Introduction
Aquaculture is one of the fastest growing food production sectors, with feed production representing a major contributor to its environmental impact. The reliance on fishmeal and other conventional protein sources raises concerns regarding resource use and long-term sustainability. In this context, insect-derived ingredients have emerged as promising alternatives, as they can valorise organic side-streams while reducing dependence on traditional feed resources (Gasco et al., 2023).
This study combines results from the newRIFF and HIGA projects to evaluate the environmental performance of using Hermetia illucens (HI) meal in diets for rainbow trout (Oncorhynchus mykiss) through a Life Cycle Assessment (LCA) approach.
Materials and methods
In the newRIFF project, a benchmark LCA was performed on a conventional Italian trout farm using a cradle-to-farm gate approach and 1 t of live fish as functional unit. Primary data were collected from an industrial-scale trout farm and included feed use, energy consumption, oxygen use and infrastructure. Emissions to water were estimated as secondary data through mass balance modelling. Additionally, alternative feed scenarios were formulated by partially replacing fishmeal (5% and 10%) with HI meal produced from locally available agri-food by-products.
Within the HIGA project, a feeding trial was conducted using six experimental diets containing 10% HI meal. Four diets included increasing levels of chitinase (0–0.75%), while two diets used thermally pre-treated HI meal, with or without enzyme addition A total of 480 juvenile trout (initial average weight of 16 g) were reared in 24 tanks over 74 days, reaching three times their initial body weight at the end of the trial. Growth performance, feed intake and feed conversion ratio (FCR) were monitored and used as primary data to build the Life Cycle Inventory (LCI). The LCA was applied using a cradle-to-farm gate approach with 1 kg of trout weight gain as functional unit.
Environmental performance of feeds was estimated based on ingredient composition and literature datasets (e.g., Ecoinvent), while HI meal production was modelled using a combination of primary data (substrate composition and rearing efficiency) and secondary data for energy use and emissions.
Results and discussion
The LCA of the conventional trout farm showed a climate change impact of approximately 1,980 kg CO2 eq t-1 of live fish, in line with literature values for flow-through systems. Feed production was identified as the main hotspot, contributing around 50% of the climate change impact and up to 90% in some impact categories such as land use.
The comparison of feeds in the newRIFF framework showed differences generally within ±10% across all impact categories. Diets including insect meal (5–10%) showed an increase in climate change impact ranging from +3% to +8% and in fossil resource use up to +10%, while reductions were observed for Net Primary Production Use (���10% for 5% inclusion and ���20% for 10% inclusion).
When integrating the HIGA experimental parameters into the LCA model, the similar growth performance observed across diets resulted in comparable environmental impacts per kg of fish produced. In particular, differences in FCR within the observed range (0.91–0.98) translated into variations in climate change impact of approximately ���5% to +6% compared to the baseline diet scenario (standard insect meal without chitinase). Lower FCR values were associated with reduced feed demand and consequently lower impacts.
Overall, the partial replacement of fishmeal with HI meal, under equivalent productive performance conditions, resulted in stable or moderately improved environmental performances. Benefits were mainly associated with resource-related indicators and circularity aspects, especially when low-impact side-streams were used as insect substrates. However, energy use during insect production remains a key factor influencing climate change impact.
ConclusionsThis study provides integrated insights into the use of insect meal in aquafeeds by combining experimental feeding trials and LCA-based modelling. Results confirm that insect meal can be included in trout diets without compromising growth performance, while offering environmental benefits under specific conditions.
However, current impacts are strongly influenced by the scale and efficiency of insect production systems. Further optimisation is needed to fully exploit the potential of this circular approach. Within the newRIFF project, feeding trials will be carried out in the coming months and will be tested through growth trials to validate these findings at full system level and enable a complete LCA of the fish production phase.
AcknowledgmentThis work was supported by the newRIFF project (Fondazione Cariplo) and the HIGA project. The newRIFF project is supported within the call Circular Economy – Promoting research for a sustainable future – 2022 - funded by Fondazione Cariplo. The HiGa project is supported within the Green Era Hub call by the Green Development and Demonstration Programme, GUDP, under the Italian Ministry of Agriculture, Food Sovereignty and Forests (MASAF) (CUP: D23C23000570005).
References
Gasco, L., Renna, M., Bellezza Oddon, S., Rezaei Far, A., Naser El Deen, S., Veldkamp, T. 2023. Insect meals in a circular economy and applications in monogastric diets, Animal Frontiers, 13(4): 81–90. https://doi.org/10.1093/af/vfad0164