Automatic control of biomass inventory is seldom used in wastewater treatment plants today, despite the high impact on treatment capacity. In this study, a smart biomass control system was used to find the required sludge age of a continuous feed sequencing batch reactor (SBR) based on real-time measured process parameters. The control system further adjusted the amount of biomass wasted to maintain this sludge age. It was found that the system was capable of controlling the process to the sludge age required to reach the desired level of nitrification. The test period was compared to a subsequent test period operating at a sludge age two-folded the required as calculated by the control system. The comparison showed no impact on the treatment performance from increasing the sludge age further. However, the higher endogenous respiration of the older sludge increased the energy consumption with 12 %. The results show that the use of a smart biomass control system has potential to automatically recognize and maintain the sludge age to the current process conditions while providing significant energy savings.