Investigating plastic in organic fertilizers: A 2-year comparative study.

Area of Science:

• Environmental Science
• Soil Science
• Materials Science

Background:

• Organic fertilizers (compost, sewage sludge) are significant sources of microplastic contamination in agricultural soils.
• Potential risks include groundwater leaching, soil organism ingestion, and plant uptake, impacting the food chain.
• Current understanding of plastic quantity, polymer type, and particle size distribution from different fertilizers is insufficient.

Purpose of the Study:

• To investigate and quantify plastic contamination in seven types of organic fertilizers over two years.
• To analyze polymer composition, particle size distribution, and surface area of foreign matter.
• To contextualize plastic loads per square meter based on application rates.

Main Methods:

• Manual analysis of visually isolated foreign particles from fertilizer piles.
• Identification of polymers using Attenuated Total Reflectance with Fourier Transform Infrared Spectroscopy (ATR-FTIR) and siMPle.
• Calculation of plastic loads per square meter, considering pile surface area and application rates.

Main Results:

• Plastics constituted 82% of the identified foreign substances across analyzed fertilizers.
• Biowaste compost in 2023 showed the highest plastic mass (1.51 g/m²), while green waste compost and sewage sludge had lower levels.
• Significant year-to-year variability in contamination levels was observed, complicating definitive trend conclusions.

Conclusions:

• The quality of input materials and processing significantly influences foreign matter content in organic fertilizers.
• Further long-term research is crucial for establishing surveillance guidelines and regulatory frameworks for plastic contamination.
• Stricter monitoring protocols are necessary to mitigate the environmental impact of plastics in organic fertilizers.