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New Carbon Capture System with Record-Breaking Efficiency to Revolutionise Direct Air Capture

Newly discovered sorbent is 99 per cent efficient in absorbing low concentrations (400ppm) of carbon dioxide from the atmosphere at unprecedented rates.

A team of researchers from Tokyo Metropolitan University has developed a new carbon capture system that removes carbon dioxide directly from the atmosphere at a never-before-seen rate.

The system comprises isophorone diamine (IPDA) in a “liquid-solid phase separation” system that was found to remove low concentrations of carbon dioxide from the atmosphere with 99 per cent efficiency. It is also energy efficient as IDPA may be reused without much energy-intensive processing and captures carbon at around double the rate compared to current direct air capture technologies.

As climate change threatens to destabilise the world on all fronts, it has been understood that carbon dioxide emissions need to be drastically reduced to slow down this trend. This might be achieved through changes in lifestyles and policies and the invention of new technologies with the ability to remove carbon dioxide from the atmosphere.

In an extension of the goal of reduced emissions, many scientists are hoping to innovate and achieve a “beyond-zero” future where atmospheric carbon dioxide may be actively reduced. As such, the field of carbon capture, which explores technology regarding the removal and storage of carbon dioxide from the atmosphere, is expanding swiftly, but most innovations still face the major issue of scalability.

The most significant challenge faced by the processing of atmospheric air in direct air capture (DAC) systems is efficiency. Despite the ever-increasing concentrations of carbon dioxide in the atmosphere, the amount of carbon dioxide in proportion to the other gases in the atmosphere is very low. Thus, this low concentration of carbon dioxide results in a slow rate of reaction for reactions involving sorbents. The technologies that involve capture-and-desorption cycles for enhanced sustainability are very energy-intensive and still rely on fossil fuels to power them. Existing efforts to build DAC plants using existing technologies involving potassium hydroxide and calcium hydroxide have proved to be both expensive and inefficient, highlighting the urgency in finding better alternative technologies.

Led by Professor Seiji Yamazoe, researchers at Tokyo Metropolitan University, have been studying a category of DAC technology known as liquid-solid phase separation systems. The system aims to solve the issue of slowing rates of reaction over time in conventional DAC systems. Some conventional DAC systems involve the bubbling of atmospheric air through a liquid, where carbon dioxide reacts with the liquid and is removed from the air. As the reaction product accumulates in the liquid, the rate of reaction slows, reducing the overall efficiency of the system as time passes.

Utilising a liquid-solid phase separation system solves this issue as it ensures that the product is insoluble and precipitates out of the reaction mixture. Therefore, there is no accumulation of the product in the liquid phase of the mixture, resulting in less slowdown of the chemical rate of reaction.

In their search for a suitable liquid chemical for the removal of carbon dioxide from the air, the researchers investigated the properties of liquid amine compounds, modifying their structures to maximise reaction speed and efficiency for a range of concentrations of atmospheric carbon dioxide.

Eventually, they discovered that the aqueous solution of isophorone diamine (IPDA), could convert 99 per cent of gaseous carbon dioxide of concentrations between 400ppm to up to 30 per cent to a solid carbamic acid precipitate.

Most importantly, they discovered that the precipitate formed through this process could be separated from the liquid through mild heating at 60°C, demonstrating this compound’s potential for use in systems with capture-and-desorption cycles to enhance energy efficiency. This makes the developed system the fastest carbon capture technology for low concentrations of gaseous carbon dioxide (400ppm).

The researchers’ innovation promises enhanced efficiencies, lowered costs for future DAC systems, and might revolutionise the scaling up of carbon capture technologies. Beyond enhanced carbon capture efficiency, their innovation also opens new avenues for exploration of the usage of the carbon capture system by-products in the industrial or household setting. [APBN]

Source: Kikkawa et al. (2022). Direct Air Capture of CO2 Using a Liquid Amine–Solid Carbamic Acid Phase-Separation System Using Diamines Bearing an Aminocyclohexyl Group. ACS Environmental Au.