  A waste-to-protein system that integrates a range of waste-to-protein
upgrading technologies has the potential to converge innovations on zero-waste
and protein security to ensure a sustainable protein future. We present a
global overview of food-safe and feed-safe waste resource potential and
technologies to sort and transform such waste streams with compositional
quality characteristics into food-grade or feed-grade protein. The identified
streams are rich in carbon and nutrients and absent of pathogens and hazardous
contaminants, including food waste streams, lignocellulosic waste from
agricultural residues and forestry, and contaminant-free waste from the food
and drink industry. A wide range of chemical, physical, and biological
treatments can be applied to extract nutrients and convert waste-carbon to
fermentable sugars or other platform chemicals for subsequent conversion to
protein. Our quantitative analyses suggest that the waste-to-protein system has
the potential to maximise recovery of various low-value resources and catalyse
the transformative solutions toward a sustainable protein future. However,
novel protein regulation processes remain expensive and resource intensive in
many countries, with protracted timelines for approval. This poses a
significant barrier to market expansion, despite accelerated research and
development in waste-to-protein technologies and novel protein sources. Thus,
the waste-to-protein system is an important initiative to promote metabolic
health across the lifespan and tackle the global hunger crisis.
