Environmental performances of the yellow mealworm defatted meal supply chain: a life cycle assessment study focused on different rearing substrates

The increasing demand for sustainable protein sources has positioned edible insect farming as a promising alternative to conventional feed resources. This study explored the implications of Tenebrio molitor meal production, examining how different rearing substrates influence its environmental footprint. Through a site- specific Life Cycle Assessment (LCA), environmental trade-offs were investigated between wheat bran (WB) and dried brewer’s spent grains (BSG) as the main rearing substrates for yellow mealworm production. The dataset was obtained from a pilot-scale trial including 17 and 13 rearing cycles on WB and BSG, respectively, followed by drying and defatting steps. The feed conversion ratio was more efficient using BSG than WB (1.73 vs 2.34 kg of dry feed per kg of fresh larvae, respectively), although it required higher intake of fresh vegetables. WB-reared larvae showed higher dry matter, nearly double the fat content, and similar protein levels compared to BSG-reared larvae. After processing, WB-based meals contained more protein (55 vs 52%) and yielded more extractable fat. The LCA results showed that substrate choice shaped environmental profiles, creating trade-offs across the nine environmental impact categories considered. Compared to the BSG-based diet, the WB-based diet performed significantly better across all impact categories, except for Freshwater Ecotoxicity and Photochemical Ozone Formation (approx. 70 and 7% higher, respectively). The most notable difference was observed in the Climate Change category, where the WB-based diet showed 44 to 80% lower impacts, depending on the BSG allocation approach. Meal yield emerged as the relevant driver in environmental impacts variability, followed by dry and fresh feeds. The rearing phase was the most impactful in six environmental categories, while defatting phase was the main contributor in two categories. Mealworm protein content resulted in a critical factor in determining the feed environmental efficiency, suggesting that future developments should prioritize both nutritional value and process efficiency.