Engineering solutions to optimize Black Soldier Fly production
Denis Ruto joined Sanergy’s Black Soldier Fly team earlier this year as part of the Sanergy Fellows Program. He has since transitioned to a full-time position. Below, he shares his experience working on Sanergy’s Black Soldier Fly project.
Last year, Sanergy’s Godwin Ruto and a group of engineers came to Nairobi University to talk about opportunities at Sanergy. I found the session interesting for two reasons. First, because, as an environmental engineer focusing on water systems, I am passionate about sanitation; and second, Sanergy’s solution adhered to a key engineering principle: Always close the loop. Listening to Ruto’s presentation, I was intrigued to learn how Sanergy is closing the sanitation loop by converting waste to energy and agricultural end-products.
Before learning about Sanergy, I had known that Nairobi’s sanitation system had recurring and systemic challenges, so I was really inspired to be part of the solution! Just as I was concluding school, I applied and got accepted as an engineering fellow to work on Sanergy’s Black Soldier Fly Larvae (BSFL) project, providing Kenya’s animal feed millers with a high-quality protein input for animal feed.
Currently, fishmeal is the primary protein input for animal feed in the region. However, feed millers are displeased with fishmeal for a variety of reasons: Harvested unsustainably from Lake Victoria, fishmeal stocks are difficult to predict, and the quality of the product is highly variable. Sanergy’s PureProtein animal feed input addresses these concerns, while offering a sustainable solution for the treatment and reuse of waste,
The Black Soldier Fly is by far one of nature’s most efficient organic waste converters, with an average conversion rate around 10%. Not only does it efficiently break down any type of organic waste by over 50%, it also assimilates it to 40% protein and 25% fat by storing it up in its body. Just like any other fly, it has four stages in its four-week lifecycle. At the larval stage, it feeds on decomposing organic waste material and assimilates it in its body as protein and fat.
After several years of learning and trialling PureProtein’s commercial production viability, this year the team set out to upscale BSFL production to one tonne per month while optimizing its operational costs for maximum production efficiency.
When I joined the team, I was tasked with researching and prototyping efficient ways to harvest black solder fly larvae as well as developing post-treatment procedures that would ensure the larvae is pathogen free and nutritious for animal consumption. I, therefore, began research to have a complete understanding of the behavioural and psychological characteristics of the black soldier fly. One of the interesting traits I discovered is that the black soldier fly is photophobic (sensitive to light).
These traits helped our team prototype several models of harvesting the larvae, including: water separations, tub collection, light separation, heat separation, sieving and rotating-drum sieve. We assessed all these techniques using a scoring matrix that rated each method’s technical and financial feasibility.The tub-collector, for example, proved very effective in separating the larvae; however in the long run it would not be readily scalable. This is because the method depends on the BSFL’s natural instinct to “self-harvest” and thus would affect consistent production rates. After trialling a variety of methods, we selected the one that would be most effective in separating the larvae from the residue with minimal distortion of the end products, while also easy to scale as we increased production. We are proud to be launching this new harvesting model in the next few months. Throughout this process, our team has learnt a lot about how to standardize our general BSFL production procedures.
We have learnt that regulating the amount of larvae and feed in each bin, coupled with the design of the bin itself, are paramount considerations for temperature control. Striking the right ratio and providing the right environment ensures that black soldier flies have an ideal climate for maximum production.
These learnings have helped our team design colonies that provide as natural as possible a habitat for growing and harvesting Black Soldier Flies (BSF). Creating this optimal environment helps us maximize the amount of end-product we can generate from the waste we collect. In the future, I hope that our learnings can also help peers in this sector to replicate and adapt a similar model for deriving value from waste.
My fellowship was a success because of the immense support I received from my teammates and my manager Laura Kimani. Everyone had something to share; from the fundamentals to keep in mind when handling BSF colonies to recommended literature, I could read to further my understanding of the black soldier fly.
The Sanergy Fellows Program also offered opportunities for broader learning and development: interesting lectures from leaders of similar organizations through the Sanergy Speaker Series and events for fellows to interact and learn from one another, as well as employees across Sanergy.
As I transition to a full-time associate engineer, I am thrilled to be a part of Sanergy’s movement: one that not only advocates for innovative solutions toward a sustainable sanitation model but also demonstrates building healthy, prosperous communities through practice.