What is river-collected plastic actually made of — and what does that mean for recycling?
In our latest report within the Circular Ocean-bound Plastic (COP) project, we take a closer look at the polymer composition of plastic collected from rivers in the South Baltic region.
The report brings together two case studies from:
🇩🇰 Aarhus River, Denmark
🇵🇱 Motława River, Gdańsk, Poland
Using polymer identification methods such as visual sorting, Resin Identification Codes (RIC), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA), the study examined what types of plastics are present in river-collected ocean-bound plastic — and what this means for realistic recycling pathways.
Some of the key findings:
✔️ River-collected plastic is a highly heterogeneous material stream
✔️ Common consumer polymers such as PP, PE and PET were frequently identified
✔️ The Aarhus case identified six main polymer types, while the Gdańsk case showed an even broader material diversity
✔️ Many items were contaminated, degraded or made from several materials
✔️ Polymer identification alone is not enough — successful recycling depends on sorting, cleaning and separating the material into cleaner, more uniform plastic streams
The report highlights that ocean-bound plastic can contain valuable recyclable fractions, especially polyolefin-rich streams such as PP and PE. However, it is not a uniform or ready-to-use raw material. Its recycling potential depends on proper pre-treatment, including sorting, washing, drying, polymer verification and quality control.
Why it matters:
If river-collected plastic is mixed and processed without proper fractionation, the result can be unstable material quality and reduced performance. But when it is separated into cleaner and more consistent fractions, it can support more realistic recycling pathways — from mechanical recycling to complementary solutions such as chemical or solvent-based recycling for more difficult fractions.
This work provides an important step toward understanding how ocean-bound plastic can move from waste to resource — not by treating it as one uniform stream, but by identifying what it is, how it behaves, and how it should be handled.
A big thank you to the authors Geraldo Mihut and Hatice Tüzün from Plast Center Danmark, Patrycja Jutrzenka Trzebiatowska and Emilia Gontarek-Castro from University of Gdańsk, and all partners in the COP project.
