BSF Bio-composter assembly, set up, and basic instructions.
Components and Assembly

You may view a video of the assembly process here: LINK

The cover

The cover comes in two sections, an upper lid with bolts attached, and a lower lid that has ventilation cut-outs and the egg laying material attached.

Starting with the upper lid (bolts pre-installed): With the bolts facing up, slide the spacers (short pieces of 3/4 inch pvc pipe) over the bolts.

Wrap the lizard barrier (long black mesh) around the spacers, and continue assembling the lid as instructed below.

With the edges facing up, align the Sterilite logo on the bottom lid (with vents) with the logo on the top lid, and insert the bolts through the corresponding holes in the bottom lid.

Thread the wing nuts supplied onto the bolts until they touch the lid and tighten them by hand only. Do not over-tighten the wing nuts – watch the hex head of the bolt to make sure that it doesn’t press down too much and distort the top lid.

Drain tube and valve

*The cable ties are meant to hold the flexible drain tube on the pvc pipe with enough friction that it stays in place, but still allows the vinyl tube to rotate on the drain outlet. It becomes easier to rotate the tubing once the unit has been in operation for a few days and moisture is present. This allows more convenient re-positioning of the drain tube as you work with the unit.

*Keep the slotted vertical drain pipes in an upright position throughout the installation procedure. The drainage system is attached to the floor of the composter with a screw, and twisting the plumbing could damage the composter. 

6 gallon bio-composter – The drain tube is shipped with the shut off valve installed.  The other end of the tube attaches to the composter the same way it was attached to the valve. Slide the tube over the drain outlet pipe and secure with the cable tie provided. The end of the tube was treated on the inside with a water based lubricant to help make this process easier. You may want to add a few drops of water to reconstitute the lubricant. We recommend a back and forth motion for installing the tube, as opposed to a twisting motion. If during the tube installation you find that you’re twisting the drain outlet pipe, it’s best to stabilize the vertical drain pipe as excessive twisting may damage the bottom of the composter where it’s attached to the drain pipe.

12 gallon bio-composter – The drainage plumbing ships with a temporary nut threaded onto the male fitting that exits the composter. Hold the slotted vertical drain pipes in place and remove the nut. It is best to have someone hold the drain plumbing steady while you attach the flexible drain tube. Once the metal nut has been removed, thread the female fitting which attached to the flexible vinyl tube onto the male fitting that exits the composter. There is an o-ring inside the composter on the threaded male fitting, which creates a watertight seal. Hand tighten the female fitting until enough pressure is exerted on the o-ring to firmly press it against the composter wall. Over-tightening could distort the o-ring, causing a leak. It’s better to tighten the fitting too little than it is to over-tighten it. If you find that the connection leaks when the unit is flooded you can simply tighten it more, while supporting the vertical slotted pipes, until the leak stops.

Larva barrier

An extra piece of Velcro hook tape is included with your composter for possible future repairs. If a large bubble forms in the installed barrier, you can cut the section away, thoroughly clean surface with alcohol, and replace the tape. Care should be taken to never touch the adhesive backing with your fingers, and any air bubbles should be smoothed out immediately. The adhesive takes 24 hours to cure so if possible the lid should be left off of the unit and it should be kept as dry as possible.

Small bubbles in the installed tape can usually be fixed by cutting away a thin (2-3 mm, or less than 1/8 inch) vertical sliver of the tape and then pressing the tape back into place.

Collection canister

collection canister detail

Included with your Bio-composter is a short length of 1 inch inside diameter pvc pipe and 90º elbow. Friction along should be enough to hold these pieces in place. Push the elbow onto the exit pipe of the composter pointing pointing to the side, and slightly upward.  Insert the short pipe into the elbow, and slide the canister onto the pipe. The upward angle of the pipe directs rainwater away from the collection canister, and it also encourages the larvae to move through the pipe.

Egg laying material

Your Bio-Composter ships with a strip of corrugated cardboard sandwiched between two strips of corrugated plastic installed on the lid. These are attractive egg laying sites for female BSF entering your composter. The plastic pieces can be cleaned as old egg casing build up, and of course you can add more cardboard strips as needed. Cardboard strips are handy if you want to transfer eggs to another unit in that you can simply drop them into the new composter and they will protect the eggs until they hatch and then the cardboard will break down in the compost.

Setting up your Bio-Composter

Bulking material – not included (some type of bulking material must be added for proper operation)

This system is designed to be used with some type of bulking material, and the drainage system will not function properly without it. The amount required is between 1/3 and 1/2 of the total volume of the composter. This can include wood mulch, hardwood lump charcoal (see below), pine bark, etc. Our current favorite is a combination of half charcoal and half pine bark. We have discovered that while pine bark mulch works very well in most cases, some batches contain a lot of resin which can possibly gum up the system. We easily fixed the resin issue by rinsing the system with Dawn Ultra dish soap (LINK), and we prefer pine bark in our own composters. The bulking material is simply placed in the bottom of the composter before adding any waste.

