The project explored the feasibility of using Black Soldier Fly (BSF) larvae as a supplemental feed source for tilapia. BSF were raised inside a heated greenhouse and outside in a large compost bin, and fed food waste year round. To monitor abundance mature pupae were counted after emerging from containers. There were as few as 0 and as many as 632 larvae collected in a given month. The quantity of larvae collected each month was inconsistent over the 18 month research period, averaging out to 119 larvae collected each month. The results showed that this method of raising BSF was not effective on a small farm scale. There were not enough mature pupae collected in order to significantly supplement normal feed. However, the BSF larvae were very useful in breaking down large quantities of food waste and unwanted dead fish quickly during warm months. I recommend using BSF larvae as fast and effective decomposers.
- Black soldier flies feeding on squash
- Mature larvae that have crawled out of containers, ready to become fish food
Black Soldier Fly larvae have great potential to convert organic waste into protein rich biomass capable of feeding a wide range of livestock. BSF are ideal insects to raise because they contain 42% protein, are resistant to harsh environmental conditions, and can not spread disease. Larvae grow very quickly with little maintenance and also generate useful byproducts such as high quality compost and liquid leachate.
Current protein sources for livestock mainly come from expensive, conventional, fossil fuel based grain farms. Protein is the most expensive and energy intensive component of feed for poultry, cows, pigs, and fish. There is a large demand by small organic farmers for sources of protein that do not rely on heavy fossil fuel use and can be produced locally at less cost. Feed source has been an underlying and enduring issue for Main Street Farms in Homer, NY owned by Allan Gandelman. The farm’s aquaponic’s system raises 9000 tilapia on food made of grains and other fish in form of fish meal. It is dredged up off the sea floor, causing serious negative impacts on biodiversity and fish populations. The world’s oceans are currently being overfished, so much so that 70% of total fish stocks are either fully exploited or depleted (UN Food and Agriculture Organization). It is possible that future aquaculture production based on fishmeal might not even be possible because of the scarcity of fish meal.
The project aimed to create a sustainable, self produced, and protein rich food source capable of being a major food supplement year round at Main Street Farms. The goal was to increase productivity of fish growth, decrease costs, and conserve natural resources by raising BSF as a food source for the fish. By substituting BSF larvae grown with on-site and community food waste, the farm could bypass the need for conventional feed and therefore become less dependent on the world’s oceans and agricultural land to harvest feed for livestock. It would also reduce fossil fuel input to the farm while recycling nutrients from the land. If enough larvae were grown, aquaculture and livestock operations would reduce the amount of feed typically bought in for their animals. It would mean higher productivity on farms, greater net income for farmers, and more sustainable best practices.
The objective was to explore the feasibility of raising BSF larvae year round in upstate NY on a small scale farm to supplement feed for 9000 tilapia. The project aimed to collect one pound of BSF larvae each day during the year from a colony fed only by on-site and community food waste. Additionally, there was a controlled breeding process to build colony to appropriate size.
I was interested in measuring how temperature affects production because it is an essential component to the life cycle. Additionally, I wanted to know the amount of nutrient-dense digestion byproduct (known as “compost tea”) produced in relation to the number of larvae collected.
My goal was to give others access to the information found through outreach on Farm Hack and facebook groups. To target the specific audience of farmers local to the Northeast I hosted a workshop through Cornell Waste Management Institute about how others can build upon my methods to successfully raise Black Soldier Flies.
The larvae were sourced from the Phoenix Worm Store, which sells the BSF (Hermetia illucens) under the name Phoenix Worms. Larvae prefer warm (85-95F), dark, and humid conditions to grow quickly. It took approximately 14 days to develop from hatching to final prepupae stage during optimal conditions. At this time they instinctively leave the compost pile in order to pupate and develop into adults; this is why they are considered to be self-harvesting insects.
After leaving the compost pile larvae undergo metamorphose and turn into adult flies. Flies mate and lay eggs, but do not eat before dying in about 8 days. The male to female ratio is 1:1, and each female produces 500-900 eggs.
