Scientists Consider Storing Carbon in the Deep Down the Ocean Floor

One of humanity's most critical issues is climate change. Scientists are looking for new technologies that might help the world achieve carbon neutrality to prevent its possibly disastrous impacts.

Carbon Capture and Storage

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Capturing and storing carbon dioxide (CO2) emissions in the form of hydrates beneath ocean floor sediments, locked in place by natural pressure caused by the weight of the saltwater above, is one potential solution that is gaining traction. However, how stable would this stored CO2 be during the long periods of storage necessary to keep the carbon in place and out of the atmosphere.

Researchers from the National University of Singapore's (NUS) Department of Chemical and Biomolecular Engineering have proven the first-ever experimental proof of CO2 hydrate durability in marine sediments, paving the way for this carbon storage technique to become a reality.

Professor Praveen Linga, the study's principal researcher, stated, "It's the first of its experimental type data that we hope will inspire additional action on this technology development." The team's findings were initially published in the scholarly journal Chemical Engineering Journal as part of research financed by the Singapore Energy Centre.

The NUS team demonstrated that CO2 hydrates might be stable in oceanic sediments for up to 30 days using a specially built laboratory reactor. According to the researchers, the same procedure may now be used to validate the stability of CO2 hydrates for considerably longer periods of time.

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Trapping in Carbon

CO2 may be trapped among water molecules at low temperatures and high pressures caused by the ocean, generating an ice-like material. These CO2 hydrates occur at temperatures slightly beyond the freezing point of water and may store up to 184 cubic meters of CO2 in a single cubic meter.

The presence of large volumes of methane hydrates in comparable places across the planet, as well as their safe existence, provides a natural analog to support the notion that CO2 hydrates deposited in deep-oceanic sediments will stay stable and secure.

According to the researchers, this method might be evolved into a commercial-scale process, allowing nations like Singapore to efficiently store more than two million tons of CO2 yearly as hydrates to achieve emission reduction objectives.

Prof. Linga and his team used specifically constructed equipment to reproduce the conditions of the deep ocean floor, where temperatures range from 2°C to 6°C and pressures are 100 times greater than at sea level. It was challenging to build a macro-scale reactor that could sustain such conditions, which is one of the reasons why prior studies to verify the stability of CO2 hydrates were not possible. The NUS team surmounted this obstacle by employing a pressurized tank created in-house and coated with a silica sand bed that mimicked ocean sediments.

The team was able to generate solid hydrates on top of and inside the silica sand layer and then transitioned the pressurized tank to simulate oceanic conditions to test the stability of the solid CO2 hydrates in sediments. The hydrates were studied for 14 to 30 days under pressurized circumstances and high stability.

In addition to how carbon is now stored in exhausted oil and gas reserves and saline aquifer formations, this hydrate technique would allow governments to retain enormous quantities of carbon emissions in deep-ocean geological formations. The technology might be a crucial tool for lowering CO2 emissions for nations like Singapore, which has set a goal of becoming carbon neutral by 2050.

The team's next step will increase the experiment's volume and duration.

Financing

The team's recent announcement of financing from the Singapore government under the Low-Carbon Energy Research Funding Initiative to create cutting-edge low-carbon energy technology solutions would considerably aid the development of this storage technology. The team wants to construct and evaluate models that can forecast the stability of CO2 hydrates thousands of years in the future with the planned future trials.