Steam pre-treatment of sugarcane bagasse and wheat straw as a cleaner feedstock for black soldier fly larvae rearing

Abstract

With the pressing need for alternative waste management strategies that are friendly to the environment, black soldier fly larvae (BSFL) are being cultivated as exceptional insects for the bioconversion of organic waste into larval biomass rich in protein and fat content. Agricultural residues, such as wheat straw and sugarcane bagasse are recognised as important renewable biomass sources, with potential to replace insufficient amount of suitable organic wastes available for BSFL feeding. This study evaluated the steam pre-treatment from 140 to 215 °C and enzymatic hydrolysis of lignocelluloses as BSFL feed supplement prior to blending in an equal ratio (50:50) with the standard feed for BSFL rearing. Key findings illustrated that steam pre-treatment and enzymatic hydrolysis are vital in liberating the sugar monomers of the lignocellulose biomass for BSFL utilisation, with an optimum steam pre-treatment temperature of 185 °C. With a lignocellulosic feed prepared at this temperature plus supplemented standard feed, a BSFL dry-weight bioconversion of 16% was achieved in 8 to 11 days of rearing. The inhibitory by-products formed by degradation of lignocelluloses during pre-treatment had a significantly negative effect on the rearing of the BSFL, particularly a furan concentration of 0.2 g/L, which should be investigated for efficient BSFL rearing. Finally, the crude protein content in the BSFL reared on the standard feed was higher than the feed substrate supplemented with lignocellulose. This study demonstrated the need for process optimisation and component supplements in the BSFL feed substrates that contain lignocellulosic feedstocks.