Uncertainty analysis of environmental sustainability of biodiesel production using Thai domestic rare earth oxide solid catalysts

Abstract

Life Cycle Assessment (LCA) is increasingly used as a valuable tool to evaluate and assess the environmental profile of rare earth element (REE) production due to rapid growth in the application of these elements. Rare earth elements including cerium (CeO2), lanthanum (La2O3) and neodymium (Nd2O3) oxides were synthesized by the decomposition of Thai monazite ore using the alkali method following the solvent extraction process. The rare earth oxides (REOs) were utilized as catalysts for biodiesel production of palm oil with methanol. LCA methodology is applied to evaluate the environmental impact of biodiesel production using REO catalysts in terms of the potential for global warming, abiotic deletion, acidification, human toxicity, and eutrophication. This study applied statistical methods to LCA models to analyse uncertainty in the production system. The LCA results show that La2O3 catalyst production has lower environmental impact than the production of the other synthesized catalysts. The environmental impact from cradle-to-gate biodiesel production using the La2O3 catalyst is better than the other options in terms of all impact categories. In cradle-to-grave, the global warming potential of the studied biodiesel process is lower than that of conventional diesel by 1.22–1.67 times due to its lower CO2 emissions. The effect of key environmental benefit obtained from biodiesel production using the REO catalysts is avoidance of CO2 emissions from combustion because of its biogenic origin. Uncertainty analysis of the LCIA showed that the biodiesel–La2O3 has 100% probability of lower environmental values than the biodiesel–CeO2 and biodiesel–Nd2O3. The LCA results are expected to aid the improvement of the environmental performance of REE production and the biodiesel process using the catalysts in Thailand and provide transparent data for government plans.