The objective of this work was to assess the environmental impacts of producing biodiesel by heterogeneous and homogeneous catalysis. The raw material for the process was the waste cooking oil (WCO) generated at 27 food courts of Autonomous University of the State of Mexico. The study was conducted by applying Life Cycle Assessment methodology and the environmental impacts were calculated with the SimaPro 9.1.0.11 PhD software with the Ecoinvent database. The method was CML-IA base line

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... 25. The assessed impact categories were: Abiotic Depletion Potential (ADP, elements), Abiotic Depletion Potential (ADP, fossil fuels), Global Warming Potential (100 years) (GWP), Ozone Layer Depletion (ODP), Human Toxicity (HT), Freshwater Aquatic Ecotoxicity (FWAE), Marine Aquatic Ecotoxicity (MAE), Terrestrial Ecotoxicity (TE), Photochemical Oxidation (PO), Acidification (A) and Eutrophication (E). In addition, end point environmental indicators were also calculated (Ecosystems Quality, Human Health Damage and Resources Availability) by the method ReCiPe 2016 Endpoint (H) V1.04 / World (2010) H/A. The system boundary enclosed three main stages, WCO collection, pre-treatment and reaction (to produce biodiesel). It was concluded that the reaction stage is the one with the highest environmental impact. In this sense, the highest impact categories were ADP (fossil fuels) (105.56 MJ), GWP (8.91 kg CO2 eq) and MAE (2387.89 kg 1, 4-DB eq). Nevertheless, it was also found that the GWP for the heterogeneous process is 82.52 % lower than that calculated for the homogeneous process. In addition, the human health damage of the homogeneous process is 1.77 points and is higher than the observed with the heterogeneous process.