Optimization of CCSM (carbon dioxide capture and storage with mineralisation) using RAS (recyclable ammonium salts) was studied here in order to minimize the energy consumption of this process. Water evaporation is required for the recycling of ammonium salts in the process, however the water evaporation technologies normally impose high energy penalty. In the optimized process, solid to liquid (S/L) ratio was increased to reduce water usage, but this change impacts dissolution efficiency, where the dissolution efficiency decreased from 100% at S/L of 50 g/l to 71% at S/L of 300 g/l. However, a 6% increase of dissolution efficiency was reported when the S/L ratio increased from 200 g/l to 300 g/l, probably due to increasing mineral inter-collisions. Besides, the optimized process employed the pressurized reactor, this change resulted in the mineral phase of product changed from hydromagnesite to magnesite. The carbon fixation efficiency was significantly improved by using (NH4)(2)CO3 compared to NH4HCO3, and the highest CO2 fixation efficiency achieved was 46.6% at S/L of 300 g/l. The mass balance for the optimized process was 4.9 t of serpentine, 0.6 t of NH4HSO4, 4.7 t of (NH4)(2)CO3 and 16 t of water required to sequester 1 t CO2. (C) 2013 Elsevier Ltd. All rights reserved.