Phd in ENVIRONMENTAL AND HYDRAULIC ENGINEERING

Thesis title: Monitoring degradation reactions of bioplastics. Mechanisms and environmental implications.

Bioplastics are emerging as an alternative to traditional fossil-based plastics with the aim of addressing the stringent issue of plastic pollution. The biodegradability of these materials could play a strategic role in the transition to a circular economy, while leading to the decarbonization of a whole industrial sector. The possibility of applying biological endof- life treatment using the existing waste collection infrastructures and biological aerobic/anaerobic treatment facilities is one of the major advantages. However, there are many challenges related to the assessment of the actual biodegradability of bioplastics and to the combined management of bioplastics and biowaste. The present work addresses from different perspectives some of the major scientific issues that are currently regarded as open questions on the topic, with the aim of understanding the potential benefits and drawbacks associated to an extensive use of bioplastic products. The biodegradation of commercial single-use bioplastic items was investigated under different anaerobic and aerobic conditions. In a first part of the investigation, the evaluation of the anaerobic degradation process oriented towards the valorization of bioplastic as the sole substrate was carried out. Then, the same products were codigested with synthetic food waste in an attempt to simulate the real treatment conditions of an anaerobic digester. For both of the experimental campaigns a number of combinations of operating conditions was tested and correlated to the process results. Moreover, the assessment of the biological process was complemented with advanced chemical, thermal and microstructural characterization of the feedstock materials and of the final digestates. A subsequent experimental campaign was then carried out under aerobic conditions in compost and soil environments both on individual bioplastic items and on digestate samples derived from the anaerobic experiments. The final aim of the research work was to derive an in-depth analysis of the behavior of single-use bioplastic products at their end of life and propose a systematic assessment strategy of commercial bioplastic degradability.