Charcoal may provide an important functional group support for heterogeneous catalysis due to the combination of high surface area, thermal stability, and chemical resistance. In this study, the functionalization of activated charcoal was investigated either by mixing nitric and sulfuric acid in an ultrasonic bath at room temperature or by heating it to 250 oC in concentrated sulfuric acid. The textural properties of the resulting acid-functionalized charcoal were comparable to that of unfunctionalized charcoal. The catalytic performance of the acid-functionalized charcoal catalysts was investigated for the hydrolysis of cellulose present in distillers' dry grains (DDG), a byproduct of ethanol production in dry milling process. The catalytic activity of the acid-functionalized charcoal catalysts was 20% faster than unfunctionalized charcoal. The overall hydrolysis rate with acid-functionalized charcoal was ~30% greater than observed with hydrothermolysis at 200 oC. Overall, this study demonstrated the feasibility of functionalizing activated charcoal for catalytic purposes.