Recent findings on environmental sustainability and conversion efficiency of waste-to-protein pathways

Research on the environmental sustainability and nutrient conversion efficiency of bioconversion technologies applied in waste-to-protein pathways is relevant from an early development stage on to identify optimal applications. This review summarizes the recent advances and remaining issues in this emerging research field. While black soldier fly larvae (BSFL) have been intensively studied, various other technologies such as other insect species, bacteria, fungi, microalgae, and worms, are currently underrepresented. Regarding environmental sustainability, which is mainly studied through life cycle assessment, the choice of functional unit is highly relevant for overall outcomes and comparability. Additionally, decisions on the burden of input materials and process substitution strongly influence the overall results. Substrates composed of different residual biomass streams strongly influence the process efficiency of BSFL, which is commonly expressed in feed conversion and protein efficiency rates. In contrast, residual biomass type, protein content, and amino acid profile are of minor importance for the protein composition of BSFL. Overall, the large variability of residual biomass types and bioconversion technologies necessitates better methodological alignment to produce comparable results across studies that collectively support decision-making. •Summary of recent findings on the sustainability of bioconversion technologies.•Comprehensive overview on crude protein and amino acid content in residual biomass.•Feed applications of black soldier fly larvae BSFL dominate bioconversion research.•Effect of residual biomass on efficiency, protein, and amino acid content of BSFL.•Functional unit, process substitution, and input material burdens are crucial in LCA.