The apparent digestible energy (DE) value of crude glycerol, a co-product of biodiesel production, was determined in two studies conducted at the Iowa State University Swine Nutrition Research Farm, Ames, IA. In the first study, 24 barrows with an average BW of 11.0 ± 0.5 kg were fed 376 g/d of a basal diet combined with 0, 19, 38, or 75 g/d of crude glycerol. In the second study, 23 gilts with an average BW of 109.6 ± 5.5 kg were fed 2.29 kg/d of a basal diet combined with 0, 115, 229, or 458 g/d of crude glycerol. Crude glycerol (86.95% glycerol) from AG Processing Inc., Sergeant Bluff, IA was used in this experiment. Dietary treatments for each study were 0, 5, 10, or 20% glycerol addition to basal diets. Each diet was fed to six pigs in individual metabolism stalls. Pigs were fed twice daily. Following a 10 d adjustment period, total collection of feces occurred. Feces were collected following each meal and stored at 0°C. Gross energy (GE) values of each dietary regime and feces from each pig were determined by adiabatic bomb calorimetry. Apparent DE value of crude glycerol was calculated by subtracting the energy in feces from the GE of the feed. Daily DE intake was regressed against total intake for starter and market pigs. The slope of the regression line is reported as the DE of crude glycerol. In starter pigs the DE of crude glycerol is 3386 ± 149 kcal/kg, in market pigs the DE of crude glycerol is 3772 ± 108 kcal/kg. These values are not different (P = 0.02) from the GE of the crude glycerol examined. For the sample examined, the GE of crude glycerol is 3625 ± 26 kcal/kg. Crude glycerol may be a source of energy for growing pigs.