Assessing the feasibility of ocean plastic waste as secondary feedstock for the production of base chemicals

Abstract

Plastic pollution in the marine environment is a growing concern, with around 10 % of globally produced plastics ending up in oceans annually. Most ocean plastics are incinerated for energy recovery if harvested, since harvesting remains a key challenge. This study evaluated the feasibility of recovering base chemicals from the polyethylene (PE) and polypropylene (PP) fraction of ocean plastic waste through a single-step olefin production method. The approach employed a micropyrolyzer unit coupled with comprehensive two-dimensional gas chromatography (µP-GC × GC) and dual detectors to analyze gaseous product yields. Elemental and matrix analyses of the waste were performed using CHNS/O elemental analysis, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and Combustion Ion Chromatography (CIC) to identify potentially harmful components. We present here the yields of critical light olefins such as ethylene (13 wt% from PE samples, 9 wt% from PP samples) and propylene (10 wt% from PE samples, 17 wt% from PP samples) at 700 °C. Pyrolysis products detected in PP samples included 24 wt% of branched olefins, whereas 54 wt% of linear olefins were detected in PE samples. The aromatics detected in the samples ranged between 1–3 wt%, with naphthene levels ranging between 4–7 wt%. Furthermore, metal contaminants, such as nickel, silicon, copper, iron, sodium, calcium, and potassium, were detected from the waste via ICP-OES, and chlorine levels via CIC. The results suggest that ocean plastic waste could serve as feedstock for production of light olefins, provided pre- and post-treatment procedures are implemented to mitigate contamination.