An important aspect of sustainable food systems is the recycling of residual products, such as primary production waste (crop residues etc.) as well as pre-consumer food waste (e.g. reclaimed bread, fruit and vegetable wastes at food wholesalers or at supermarkets).
Due to legislation, only primary production wastes and pre-consumer food waste is allowed, however, in many places outside the European Union also post-consumer food waste can be utilized. Some of these biodegradable wastes can be used as feed directly to herbivorous fish, while others must be treated before recycling can take place. The possibility to make use of residuals are abundant where there is great access to biological waste, such as in urban areas.
At SLU research is undertaken on how to convert biological waste into forms that can be recycled back into the food chain. The Environmental Engineering group at the Department of Energy and Technology has been working with different technologies for safely recycling plant nutrients in urban waste back to the food chain. One technology investigated is fly larvae composting, in which organic waste is converted into insect biomass that can be used as protein-source in animal feed (Wang and Shelomi 2017) and a treatment residue (frass compost) that can be used as an organic fertilizer (Poveda et al 2021). The most commonly used fly for organic waste treatment, and the fly that the Environmental Engineering group works with, is the black soldier fly (BSF, Hermetia illucens (L.), Diptera: Stratiomyidae). At Ultuna campus, the group has a BSF facility comprising both a mobile fly larvae treatment unit and a fly rearing unit. At this facility, different aspects of the fly larvae composting technology are investigated, in order to find more efficient ways in which organic waste can be converted into product that can be used for food production (pub on BSF research at SLU).
Fly larvae composting. Photo: Cecilia Lelander
Cecilia Lalander, Researcher, Department of Energy and Technology.