A thermodynamic analysis of hydrogen production via steam and autothermal reforming of beef tallow has been carried out via the Gibbs free energy minimization method. Equilibrium calculations are performed at atmospheric pressure with a wide range of temperatures (400-1200 degrees C), steam-to-beef tallow ratios (1-15) and oxygen-to-beef tallow ratios (0.0-2.0). The results show that the optimum conditions for steam reforming can be achieved at reforming temperatures between 700 degrees C and 900 degrees C and a steam-to-beef tallow ratio of approximately 5. Optimal operating conditions of T = 700 degrees C and a steam-to-beef tallow ratio of 5 are proposed. With this condition, a hydrogen yield of 170 moles/kg beef tallow and a CO concentration in the synthesis gas of 4.77% with a trace content of CH4 (0.01%) can be obtained without coke formation. The most favorable conditions for hydrogen production from autothermal systems are achieved at the temperature, steam-to-beef tallow ratio and oxygen-to-beef tallow ratio of 600-800 degrees C, 3-5 and 0.0-0.45, respectively. Thermoneutral conditions can be accomplished with an oxygen-to-beef tallow ratio of 0.384-0.427. The recommended conditions are a steam-to-beef tallow ratio of 5, T = 600 degrees C and an oxygen-to-beef tallow ratio of 0.422. Under these conditions, 150 moles H-2/kg beef tallow can be produced with only 2.92% CO and 0.07% CH4 in the synthesis gas. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.