Fortification of black soldier fly larval feeding substrate for producing biodiesel

Abstract

Numerous amounts of sewage sludge have been generated as an organic waste annually at the present time and requires a proper disposal management. However, the conventional methods for sewage sludge disposal may enlarge the carbon footprint and incur a high operating cost due to various hazardous substances that exist in sewage sludge. Hence, a novel secure method is opted in this study by utilizing insect larvae to consume sewage sludge and subsequently, being converted into a high value-added biofuel. As such, black soldier fly larvae (BSFL) were selected to serve this purpose due to the high lipid content (20-40%) within their body and can be extracted for further utilization as biodiesel production feedstock. In addition, BSFL are competency to withstand heavy metals in sewage sludge without any contamination in larval biomass. However, as inadequate nutrition in sewage sludge can possibly retard the larval growth and biomass accumulation, fortification of sewage sludge nutrition will be studied by blending with palm kernel expeller (PKE), a nutrition enriched and low-cost organic waste substrate prior feeding to BSFL to assist larval growth and increase amount of larval lipid accumulation for producing biodiesel. Through the blending, an optimum ratio of sewage sludge to PKE of 2:3 had resulted in highest growth rate at 3.36±0.15 mg/larva/day and survival rate of larvae increased proportionately with PKE in larval feed. The extracted lipid from BSFL paved a pathway towards a new generation of sustainable feedstock in producing biodiesel. The highest lipid content was 17.00±1.77% when fed with sewage sludge to PKE at the ratio of 3:2.