Insects to pigs and back : an attributional life cycle assessment

Intensive livestock farming in the European Union requires extensive feed imports, such as soybean meal (SBM), which is associated with negative environmental impacts. Black soldier fly larvae (BSFL) have been identified as an option to substitute SBM in pig diets and as bioconverters of pig manure, contributing to closing the loop between manure production and the provision of protein-rich pig feed (pig–insect–pig nutrient loop). This option is not legally permitted in the European Union (EU) but is practised on other continents and could contribute to closing the EU protein gap. However, its influence on the environmental impact of pig production, compared with permitted substrates such as pig feed used as feed for BSFL, is still unclear. In this study, we conducted an attributional life cycle assessment (LCA) to compare the environmental impacts of pig production using pig feed-fed and pig manure-fed BSFL meals at different SBM substitution levels. Our LCA revealed that pig manure-fed BSFL performed better in 4 out of the 7 selected impact categories, causing a slightly lower impact on GWP than pig feed-fed BSFL. Compared with using SBM, pig feed-fed or pig manure-fed BSFL meal could not improve the environmental impact of pig production, except for land use using pig manure. Considering manure as a burden-free resource or frass as an avoided process could not sufficiently improve the environmental performance of BSFL meal to make it more competitive with SBM in this study. BSFL meal production is a promising approach that utilises nonedible residual side streams, thereby contributing to reduced land use pressure and mitigating feed–food competition in the EU. Further research should focus on improving the BSFL conversion efficiency and protein yield to increase the substitution rate with SBM, which we identified as the key factors for improving the environmental impact of BSFL meal in pigs.