We are excited to share the new research on macro- and microplastics in composts from municipal solid waste industrial composting plants in Uganda, highlighting a critical and underexplored pathway for plastic contamination in Sub-Saharan Africa.
Organic fertilizers are vital for sustainable agriculture but can unintentionally introduce macro- and microplastics into the environment, especially in regions with limited biowaste source separation.
In this study, we assessed macro- and microplastic contamination in composts from two composting facilities in Uganda over several months. Our results showed heavy plastic contamination, with total microplastics exceeding previous literature values, averaging 49,000–62,000 items/kg dry weight.
Key findings:
The 0.212–0.6 mm fraction showed the highest microplastic contamination.
Contamination levels depended on pile turning, feedstock contamination, and local population density.
Polyethylene and polypropylene were the dominant polymers, with fragments and fibers as the most common shapes.
Application of these composts to soil could lead to macroplastic loads of 2.0–106.7 kg/ha and microplastic loads of 2.9×10⁸ – 2.4×10⁹ items/ha at recommended compost application rates.
This study highlights the need for improved source separation and pre-treatment of biowaste to mitigate environmental plastic contamination while enabling safe organic waste recycling in urbanising regions.

Authors:
Francis Okori, Therese Schwarzböck, Sara Neuburg, Allan John Komakech, Jakob Lederer, Johann Fellner

Read more here, opens an external URL in a new window