Multiple aspects of direct air capture processes have associated carbon emissions, including the (1) energy source, (2) sorbent materials (including their synthesis, manufacturing, and disposal), (3) equipment materials and manufacturing, (4) sorbent transport and storage, and (5) CO2 compression, purification, transport, utilization, and storage. In this analysis, we considered cradle-to-gate carbon emissions from energy, sorbent materials, and equipment materials and manufacturing. Cradle-to-gate analysis is sufficient for this comparative study; the amount of CO2 captured is a fixed parameter, and thus the downstream environmental impacts are identical across the scenarios. However, it is important to note that CO2 transportation and storage emissions can contribute significantly (accounting for over half of the total DAC greenhouse gas emissions in some cases), and the downstream emissions will vary significantly depending on the plant and storage locations and end-use of the CO2 product (storage vs. utilization). Optimizing and assessing downstream emissions is the subject of ongoing research. To determine the electrical energy carbon footprint, the cumulative electrical energy consumption is converted to a cumulative amount of CO2 emissions based on the energy source (section S3.L of SI). A carbon footprint is also calculated for thermal energy based on its electricity equivalent. The electrical and thermal energy carbon footprints are combined with the carbon footprint of the sorbent and equipment materials and construction to determine the total carbon footprint.