When composting with BSF larvae & you don't want the smell, go for some fruits/veggies & never let any liquid pool inside. The high-protein stuff like fish or meats can give off quite an unpleasant smell when decomposing. If there's some liquid pooling inside, it creates an anaerobic environment that may attract houseflies & make it smell even worse. So we'd want good oxygen flow around. It's a really fun project. Let's see some ideas to get started.
The base of your BSF compost bin
It's good to elevate the base of your compost bin so it's not directly touching the ground. This helps with the thermal balance, meaning, not making the inside pod too hot or too cold. Also, this gap allow some good air flow & gas exchange in and out, which is good to create an abundant oxygen supply for the larvae.
For this purpose, you can design a compost bin with four short or tall legs. Some people hook wheels underneath the box, which also works. Or we can use some bricks, rocks or coconut shells to nudge underneath the base.
Remember to drill some holes at the bottom of the bin. Half-inch hole would work fine. We don't want anything bigger than that because the rodents might find their way into bigger holes.
These holes are for air & the excess liquid to drain out. This liquid works great as a fertilizer and an attractant to attract other pregnant BSF female to the bin. So keep about a mason jar of this stuff for your next colony. Some people drill a lower hole so the liquid flow down there. You can hook a water-dispensing spout to collect the liquid.
Stacking up the bottom layer
For the bottom layer, we'd want something that drains well & create good ventilation. From these purposes, we can begin searching for the suitable materials.
At the bottom, you can lay some mesh or coco fiber carpet & put some gravel on so water can flow out easily. The mesh piece or coco fiber carpet makes it easy to grab the whole thing & pull it up if we need to do some maintenance here and there.
Coconut shells, sawdust, wood chips or sand also work. Straw may not be ideal because it takes up quite a bigger volume than the other materials.
On top of that, we can add some mulch. Pine mulch is okay for this. A weed barrier helps separate the bigger pieces from the smaller pieces for easier cleaning.
Pouring the foods in
Now on top of that bottom layer, we can pour the foods in. These are whatever we have left in the kitchen or take-home foods from the eateries. When you're starting, it's good to make the foods a bit more moist. This prevents them from drying out & hardening up. We'll put in a little bit of food first just enough for the BSF larvae & to keep the mold & houseflies away.
If the foods get too moist or runny, it may create a bad smell. To get rid of the smell, fluff up or air out the stuff in the bin. For example, if it gets quite jelly-like, put in some paper to suck up the moisture. Add dry food stuff like crumbled cookies or crackers to wick out the excess water. If the foods rot, we can take it out & put it in another compost bin to get rid of the smell.
When you see the foods start to go down a bit, you'll know then to add some more foods to the bin. Some foods may disappear the next day and others may turn into a darker color. These are some signs to tell us when we can fill in new foods.
The top layer
On top of the food scraps, place a piece of fabric or burlap on. This provides good shade for the larvae when eating. They are photo-sensitive so less sunlight is okay for them. It helps block out the houseflies that may be buzzing around. Also, this top layer can keep the humidity & temperature more balanced to prevent the foods from drying out.
After about 15 days
When the larvae have eaten enough, they'll turn more dark or charcoal. They'll move themselves out from the bin. When the walls are too dry or too clean, they may have difficulty climbing out. To make it easier for the larvae, spray some water around the walls. It helps them latch onto the surface easier even when the slope is 90 degrees vertical.
With the remaining foods in the bin or the frass, we can use it as a smell-free fertilizer. The liquid that get discharged can be infused with bio-char or mulch to make a great nutrient-rich & microbe-rich attractant. If we let it mature a bit more, the microbial activity will be even greater for many applications in the garden or as a great soil amendment.
As for the larvae, we can harvest them to feed our chickens, aquaponic fish or pets. When the larvae turn charcoal, they'll pack the maximum amount of nutrients inside. Before turning dark, they'll excrete out any undigested foods from their guts, making it relatively clean for feeding.
If you don't want too much fat in the larvae, fermenting or drying them may help de-fatten the grubs. In late summer or early fall, you can harvest these larvae, freeze them & put them in Ziploc bags. Below 20F (-6C), the grubs will die. If you want the grubs alive, a wine fridge in the 50F (10C) range is good for storing these yummy treats. It's a great feed for birds in the winter.
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