The Use of Pig Manure as Feed for Black Soldier Fly: Research by Insect Engineers
Introduction
Due to the increasing demand for food and animal feed, industries are exploring alternative and more sustainable production methods to reduce pressure on natural resources and the environment. In this context, one promising innovation is the use of BSF larvae to process organic waste streams.
Within a bio-based circular economy, BSF larvae play a crucial role. For example, they efficiently convert organic waste into high-quality insect biomass, which serves as a rich source of proteins and fats. At the same time, they produce frass, a valuable organic fertilizer. As a result, by processing manure, BSF larvae help close nutrient cycles and support more sustainable agricultural systems (Siddiqui et al., 2022).
However, despite these benefits, current regulations do not allow the use of BSF larvae reared on animal manure as animal feed. Nevertheless, regulatory bodies in the EU are actively working toward relaxing these restrictions.
To further explore this potential, Insect Engineers conducted a trial in December 2024 to evaluate whether pig manure can serve as a suitable feed substrate for BSF larvae. In this study, Görtz Group supplied the pig manure, while FreezeM provided five-day-old larvae. Meanwhile, Nijsen Company developed the specialized BSF feed used in the experiment.
Why Use BSF Larvae for Manure Processing?
Insects are increasingly emerging as promising candidates for manure processing and upcycling (Aartsma et al., 2024). Using BSF larvae to process organic waste streams offers several key benefits:
- Nutrient Recycling: BSF larvae convert manure into valuable proteins and fats that producers can use in animal feed.
- Reduced Environmental Pressure: BSF larvae lower greenhouse gas emissions and reduce ammonia release.
- Alternative to Traditional Manure Processing: Conventional manure processing technologies often require high investment and operational costs. These systems also face logistical challenges and limited social acceptance, which restrict large-scale adoption.
- Bioenergy Potential: Producers can use the fats extracted from BSF larvae to produce biofuels.
In regions with intensive livestock farming, manure surpluses frequently lead to environmental pollution and public health risks. BSF technology offers an innovative and scalable solution to address these challenges.
Research Setup and Materials
Small-Scale Test: Optimization of Feed Compositions
A small experiment was first conducted to determine the optimal feed ratio for desired conversion, digestion duration, and larval growth before large-scale testing.
Three different tests were conducted in 60×40 cm crates to assess the appropriate balance between the following elements (Table 1):
- Wet pig manure (99% moisture)
- Dried pig manure (7% moisture)
- BSF feed (10% moisture)
Each crate contained 12 kg of feed and 12,000 larvae.
Results of the Small-Scale Test
- Moisture Content is Crucial: At moisture levels above 70%, the larvae could not properly process the feed and attempted to escape. A moisture level below 65% resulted in lower growth and conversion rates.
- Odor Reduction: After processing by the larvae, the pig manure odour was eliminated.
- Optimal Growth: Larvae grew better when BSF feed was added to the pig manure.
Large-Scale Test: Processing on a Larger Scale
Based on the findings from the small-scale test, a larger test was conducted in a 12-meter ZOEM bed, where 1,200,000 larvae were added to 666 kg of feed. This feed consisted of:
- 60% wet pig manure
- 30% Nijsen BSF feed
- 10% dried pig manure
This mix was drier than the crate test, possibly because a larger surface area was used and the climate in the ZOEM racks could be effectively controlled via the Insect Engineers system.
After 9 days, the feed was fully digested, aligning with the estimates from the small-scale test.
A total of 41 kg of larvae and 150 kg of frass were produced, indicating a conversion ratio of 22.5%. The weight of the larvae was calculated by sieving the larvae from the frass. A sample of 50 larvae was taken and weighed on a milligram scale, from which the average weight was determined:
0.03 x 1,200,000 = 41,000 grams of larvae
This calculation assumes that all larvae survived.
The amount of frass was measured by filling 25-liter containers, which were then weighed. Approximately 12 containers were filled with frass, each weighing about 12.5 kg:
12.5 x 12 = 150 kg of frass
Financial Analysis
To produce 10,000 kg of feed, the costs are as follows:
- 7,000 kg wet pig manure (-€10 per m³) (farmers currently pay €25-32 per m³ for manure disposal)
- 3,000 kg BSF-feed (€120 per ton) =
Total cost: €273 per 10,000 kg feed (€27.30 per ton)
To be economically viable, 50 tons of wet feed per day must be processed.
A profitable model depends on numerous factors:
- Price of larvae
- Selling price of live or dried larvae
- Production capacity and labour costs
- Savings on manure disposal
References
Aartsma, Y., Van de Zande, E. M., & Dicke, M. (2024). Potential of insects for circular, sustainable livestock feed production: From policymakers’ perspectives. https://doi.org/10.18174/670644
Siddiqui, S. A., Ristow, B., Rahayu, T., Putra, N. S., Yuwono, N. W., Nisa, K., Mategeko, B., Smetana, S., Saki, M., Nawaz, A., & Nagdalian, A. (2022b). Black soldier fly larvae (BSFL) and their affinity for organic waste processing. Waste Management, 140, 1–13. https://doi.org/10.1016/j.wasman.2021.12.044
