| dc.description.abstract | Black soldier fly larvae (BSFL) can effectively convert organic waste into nutrient rich insect biomass as feed and frass as fertilizer for food production. With over 40% extractable lipids from BSFL that are more than half saturated fatty acids, insect farming introduces yet another dimension of exploitation as a part of the circular economy beyond food, feed and fertilizer while creating cleaner cities. In this study, each of the four weighed replicates of 5-day old BSFL were randomly assigned to one of the 4 growth substrate treatments with either 0%, 10%, 20% or 30% maize bran that was uniformly mixed with shredded fruit and vegetable municipal market waste. Data on the substrate (proximate composition, metabolic energy, pH, temperature and moisture content) and on the larvae (length, girth, weight, proximate composition, oil weight, fatty acid profile, and oil specific density and saponification value) were recorded for 12 days. Saponification value and profile of the triglycerides extracted from BSFL was used to assess its value as either an industrial raw material for soap manufacture or as feed. Results were analyzed with R-studio where polynomial orthogonal contrasts were used to test the linear and quadratic effect of maize bran inclusion, which was presented as either tabular or box plots.
Substrate dry matter (DM), metabolizable energy (ME) and nitrogen free extract (NFE) increased linearly (P<0.05) from 17.4 to 30.3 g100g-1, 11.2 to 11.4 MJkg-1 DM and 49.1 to 63.2 g100g-1, respectively, with maize bran inclusion. However, crude protein (10.2 to 12.1 g100g-1) and ether extract (4.91 to 9.64 g100g-1) as well as the substrate temperature (36.8 to 41.80C), pH (4.24 to 8.23) and moisture content (81.5 to 58.5 g100g-1) followed a curvilinear trend (P<0.05). The larval girth (0.8 to 4.59mm), length (0.468 to 1.72cm), weight (2.83 to 97.2mg) and weight gain (0.034 to 0.093g) increased linearly (P<0.05). Municipal waste to unit insect biomass conversion ratio decreased linearly at a decreasing rate from 48.6 to 17.7 gg-1(P<0.05). The larval ether extract, saturated fatty acids and the oil weight per unit larval biomass increases at a decreasing rate (P<0.05) from 19.6 to 48.7 g100g-1, 54.2 to 63.2 g100g-1, 0.196 to 0.487gg-1. The crude protein (31.8 to 35.3 g100g-1), mono unsaturated fatty acids (MUFA) (17.5 to 19.3 g100g-1), polyunsaturated fatty acids (PUFA) (18 to 19.3 g100g-1), omega-3 (1.95 to 2.87 g100g-1) and omega-6 (16 to 17.2 g100g-1) did not take a clear trend and were low. However, relatively high saponification values ranging from135 to 208 gKOHg-1 and the oil specific density of 0.9285gml1 suggests that the triglyceride in BSFL provide a suitable industrial raw material for soap formation. Conversely, essential PUFA, docosahexaenoic acid and Octadecaenoic acid, were below detectable levels but among those detectable, saturated Lauric acid was the highest and ranged from 28.3 to 37.1 g100g-1 while arachidonic acid ranging from 0.018 to 0.02 g100g-1 was the lowest. BSFL can, therefore, be used in an industrial symbiosis model for cleaner cities and in a circular livestock feed and fertilizer production system if shredded municipal waste is supplemented with intermediate levels of maize bran for efficient larval growth and lipid production. | en_US |
