Integrating insects in circular food systems: evidence, gaps and research priorities.

Background: Many of today's food production systems follow a linear model, where natural resources are extracted, converted into food, and discarded as waste. Efforts to reduce the environmental impact of this model have primarily focused on improving nutrient conversion efficiency. However, because linear systems are open-ended, scaling up production typically results in increased environmental costs, making sustainability goals increasingly difficult to achieve. By contrast, circular food systems (CFS) aim to recycle internal waste streams, using intermediary organisms to transform organic waste into resources that can be reused within the system. Insects are particularly promising in this context due to their dual ecological role: they convert plant and other waste into edible biomass and produce frass-a residual waste product with fertilisation potential for supporting plant growth. Methodology: To assess the current state of knowledge, a structured literature review with a systematic search of peer-reviewed studies was conducted. The Web of Science Core Collection was used to search for two topic queries ("circular food system AND insect" and "circular food production system AND insect") and included all peer-reviewed articles published through December 2024. This resulted in 395 articles identified, of which 63 met the inclusion criteria, focusing on insect integration within circular food systems. Results: Although insects are being actively studied in linear systems for their efficient biomass conversion and nutrient-rich outputs, their central role in circular food systems has so far been explored mostly through theoretical and modelling studies, with limited empirical validation. Unlocking their full potential in circular food systems requires a deeper understanding of how insects process waste, generate harvestable nutrients, and interact with other organisms in closed-loop conditions. Three urgent research priorities were identified: understanding the suitability of residual waste streams as insect feed, elucidating insect ecology and life-cycle dynamics under circular conditions, and exploring multi-species interactions within integrated systems. Conclusions: Because circular systems must function as simplified ecosystems with producers, decomposers, and consumers interacting across trophic levels, an ecosystem engineering approach will be needed to design and maintain them. This transition demands transdisciplinary collaboration and new ecological insights. Addressing these gaps is essential for realising the full ecological and functional potential of insects in sustainable circular food production.