Effect of Food Waste Composition on Growth of Black Soldier Fly Larvae at UD’s Upcycling Site

• Ava Sharett, Environmental Science, Spelman College

• Michael Crossley, Department of Entomology and Wildlife Ecology, University of Delaware

Roughly half of US land is devoted to agriculture, but over a third of it ends up in landfills. This not only exhausts finite natural resources but exacerbates food insecurity in America. However, food waste can be converted into useful feed and fertilizer with the help of an insect, the black soldier fly (Diptera: Stratiomyidae), through a process termed “waste upcycling” that adds circularity to our food system. Still, questions remain about what composition of food waste this insect can handle, and how to balance waste reduction with the production of useful insect material. Here, we examined the growth and behavior of black soldier fly larvae (BSFL) on three food waste mixtures: brewer’s spent grains, spent grains + produce, and spent grains + meat. We did so using food waste from a local brewery and restaurant, supplied to BSFL in outdoor bins on the Newark farm. We made daily observations of average larval mass, larval behavior, and substrate conditions (pH, humidity, temperature). We found that BSFL achieved the highest mass on diets including produce, while spent grains alone produced the lowest mass. Across treatments, BSFL were typically observed consuming food waste, rather than crawling out of bins as occurs when feeding conditions are suboptimal. While bin conditions varied widely over time, we did not uncover any significant effects on BSFL growth. Overall, our findings suggest that BSFL can break down a diversity of food wastes typical of our food systems, with our upcycling site converting nearly two tons of food waste into insect biomass and frass since April 2025. Ultimately, waste upcycling with help from insects could help us achieve a more circular food system, promoting environmental sustainability in our homes, grocery stores, and restaurants.