Compared to the conventional MEA process for the capture of carbon dioxide from flue gas, the ammonia scrubbing technique provides advantages of lower material costs and less corrosion to absorber, as well as the potential for saving energy, which will eventually make the process less expensive. However, in addition to the highly volatile nature of ammonia, the lack of a method to separate ammonia from CO2 after thermal decomposition of ammonium bicarbonate also hinders the ammonia scrubbing technique from being applied in practice. This paper investigates a method to regenerate ammonia so as to allow for the ammonia scrubbing technique to be practical in the capture of CO2. In the new method, a weakly basic ion-exchange resin containing amine functional groups is used to regenerate ammonia through absorbing carbonic acid at ambient temperatures from ammonium bicarbonate, the main product formed after the absorption Of CO2 by ammonia. The resin can then be regenerated when it is heated by water at temperatures equal to or greater than 50 degreesC. A 50% energy saving can be expected of the new method when compared to the energy requirement of the MEA process. Also, through several runs of a resin absorption--desorption experiment, the sustainability of the resin for the regeneration of ammonia from ammonium bicarbonate was evidently demonstrated. The regeneration capability of the resin can be maintained consistently at 87% of the original regeneration capability of the resin. The issue of the volatility of ammonia is also addressed.