(258d) A Systems Approach in the Production of Bioplastics from Waste Cooking Oils Using Novel Biotechnology Paths and Process Integration

A systems approach in the production of bioplastics from waste cooking oils using novel biotechnology paths and process integration

Abstract

Waste Cooking Oils (WCO) are a valuable carbon source, but still a harmful waste. State of the art valorization chemistries include transesterification and hydrogenation for biofuels production. However, such approaches are questioned for their environmental impacts (land use, CO2 footprints), cost effectiveness (hydrogen cost and yields) and competitiveness with bio-fuels from larger waste flows at lower costs. Instead, this work advocates a new chemistry (TRL4) that valorizes WCO into high-value bioplastics at high materials yields. The core fermentation chemistry utilizes enzyme oleate hydratase that is expressed into engineered Escherichia coli cells and is used as a whole-cell biocatalyst for the transformation of unsaturated fatty acids into the key building block of 10-Hydroxystearic-Acid (10-HA). The latter is esterified into monomer 10-Hydroxystearic-Acid-Mehthyl-Ester (10-HAME) that is polymerized into poly-10-HAME. To this end, this work face challenges for systems analysis of the novel chemistry, which requires for additional stages at plant integration. The scope of this paper is to scale-up the laboratory validated chemistry and explore opportunities from process integration providing flowsheets developed from scratch.

The process systems analysis is challenged by modelling of (a) the bio-chemistries kinetics and (b) the surrounding processing stages (pre-treatment, cultivation, separations, end-product formulation) as well as by exploring integration schemes for sustainable production. The process diagram begins with pre-treatment of WCOs by saponification-acidification forming soaps that are upgraded to FFAs. Biocatalysis is then performed catalyzing the FFAs conversion into 10-HA. Esterification is next explored to upgrade 10-HA into 10-HAME monomer and residual FFAs into FAME. Next, distillation recovers high purity 10-HAME, biodiesel fuel co-product (FAME) and solvents for recycling. Finally, polymerization is producing the bio-polymer (poly-10- HAME), while unreacted monomers are recovered by distillation. The overall WCOs-to-biopolymer yield is estimated to 77%, while the rest is returned as biodiesel co-product achieving full valorization of carbon source.

The proposed flowsheet is developed and simulated in ASPEN plus, where biocatalysis kinetics are also embedded. The kinetics followed an extended version of Monod combined with models for oxygen inhibition and fermentation temperature and pH effects to address optimization in conditions; also with regard to the operations integrated upstream/downstream biocatalysis. Furthermore, energy integration resulted in 47% less energy use for the integrated system, while techno-economics (CAPEX=$15.5M, OPEX=$ 7.2M, 3000 kg/hr of WCO) ensured economic feasibility of the upcoming chemistry. Finally, LCA investigated the environmental benefits of the biopolymer production (2-3 kg CO2eq/kg_poly) against conventional fossil-based/recycled polymers.

Keywords: Biocatalysis, biopolymer, Escherichia Coli, FFA, WCO.

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