Preliminary Investigations on the Performance and Characterization of Municipal Wastewater Sludge-Derived Biochar–Plastic Composites: A Resource-Oriented Solution to Sludge and Plastic Waste

Abstract

Plastic waste has emerged as a pressing global concern, with a significant portion of it being discarded into the environment. Concurrently, wastewater sludge has also become an environmental threat due to the potential contaminants in it. In response, in this study, we took a novel approach that focused on the development of a sustainable composite matrix made from sludge-derived biochar and plastic. The physical, mechanical, and mineralogical properties of plastic–biochar (PB) composite matrices, including water absorption capacity (WAC), bulk density, wet transverse strength, and thermal conductivity, were assessed. The WAC increased with a higher biochar content in the matrix, ranging from 1.39% to 2.40%. The bulk density increased from 0.66 to 0.94 g/cc with increasing biochar content. The wet transverse strength exceeded the minimum requirement of 3 MPa in all tested samples, demonstrating the matrices’ robustness. The thermal conductivity values ranged from 0.2 to 0.3 W/m · K, indicating the matrices’ potential as insulating materials. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of the biochar and its bonding with polyethylene terephthalate (PET) in the composite matrices. X-ray diffraction (XRD) analysis revealed shifts in the peak patterns with varying biochar content, demonstrating alterations in the crystallinity. Field emission scanning electron microscopy (FE-SEM) micrographs illustrated the interactions between the biochar and the PET, highlighting their distinctive attributes. A cost analysis showed that the PB composite matrices were cheaper than traditional cement concrete tiles. Finally, the potential of PB composite matrices to sequester carbon was assessed, which could contribute to reducing the carbon footprint of construction. This study demonstrated the potential of BP composite matrices as sustainable and cost-effective materials with satisfactory physical properties and the ability to reduce environmental impact.