Soldier fly larvae, also known as black soldier fly larvae (BSFL), are the larval form of the black soldier fly. As their name suggests, these larvae are commonly black in color. BSFL play an important role in the decomposition of organic waste and are sometimes used in composting operations to help break down material. But are BSFL actually good for compost? There are several factors to consider when determining whether soldier fly larvae are beneficial additions to a compost pile.
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What are soldier fly larvae?
Soldier fly larvae are the immature form of the black soldier fly before they pupate and turn into adults. The adult black soldier fly does not actually eat—its sole purpose is to reproduce. BSFL, on the other hand, are voracious eaters that can consume large amounts of decaying organic material.
Some key facts about soldier fly larvae:
– They are able to eat a wide variety of decaying organic material including food scraps, manure, and yard waste.
– A single larva can consume up to 500 mg of organic waste per day.
– BSFL contain a high amount of protein and fat. This makes them useful as animal feed.
– They are not considered pests like house flies or blow flies. Adult soldier flies do not bite or transmit disease.
– Larvae go through 6 instars (growth stages) over 2-3 weeks before pupating.
So in summary, soldier fly larvae are essentially living garbage disposals that can help break down large quantities of organic waste. This ability is what makes them potentially useful for composting.
Benefits of soldier fly larvae for compost
There are several ways that BSFL can potentially benefit a compost pile:
They speed up decomposition
Composting relies on the actions of bacteria, fungi, and other decomposer organisms to break down organic matter. However, the rate of decomposition can vary depending on conditions like oxygen, moisture, and carbon-to-nitrogen ratio.
BSFL are voracious eaters that can quickly break down and digest all kinds of organic waste. Adding larvae to a compost pile can significantly speed up the rate of decomposition. The larvae essentially digest and pre-process the materials, making it easier for beneficial microbes to further break it down.
They can reduce pathogens
Proper composting requires reaching high enough temperatures to kill off pathogens like bacteria and fungi that can cause disease. Some compost piles do not effectively reach these sanitizing temperatures.
Research shows that BSFL can reduce pathogens like E. coli and salmonella in manure and other organic waste. The larvae’s digestive process seems to eliminate many harmful organisms even at lower temperatures. Adding larvae may help create a safer end product.
They add nutrients
BSFL contain high levels of nitrogen and other nutrients like magnesium and potassium. As the larvae consume waste, these nutrients are incorporated into their bodies. When the larvae eventually die, the nutrients are released back into the compost.
The nitrogen provided by the decomposing larvae balances out the carbon-heavy materials usually found in yard waste. This helps achieve an optimal C:N ratio for effective composting.
They produce castings
Like earthworms, BSFL produce worm-like castings full of digested organic matter and nutrients. These castings add value to the finished compost product. The castings contain microorganisms that continue breaking down waste.
They reduce volume
BSFL can decrease compost volume by digesting waste and drying out excess moisture. Larvae burrow into piles, creating more air flow. The reduced volume makes the compost easier to manage.
Challenges of using soldier fly larvae in compost
While soldier fly larvae provide some clear benefits, there are also a few potential challenges to consider:
Temperature regulation
BSFL prefer temperatures around 85-90°F. If the internal compost pile gets significantly hotter, it can kill off the larvae. So their use requires monitoring and managing temperatures to keep it in the larvae’s ideal range.
Accidental escape
The larvae may try to escape the compost if conditions become unfavorable. Keeping them contained requires an enclosed composting system. Any escaped larvae will quickly die off or be eaten by predators.
Attracting pests
The larvae themselves are not pests, but a compost pile full of BSFL may attract other insects, rodents, or predators looking for an easy meal. Proper containment is important.
Odor management
BSFL produce frass which has an ammonia-like smell. Too many larvae can make the compost pile odorous. Monitoring their population and maintaining aerobic conditions is important.
Safety concerns
Some people may prefer not to handle the larvae during composting. Safe practices should be used to avoid accidental ingestion or contact with eyes and mouth.
Are soldier flies good for vermicomposting?
Vermicomposting uses red wiggler earthworms to break down organic material. Since BSFL also consume and digest waste, some wonder whether combining larvae and worms is beneficial. Here are some considerations:
Can larvae and worms co-exist?