The colony was started in May 2013 with 5000 larvae in three trial bins of different styles in a heated greenhouse (see images below). After one month they were separated into nine containers, three of each style. The experiment was conducted over an 18 month period. Each bin style included a ramp from the inside allowing mature larvae to crawl out and be collected in buckets. The bins also had a small holes drilled on the bottom at the lowest point for excess liquid to drain out into a collection dish. Each indoor container was given an equal amount of food waste. June to October, each bin was fed a half pound of food waste two times a week. November to May the bins each received a quarter pound of food waste one time a week. Food waste consisted of a mix of bulk coffee grounds, vegetable farm waste, household kitchen scraps, and cafeteria scraps. Once the food waste was decomposed by the larvae it became a very thick, mucky, clay-like substrate. It was removed from the indoor bins on an as needed basis, about twice a year, in order to make enough space in the small bins for new food waste. The decomposed food waste was added to our farm compost.
During the spring, summer and fall the containers were placed along the sides of the 30’x96’ greenhouse used for aquaponics. Two times a week the larvae that had crawled out into the buckets were counted. During winter months the bins were moved onto a table draped in plastic with a space heater placed underneath the table. The bins were slanted with a bucket on the higher end to catch larvae and small perforations on the lower end to allow excess liquid drain into a gutter system.
Additionally, from November to May a small side experiment was conducted for the interest of the farmers in order to test what substrate allowed larvae to pupate in the largest number. When the larvae crawled out of the bins they were divided equally into three dishes; one filled with potting soil, one with dry leaf material, and the other without any substrate. These dishes were placed on the bottom of the breeding cage in the heated space. Each week a comparison was made between the number of empty larvae casings from the three dishes (an indicator of metamorphosis). The dish with the highest number of larvae was recorded, but not the specific number, making this part of the experiment unverified and therefore inconclusive.
After the larvae crawled out of the bins they were moved to a breeding cage to control and increase the population size. A 4’x3’x3’ screen cage was used to contain the flies. In order to aid fly development the cage included a section of soil on the bottom for pupation, a live plant for mating purposes, and a shallow water dish. The cage was placed in basement with artificial light. After 6 months the experiment was changed and it was moved to the heated greenhouse.
During the second season of research the original project proposal was expanded to raise BSF larvae in an outdoor container in order to provide more space. The outdoor bin dimensions were 4’x4’x8’, the open bottom was lined with 2 feet of wood chips to help soak up extra liquids. Two ramps with buckets at the ends were installed to catch larvae crawling out. These were checked two times per week.
The major finding was raising enough BSF larvae to supplement fish feed is not feasible in a small scale system. However, the larvae did provide excellent compost faster than traditional vermiculture. It was determined not enough larvae could be produced in the bins tested inside the greenhouse because the volume of food and number of larvae were too small to substantially contribute to supplementary fish feed. The outdoor bin, which was much larger in size, produced enough larvae but they were not able to be extracted. Results showed that the number of larvae collected each month was very inconsistent over the 18 month research period (see spreadsheet attached). The minimum number of larvae collected in a given month was 0 while the maximum was 632, averaging out to 119 larvae per month. The quantity of food waste consumed was largely based on temperature, shrinking during cool periods.
A main challenge was removing larvae from the containers. Many of the mature larvae did not crawl up ramps. Instead larvae pupated into flies while still inside the container, which was unexpected. Based on general observation this occurred more frequently in the outdoor container than the indoor container despite the outdoor container having a greater quantity of larvae. The outdoor bin had two ramps, one was a gutter and the other a gritted plastic plank. They did not provide sufficient access for larvae to crawl out.
The majority of larvae pupated into flies inside the containers instead of the intended breeding cage. The adult flies flew in and out of the greenhouse, mated, and laid eggs back into the containers thus increasing the population regularly and uncontrollably May to October. The flies did not cause any problems with normal operations in the aquaponic greenhouse or on the farm.
The project began in the May 2013 and by November 2013 the larvae were eating much less due to cold (and we suspect shortened hours of light) despite being inside a heated greenhouse. Winter greenhouse daytime temperature high was 65-75F, dipping into the 40’s at night even within the heated table system. We began the project with the intention that the bins would be given the same weight of food waste year round. However, due to slower metabolism and eating habits during cool months, each bin was given less food during the winter to prevent rot and odor in the greenhouse. If too much food was given in the winter months the larvae could not consume it causing mold growth. Also, the number of larvae crawling out dropped to almost zero in winter months. The larvae were kept alive over winter, but very few matured into flies compared to summer months.
