From carbon dioxide to solid carbon using RMIT technology

Australian researchers have developed a way of capturing carbon dioxide and converting it to solid carbon, to help advance the decarbonisation of heavy industries.

The carbon dioxide utilisation technology from RMIT University is designed to be integrated into existing industrial processes.

Decarbonisation is a technical challenge for heavy industries like cement and steel, which are not only energy-intensive but also directly emit CO₂ as part of the production process. The new technology offers a pathway for instantly converting carbon dioxide as it is produced and locking it permanently in a solid state, keeping CO₂ out of the atmosphere.

The research is published in the journal Energy & Environmental Science.

Co-lead researcher Associate Professor Torben Daeneke said the work built on an earlier experimental approach that used liquid metals as a catalyst.

“Our new method still harnesses the power of liquid metals but the design has been modified for smoother integration into standard industrial processes,” he said.

“As well as being simpler to scale up, the new tech is radically more efficient and can break down CO₂ to carbon in an instant.

“We hope this could be a significant new tool in the push towards decarbonisation, to help industries and governments deliver on their climate commitments and bring us radically closer to net zero.”

A provisional patent application has been filed for the technology and researchers have recently signed a $2.6 million agreement with Australian environmental technology company ABR, which is commercialising technologies to decarbonise the cement and steel manufacturing industries.

Co-lead researcher Dr Ken Chiang said the team is keen to hear from other companies to understand the challenges in difficult-to-decarbonise industries and identify other potential applications of the technology.

“To accelerate the sustainable industrial revolution and the zero-carbon economy, we need smart technical solutions and effective research–industry collaborations,” Dr Chiang said.

The steel and cement industries are each responsible for about 7% of total global CO₂ emissions (International Energy Agency), with both sectors expected to continue growing over coming decades as demand is fuelled by population growth and urbanisation.

Technologies for carbon capture and storage (CCS) have largely focused on compressing the gas into a liquid and injecting it underground, but this comes with significant engineering challenges and environmental concerns. CCS has also drawn criticism for being too expensive and energy-intensive for widespread use.

Assoc Prof Daeneke, an Australian Research Council DECRA Fellow, said the new approach offers a sustainable alternative, with the aim of both preventing CO₂ emissions and delivering value-added reutilisation of carbon.

“Turning CO₂ into a solid avoids potential issues of leakage and locks it away securely and indefinitely,” he said.

“And because our process does not use very high temperatures, it would be feasible to power the reaction with renewable energy.”

The Australian Government has highlighted CCS as a priority technology for investment in its net zero plan, announcing a $1 billion fund for the development of new low-emissions technologies.

How the tech works

The RMIT team, with lead author and PhD researcher Karma Zuraiqi, employed thermal chemistry methods widely used by industry in their development of the new CCS tech.

The ‘bubble column’ method starts with liquid metal being heated to about 100–120°C.

PhD researcher Karma Zuraiqi holding a test tube of liquid metal, used as a catalyst to instantly convert carbon dioxide into solid carbon. Image credit: RMIT University.

Carbon dioxide is injected into the liquid metal, with the gas bubbles rising up just like bubbles in a champagne glass. As the bubbles move through the liquid metal, the gas molecule splits up to form flakes of solid carbon, with the reaction taking just a split second.

“It’s the extraordinary speed of the chemical reaction we have achieved that makes our technology commercially viable, where so many alternative approaches have struggled,” Dr Chiang said.

The next stage in the research is scaling up the proof of concept to a modularised prototype the size of a shipping container, in collaboration with industry partner ABR. ABR Project Director David Ngo said the RMIT process turns a waste product into a core ingredient in the next generation of cement blends.

“Climate change will not be solved by one single solution; however, the collaboration between ABR and RMIT will yield an efficient and effective technology for our net zero goals,” Ngo said.

The team is also investigating potential applications for the converted carbon, including in construction materials.

“Ideally the carbon we make could be turned into a value-added product, contributing to the circular economy and enabling the CCS technology to pay for itself over time,” Assoc Prof Daeneke said.

The research involved a multidisciplinary collaboration across engineering and science, with RMIT co-authors Jonathan Clarke-Hannaford, Billy James Murdoch, Associate Professor Kalpit Shah and Professor Michelle Spencer.

‘Direct Conversion of CO₂ to Solid Carbon by Liquid Metals’, with collaborators from The University of Melbourne and Deakin University, is published in Energy & Environmental Science (DOI: 10.1039/d1ee03283f).

Top image caption from left to right: PhD researcher Karma Zuraiqi with Dr Ken Chiang and Associate Professor Torben Daeneke. Image credit: RMIT University.