DUAL-STREAM BIOREFINERIES: SUSTAINABLE PROTEIN BIOPLASTICS FROM AGRICULTURAL WASTE

Abstract

How to sustainably utilize agricultural waste is a global challenge in the transition to a circular bioeconomy. We introduce a unique biorefinery concept that simultaneously generates protein-enriched biomass suitable for food and feed, along with PHAs (polyhydroxyalkanoates) bioplastics for environmentally friendly packaging. In contrast to mono-product biorefineries, our approach integrates thermochemical and enzymatic pretreatments to bioprocess wheat straw, corn stover, and rice husks. Engineered strains of Escherichia coli and Ralstonia eutropha (a chemoautotrophic bacterium capable of oxidizing hydrogen and accumulating P(3HB) within its cell, using fructose or CO2 as the sole carbon source) perform the subsequent fermentation. This approach allows the simultaneous production of high-value protein and bioplastics from one substrate. We obtained protein recovery yields reaching 21.4% (dry weight), with PHA synthesis efficiency exceeding 78%. Biochemical analysis confirmed favorable amino acid profiles and material properties. LCA (Life Cycle Assessment) and TEA (Techno-Economic Analysis) attributed a reduction of 43% GHG emissions and over 50% improvement in energy efficiency relative to fossil-based systems. In addition, preliminary scale-up simulations suggest industrial viability with low retrofit needs. This dual-output system transforms agricultural waste into a versatile feedstock stream for biomanufacturing, providing important co-benefits of waste reduction, improved food security, and climate change mitigation. Its flexible integration potential is especially interesting for low- and middle-income countries that are looking for resilient, circular, and inclusive industrial policies.