping down in height as they chow through everything so quickly.

Composting with Black Soldier Flies produces leachate which seeps out into the surrounding soil ready for your plants and worms to turn it into composted soil.   When you water your garden the leachate mixes with water to make nutrients available for your plants.   This also works well when you collect all your wastewater (with or without detergent)  along with your scraps and fill your Compot up with water and waste.  So you are not only saving water, but you are watering the garden at the same time and providing a solution for the leachate to mix with, which in turn provides nutrients for your plants.

Vinegar Fly Casings?

The larvae casings in the above picture are Vinegar Fly Casings.  I previously thought they were Soldier Fly Casings but I collected a few to see what came out of them and it was in fact Vinegar Flies and definitely not Soldier Flies.

Vinegar Flies can be attracted to waste that is not covered with a lid of some sort especially food waste in your kitchen that is not keep in a sealed container.   I found these casings inside my kitchen bench container because the lid was broken and easily accessible to the wrong type of fly.

So make sure the container you keep in your kitchen to collect your waste has a nice sealable lid that is also easy to remove to fill with more waste but one that will keep unwanted flies out.   I get ordinary containers from the $2 shops but you can buy more expensive ones if you want.   I personally have not found this necessary.  Do not use tin or aluminium to collect your waste as horrible chemicals leach out into the water and nothing will touch this waste for over 3 months till the chemicals have dissipated into the soil, and you don’t want these chemicals in your garden.

How do they deter house flies?

If you watch the video at the beginning of this article about composting with Black Soldier Flies, you will see a container with some ham covered in house flies.  There are in fact heaps of Soldier Flies mixed in with this waste.   The blow flies are not deterred at this stage by the Soldier Flies.  But the Soldier Flies will take over the space and most likely eat the fly larvae.

In the above picture, you can see house flies trying to get out of the Compot. It is possible inside the Compot that the fermented smell of the food along with a fermone that the Soldier Fly produces, is enough to drive the flies crazy and scare them off.   You can see them desperately trying to get out through the holes in the lid of the Compot (in the video).

It is unusual to get house flies in your Compot but if you do don’t worry as they are part of the decomposition process and will die in there as they can’t find their way out.

Covering your Compot with a suitable cover will keep the hot air out in summer and the cold air out in winter plus prevent house flies from managing to find a way in.   If they are buzzing around your Compot you haven’t covered it properly. This is only necessary for the house flies and vinegar flies as the Soldier Fly will usually find your waste even with a covering on your Compot.

What do they look like in the prepupal stage?

When they are ready to change to a mature soldier fly they find their way out of the Compot and develop a hard black casing around their bodies.  It takes about 2 weeks to pupate and emerge as a mature Soldier Fly to start the process all over again.

Why is Composting with Black Soldier Flies so good?

  • It is fast, efficient, and no hassle
  • Soldier Flies are found almost everywhere but mostly in warm climates.
  • You can feed them anything biodegradable
  • Meat and fermented waste are one of their favorite foods
  • No special conditions are required for them to thrive
  • They love darkness when in their larval stage
  • Unlike the good old house fly, they don’t carry diseases
  • With no real mouth, they don’t bite or hang around your bar-b-q
  • Frass and leachate – is amazing fertilizer for your garden
  • They dispose of ALL your waste quicker than worms,
  • Even good for human and animal waste.
  • Maintenance is non-existent,  unlike a worm farm or tumbler
  • Go on holidays and they look after themselves
  • When used in a Compot they will reduce your council waste by over 50% because you can feed them ALL your kitchen waste including meat, dairy, citrus, onions, oil, egg shells, fish, prawns, paper towels,  absolutely anything bio-degradable.

If you find them in your garden be grateful. They are awesome.

Life cycle of the Black Soldier Fly.

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