Black Soldier Flies: A New Way To Compost
I have composted in many ways through the years. I have made compost piles, used the lasagna method, blenderized (yeah I know it’s a made up word) and used worms to make beautiful compost and tea. I recently started converting my Sanibel yard to a ‘food forest’. As anyone who has tackled a big landscaping project knows, soil and irrigation are the most expensive parts of the job. I need a continual supply of compost to build up the poor soil on my property, and I need it fast! It’s time to try composting with the help of black soldier flies.
The Black Soldier Fly
The solitary black soldier fly (Hermetia illucens) is a beneficial and useful garden insect. It is rarely seen and often mistaken for a black wasp. The black soldier fly is harmless. It has neither a stinger or a mouth. It’s short adult life is spent breeding and laying eggs. The larvae of Black Soldier Flies (BSFL) are detritivores, useful in household garden composting. The larvae work organic waste material faster than worms used in vermicomposting. A colony of 2000 larvae can consume about 2.2 lbs of household food waste per day. As detritivores, BSFL break down both rotting plant and animal matter, giving the home gardener the ability to add meat scraps to their compost.
If that wasn’t enough good news, black soldier flies do not spread human disease as do some other flies; and black soldier flies naturally repel nuisance fruitflies and blowflies. Besides providing you with a finished compost, black soldier fly larvae are used in other ways. The larvae are raised and sold as feeders for reptiles, tropical fish, as composting starts and are a high quality source of protein and calcium for laying hens. They are also used as fishing bait.
Black Soldier Fly Life Cycle
Black soldier fly eggs (pale yellow, elongated oval about 1mm) deposit their eggs in crevices or on surfaces above or next to decaying matter like food scraps. The eggs take about four days to hatch; the new larvae are off white and about 1.8 mm long. They go through multiple instars, the last of which is reddish-brown,elongated and slightly flattened, the skin is tough and leathery.
The mature larvae are about 18 mm long and 6 mm wide. During this last stage of larval development, the mouth has become a set of ‘arms’ that help a prepupate move towards a dry, safe place to await pupation to its adult form. The adult soldier fly, measures about 16 mm, very close in size and appearance to the wasp. It has no functioning mouth parts; it spends its time searching for a mate and reproducing. It’s life span is 5 to 8 days. Adult Black soldier flies do not swarm are rarely a nuisance. In fact they are rarely seen.
Do Your Research
Like microbes in the compost pile and worms in vermicomposting, black soldier flies need certain conditions to thrive. As many gardeners find a thriving colony in their compost piles, these conditions aren’t difficult to meet, but it is a good idea to check out multiple resources so you have a good idea of what you can accomplish with what you have.
I live in subtropical SW Florida (zone 10). We have poor, salty and sandy soil. I am looking for a fast, easy, inexpensive and reliable method of producing an ongoing supply of compost. Our ‘food forest’ is very new and is not yet producing. We are a small family and we eat out often. For the next 6-12 months we will not have as many food scraps as some families who cook regularly. I had to figure out how I was going to feed the BSF larvae. Fortunately one of the restaurants I frequent has agreed to let me pick up their kitchen scraps each evening. We both win! Less garbage in the landfill and a steady supply of food for the larvae.
Next hurdle. We live in a neighborhood where I cannot keep a traditional compost pile. I decided to make an initial investment of a contained unit from the folks at blacksoldierflyblog.com This BSF composter will work well for us because it is small (i.e. easy to hide) and is self-contained. I purchased the 5gal unit for $76 shipped. This is a well-engineered and constructed unit. The folks have been available to answer questions and even let me grab several photos from their blog for this story. (credits are given in links back to all the sources of photos that are not my own.)
So, I have a composter and I have a steady supply of food available. Now I need BSF larvae. Lots of them. Rotting food in a composter without enough BSFL can smell and attracts bad things. This is where research is really saving me from problems with neighbors and undesirable critters. A ‘mature colony’ in my BSFL composter can process about 2.2lbs of food a day. That is somewhere around 2000 larvae. If I was in a position to go the DIY route, I could just put a small amount of food scraps in the composter and wait for nature to take its course. I wish I could be patient and wait.
Here’s what happens and it’s the stuff of CSI! Seriously, Forensic Entomologists use black soldier flies as an indicator of how long something has been decomposing. BSFL are detritivores. This means that they consume rotting food and flesh. So if I were to start my colony the natural way, food would go in the bin and start to decay. In nature, the fruit flies and blow flies show up first. These are the bad bugs you do not want. They are pests and vectors for human diseases. Then the solitary BSF comes along and lays her eggs near the decaying matter (in this case the provided media on the lid of the composter where the BSF lays her eggs. This is great not only because you are getting the beneficial larvae; BSF eggs and larvae emit a scent (not detectable to humans) that repels the bad bugs. Then the life cycle begins and the amount of larvae would increase over time, according to the food supply.
Because of the potential for an initial ‘ick’ factor and the time it takes to build up a BSFL colony; again I opted to trade-off. A higher initial monetary investment for the return of more quickly developed colony. I ordered close to a thousand small and medium, and a few dozen large BSFL to add to my composter. I decided to order different larval sizes (or instars) to help the cycle establish more quickly. Time will tell how well my BSF experiment will pay off. I will be taking photos and updating as things progress. I have included links below that will help you with your own research would love to hear about your experiences with BSF composting. Thanks for reading and happy gardening!
Useful Links Black Soldier Fly Blog– This is where I got a ton of information, and where I purchased my BSF composter. Black Soldier Fly Farming– Another great site with a forum, DIY info, etc. The Modern Homestead– I haven’t had time to go through the blog, but this particular article on BSF is well written and informative. Fermented Farm and Forage– Again, haven’t perused the entire blog but LOVE this post about their experiences using different composting methods, including BSF. The Biopod– I have no personal experience with this product. It looks great and the design seems consistent with what I have read about BSF composting. Bug Guide– This is a fantastic resource. It’s nice to identify bugs you encounter in your garden and are not familiar with.