The energy value of crude glycerin (CG) from a palm oil biodiesel facility was determined in growing pigs to estimate its digestible energy (DE) based on chemical composition. The study was conducted using the mobile nylon bag technique (MNBT). Nylon bags were inserted into the duodenum of 8 barrows (average body weight of 57.7 kg) through simple duodenal T-cannulas. Carboxymethylcellulose was used as a carrier of CG. Treatments consisted of a control (carboximethylcellulose) and 15 mixtures containing 10%, 20% and 30% of CG from 5 different batches of biodiesel production. Each batch showed variation in the content of glycerol and it was analyzed for dry matter (DM), gross energy (GE), ether extract (EE), ash, glycerol (GLY), pH and acid index (AI). Eight bags were administered to each pig daily (2 bags being inserted at 8, 10:30, 13:00 and 15:30 h into each of the 8 barrows). Sixteen nylon bags were prepared for each mixture (one gram per bag) therefore 256 bags were inserted over a 4-d period. The GE of each mixture was determined in a bomb calorimetry. The DE values of each mixture were estimated by difference, where by the DE content of the control was subtracted from each mixture containing CG. A multiple linear regression model was used to determine the value of the DE of CG as the slope relative to the DM of the CG included. The DE values of CG were correlated with its chemical composition and the value ranged from 3264 ± 202 to 3731 ± 202 kcal/kg DM (P < 0.01). The prediction model with the lowest AIC (Akaike's information criterion) was selected. DE (kcal/kg as fed) = [1.29 × GE (kcal/kg as fed)] + [109.7 x ash (%)] – (19.4 × GLY), (R²-adj = 0.999, P < 0.02). According to these results, the CG from palm oil biodiesel is a valuable energy source, with DE concentration depending on the concentration of GLY, GE and ash. The DE of crude glycerin was 77.5% of the GE.