Towards sustainable solutions: A review of polystyrene upcycling and degradation techniques

This review comprehensively examines the latest methodologies for upcycling and degrading polystyrene (PS) wastes, a predominant contributor to environmental pollution. PS, known for its extensive use in disposable products and packaging materials, significantly burdens landfills and oceans. We delve into eight major upcycling pathways: composite materials, nanocomposites, hydrothermal, catalytic, photodegradation, enzymatic, microwave-assisted, and mechanical degradation processes, each offering unique advantages for PS waste transformation. Composite and nanocomposite approaches are favored in industrial applications due to their low cost and enhanced material properties. The hydrothermal degradation, a popular method, efficiently converts PS waste into valuable chemicals, albeit at high temperatures, raising cost and environmental concerns. Catalytic degradation emerges as a promising alternative, reducing the need for high temperatures and offering diverse product outputs. Photodegradation, utilizing light energy and low-cost catalysts, presents an economically viable and environmentally friendly option, while enzymatic degradation offers an eco-friendly, gradual breakdown of PS. Microwave-assisted degradation is noted for its high conversion yield, though cost and scalability issues persist. Mechanical degradation, involving physical processes like milling, shows potential for industrial-scale application without the need for intensive energy or chemicals. While each method presents unique advantages and limitations, ongoing research continues to seek more efficient, sustainable, and eco-friendly solutions for minimizing PS waste's environmental impact. This review aims to highlight these technologies, paving the way for further innovation in PS waste management.