Abstract: In a general aspect, a carbon dioxide removal system is presented. In some cases, a gas-liquid contactor is wetted with an alkaline capture solution. A first flow from a first gaseous feed including CO2 from a first source is directed to interact with the alkaline capture solution in the gas-liquid contactor, which forms a first CO2-rich alkaline capture solution. A second flow from a second gaseous feed including CO2 from a second, distinct source is directed to interact with the first CO2-rich alkaline capture solution, which forms a second CO2-rich alkaline capture solution. In some cases, the second flow is independent of the first gaseous feed, and a concentration of CO2 in the second CO2-rich alkaline capture solution is higher than a concentration of CO2 in the first CO2-rich alkaline capture solution. CO2 can be separated from the second CO2-rich alkaline capture solution.