Life cycle assessment was applied to evaluate the environmental impact of cerium oxide (CeO2) production systems from monazite ore using integrating and excluding liquid-liquid extraction methods. It is a heterogeneous rare earths oxides catalyst which can be utilized for catalysed transesterification to produce biodiesel. The impact assessment methodology used for characterization was the midpoint CML baseline method in terms the potentials of abiotic depletion, global warming, ozone layer depletion, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, terrestrial ecotoxicity, photochemical oxidation, acidification, and eutrophication. The Eco-indicator 99 method was performed an endpoint approach: human health, ecosystem quality, and resources. The data on process was available from a field study conducted in Thailand Institute of Nuclear Technology and applied into SimaPro 8.2.5. The LCA results showed that the removal of solvent extraction process can achievable the higher purity of CeO2 concentration and presented the most attractive process for cerium oxide from monazite ore in term of environmental impact assessment. Approximately 35-85% of the total environmental values and 79% of the total damage scores to human health and resources occurred during the separation step with integrating liquid-liquid extraction. The digestion step is the primary cause of the characterization impacts (30-56% of the total impacts) and damage to human health, ecosystem quality, and resources (37% of the total scores).