Abstract for presentation at 13th International Symposium on Bioplastics, Biocomposites & Biorefining: Moving towards a Sustainable Bioeconomy, May 19-24, 2014 in Guelph, Ontario.
Life Cycle Assessment Comparison of Bio-based and Petroleum-based Composite Materials
H.I. Moussa and Steven B. Young
A life cycle assessment (LCA) compared composite materials made of switchgrass (SG) reinforced hybrid polybutylene succinate (PBS) and mechanically-equivalent conventional petroleum polypropylene (PP) reinforced with glass fiber (GF). A biodegradable polymer, PBS may be produced from petroleum or bio-based feedstocks. In this case the hybrid material included bio-based succinic acid (SAC) sourced from sorghum and petroleum-based 1,4-butanediol (BDO). The LCA modelled an end-product application based on recent work in Ontario that identified bio-based composite materials as promising for automotive parts.
The cradle-to-gate system boundary was developed for the life cycle inventory and eleven environmental performance indicators were assessed. Detailed primary data on bio-SAC production were provided by a commercial producer operating in the southern United States. Other data were obtained from the pre-existing ecoinvent LCA database and secondary sources. SimaPro software and the TRACI impact assessment method were employed.
Results showed production of the hybrid composite to be lower for seven of the eleven life cycle assessment indicators, including cumulative energy demand by 40%, global warming potential by 35% and ecotoxicity by 45%. The biobased product had higher indicators for acidification and eutrophication, by 14% and 76% respectively. The dominant influences on LCA results were not related directly to bio-based make-up. Rather, the biggest factors in the environmental profile of the composite materials were the sources of heat used in petroleum-processes, the mix of electricity used in processing bio-based chemicals, and the type of reinforcing fibre in the composite. The choice of LCA allocation methodology was influential.
This study helps to identify environmental strengths and weaknesses associated with the production of the hybrid composite, and bio-based materials more generally. It supports the choice of alternative material options for use in the automotive industry, and points to opportunities for future research on feedstocks for industrial composite materials.