Hardwood Lump Charcoal (biochar) – not included

In theory, charcoal has several advantages in a BSF composter. If you would like to research biochar this article is a good place to start: LINK

The charcoal we use is sold for cooking on barbecue grills, and is fairly common. Lump charcoal is different than charcoal briquettes which we do not recommend. Lump charcoal typically comes in irregular shapes and sizes, and it’s probably best to break it into pieces that are approximately 1 inch/2.5cm square or smaller, but not so small that it could clog the drainage slots. You can easily break it up with a hammer.

A shady location (usually)

In most areas of the country you will want to place the Bio-Composter in a fully shaded location. The reason for shading the unit is to keep the internal temperature of the colony in the safe zone. Reports vary, but around 115ºF (46ºC) is considered lethal to BSF larvae.

If you are in a cool climate you can probably afford to let a little morning sunshine fall on your unit. If you live somewhere like Seattle, you might be able to keep the composter in full sun for several hours per day. The key is the temperature of the colony, not the ambient (outdoor) temperature. Other things also effect the temperature inside the colony including its density (population) and the type of waste you feed it. One indication that your colony is overheating is when you see a large number of light colored juvenile larvae trying to migrate out of the unit.

Another exception to the rule of full shade happens early or late in the BSF breeding season, when temperatures are typically lower than the peak of the season. It’s especially helpful to keep the unit in a sunny location early in the season when the primary goal is to attract as many female BSF as possible to the composter for egg laying. Allowing the colony to warm up increases activity which and also warms the waste, both of which help attract females.

The size of this composter gives you the advantage of being able to move it fairly easily. This allows you to move the unit if you determine that it’s in a location with too much or too little sun.

Preventing infiltration by ants

Some types of ants will target either the larvae in your composter, or the waste.

Ants won’t swim across water to get to the unit so a mote system is very effective. One method is to set the legs of a shelf unit into containers which can be flooded with water. I use a metal wire shelf unit with the feet set in large tuna cans filled with water. These will dry out in a few days of hot weather so they need to be monitored. Another mote method is to set a large container filled with water on the ground and add a few concrete blocks to form a base for the composter. This method won’t dry out as quickly. The downside to using a water bath or mote is that mosquitoes will use it to breed. A few drops of bleach will kill the mosquito larvae but it must be added regularly since it dissipates quickly.

Another method is to set the composter on a shelf unit and then able an insecticide or an insect repellent to the legs. This requires less maintenance if you don’t mind the chemicals.


Basic operation

Establishing a new BSF colony

This composter is an open system where reproduction takes place outside of the unit, by free flying adult BSF. Once the females mate and are ready to lay their eggs they will seek out an appropriate food source to lay their eggs near. What the BSF females are seeking is rotting food or manure. Attracting BSF is fairly straightforward, but there are several common mistakes people make.

You can find an overview of how to attract BSF at our forum, called “Attracting black soldier flies – the basics: LINK

Feeding the colony

In my opinion, a steady supply of food/waste will result in a more stable colony; excess waste attracts more females and a spike in egg production, and withholding waste reduces egg laying.

The list of what BSF larvae can process is very long. Anything that a human can eat, larva can eat. The waste that you give your BSF larvae can be fresh food scraps, like the ends of onions, melon rind, celery tops, etc., or it can be moldy and quite far along in the process of decomposition.

Until you have enough larvae to completely cover the surface area, I suggest limiting how much animal flesh you give them. I simply don’t like the idea of meat sitting around in a warm environment for several days. Once the colony can process meat quickly it’s fine to include in the diet. Other than that caveat, almost anything goes except high cellulose items like leaves, paper, stems and grass.

Flushing with water

This system is designed to be flushed with water regularly. I originally began this practice because I wanted to mimic nature, where waste is exposed to rains. Flushing helps keep the waste aerated/aerobic because the fine BSF castings are washed through the system.

Mature larvae will often pupate in the waste, as opposed to migrating up the ramp in search of a safe dry place to pupate. For that reason, I usually flood my units almost to the top of the waste, once or twice per week. This induces the mature larvae to migrate out. To facilitate flooding, the drainage systems on all my units can be closed off, either via a valve or by keeping the end of the drainage hose elevated.

I normally drain the effluent (liquid waste) into a bucket, pour it through a fine mesh kitchen strainer, and then return the strained larvae to the composter.

Regular flushing creates a steady supply of effluent (liquid waste) rich in BSF castings which may be useful for gardeners.