LAUSR

Abstract A comparative cradle-to-gate life cycle assessment (LCA) including raw material acquisitions, rubber production and transportation of synthetic rubber (SBR) and two natural rubbers, namely imported Hevea and US-grown guayule, was conducted to quantify environmental impacts and to identify area(s) of environmental improvement. The use of co-products from the two natural rubbers as a source of energy was explored for their impacts and energy offset potential. Three environmental impact categories-ozone depletion (ODP), global warming (GWP), and acidification potential (AP)-and net energy were evaluated. Results indicated that guayule rubber had a lower ODP impact compared to SBR, and lower GWP and AP impacts compared to Hevea rubber. The Hevea rubber production with biodiesel co-product from seed oil scenario had the highest GWP and AP impacts, whereas guayule rubber production with bio-oil co-product from bagasse had the highest ODP impact. Only the scenario of Hevea rubber production with biodiesel production indicated an overall energy production of 3.25 MJ/kg rubber, whereas all other scenarios indicated a net energy consumption. However, co-products contributed to reduction in total energy consumed in every scenario that was investigated. The most promising guayule rubber scenario among the six examined was that with electricity production from bagasse, as it contributed the least to all three impact categories and yielded the most net energy. Sensitivity analysis on this most promising guayule scenario indicated rubber yield, water use and electricity for water pumping in guayule irrigation as the key parameters that have significant impacts on results.