▁fact ▁that , ▁despite ▁the ▁capital ▁costs ▁in cur red ▁in ▁construct ing ▁the ▁carbon ator ▁for ▁Ca - loop ing , ▁CO 2 ▁will ▁not ▁only ▁be ▁captured ▁from ▁the ▁o xy - f ired ▁comb ust ion , ▁but ▁also ▁from ▁the ▁main ▁comb ust or ▁( before ▁the ▁carbon ator ). ▁The ▁o xygen ▁required ▁in ▁the ▁cal cin ers ▁is ▁only ▁ 1 / 3 ▁that ▁required ▁for ▁an ▁o xy f uel ▁process , ▁lower ing ▁air ▁separation ▁unit ▁capital ▁costs ▁and ▁operating ▁costs . ▁ ▁S ens itivity ▁Analysis : ▁Figure ▁ 3 ▁shows ▁how ▁varying ▁ 8 ▁separate ▁parameters ▁affect s ▁the ▁cost / metric ▁ton ▁of ▁CO 2 ▁captured ▁through ▁Ca - loop ing . ▁It ▁is ▁evident ▁that ▁the ▁dominant ▁variables ▁that ▁affect ▁cost ▁are ▁related ▁to ▁sor b ent ▁use , ▁the ▁Ca / C ▁ratio ▁and ▁the ▁Ca O ▁de activ ation ▁ratio . ▁This ▁is ▁because ▁the ▁large ▁sor b ent ▁quantities ▁required ▁domin ate ▁the ▁econom ics ▁of ▁the ▁capture ▁process . ▁ ▁These ▁variables ▁should ▁therefore ▁be ▁taken ▁into ▁account ▁to ▁achieve ▁further ▁cost ▁redu ctions ▁in ▁the ▁Ca - loop ing ▁process . ▁The ▁cost ▁of ▁lim estone ▁is ▁largely ▁driven ▁by ▁market ▁forces , ▁and ▁is ▁outside ▁the ▁control ▁of ▁the ▁plant . ▁Currently , ▁carbon ators ▁require ▁a ▁Ca / C ▁ratio ▁of ▁ 4 ▁for ▁effective ▁CO 2 ▁capture . ▁However , ▁if ▁the ▁Ca / C ▁ratio ▁or ▁Ca O ▁de activ ation ▁is