that the dominant variables that affect cost are related to sorbent use, the Ca/C ratio and the CaO deactivation ratio. This is because the large sorbent quantities required dominate the economics of the capture process. These variables should therefore be taken into account to achieve further cost reductions in the Ca-looping process. The cost of limestone is largely driven by market forces, and is outside the control of the plant. Currently, carbonators require a Ca/C ratio of 4 for effective CO2 capture. However, if the Ca/C ratio or CaO deactivation is reduced (i.e. the sorbent can be made to work more efficiently), the reduction in material consumption and waste can lower feedstock demand and operating costs. Cement production Finally, favorable economics can be achieved by using the purged material from the calcium looping cycle in cement production. The raw feed for cement production includes ~ 85 wt% limestone with the remaining material consisting of clay and additives (e.g. SiO2, Al2O3 etc.). The first step in the process involves calcinating limestone to produce CaO, which is then mixed with other materials in a kiln to produce clinker. Using purged material from a Ca-looping system would reduce the raw material costs for cement production. Waste CaO and ash can be used in place of CaCO3 (the main constituent cement feed). The ash could also fulfill the aluminosilicate requirements otherwise supplied by additives. Since over 60% of the energy used in cement production goes into heat input for the precalciner, this integration with Ca-looping and the consequent reduced need for a calcination step, could lead to substantial energy savings (EU, 2001). However, there are problems with using the waste CaO in cement manufacture. If the technology is applied on a large scale, the purge rate of CaO should be optimized to minimize waste. Political and environmental implications To fully gauge the viability of calcium looping as a capture process, it is necessary to consider the political, environmental, and health effects of the process as well. Political implications Though many recent scientific reports (e.g.: the seven-wedge stabilization plan by Pacala and Socolow) convey an urgent need to deploy CCS, this urgency has not spread to the political establishment, mainly due to the high costs and energy penalty of CCS The economics of calcium looping are integral to its political viability. One economic and political advantage is the ability for Ca-looping to be retrofitted onto