Butanol fermentation has garnered renewed interest due to the search for renewable sources of energy. Although acetone-butanol-ethanol (ABE) fermentation has been studied for a long time, the methods utilized yield either a high butanol/ABE productivity and low titer or high butanol/ABE titer at a low productivity. In this work, we report the utilization of a highly dense calcium alginate immobilized Clostridium acetobutylicum cells in combination with fed-batch mode of fermentation to attain a high butanol/ABE productivity and concentration. A butanol concentration of up to 21.6 g/L was attained with a productivity of 0.40 g/L·hr, which is a 65% and 192% improvement to the conventional batch fermentation.