Several environmental and techno-economic assessments highlighted the advantage of placing polystyrene-based materials in a circular loop, from production to waste generation to product refabrication, either following the mechanical or thermochemical routes. This review provides an assortment of promising approaches to solving the dilemma of polystyrene waste. With a focus on upcycling technologies available in the last five years, the review first gives an overview of polystyrene, its chemistry, types, forms, and varied applications. This work presents all the stages that involve polystyrene's cycle of life and the properties that make this product, in mixtures with other polymers, command a demand on the market. The features and mechanical performance of the studied materials with their associated images give an idea of the influence of recycling on the structure. Notably, technological assessments of elucidated approaches are also provided. No single approach can be mentioned as effective per se; hybrid technologies appear to possess the highest potential. Finally, this review correlates the amenability of these polystyrene upcycling methodologies to frontier technologies relating to 3D printing, human space habitation, flow chemistry, vertical farming, and green hydrogen, which may be less intuitive to many.
Keywords: environmental assessment; plastic pollution; polystyrene; recycling; sustainability; waste plastics.