Valorisation of solid sisal leaves decortication wastes using black soldier fly (hermetia illucens l.) larvae

Abstract

The amount of waste generated from sisal industries during sisal fiber production is huge and its management is still challenging and a menace to the environment. These wastes include sisal wastewater and sisal leaf decortication wastes (SLDW) which represent an opportunity for valorization into products. Nevertheless, the sisal leaf decortication wastes is suitable for resource recovery in order to reduce the impacts it causes by just being discarded in the environment without treatment. This study aimed at managing the SLDW using insect-based technology. Specifically, the study characterized the SLDW for its physical and chemical constituents, pretreatment of SLDW to render it suitable for the growth of the insects and optimization of the waste and other blends for production of livestock feed. The use of SLDW for various applications is limited due to its high acidic content and presence of saponin within it. This is the first study of its kind regarding the use the SLDW as a substrate for growth of BSFL. Pre-treatment was a necessary and challenging step done on the waste to meet minimum requirements for rearing of BSF. The resultant waste had Ca, P, K, Mn, Fe, Cu and Zn at varying levels which are all essential for animal growth. The SLDW contained 10 ± 0.01 percent of crude protein, 11 ± 0.02 moisture and energy (1615 kcal/g of Sisal de-corticated waste). The sun dried BSF larvae reared on SLDW contained 53 ± 0.005 percent crude protein, 4 ± 0.01 percent of crude fat, moisture content (10 ± 0.1) %, carbohydrate (43 ± 0.01) % and ash (37 ± 0.08) %. When rearing was done on SLDW, 3000 g of dried pre-treated waste yielded more wet BSF larvae (336 ± 41.3) g compared to 3000 g of fruit waste which yielded (244 ± 4.16) g of wet BSF larvae. Furthermore, the harvested BSFL after optimization process through blending of SLDW, RB and CDW improved growth rate of BSFL (2.2 gram per larvae) and contained sufficient nutritional value to feed poultry and fish, reducing the necessity to de-fatty the larvae as it is being practiced when market waste is being used. The SLDW is a promising feedstock for rearing BSFL because it has good reduction of the waste by 52%. This study eventually creates resource recovery sustainability in sisal industries.