Microplastics in Composting Plants - Challenges to Challenges in Analytical Detection, Quantification of a Case Study Plant, and Electrostatic Separation as a Potential Remediation Approach

Microplastics (MP) are an emerging environmental contaminant, increasingly detected in terrestrial, aquatic, and atmospheric systems. While extensive research has focused on MP in marine environments, their presence in solid waste streams and compost remains understudied. As organic waste processing and composting play a critical role in sustainable waste management and the circular economy, the contamination of compost with MPs poses a challenge to both agricultural applications and environmental health. This dissertation aims to address this gap by developing an analytical methodology for MP detection and quantification in compost, evaluating MP emissions from a municipal composting plant, and investigating electrostatic separation as a potential remediation strategy. To achieve these objectives, a comprehensive multi-step analytical approach was developed. Fourier-transform infrared (FTIR) microscopy and pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) were employed to quantify both MP particle concentrations and polymer mass fractions. Prior to analysis, an optimized sample preparation protocol was established, integrating chemical digestion, density separation, and freeze-thaw processing to effectively isolate MP from complex organic matrices while minimizing polymer degradation and contamination risks. Applying this method to compost samples from a municipal composting facility in Darmstadt-Kranichstein, this study quantified seasonal variations in MP emissions, with higher contamination levels recorded during peak organic waste intake periods (July, October, and November). Results indicated that despite the biological degradation processes inherent in composting, MP persists throughout the treatment cycle, accumulating in the final compost product. The estimated annual output of the investigated facility was 13 billion MP particles, or 1.8 tons of polyethylene, polypropylene, and polystyrene MP entering the environment through compost application through the observe case study plant alone. To explore potential remediation pathways, this dissertation also assessed electrostatic separation as a novel technique for MP removal from compost. A custom-built triboelectric separator prototype was evaluated using a systematic Taguchi experimental design, evaluating the effects of material properties, voltage, and separation field geometries on MP extraction efficiency. Findings demonstrated that optimized triboelectric conditions improved MP separation rates, though significant challenges remain in scaling the technology for industrial applications. Further refinements in separator design, material handling, and process control are necessary to integrate this technology into composting operations. This research contributes to the growing body of knowledge on MP contamination in terrestrial environments, providing an analytical framework and an initial engineering approach for mitigation. The findings highlight the urgent need for improved waste input stream quality management, large scale monitoring, and technological advancements to reduce MP contamination in compost and enhance the sustainability of organic waste management. Future research should focus on the development of standardized MP monitoring protocols, the longterm impact of MP-contaminated compost on soil health, and the integration of MP detection and separation technologies in waste treatment facilities.