In this new sequestration process proposed by Iizuka, waste cement used in reference to concrete that is being torn up from how it had been used. Since there is a continual source of waste concrete from dismantled buildings, a long-term source of waste cement is expected. This waste is considered to be source of the necessary ions that are needed for the sequestration of carbon dioxide. By sequestering carbon with calcium and magnesium in the form of carbonates, a stable solution that is environmentally benign is produced. Other methods may sequester carbon dioxide as liquid, which could result in the reduction of pH in seawater or could evaporate to the surface and back to the atmosphere. The process of using waste concrete as a means to sequester carbon dioxide is demonstrated in Figure 1, which shows the order of events that can lead to the recycling of waste cement or as just a means of sequestration.
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