Environmental and cost analysis for polyhydroxyalkanoate production from glycerol byproduct: A case study from integrated soap and biodiesel plants

This work focuses on the sustainable integrated production of bioplastic, also known as Polyhydroxyalkanoate (PHA). Glycerol by-product generates from soap production and biodiesel production plant were utilized as the feedstock to overcome the current drawbacks in PHA production. Different purities of glycerol (i.e,16 wt%, 40 wt% and 60 wt%) were undergone pretreatment steps such as acidification, filtration, evaporation, hexane washing, methanol recovery and ion exchange to obtain 98 wt% of glycerol prior to PHA production. Capital of equipment purchase was estimated by using correlation and graphical method. It was found that, cost of chemical purchase for pretreatment has a high impact on the overall economy of the production. Economic feasibility of all proposed process routes was assessed by calculating the Payback period. Lastly, environmental impact of each pretreatment method was assessed by conducting an LCA by setting the annual target of 750,000 kg as the functional unit. Global warming potential, acidification potential and ecotoxicity of freshwater were chosen as the impact categories in this process. It was found that route 4 with feedstock purity of 60 wt% CG and pretreatment steps of methanol recovery, neutralization, centrifugation, water evaporation and distillation was found to be the most economically and environmentally sustainable among the assessed process routes.