The sustainability of recycled polylactic acid via fused filament fabrication: environmental impacts across cycles

Recycling material for manufacturing new products is a promising approach toward sustainability and circular economy. Recycled polylactic acid (PLA), a thermoplastic, lightweight, and biodegradable polymer, is desirable for sustainable production in the automotive industry, medical applications, and aerospace industry specifically for non-load-bearing components. Developing PLA-based products through additive manufacturing (AM), particularly fused filament fabrication (FFF), has advantages over conventional manufacturing methods such reduced material waste, lower cost, and rapid prototyping. However, the environmental impact of recycled PLA through its entire life cycle has not been assessed yet. In this study, we investigated the cradle-to-cradle life cycle assessment (LCA) of PLA through five mechanical recycling cycles. The functional unit is 1 kg of PLA fabricated into ASTM D638 Type 1 specimens through FFF and recycled in a three-step approach: (1) mechanical grinding, (2) extrusion, and (3) FFF at the laboratory scale. Impact World + methodology is employed to calculate two midpoint indicators: climate change and fossil and nuclear energy, and one endpoint indicator: ecosystem quality. Our research results show an inverse relationship between the number of recycling cycles and environmental impact, suggesting a reduction in environmental burden with increased recycling. The highest impact for climate change in the fifth recycling cycle is associated with power consumption of about 58% followed by 36% for PLA production and 6% for transportation.