Schematic diagrams of each component of the ZAP-C 3 system are shown in Figures and. The first component of the ZAP-C 3 system comprises a container in which a moving platform is located (Figure ) onto which the raw BOS slag, or waste recycled concrete aggregate (RCA), is deposited from an entrance in the top of container. At any time approximately 20 tons of BOS slag is on the moving platform during the process. The slag is supplied using a hopper (Figures 3) to allow continuous delivery. The perforated moving platform (Figure ) is designed to facilitate controlled movement of the BOS slag from one end of the container to the other. The moving platform constructed of multiple channels that are linked as independent sets of moving components in a particular configuration (Figures 4a). The moving platform is perforated (Figure ) such that leachate may be removed continuously during the process. The movement of the platform is controlled by hydraulic actuators using only 5 kW per day/loading & unloading energy and moved a layer of slag from the input end of the container to the output end. Prior to injection of water or CO2 rich gas the slag is spread out on the moving platform using the linked channels. First, all the linked channels move forwards 150 mm, then each set of linked channels in the platform is retracted sequentially. This is repeated until the BOS slag is spread completely covering the moving platform. A hot (>100 °C) 100 kg CO2 containing flue gas stream is injected into the container at the opposite end from the slag and unreacted CO2 depleted gas is extracted at the other end to be used in the second component of the ZAP-C 3 system (see below). If required or desired additional CO2 containing gas streams may be co-injected from DAC or other sources. The ZAP-C 3 system container is designed for up to 18,000 m 3 per hour gas flow at a pressure of 170 mbar. At the top of the container above the moving platform is a spray system (Figure ) that delivers water at near neutral pH, pumped by a 0.75 kW/h pump at 300 L/hour, at 4.7 bar pressure passing through the CO2 containing gas stream and onto the BOS slag (Figure ). The ZAP-C 3 system container is designed for up to 13,000 L/hour at 2.58 kW/h at 5 bar. To prevent the loss of water, it is operated at lower water flow rate until the second ZAP-C 3 reactor is coupled to the first reactor. The second ZAP-C 3 reactor has a blower (18 kW/h) and unique system to capture and sequester CO2 and water exiting first reactor. The CO2 dissolves into the sprayed water causing a reduction in the pH due to carbonic acid formation (pH <4). A collector is placed on top of the BOS slag or RCA allowing for measurement of the water/CO2 solution that drips onto the BOS slag (Figure ).The acidic CO2 solution passes through and reacts with the BOS slag or RCA resulting in an alkaline carbonate solution (pH >10), which drains under the moving platform (Figure ) and is pumped into the micro-bubbling reactor (1 -12 kW/h) for the second component of the ZAP-C 3 system (see below). Once the pH of the carbonate solution drops below pH 9, the BOS slag or RCA is moved using the moving platform into a hopper at the end of the container (Figure ) from which it is transported via conveyor belt to be bagged for transport and use as volumetrically stable aggregate.