The second component of the ZAP-C 3 system comprises a container into which the alkaline (pH >10) water from the first component is transferred (Figure ). Micro bubbles of the unreacted CO2 depleted gas are passed through the alkaline water using micro-bubble generation. The pH is monitored, and bubbling is terminated once the solution becomes neutral (pH = 7). The solution formed is cloudy with precipitated calcium carbonate (PCC) which is either left to settle overnight or separated by centrifuge, after which the pH 7 water is decanted and reintroduced to the water supply for the first component of the ZAP-C 3 system.