The valorization of industrial waste is a key strategy for advancing sustainable materials in additive manufacturing. This study investigates the incorporation of granite sludge, a by-product of quarrying operations, into a thermoplastic matrix to produce eco-efficient composite pellets for extrusion-based 3D printing. After drying and sieving, the sludge was melt-blended with polylactic acid (PLA) at filler ratios of 25 and 50 wt.%. The resulting composites were processed using a pellet-fed 3D printer to fabricate tensile specimens. Mechanical testing revealed an approximately 160% increase in Young’s modulus for the 50 wt.% granite composite compared to neat PLA, indicating a substantial stiffness enhancement, while tensile strength and ductility decreased, consistent with filler-induced embrittlement. A preliminary Life Cycle Assessment (LCA) was conducted to evaluate the environmental implications of substituting virgin polymer with granite sludge. Results indicate that although the overall impact reductions are modest, incorporating granite sludge into PLA-based composites supports circular economy principles by diverting waste from landfill and reducing reliance on virgin materials. However, the energy required for sludge processing, particularly drying, plays a decisive role in shaping environmental trade-offs, often offsetting the benefits of polymer substitution. Overall, the study demonstrates the technical feasibility of processing granite-filled PLA composites into test specimens via FPF, while emphasizing the need for process optimization to improve environmental performance. The findings highlight the potential of locally sourced industrial by-products as sustainable fillers in polymer processing, contributing to the development of circular, resource-efficient material systems for additive manufacturing and related sectors.
Netto et al. (Thu,) studied this question.