Techno-economic analysis of a photobiorefinery for the production of polyhydroxyalkanoates from food waste

This study presents the design and economic evaluation of a photobiorefinery using a mixed culture of purple phototrophic bacteria for the production of polyhydroxyalkanoates (PHAs) from food waste. The process was simulated using SuperPro Designer™. Two downstream processes were assessed: solvent extraction from dry biomass and solvent extraction from wet slurry. The facility had a treatment capacity of 102.4 kt/y and an annual PHA production of 5000 t. Biohydrogen was produced as a by-product at 322 t/y. The NPV was estimated at $38.6 M and $51.3 M for dry and wet extraction. The PHA minimum selling price was 4.81 $/kg and 4.41 $/kg, respectively, with wet extraction significantly improving profitability. However, both designs proved less cost-competitive compared to non-photosynthetic PHA production in the literature, mainly due to low volumetric productivity and high PHA recovery costs. A PHA price below 4 $/kg can be achieved by increasing the PHA yield of photofermentation.