Cellulose succinates (CSs) having degrees of substitution (DSs) ranging from 0.78 to 2.77 were successfully obtained by reacting cellulose with succinic anhydride (SA) in dimethyl sulfoxide at room temperature using a small amount of inexpensive solid potassium carbonate as a catalyst. Interestingly, CSs with higher DS values were obtained with a much smaller amount of catalyst than previously reported. Moreover, it is possible to control the DS by tailoring the reaction time and mass ratio of cellulose/SA. The hydroxyl groups at the C-6, C-2, and C-3 positions were the main esterification positions. In this process, most of the raw materials are either incorporated into the product or are recoverable. The E-factor, which reflects the sustainability of a given process, was demonstrated to be reduced by 93% by recovering the raw materials.