Process efficiency in relation to enzyme pre-treatment duration in black soldier fly larvae composting

Area of Science:

• Waste Management
• Insect Farming
• Biotechnology

Background:

• Black soldier fly larvae (BSFL) composting converts biodegradable waste into valuable products like animal feed and fertilizer.
• Current EU regulations restrict BSFL composting to plant-based waste, which has lower biomass conversion efficiency (BCE) compared to mixed food waste.
• Enzyme pre-treatment is a potential method to enhance BCE for plant-based waste, but its application duration effects are not well understood.

Purpose of the Study:

• To investigate the impact of enzyme pre-treatment duration on the process efficiency of BSFL composting using lettuce-cabbage waste.
• To determine the optimal enzyme pre-treatment time for maximizing BCE in BSFL composting of plant-based waste.

Main Methods:

• Lettuce-cabbage waste was pre-treated with enzymes for durations ranging from 0 to 4 days.
• BSFL composting was conducted, and key parameters such as total solids (TS) and volatile solids (VS) were measured.
• Biomass conversion efficiency (BCE) was calculated to assess the impact of enzyme pre-treatment.

Main Results:

• Direct enzyme addition (0-day pre-treatment) resulted in a 22% increase in BCE on a volatile solids (VS) basis compared to the control.
• Total solids (TS) in the larvae decreased with increasing enzyme pre-treatment duration.
• Longer pre-treatment durations (beyond 0 days) did not yield further improvements in BCE and led to increased microbial respiration.

Conclusions:

• Enzyme pre-treatment is beneficial for enhancing BSFL composting efficiency of plant-based waste, particularly when applied immediately at the start of the process.
• Extended enzyme pre-treatment can lead to the consumption of easily digestible carbohydrates by microbes, counteracting the intended benefit of enzyme pre-treatment.
• Optimizing enzyme pre-treatment duration is crucial for maximizing resource recovery and process efficiency in BSFL composting.