The basis for the solid sorbent temperature vacuum swing adsorption process was two units containing 18 contactors each, as is the set-up at the Climeworks plant in Hinwil, Switzerland. The contactor design was based on a 2020 patent, and the sorbent used is Lewatit® VP OC 1065 due to its commercial availability. Note that the heating mechanism of the contactor in this patent is indirect via pipes inside the sorbent bed and not using steam stripping. We used a model and Lewatit® VP OC 1065 data from previous work to calculate the energy and productivity values of a process optimised for maximum productivity. Here, we adjusted the sorbent volume based on one plate in the chosen contactor design and calculated a heat transfer coefficient using a one-dimensional radial approximation around a heat transfer pipe. The parameters used can be found in the ESI Tables We considered natural gas only for the two processes powered by high-grade heat, i.e., KOH-Ca looping and MgO ambient weathering, since the process configurations reported both use natural gas in an oxy-fired calciner. Nevertheless, we did investigate the impact of low-grade heat choice on the solid sorbent process. The three investigated low-grade heat sources are electricity with an airsource heat pump, dedicated geothermal heating, and solar heating. The ESI Figure compares the effect of different heat sources on net removal cost, and we find that all of the options have the potential to be competitive, but for simplicity, we selected a heat pump to use in the analysis for the rest of this study due to its lower median cost estimate. Here, we assumed a coefficient of performance (COP) of 2, which is consistent with an 85°C temperature rise, and we did not consider the effect of location. There is also the option of using waste heat, especially for FOAK and pilot plants. This will reduce the early costs, supporting initial scale-up, but this is expected not to significantly impact cost at the scale of carbon removal we will require. The ESI Figure further compares the heat sources for solid Email: jpy1@hw.ac.uk RCCS, Heriot-Watt University sorbent DACS powered by grid electricity in the USA. Due to the high carbon intensity of grid electricity, solar and geothermal heat becomes much more attractive, compared to when low carbon electricity is available.