Aiming to Solve Global Warming: Research and Development of New CO2 Capture and Reuse Technologies

Tokyo Institute of Technology, Associate Prof. Takuya HARADA

"Global warming", we have been hearing this term on the TV news for quite some time now. The average global temperature is rising, the Antarctic and Arctic ice sheets are melting, sea levels are rising, and we are being hit more frequently by severe typhoons and heat waves. Many studies and analyses around the world have shown that such serious global climate change is advancing. The substance responsible for global warming is carbon dioxide (CO₂), which we humans are releasing into the atmosphere in large quantities, and the CO₂-rich atmosphere is like a plastic greenhouse, trapping heat from the sun and raising the global temperature as a result.

Naturally, reducing atmospheric CO₂ emissions is essential to halt this global warming process. There are two major technological approaches to this end. One is the use of renewable energy sources such as solar and wind power and carbon-free energy sources such as nuclear power, and the other is technology to capture and reuse CO₂ emitted from the consumption of fossil fuels. The latter technology is called CCS (Carbon Capture and Storage) or CCUS (Carbon Capture, Utilization and Storage) in particular, and its establishment is highly anticipated.

As one of the activities of Tokyo Tech GXI, our laboratory has been conducting research focusing on CO₂ capture and reuse technology. In particular, we have been developing a new CO₂ capture system using a unique material called "molten oxide" (Figure 1). Oxides are generally in solid form, such as ceramics and glass, but molten oxides are those that have been heated and melted to a liquid state.

We have developed a material with excellent CO₂ reactivity and high thermal stability from among these molten oxides, and by using it as a new CO₂ absorbent, we have realized a system that can directly capture CO₂ from high-temperature combustion gases emitted from factories and thermal power plants. This new high-temperature-liquid CO₂ recovery system can also efficiently convert the large amount of thermal energy generated by the CO₂ reaction into electrical energy (i.e., "power generation"), resulting in a significant reduction in process energy consumption. This has led to a significant reduction in process energy consumption. Such simultaneous CO₂ capture and heat recovery power generation would not have been possible with conventional CO₂ absorbers that operate at low temperatures or with solid CO₂ absorbers that have low thermal conductivity.

Reuse of recovered CO₂ is another important technical issue. We are considering the reuse of CO₂ as a new carbon resource that can replace petroleum as a raw material for synthesizing various chemical products such as polymers and chemical fuels. Our newly developed CO₂ recovery method using molten oxides has a great technological advantage in terms of CO₂ conversion and reuse, as it can easily extract CO₂ to a high purity after recovery.

The problem of global warming is a major global issue that confronts us in this day and age. However, I believe that we can surely solve this problem if we all work as one and continue to make great efforts. Through the research of CO₂ capture technology at Tokyo Tech GXI, I would like to accelerate our progress together with our many partners.

Figure1 Conceptual diagram and characteristics of a new molten oxide type CO2 absorber.