<p>Processing underutilized bioresidues (for example, straw, manure and wood) into novel food and feed products such as fungi-based proteins, microbial proteins and insects represents ‘waste-to-nutrition’ pathways that are increasingly promoted to reduce the environmental impacts of food systems, including pressures on climate change, land and water resources. However, the actual environmental mitigation potential of this strategy depends on future technological advancements and contextual factors, which remain uncertain. Here we compare five conventional bioresidue valorization pathways with insect farming, microbial conversion and protein extraction by simulating their life-cycle assessment across 8,820 combinations of future process efficiencies, 9 food and energy systems scenarios and 11 representative bioresidues across France. Overall, processing bioresidues into novel ingredients is competitive only in certain conditions. These include access to decarbonized energy, substantial technological advancements and scenarios where novel ingredients replace meat rather than animal feed. The microbial conversion of woody residues, manure and sludge into feed will constitute the more sustainable valorization strategy only in contexts where current demand for animal-based food is maintained. However, the sustainability of this scenario must still be further appraised in terms of scaling these systems to a broader level.</p>