Bioconversion of municipal organic solid waste in to compost using Black Soldier Fly (Hermetia Illucens)

Authors

• Priscilla Addo * ¹
• Sampson Oduro-Kwarteng ¹
• Samuel Fosu Gyasi ²
• Esi Awuah ¹

1. Department of Civil Engineering/Regional Water and Environmental Sanitation Centre, Kumasi (RWESCK), Kwame Nkrumah University of Science and Technology (KNUST), Kumasi-Ghana
2. Department of Energy and Environmental Engineering, University of Energy and Natural Resource (UENR), Sunyani- Ghana

Abstract

Purpose The study assessed the quality of compost produced by the Black Soldier Fly Larvae (BSFL) in terms of the compost nutrient level, microbial activities, and the bioaccumulation of possible heavy metals in the organic solid waste.
Method The study used the pre-experimental study design, one-group pretest-posttest to obtain the data. Five experimental units were used for the study, which include the daily feeding rate for the five different groups of larvae. The experiments were replicated three times. The nutrient level, heavy metal content and presence of microbes were analyzed before and after the decomposition process.
Results The study discovered that the Nitrogen, Phosphorus and Potassium (NPK)content   increased in the compost produced. Cross-contamination of Total Coliform from feed to the prepupae were significant while regrowth of Total Coliform in compost were insignificant. After the composting process most heavy metals like Fe had insignificantly increased in the compost .
Conclusion It can be concluded that larval composting enhance the regrowth of pathogens since the process is entirely mesophilic. Bioaccumulation of most heavy metals was minimum, increasing the level of these heavy metals in the compost. The nutrients were extremely high in the compost to the extent that can cause phyto-toxicity. Post-treatment of the compost is needed to make BSFL compost viable for the market.

Highlights

• The study assessed the quality of compost produced by the larvae of Black Soldier Fly using municipal organic solid waste (MOSW) as substrate in terms of nutrient, microbial activities and heavy metal bioaccumulation.
• The study observed high level of nutrients like nitrogen in the compost produced even though the larvae uses nitrogen and fat in its biomass formation. The level of nitrogen was higher than what is required in fertilizers as reported in other studies.
• The larval composting process by the BSF were mainly mesophilic hence most pathogenic microbes were increased in the compost disputing the studies which reported reduction in microbial activities as a result of larval enzymes during decomposition.
• Bioaccumulation of heavy metals in the larval composting process by the BSF were mainly dependent on the chemical properties of the elements as reported in previous studies. While some were reduced in the compost like Al as a result of its accumulation in the larval biomass, others like Ca were increased in the compost.
• Compost produced by larvae of BSF using municipal organic solid waste may require further processing to reduce pathogenic microbes and also to become more stable and mature before it can be used as a soil conditioner.

Keywords

• Heavy metals
• Activities
• Bioaccumulation
• Microbes
• Nutrients