Blended Sewage Sludge–Palm Kernel Expeller to Enhance the Palatability of Black Soldier Fly Larvae for Biodiesel Production

Ratchaprapa Raksasat,Yeek Chia Ho,Jun Wei Lim,Man Kee Lam,I Wayan Koko Suryawan,Chung Yiin Wong,Worapon Kiatkittipong,Wen Da Oh,Kunlanan Kiatkittipong

doi:10.3390/pr9020297

Abstract

Black soldier fly larvae (BSFL) have been employed for valorizing organic waste materials as the larvae are able to consume organic waste and transform it into valuable larval biomass. In this study, BSFL were found to potentially reduce blended sewage sludge. The addition of palm kernel expeller (PKE) fortified the protein and lipid content in blended sewage sludge substrates, leading to larval growth enhancement. In addition, the larval weight also influenced the lipid yield and fatty acid methyl ester (FAME) profile. However, the optimum ratio of sewage sludge to PKE had to be determined as excess PKE content could become a threat to larval growth by contributing to the reduction of non-fiber carbohydrates content in the feed, thereby resulting in the decrease in lipid yield and FAME content. In this work, a sewage sludge to PKE ratio of 2:3 proffered the highest larval weight gained at 46.99 ± 2.09 mg/larva. Meanwhile, a proportion of 3:2 of sewage sludge to PKE was able provide the highest lipid yield of 17 ± 1.77%. Furthermore, the FAME profile revealed the presence of a significant amount of saturated and monosaturated fatty acids, indicating a good quality biodiesel. Thus, BSFL-based biodiesel fed with blended sewage sludge and PKE could be utilized for producing a high quality biodiesel. However, further improvement on the amount of lipid yield and FAME content should be further investigated.

Highlights

IntroductionThe increase in environmental concerns, especially climate change, has become an awareness issue for industries at the present time to reduce the amount of greenhouse gases emitted into atmosphere [1,2]
The growth of Black soldier fly larvae (BSFL) was studied in terms of rearing duration and final larval dry weight when fed with various blended sewage sludge (Figure 2)
This could be rationalized by the presence of extracellular polymeric substances formed by bacterial cells as a protective shield to prevent the digestion process by other microorganism colonies. This hindered the digestion by BSFL in assimilating the nutrients in sewage sludge, leading to the retardation of larval growth [31,41]

Summary

Introduction

The increase in environmental concerns, especially climate change, has become an awareness issue for industries at the present time to reduce the amount of greenhouse gases emitted into atmosphere [1,2]. Combustion of fossil fuels stemming from myriad human activities, such as transportation, coal-fired power plants, and large industries, can pollute the air by producing greenhouse gases, nitrogen oxides and ammonia. The presence of excessive nitrogen oxides in the atmosphere can contribute to environmental problems via the formation of smog and acid rain [3]. The utilization of biodiesel instead of fossil fuels is considered clean in addition to its renewability, since biodiesel can be generated from biomass materials [1].

Methods

Results

Conclusion