From waste to wealth: upcycling of plastic and lignocellulosic wastes to PHAs

Over the past fifty years, environmental pollution from non‐biodegradable petroleum‐based plastics has worsened and become a real threat to marine life and human health. Thus, solutions to plastic pollution are urgently needed for reducing the contamination of soil and water resources. Developing alternative biodegradable plastics derived from renewable resources is an emerging research focus that can alleviate the accumulation of plastic waste in the environment. Polyhydroxyalkanoates (PHAs) are promising biodegradable biopolymers for replacing plastics derived from fossil fuel resources. The large scale commercialization of PHAs is not yet feasible due to their high production cost, which is largely associated with the feedstock cost. Using readily available carbon sources from underutilized lignocellulosic biomass and non‐recyclable plastic wastes allows for feedstock cost reduction and for the production of value‐added PHA bioplastics, and this significantly contributes to the solution of plastic pollution in a circular economy approach. This review highlights the recent efforts for valorizing plastic and lignocellulosic wastes to produce PHAs through a biotechnological approach using a two‐step methodology. In the first step, plastic (PE, PP, PS, PET) and lignocellulosic (cellulose, hemicellulose, lignin) macromolecules are depolymerized and converted to smaller fragments/monomers, which will be utilized for the subsequent bio‐upcycling step via fermentation process to produce PHAs. Pyrolyzed plastic wastes and hydrolysates from lignocellulosic waste biomass will facilitate the transition from linear to circular economy, lower the production cost of PHAs, and contribute to the solution of plastic pollution in a practical, economical, and sustainable approach. © 2021 Society of Chemical Industry (SCI).