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, alternative and more sustainable production methods are being explored to reduce pressure on natural resources and the environment. A promising innovation is the use of BSF larvae for processing organic waste streams. 

In the context of a bio-based circular economy, BSF larvae play a crucial role: they convert organic waste into high-quality insect biomass (a source of proteins and fats) and produce a valuable organic fertilizer (frass). The use of BSF larvae for manure processing has the potential to close nutrient cycles and contribute to more sustainable agriculture (Siddiqui et al., 2022). 

However, it is currently not legally permitted to trade BSF larvae that have been grown on animal manure as animal feed. Steps are being taken to relax EU regulations in this area. 

In December 2024, Insect Engineers conducted a test to determine whether pig manure is suitable as feed for BSF larvae. The pig manure was supplied by Görtz Group, and the larvae (5 days old) came from FreezeM. The special BSF feed was produced by Nijsen Company. 

Why Use BSF Larvae for Manure Processing? 

Insects are increasingly considered promising candidates for manure processing and upcycling (Aartsma et al., 2024). Feeding BSF larvae with organic waste streams offers several benefits: 

• Nutrient Recycling: Larvae convert manure into usable proteins and fats for animal feed. 

• Reduction of Environmental Pressure: They help reduce greenhouse gas and ammonia emissions. 

• Alternative to Traditional Manure Processing: Conventional manure processing technologies are often expensive and are applied on a limited scale due to high investment and operational costs, logistical challenges, and social acceptance issues. 

• Potential for Bioenergy: The fats in BSF larvae can be used for biofuel production. 

In regions with intensive livestock farming, where manure surpluses often cause environmental pollution and public health risks, BSF technology can provide an innovative solution. 

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