Monitoring presence of pathogenic bacteria in black soldier fly waste upcycling

• Elizabeth Heintzelman, Animal Science, University of Delaware

• Michael Crossley, Entomology and Wildlife Ecology, University of Delaware
• Kali Kniel, Animal and Food Sciences, University of Delaware

It is estimated that over 30% of food produced within the US gets thrown away. In order to not waste the resources we used to create the food, we can upcycle food that is no longer safe for human consumption. Insect-driven waste upcycling turns food waste into two usable products: the excrement of the larvae, which can be used as compost, and the larvae themselves, which can be fed to livestock as a protein source. Black soldier flies are one of the most common insects used in upcycling due to their apparent ability to reduce bacterial pathogens within a controlled environment. We wanted to monitor the presence of pathogenic bacteria when this process is used outside a lab environment. Over 6 weeks, samples were collected from black soldier fly larvae bins being fed 3 different types of food waste (grains, produce, and meat). Samples included: food added to the bins, the black soldier fly larvae and excrement in the 3 types of bins, compost from bins that were given food waste but were not stocked with larvae, and blow flies, a common invader which may impact pathogen reduction. These samples were plated on selective media to track the amount of Salmonella and Staphylococcus bacteria present in and around our site. Within all samples, bacterial load appeared to increase over time. Blow flies often had larger amounts of Salmonella than the black soldier fly larvae, which may indicate that they are able to contaminate the bins. Sanitization needs to be heavily considered prior to the use of black soldier fly compost for crops or larvae for livestock feed to reduce the chance of infection.