Polyhydroxyalkanoate (PHA) Production From Plastic Waste

Due to its extremely long decomposition time and harm to natural environments, the accumulation of plastic waste has become a critical issue that has worsened over the past decades; plastic production has increased over 200x since 1950. Despite growing awareness of the plastic pollution problem, the vast majority of plastic still ends up in landfills; furthermore, this plastic takes >500 years to degrade and the remaining microplastics can be toxic to animals and the environment alike. Fast-degrading, sustainably sourced biodegradable plastics are becoming an increasingly popular alternative to standard thermoplastics. One of the most promising biodegradable plastics is polyhydroxyalkanoates (PHA) – the product produced from this process – which has enhanced thermal stability compared to bioplastic alternatives such as polylactic acid (PLA). The market for PHA has grown significantly over the past few years and the market currently has a promising CAGR of 15.9%. This two step process aims to address the critical plastic pollution problem from two fronts: 1) the feed stream for this process is mixed consumer plastic waste, so this process will actively reduce the amount of thermoplastic present in the environment; 2) the product is a biodegradable plastic. This process converts 11,000 tons of mixed plastic waste (polystyrene, high density polyethylene, and polyethylene terephthalate) to 324.457 tons of PHA per annum. The process consists of two distinct steps: 1) chemical oxidation and depolymerization of plastic polymers and 2) bioconversion of organic monomers to PHA (and subsequent product isolation). Currently, this process has a Net Present Value (NPV) of -$178 million with an ROI of -22.61%. As it stands, this process is not profitable, but this is still a promising concept and the methods of production could be refined with more lab scale studies focused on cheaper catalysts and increasing PHA yield from the bioreaction.