Identification and quantification of microplastics in compost from municipal landfills in Uganda

The expansion of municipal solid waste in Uganda has been increasingly characterized by a surge in plastic waste. Consequently, this has led to severe plastic contamination at composting sites, where the progressive degradation of these materials introduces microplastics (MPs) directly into the compost. This study evaluated the abundance of microplastics in compost produced from 11 composting sites from Municipal Landfills in Uganda. The samples were collected in the dry season of June 2025 over two weeks. The MPs were extracted using an adapted wet peroxide oxidation protocol followed by density separation using saturated zinc chloride. The extracted MPs were analysed under a stereomicroscope with a ZEISS Axiocam 208 color camera connected to Labscope imaging software. The numerical data were analysed using Microsoft Excel (V. 2404) and SPSS (V. 20.0). A one-way ANOVA, followed by Tukey’s HSD while controlling the family-wise error rate at α = 0.05, was conducted to compare abundance across sites. The results indicated that the average abundance of MPs was 2100 ± 409.4 particles/kg for 11 sites. The fibre accounted for 54.98% of the identified MPs across all sites. The results showed the presence of microplastics at all sites, with the Hoima compost site exhibiting the highest abundance. MPs were identified in both primary and secondary forms. The occurrence of secondary MPs likely reflects poor waste management and inadequate waste segregation practices. MPs in compost may enter the food chain, raising concerns for ecosystem health. These findings show the significant MP contamination in compost and highlight the need for improved solid waste management strategies to reduce plastic pollution.