Sustainable management of beach litter: densimetric and tribo-electrostatic separation technologies for material recovery

Beach Litter represents a significant environmental and economic issue for many coastal areas in Italy, characterized by a mix of natural materials, such as Posidonia leaves, and anthropogenic fractions like plastics, wood, and metals. Posidonia, an endemic plant of the Mediterranean, plays a crucial ecological role by protecting coastlines from erosion and contributing to marine biodiversity. However, although these biomass accumulations are ecologically important, their presence, particularly in tourist areas, can become problematic due to degradation processes and the mixing with anthropogenic waste. The management of such accumulations is regulated by Ministry of the Environment Circular n. 8838/2019, which suggests several strategies, ranging from leaving them in place to removing them for recycling, while acknowledging that their treatment and removal involve significant economic costs. My current research focuses on designing sustainable and technologically advanced management systems for the recovery and reuse of stranded materials, with the aim of minimizing environmental impacts and promoting the circular economy. In this context, my research project aims to address the issue of Posidonia beach accumulations by exploring the technical feasibility of an innovative circular management system. The proposed system is based on waste treatment through a mobile recovery plant and recycling chains, which will enable the separation of natural organic fractions from inorganic natural and anthropogenic ones. Specifically, the organic fraction, if primarily composed of Posidonia, could be reused on-site to protect fragile coastlines. If the Posidonia is not suitable for this use, it will be managed in external facilities for material recovery (through the production of ecodesign products based on traditional binders, Posidonia leaves, and sediments) and energy recovery (through anaerobic digestion for biogas production). The treated sand could be reallocated to the beach after characterization, while selected anthropogenic inorganic fractions could be used as secondary raw materials (SRM) in new production cycles. Experimental activities have been initiated at the Environmental Technologies Laboratory of the Polytechnic University of Bari. Integrated characterization of beach waste from Mola di Bari and Fasano has been performed, including measurements of moisture, ash, organic matter content, pH, conductivity, and redox potential. For each sample, the percentage composition of the three main fractions (natural organic, natural mineralogical, and anthropogenic) was determined. Granulometric analysis of the natural organic fraction assessed the physical characteristics of the plant material. Additionally, ecological characterization of the plant species was conducted to identify ecosystem compositions and distinguish the species present. Posidonia leaves were analyzed using Fourier-transform infrared (FTIR) spectroscopy in Attenuated Total Reflectance (ATR) mode. Ecotoxicological analysis of Posidonia and sediment samples through bioassays showed values exceeding the inhibition limit for the germination index of Lepidium sativum, indicating good ecological potential. As for the anthropogenic fraction, a manual material analysis was performed, distinguishing waste larger and smaller than 2 cm. The conducted operations allowed for the classification of stranded waste piles through a multidisciplinary approach, considering the type of natural material present, the amount of anthropogenic waste, and the physical characteristics of each material fraction. Furthermore, densimetric separation tests were initiated to select sand from Posidonia.