While experimental degradation data in literature could be fit to estimate decay constants, there are two limitations that reduce the merit of those decay constants. First, the small number of cycles limits the accuracy of the rates, as the limited number of cycles may be missing a lower degradation rate at longer sorbent lifetimes. For example, the rate of degradation of monoethanolamine (MEA) begins to slow after approx. 50 hours of oxygen exposure at high temperatures (120 -160 °C), and Fan et al. observed a shift in the degradation rate of PEI after 80 cycles with dry flue gas containing 200 ppm SO2. Thus, there is uncertainty in the long time degradation behavior. The second limitation is that decay constants are specific to cycle conditions, so economic conclusions derived from one set of data may not extend to processes with different air humidity, air temperature, desorption temperature, cycle time, etc. In real operation, these factors change continuously. Fig. compares the impact of degradation rate, working capacity, and cycle time (kinetics) on the total DAC cost. The top three figures illustrate five working capacities, and the bottom three illustrate five cycle times. The left, middle, and right panels are no degradation, 70% capacity remaining at 1 year (exponential decay), and 50% capacity remaining at 1 year (exponential decay), respectively. All figures are displayed as a function of sorbent replacement time. By comparing the three panels with varying degradation rates, we can see that the degradation rate has a substantial impact on the cost when the working capacity is low or when the cycle time is high, due to the large amount of sorbent required. It is important to note that the parameters used for these cost estimates are quite conservative. Thus, we also evaluated a "best case scenario" in which all of the model parameters are set at highly optimistic values, some of which may be beyond the current state-of-the-art (Table ). These "best case scenario" parameters result in a cost of slightly above $135/t-CO2.