The modified winter bin system, where the bins had two slits and a gutter, had limited success. Some larvae crawled down toward a gutter, escaping through the drain perforations instead of into the larvae catchment. This made it impossible to determine which bin they crawled out of and therefore which bins were most successful. Although the intended use of the gutter was to filter out excess water, very little liquid was produced because the larvae consumed so little food waste in winter.
There were several unexpected results within the eating habits of the BSF larvae. Larvae did not digest food waste high in cellulose such as leafy greens, stalks, corn husks, etc. The preferred food was vegetables especially fleshy food like squash and peppers. This was not a problem for the outdoor system because worms crawled in from the bottom to eat food waste left by the larvae. Also surprisingly the outside bin produced a lot of excess liquid when there was a lot of activity during warm months. This system had an open bottom layered with woodchips and lacked a system to collect excess liquid and measure the quantity. The large amount of liquid made the surrounding area extremely muddy. The was remedied by circling the container with wood chips. However, the much smaller indoor bins produced almost no excess water at all so there is not data included in this report.
Due to the inadequate number of larvae collected, all collected mature larvae were placed in the breeding cage to increase the population. The cage was first placed in a warm humid basement room. After six months, most larvae had matured into adult flies, but none of the adults had laid eggs. This was attributed this to the lack of natural light reaching the cage. The cage was relocated to the heated greenhouse, but the same results ensued. After 18 months we were was unable to collect any eggs from within the breeding cage, despite adjusting light, temperature, humidity, plant species inside, egg laying surface, and number of flies in the cage at one time.
The larvae were tested to find out which substrate they matured in at the highest rate. This data was inconclusive and based only on observation because exact numbers were not recorded for this side experiment. Each week we made a comparisons of the number of empty larvae casings in each substrate (an indicator of metamorphosis). Every week from November to May the experiment resulted in potting soil having the highest number of empty casings. Based on this evidence we believe potting soil had a higher rate of maturation than dry leaves or no substrate.
Main Street Farms plans to continue using BSF in outdoor composting systems after completing the research grant. BSF larvae create a more efficient decomposition process than with vermiculture alone. A large number of interested farmers, researchers, and homesteaders were reached through blogs, social media, and tour groups.
Education & Outreach Activities and Participation Summary
Outreach was done online through a blog on FarmHack.com which is a publically available website targeting innovative farmers. The blog contains details about the process, materials, and outcomes of the project. Social media posts were also made on ‘Black Soldier Fly Farming’ community page on facebook which includes 1700 members internationally.
Main Street Farms also hosted “CNY Composting Workshop and Facility Tour” sponsored by Cornell Waste Management Institute in conjunction with Cortland County Soil and Water and Sustainable Cortland to highlight BSF as alternative decomposers. The tour was attended by 38 participants interested in managing organic residue.
Raising BSF is highly recommended for any farmer’s compost as they help decompose plant and animal material extremely quickly. I believe collecting larvae can be done well on a very large scale or at the scale of home gardener for a few fish or chickens. At a mid-size scale there were not enough larvae to supplement feed for 9000 tilapia.
Production of larvae slowed during especially cold days and when daylight hours were shortest. Placing larvae in an area that can be consistently 85-95F with lamps to provide a natural spectrum of sunlight could improve production at these times of year. It is possible that flies need natural light to lay eggs, however the results were inconclusive. Additionally, anecdotal research from other individuals interested in BSF suggested that using corrugated cardboard as a material for flies to lay eggs on could be detrimental because mold growth may cause the eggs to become infertile.
A possible alternative to collect larvae in buckets is using a screening system. Lay down a metal screen on top of a section of the bin, place desirable food scrap on top (squash, pepper). When larvae crawl on top of the screen to eat, and entire screen is picked up. Another possibility is using water to force larvae to crawl out. During a period of very heavy rain all of the larvae crawled out of the outside compost bin and onto the plastic siding of the greenhouse. Perhaps the larvae aversion to saturated substrate could be leveraged to develop a new extraction system using flooding. Another solution may be to have more ramps, a ramp that spirals out, or a container walls angeling out with a gutter system would work better.