Stiffness and Strength-Related Sustainability Assessment of Natural Fibers for Injection Molded Composites

The growing demand for sustainable materials has led to an increased interest in bio-based composites reinforced with natural fibers such as flax, hemp, kenaf, and sisal. This study presents a comparative sustainability assessment of these fibers, highlighting significant differences based on processing methods and fiber characteristics. Life cycle assessment (LCA) results show that flax tow, a by-product of textile flax production, has the lowest environmental impact under economic allocation. In contrast, the impact of sisal fiber varies greatly depending on the processing method: wet separation in Tanzania significantly increases water consumption and methane emissions, while dry extraction methods in Brazil reduce these impacts. An integrated tool has been developed to incorporate material performance metrics into sustainability assessments to improve sustainable material selection, addressing the “LCA paradox.” This property-specific assessment framework enables multidisciplinary collaboration and supports the development of environmentally optimized natural fiber composites for injection molding and other applications.