Microplastic pollution during organic compost production: Occurrence and ecological risks

Area of Science:

• Environmental Science
• Waste Management
• Polymer Science

Background:

• Mechanical and biological treatments (MBT) convert organic waste to compost, a common waste management practice.
• The fate and impact of microplastics (MPs) during composting are not well understood.
• Understanding MP transformation is crucial for assessing environmental risks.

Purpose of the Study:

• To investigate microplastic levels and characteristics during composting.
• To assess the ecological risks associated with MPs in compost.
• To evaluate the effectiveness of composting in MP reduction.

Main Methods:

• Collected 54 samples from incoming waste (IW) to refined compost (RC).
• Used stereo microscopy for initial MP identification.
• Employed Fourier-transform infrared spectroscopy (FTIR) and micro-Raman spectroscopy for polymer identification.

Main Results:

• Microplastic concentration increased from 22,800 N/kg in IW to 75,928 N/kg in RC.
• Fibers were the most abundant MP type; black MPs constituted 50% of particles.
• Polyethylene (PE) and PET were dominant in IW, while PS and PET were prevalent in RC.
• Ecological risk assessment indicated a Polymer Hazard Index (PHI) of 491.7 (Risk Level III) and a Pollution Load Index (PLI) of 59 (Level IV - extremely high).

Conclusions:

• Composting significantly increases microplastic abundance and alters polymer composition.
• The process poses a high ecological risk due to MP accumulation.
• Effective pre-treatment strategies are needed to reduce MPs in waste feedstock.