Carbon Dioxide Removal
Roadmap Overview
Direct Air Capture Direct air capture (DAC) is a negative emission technology for the direct removal of CO2 already in the Earth’s atmosphere. Figure 1-1 displays sources of carbon dioxide with their associated cost of abatement. It is apparent that certain CO2 sources are difficult to abate with point source capture methods; so an indirect and distributed CO2 capture method like DAC is used to offset the hard-to-abate emissions.
DAC describes an array of chemical reactions or absorption processes that separate CO2 from the air from the atmosphere. The process consists of three steps. First, the air is fan-forced into a sorbent. Then, the CO2 reacts with the sorbent. Lastly, the CO2 is detached from the sorbent by adding thermal or electric energy.
Broadly, there two groups of DAC technology. On the one hand there are high-temperature, liquid sorbent processes, on the other hand, there are low-temperature, solid sorbent processes. Regardless of the technology used, the processes must be measured against the same dimensions. Suggested dimensions are cost, capture efficiency, water demand, energy demand and land demand.