Studies Regarding the Fertilizing Capacity of Poultry Manure Biocomposted by Fly Larvae (Diptera: Stratiomyidae)
It's that time of the week again for another addition to the Science Blog about Black Soldier Fly (cue exciting music)!
This week I am reviewing a paper published out of Romania on the use of BSF larval frass as a fertilizer agent- a topic not heavily covered in the literature.
Studies regarding the fertilizing capacity of poultry manure biocomposted by fly larvae (Diptera: Stratiomyidae)
I am not very familiar with this particular journal- but given the topic, I had to take a look at the results.
My thoughts on the topic......
For most people that have worked with the BSF, they recognize the digestate (i.e., residue remaining after BSF larvae feed on a substrate) can be quite appealing as a potential fertilizer for soils. In our case, the residue we produce has the consistency of ground coffee with a moisture content below 20%. Both factors enhance the product in terms of packing and shipping (limited wasted space as particles are all the same size and more material in a shipment as weight is not hampered by water content).
The challenges I have faced with BSF residue/digestate is not the consistency of the product in terms of nutrients but that the material was still very "hot" (i.e., lots of nitrogen); so, I had to be careful when applying it to plants (tomatoes in my case) as too much would resulting in burning and in some instances death. Of course, this experience is limited to a couple of trials conducted early in my career- nothing too in-depth.
However, over the course of the past 20 years, I have talked with BSF producers around the globe and picked up some pretty interesting anecdotal data about the potential for this material as a fertilizer. What I found most interesting besides enhanced plant growth were the claims that using the digested material as a fertilizer resulted in less insect feeding on the plants (herbivore damage). I can imagine this being partially true (lots of promise) as the presence of insects in the vicinity of a plant can induce plant defenses (been documented for a number of insect/plant systems). So I do not think it is too much of a jump to conclude placing insect frass mixed with digested biowaste around plants would result in similar responses. Is this true with regards to BSF- well, I cannot say yes or no. However, I can say that investigating such a topic would be of immense value to the industry, and I encourage others to tackle this topics. But if you do- I encourage you to recruit across disciplines (e.g., plant physiologist, soil scientist) to enhance your project impact.
Jeffery K. Tomberlin, PhD, a little bit of a green thumb
I received this paper this morning from my colleagues in Italy. If you have the time, please do take a look at it. They did an exceptional job detailing the digestive tract of the BSF larva.
Such research is sorely needed as we are attempting to harness the BSF larval process for recycling wastes. They seem to be able to digest just about anything organic (sounds like a grand challenge- "find the organic waste streams BSF are NOT capable of digesting").
Bonelli, M., D. Bruno, S. Caccia, G. Sgambetterra, S. Cappellozza, C. Jucker, G. Tettamanti, and M. Casartelli. 2019. Structural and functional characterization of Hermetia illucens larval midgut. Frontiers in Physiology 10.
In this study, the authors focused on the midgut of the fully developed larva, which had been raised on a standard grain diet. They dissected the full digestive tract and provide excellent images detailing the various anatomical features at a gross scale.
Much like a previous study presented in this blog, the authors detailed the pH of the various regions of the gut. But, they also build on this knowledge with detailed description of the morphology (physical features) of the midgut cell lining (epithelium) while distinguishing the different regions. They then proceed with a description of the digestive enzymes (through a multitude of experiments) identified and their activity in the midgut. They accomplished this goal by adding temperature as a factor and determined if shifting temperature impacted such activity. I consider this a key part of the study as they demonstrate temperature impacts enzymatic activity- with peak performance at 45C. This is really interesting as it suggests BSF larvae are capable of handling these high temperatures during development; however, temperatures above 45C negatively impacted activity).
A couple of questions for the authors and others to ponder:
1. How does the midgut vary across instars (larval development stages)?
2. How plastic is the digestive tract with regards to food provided (i.e., does the morphology shift when larvae are fed different diets)?
3. How much variation do we see across populations from around the world?
4. Any thoughts on how to better prepare larval diets to take advantage of the capabilities of the midgut of the BSF larva (i.e., can we better formulate diets to enhance digestion and protein production)?
Jeffery K. Tomberlin, PhD, Boggled by Insect Physiology
Part of EVO's mission is to open doors to expand the global knowledge-base on the use of insects as food and feed. We believe such a mission is achieved through collaborating and facilitating research and application opportunities. One such opportunity came through collaborations with Inagro in Belgium to test lights for their ability to enhance BSF breeding indoors.
Inagro is a Belgian non-profit organization for applied research and advice in horti- and agriculture. Inagro’s researchers guide farmers/companies/government into a more sustainable and innovative future. Currently we have more than 200 employees in a variety of research area’s such as: greenhouse cultivation, field vegetables, edible mushrooms, biogas production, circular economy, aquaculture, insect rearing, etc.
In the department for aquaculture and insect rearing, five people are employed involved with the insect research:
Stefan Teerlinck: Head of the department and expert in aquaculture
Dr. David Deruytter: Researcher, specialized in black soldier fly
Ir. Carl Coudron: Researcher, specialized in mealworms
Ir. Jonas Claeys: Project hunter/writer
Lukas Depraetere: Technical assistant
Our insect pilot plant is approximately 300 m² with a laboratory, processing room and 6 climate controlled rooms with a combined area of ± 150 m². Currently we are breeding three insect species (BSF, mealworm and the Argentinian cockroach) and focus our research on:
Besides research we are in close contact with the Belgian and European insect industry and government via the strategic platform for insects (Belgium) and IPIFF (Europe). Finally, we inform the general public, feed manufacturers, investors and (starting) companies about the possibilities of insect production with onsite demonstrations, tours, internships and by demonstrating techniques within the insect production. The latter, for example, has already been done (and will continue to do) for the JM Green breeding LED (https://www.evoconsys.com/blog/comparing-jm-green-breeding-led-with-halogen-lamps).
Inagro is thrilled to be part of the EVO consortium and to further work on the industrial application of BSF to reduce agricultural waste and increase the protein production. As an applied research center, we are open for suggestions from the industry to tackle specific problems.
A visual impression of our pilot plant (https://youtu.be/8WzFKFn-1OM) or our black soldier fly larvae (https://youtu.be/5o5Xr2YRLRQ).
Jeffery K. Tomberlin, PhD, Facilitator
Individuals with over 25 years research experience with the black soldier fly. We are passionate about the science behind the black soldier fly and its ability to convert waste to protein.
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