Life cycle assessment has been widely accepted as an effective tool to assess the environmental impacts of various biofuels in comparison with conventional fuels to quantify the potential benefits in both energy and environmental aspects. This work focused on life cycle assessment of the production of diesel via pyrolysis using two potential feedstocks in Thailand: crude palm oil (CPO) and waste cooking oil (WCO). The system boundary consists of the cultivation, harvesting, transportation, pyrolysis, distillation, blending, and vehicle testing (combustion). Inventory data were collected at the pilot plant of the Center for Fuels and Energy from Biomass of Chulalongkorn University located in Saraburi province. All collected data were input into SimaPro program to evaluate the relevant environmental impacts such as global warming potential, acidification, and ozone depletion based on a functional unit of 1MJ of diesel. For the fuel production, the resulting diesel was blended with conventional diesel at 2, 5, and 20wt% to obtain blended diesel fuels (B2, B5, and B20), respectively. The energy and potential environmental impacts of the diesel fuels produced from two different feedstocks, CPO and WCO, were compared based on cradle-to-grave. The results showed that net energy ratio with its co-products of WCO-based diesel (3.12) was higher than that of CPO-based diesel (2.12). Because of the large amount of energy use for diesel production in pyrolysis and distillation processes, global warming potential was the main environmental impact. From scenarios, it can be concluded that recycling methane from exhaust gas and replacing liquefied petroleum gas by natural gas lead to reduce energy input of 2% and global warming potential impact over 10%. Pyrolysis oil is possible to improve over time on account of the increase of waste palm oil and development of new technologies. Copyright (c) 2015 John Wiley & Sons, Ltd.