The production of insect protein as human food and livestock feed (entomophagy) may provide a more environmentally beneficial alternative to traditional animal agriculture. However, the resulting waste product from insect production has resulted in large accumulations of left-over substrate and frass. Due to its nutrient and microbial profile, this left-over product has the potential to be utilised as a biofertiliser for high value crop production. Studies have been conducted using the frass of various insects (e.g. black soldier flies, houseflies, and mealworms) to monitor its impact on crop productivity. Overall, frass tends to have similar or better results when compared to inorganic fertilisers, especially when combined with them. Aside from productivity and growth, frass may also preserve soil fertility by decreasing leaching and infiltration, and reducing the prevalence of disease and pathogens. In addition, chitin found in frass also has beneficial properties for plant/crop growth and disease resistance. Monitoring the dietary inputs of industrially reared insects may be the best way of mitigating the potential negative impacts of frass application, such as increased electrical conductivity and heavy metal toxicity. No single study confirms all of these benefits at once. Future studies should focus building onto these results by demonstrating systems levels benefits.

The “insects as food and feed” movement is gaining considerable momentum as a novel means to provide protein to people (i.e., food) and other animals (i.e., feed). Insects require significantly fewer resources, such as water and land, to produce, process, and distribute as a food or feed source. While the production of insect biomass has received considerable attention for use as food or feed, little is known about the value of the residual materials remaining after digestion. One insect, the black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), can generate large quantities of residual (i.e., frass) that is high in nitrogen, phosphorus, and potassium. These materials could serve as a partial replacement for fertilizer or peat, thus creating added value to the insects as food and feed sector. Greenhouse studies were designed to investigate the use of frass in vegetable production. In pot studies with tomatoes, different ratios of peat:vermicompost and peat:insect frass were compared to a 100% peat control. Across all other parameters, tomato fruits and vegetative biomass did not produce significant differences across treatments, indicating results were comparable to the control (i.e., 100% peat). Thus, replacing peat with black soldier fly frass is a viable option and could allow for the peat industry to become more sustainable and regenerative. However, it should be noted that average individual tomato fruit weight was significantly (P < 0.05) higher (by 19%) in the vermicompost 10% treatment compared to the control, which did not differ from treatments including black soldier fly frass.

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