Increased environmental awareness and depletion of resources are driving industry to develop alternative fuels from renewable resources that are environmentally more acceptable. Esters of fatty acids (biodiesel), derived from the transesterification of vegetable oils, have properties similar to components of petroleum-based diesel fuel. Cost has been a major factor slowing the commercialization of biodiesel, Glycerol is the co-product Of the esterification process. In this work the feasibility of the glycerolysis of vegetable oils with crude glycerol derived from the transesterification of vegetable oils and animal fats was studied. Utilization of the crude co-product of the biodiesel process was investigated for improving the overall economy. The transesterification of soybean oil for fuel purposes was optimized. Optimization results are presented. Transesterification of beef tallow produces a mixture of esters which is more concentrated in the saturated fatty acids. Physical properties of these esters are similar to esters of soybean oil. Reaction results and properties for esters of beef tallow are presented. (C) 1996 Elsevier Science Ltd.