Chemical composition and in-vitro fermentation kinetics of Defatted black soldier fly larvae fed sorted municipal waste Supplemented with graded levels of chicken manure

Abstract

The recent 2024 Kiteezi landslide incidence in Uganda is an indication that municipal and city authorities neither have sufficient financing nor appropriate technologies to handle the garbage challenge majorly from markets and peri-urban farms. However, there is research evidence to suggest that saprophagous black soldier fly larvae (BSFL) technology has the potential to turn biodegradable municipal waste into food, feed and fertilizers and hence reducing the challenge of municipal and farm waste. The two-fold objectives of this study were: i) to assess the proportions of biodegradable and non-biodegradable content of municipal waste from five major food markets in Kampala city ii) to optimize circular insect feed production technology when BSFL biodegradable fruit and vegetable market waste as basal substrate for 5-day old larvae is supplemented with graded levels of chicken farm manure. The BSFL technology was employed to produce defatted larval insect biomass when the basal substrate was supplemented with graded levels of chicken farm manure at inclusion rates of 0g/kg, 100g/kg, 200g/kg and 400g/kg. Chemical composition of the substrate and the resultant larvae after two weeks of inoculation was analysed using proximate procedure while the fermentation kinetics were derived by measuring gas production (GP) at 0, 2, 4, 6,12, 24, 48, 72, 96 and 120 hours. The location of the markets had no influence (p>0.05) on the proportions of biodegradable (organic) and non-biodegradable contents. The defatted larval biomass crude protein (CP) content increased linearly (p<0.05) with increase in the chicken manure inclusion levels from 36.8 to 45.4 g/100g DM CP while ash content increased at a decreasing rate (p<0.05). Conversely, the Ether extracts tended to follow a quadratic trend (p=0.07). On the other hand, the 30% and 40% inclusion levels, had better (p<0.05) in-vitro organic matter digestibility (IVOMD) 65.46% and 67.11% respectively and metabolizable energy (ME) 15.4 MJ/kg DM and 15.90 MJ/kg DM respectively. The larvae from 0% inclusion level had more Net energy of lactation (Nel) 0.136 MJ/kg DM and volatile fatty acids (VFAs) 0.122 g/Kg DM. In conclusion, the location of the markets had no influence on the proportions of biodegradable and non-biodegradable contents of the waste. Chicken manure inclusion improves substrate quality for BSFL nutrient enrichment especially protein and mineral content as well as organic matter digestibility and provides a sustainable way for managing biodegradable municipal and farm waste.