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Licentiate thesis2021Open access

Process efficiency in black soldier fly larvae composting of plant-based food industry waste

Lindberg, Lovisa

Abstract

Black soldier fly larvae (BSFL) composting, in which biodegradable wastes are converted into animal-feed protein, is a technology that meets circular economy principles. The greatest potential BSFL composting is for mixed food waste, but only plant-based waste is permitted as feed for the larvae. It has lower biomass conversion efficiency (BCE), but this could be improved by pre-treatment.

This thesis investigated process efficiency and GHG and ammonia emissions from BSFL composting using orange peel and broccoli and cauliflower, with ammonia or fungi pre-treatment. The impact of enzyme and ammonia pre-treatment time on process efficiency when using mixed lettuce and cabbage waste was also assessed. Following two weeks of substrate pre-treatment with ammonia and fungi, direct emissions of GHG and ammonia were evaluated. Lettuce and cabbage was pre-treated with enzymes or ammonia for 0-8 days prior to BSFL composting.

BCE on a volatile solids (VS) basis was greater overall for food waste and lettuce and cabbage (~20%) than for orange peel and broccoli and cauliflower (~7%). The BCE was low (6%) in the orange peel control and even lower in both orange peel pre-treatments. Direct addition of enzymes at the start of BSFL composting gave 22% higher BCE compared with the control.

Total emissions of N2O and CH4 were almost four-fold larger for the broccoli and cauliflower control than when pre-treated, indicating that ammonia pre-treatment significantly reduced total GHG emissions with no negative impact on BCE during BSFL composting, but with increased ammonia emissions.

Keywords

Biological treatment; plant-based waste; Hermetia illucens; pre-treatment; ammonia; Trichoderma reesei; enzyme

ISBN: 978-91-576-9896-4, eISBN: 978-91-576-9897-1
Publisher: Department of Energy and Technology, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Environmental Sciences related to Agriculture and Land-use

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/113633