Larvae and worms can both be used to vermicompost, but there are some challenges to using both together. BSFL prefer drier conditions while worms need adequate moisture. Worms also require temperatures below 84°F. Managing a bin with both organisms requires attention to maintaining the different ideal conditions.
Larvae may harm worms
There is some evidence that BSFL can harm or even consume worms if both are added to a bin. The larvae may disturb the worms and destroy their tunneling work. For best worm health, it is generally better to vermicompost with just worms.
Benefits are redundant
Worms already fill the role that larvae play in eating waste and aerating the pile. Including both results in redundancy without much added benefit. In most cases, worms alone will sufficiently break down material without the extra work of managing BSFL.
Larvae can be pre-composted first
An alternative approach is to let BSFL do the initial decomposition in a separate bin first. Once the larvae have processed and reduced the waste, it can then be transferred to the worm bin for further vermicomposting. This takes advantage of the abilities of both organisms.
Setting up a compost pile with soldier fly larvae
Here are some tips for setting up a compost system using BSFL:
Select an enclosed bin
The larvae need to be kept safely contained within the compost pile. Many home composters use specialized bins or trash cans for vermicomposting. Make sure the bin has ventilation holes but small enough mesh to prevent larvae from escaping.
Add bedding for larvae
Give the larvae shredded cardboard, coconut coir, or compost as bedding. The bedding provides shelter and food until waste is added.
Introduce larvae from a supplier
Larvae can be purchased from various online suppliers that ship live BSFL. Add the larvae once bedding has been prepared. For faster composting, use larvae that are at least 1/2 inch long.
Monitor moisture and temperature
Larvae prefer drier conditions around 70% moisture. Use a thermometer to ensure internal temperatures stay between 80-90°F. Make adjustments as needed.
Feed larvae a nutrient-rich diet
Larvae can eat a wide variety of waste but decompose faster when fed a nutritious diet. Feed them fruit and vegetable scraps, crushed eggshells, coffee grounds, and green waste. Avoid excessive protein like meat.
Turn and aerate the pile
Turning the compost introduces oxygen while also distributing the larvae. Use a pitchfork or compost aeration tool to mix the pile every few days.
Harvest larvae and castings
After 2-4 weeks, the larvae can be harvested and added to animal feed or bait cups. Their castings stay behind with the finished compost.
Are soldier fly larvae legal to use?
In most areas of the United States, it is legal to purchase and use black soldier fly larvae for composting and other waste management purposes. However, there are a few legal considerations:
State and local regulations
Certain states or municipalities may prohibit the cultivation and use of BSFL. Be sure to check your local laws before obtaining larvae. In most places though, larvae are exempt from exotic species bans.
Zoning restrictions
If composting with larvae at large-scale for commercial purposes, zoning laws may restrict operations. Residential composting is usually exempt from zoning rules.
Disease regulations
BSFL used for animal feed or fishing bait may be subject to health regulations. Additionally, shipping larvae across state lines requires disease testing to prevent spread of pathogens. Most small-scale composters are exempt.
Environmental protections
Introducing non-native species to natural ecosystems can cause damage. Be responsible when harvesting and disposing of larvae. Overall though, BSFL are not invasive or dangerous to the environment.
So for the average residential gardener or backyard composter, soldier fly larvae can be used safely and legally. Just practice common sense care and containment when adding larvae to compost.
Conclusion
Soldier fly larvae can provide some clear benefits for compost through accelerating decomposition, reducing pathogens, adding nutrients, producing castings, and decreasing volume. However, they also come with challenges like temperature sensitivity, attracting pests, odor, and containment. Larvae are not an absolute necessity for compost, but can be a useful addition in some scenarios.
For vermicomposting, larvae are generally more problematic than helpful when added along with worms. Pre-composting waste with larvae first before transferring to a worm bin is likely the better approach. If designing a compost system using BSFL, take into account the needs for shelter, ideal moisture and temperature ranges, and containment of the larvae. With the right setup and management, soldier fly larvae can be an asset for creating quality finished compost.