Life cycle carbon efficiency of Direct Air Capture systems with strong hydroxide sorbents

Direct Air Capture (DAC) of carbon dioxide (CO2) from ambient air has the potential to combat climate change. DAC systems capture CO2 using a sorbent material and compress it for storage. In this study, we calculated the life cycle carbon efficiency (E-c) of a DAC system which equals the net amount of carbon stored per amount of carbon captured from capture to geological storage. We included greenhouse gas (GHG) emissions during construction of the necessary facilities as well as GHG emissions from energy, water and chemicals needed during operations. The system we analysed includes a hydroxide solution as sorbent material and utilizes the pelletized variant of the Kraft process to regenerate the sorbent and separate the CO2. To our knowledge, the potential climate benefit over the full life cycle of this DAC system has not been fully investigated up to now. Using the baseline scenario, we obtained a positive E-c of 62%. For the optimistic and pessimistic scenarios, we found a E (c) of 93% and 10%, respectively. We conclude that this type of DAC system may be a feasible option to help keep limit global temperature increases to well below 2 degrees C.