Life Cycle Assessment of Hydrogen Storage Systems for Trucks An assessment of environmental impacts and recycling flows of carbon fiber

Sammanfattning

This thesis aims to extend the knowledge base regarding the life cycle environmental impacts of different hydrogen storage system (HSS) alternatives for fuel cell electric vehicles (FCEV). A Compressed Hydrogen (CH2) system was investigated and then used as the baseline for a comparison with a Liquid Hydrogen (LH2) storage system, and a Cryo-Compressed Hydrogen (CCH2) storage system. Further assessment was also made of the End-of-Life stage of CH2 system to capture how impacts alter if its most concerning material, Carbon Fiber Reinforced Polymer (CFRP), is recycled. The study was conducted in collaboration with Volvo Group. As a result, two Life Cycle Assessment (LCA) case studies were conducted: one comparative of all HSSs; and one extended investigating aspects of CFRP recycling for the CH2 system. All HSS alternatives were modeled with a storage capacity of 80 kg of useable hydrogen. In both the studies, the life cycle processes were modeled in OpenLCA. The comparative LCA was modeled based on the cut- off approach, whereas the extended study credited recycling outputs back to the studied system. The LCIA results of the CH2 system show high production related impacts, predominantly caused by the carbon fiber production. For global warming it represents almost 57% of the total impact. However, recycling CFRP shows potential to significantly reduce this life cycle impact. When comparing the CH2 system to the LH2 and CCH2 systems, both latter cause higher impacts in three out of four impact categories. This is mainly due to the use phase emissions, specifically due to the high energy demand of liquefying hydrogen compared to compressing it. Still, for global warming, the CH2 system causes a slightly higher impact. Further research should be conducted for more detailed insights, especially regarding the utilization rate of the refueling infrastructure in the use phase. Due to the high impact of carbon fiber production, it is also proposed to evaluate a bio-based carbon fiber precursor input and study the life cycle impacts of long-term cyclic use of recycled carbon fibers.