When the acid is fully recycled (over 99% for CNC61, 98% for CNC64) the consumption of sulfuric acid is equivalent to less than 1~2% of the initially required acid amount during the hydrolysis reaction. It represents the make-up of the acid loss in the CNC sulfation and waste stream. As the degree of sulfation for CNC64 is higher than that for CNC61, the acid loss for CNC64 production is higher than CNC61 (1.015 ton/day CNC-OSO3H for CNC61; 1.025 ton/day CNC-OSO3H for CNC64, as shown in Figure ). During recycling, the acid is concentrated in an evaporator at 107C, therefore it needs to be cooled down to the hydrolysis temperature (45 or 55C) using a cooler. Warm concentrated recycled acid is then sent to hydrolysis, thus avoiding external duty for the hydrolysis reactor. The steam generated in the evaporator is cooled down to ambient temperature and becomes water (containing ~ 0.02 wt.% acid, Figure ) and then recycled back to the quench and the ultrafiltration steps, thus water consumption is much lower than in the scenarios withoutacid recycling. Electricity is consumed in all unit operations, and evaporator is the main contributor at 92 ~ 93%, while drying can account for ~7% of the total electricity consumption.