Techno-economic Analysis on An Industrial-scale Production System of Biodegradable Plastics from Cheese By-products by Haloferax mediterranei

Abstract

<b><sc>Abstract.</sc></b> <b>Polyhydroxyalkanoates (PHA) are a family of biodegradable plastics used as an environmentally friendly alternative for conventional plastics in various applications. PHA can be produced through microbial fermentation of renewable feedstocks, including low-cost byproducts and waste streams from food processing plants. In this study, an industrial-scale PHA production system using cheese byproducts as feedstock was designed and analyzed for the material flows and economics. Haloferax mediterranei was utilized as the PHA-producer. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a type of high-quality PHA, was the target product. Byproduct streams from a local cheese plant, with an input of 168.7 metric ton/day (MT/day) lactose, were used as the feedstock. SuperPro Designer was used as the software for the process design and economic modeling. Three scenarios with different processes for the treatments of used enzyme and spent medium were investigated and the major factors that influence the overall economics were identified. The simulated system produces 9700 MT/year PHBV with assumed PHA yield of 0.2 g PHBV/g lactose and an overall process efficiency of 87%. The breakeven price of PHA was found to be sensitive to the lactose price. The scenario with enzyme reuse and spent medium recycling achieved the lowest breakeven price among others, which can be less than 4 $/kg PHA based on the delactosed permeate (DLP) unit price. The study suggests utilizing dairy derived feedstocks has the potential to make PHA competitive in the bioplastic market, which could be beneficial to both dairy and bioplastic industries. </b>