Life Cycle Assessment of Direct Ink Writing Additive Manufacturing Process with Hemp-Based Silicone Elastomer Materials

Direct ink writing (DIW) is an emerging additive manufacturing technique capable of processing highly viscous materials, including elastomer composites reinforced with bio-based fillers. However, limited information is available on the environmental impacts associated with DIW processing and the use of natural fiber reinforcements. This study assesses the environmental performance of hemp-silicone elastomer (SE) composites fabricated using DIW through a comparative life cycle assessment (LCA). The analysis compares a composite containing 5 wt.% hemp powder with a neat SE reference specimen under identical printing conditions. Environmental impacts were quantified using the ReCiPe 2016, Cumulative Energy Demand (CED), and IPCC 2021 GWP100 methods. Results show that replacing a portion of the SE with hemp reinforcement reduces environmental impacts, with the ReCiPe endpoint score decreasing from 6.12 mPt for neat SE to 5.95 mPt for the 5 wt.% hemp-SE composites. Similarly, the CED decreased from 2.35 MJ to 2.32 MJ, while greenhouse gas emissions decreased from 0.133 kg CO₂-eq to 0.132 kg CO₂-eq per printed specimen. Sensitivity analysis further indicates that increasing hemp loading to 10 wt.% reduces the ReCiPe score to 5.77 mPt, highlighting the potential environmental benefits of more biobased filler substitution. Overall, the results show that impacts are dominated by SE production, while DIW printing energy contributes only a minor fraction of the total life cycle impacts.