Kretsloppsteknik

Här pratar jag och Viktoria med Thomas Bjelkeman-Pettersson och Linnea Jäder i podden Matkretslopp om vår syn på insekters roll i våra livsmedelssystem.

In this review, published in Animal, Karol B. Barragán-Fonseca, Daipiero Gómez, Daniel Dzepe, Shaphan Y. Chia and I (Cecilia Lalander) investigate the current state of black soldier fly larvae (BSFL) farming in the global south. We surveyed as many producers we managed, and were able to collect data from 33 of the 100 producers we contacted: 14 in Africa, 4 in Latin America, and 15 in Asia. The review highlights the potential of Black Soldier Fly (BSF) farming has in the Global South as a sustainable solution for food production and organic waste management. By converting waste into valuable products such as animal feed and organic fertilizer, BSF farming aligns with the principles of a circular economy and supports sustainable development goals. The study emphasizes the region’s strengths, including favorable climatic conditions that reduce resource inputs and a long tradition of entomophagy, which facilitates cultural acceptance of insect farming. Smallholder farmers play a vital role in this emerging sector, and BSF farming offers them economic opportunities, such as reducing feed costs for livestock and aquaculture.

Despite its promise, the sector faces significant challenges. Producers encounter regulatory gaps, making it difficult to ensure compliance and market their products. Securing a stable supply of high-quality waste substrates is another major hurdle, while scaling up operations is constrained by technological and financial barriers. These challenges are further exacerbated by competition from conventional feed sources such as fishmeal and soybean meal, which are frequently more cost-effective.

Regional variations also influence the development of BSF farming. For instance, African producers use diverse organic waste substrates, while Asian producers tend to avoid manure due to cultural resistance. Latin America, by contrast, has fewer established facilities and producers, likely due to lower familiarity with insect farming and less institutional support.

The review underscores the growing market demand for BSF products, especially for animal feed and pet food. However, to fully realize the potential of BSF farming, there is a need for global collaboration among policymakers, researchers, and the private sector. Efforts to establish consistent regulations, improve waste substrate logistics, and develop scalable technologies will be critical for overcoming these barriers. If you are interested, read the full review here.

Over the last year, the BSF group has conducted exciting experiments as part of the Happy Salmon project. We received big batches of two species of macroalgae (Ulva and Saccharina) for the Nordic SeaFarm in Dingle, to be used as feed substrate for rearing BSF larvae. The algae was mixed with brewery spent grains, provided by Train Station Brewery in Knivsta and vegetable waste, ensuring a nutritiously balanced diet for the larvae. Interestingly, the larvae grew quite well in this blend substrate and achieved a high body protein (40%), while the fat content was considerably lower than our larvae usually are (< 15%), making this larval biomass a good feed ingredient.

The frass fertilizer obtained in these experiments also had interesting properties, having > 80% of organic matter and a NPK ratio of 3/1/3. However, the most exciting results regarding this frass fertiliser was the composition of beneficial microorganisms, stimulated by the presence of the algae in the larval diet.  Moreover, the frass container plant hormones,   including auxins, gibberellins and cytokinins, which are important regulators of plant growth and metabolism. These novel results are being investigated and assessed now to see how different plant species can benefit from frass when it is applied in the soil.

As a next step, the larvae produced with the macroalgae and brewery spent grains are being pressed and defatted, and then used as a nutritious feed ingredient for the production of fish feed. Skretting, a global leader in sustainable aquaculture nutrition, in Norway will use this feed in salmon growth trials. We believe that this BSF larvae-derived ingredient can be considered a more sustainable feed ingredient for aquaculture. Fingers crossed for interesting results to come!

The seminar is given in English and can be seen here.

On Thursday the 12th of September at 12:15 pm CET, Cecilia Lalander will tell her view on the matter. Tune in! It will be available online afterwards if you don’t have time to watch live.

Worth knowing is the SLU University Library’s popular science lunchtime lecture series. Here, exciting and recent research results from SLU are presented. We offer a light lunch, and after the lecture listeners have the opportunity to ask questions.

In our article Recirculating frass from food waste bioconversion using black soldier fly larvae: Impacts on process efficiency and product quality recently published in the Journal of Environmental Management, we showed that food waste-derived frass, an unstable fertilizer with phytotoxic properties when used fresh, can be reused in the bioconversion process as part of the larvae’s feed. This approach offers several benefits for both the process and the quality of the resulting larval biomass and frass fertilizers.

Several studies reported phytotoxicity (adverse effects on plant growth, physiology or metabolism cause by several different substances) in frass from black soldier fly larvae (BSFL), especially when growing crops in greenhouses and using frass as a fertilizer or growing media. We believe that this phytotoxicity is related to the fact that waste bioconversion with BSFL is very rapid (< 14 days), and that there therefore is no time for the organic matter to be stabilized. Stabilizing this “fresh” frass’ organic matter is crucial for its safe use as a fertilizer or soil amendment. However, studies have shown that the post-composting of frass can be the major source of greenhouse gas emissions and increase the overall environmental impact of this treatment. Finding a more viable and sustainable way of stabilizing fress frass was the main goal of this study.

The hypothesis of the study was that a significant portion of the organic matter in food waste-derived frass remains relatively undigested, allowing the BSFL to further consume and digest it, thereby increasing the degree of decomposition. This hypothesis was confirmed, as the frass produced after consuming the food waste with frass inclusion (called recirculated frass) had a lower organic matter content than the fresh frass. In addition, several characteristics of the recirculated frass pointed towards higher maturity and higher stability, which indicates that it is safer to use as fertilizer. Interestingly, not only the resulting frass, but also the larval biomass was positively affected with this frass recirculation process. A significant correlation of larval biomass composition and frass-inclusion rate was establisheda, showing that as frass inclusion increased, the larval biomass had higher protein content and lower fat content. Considering that protein ingredients are the most expensive input in animal feeds, this is likely to be of interest to the insect industry.

One of the most intriguing findings of this study was that recirculating frass back into the bioconversion process significantly increased the larval yield per unit of waste. This indicates that incorporating fresh frass into the larvae’s diet allows for a higher biomass of larvae using the same amount of waste. This innovative method for enhancing both the process and product quality is highly promising. We are now developing new studies on frass recirculation to better understand the underlying mechanisms and explore any additional benefits this approach may offer.