Tiny 'cages' could trap carbon dioxide and help stop climate change

March 17, 2006

A natural physical process has been identified that could play a key role in secure sub-seabed storage of carbon dioxide produced by fossil-fuelled power stations.

A team of researchers at the Centre for Gas Hydrate Research, at Heriot-Watt University is investigating how, in some conditions, seawater and carbon dioxide could combine into ice-like compounds in which the water molecules form cavities that act as cages, trapping the carbon dioxide molecules.

In the unlikely event of carbon dioxide starting to leak into the sea from an under-seabed disposal site (e.g. a depleted North Sea oil or gas reservoir), this process could add a second line of defence preventing its escape.

This is because, as the carbon dioxide comes into contact with the seawater in the pores of seafloor sediments above it, the compounds (called carbon dioxide hydrates) would form. This would create a secondary seal, blocking sediment pores and cracks, and slowing or preventing leakage of the carbon dioxide.

Professor Bahman Tohidi is leading the project. "We want to identify the type of seabed locations where sediment, temperature and pressure are conducive to the formation of carbon dioxide hydrates," he says. "This data can then be used to help identify the securest locations for carbon dioxide storage and can aid in the development of methods for monitoring potential CO2 leakage. In the future, it may even be possible to manipulate the system to promote CO2 hydrate formation, extending the number of maximum-security sites that are available."

Combining engineering expertise with computer modelling and geology skills, the research team is examining exactly how and where hydrates form, and establishing the optimum conditions that enable this process to take place. Their work includes the use of an experimental facility to simulate conditions in different sub-seabed environments with different types of sediment, and to observe hydrate formation when carbon dioxide is introduced. They have also developed tiny 2-dimensional 'sediment micromodels' (layers of glass etched with acid to simulate sediments) to help explore how hydrate crystals grow at pore scale in seafloor sediments.

Carbon dioxide emissions from fossil-fuelled power stations are a major contributor to climate change. With fossil fuels predicted to remain essential to world energy supplies for several decades, finding alternatives to releasing these emissions into the atmosphere is an urgent priority. Capturing them and then storing them long-term in stable geological formations under the sea is one promising option.

As well as helping to offset the environmental impact of fossil-fuelled power generation, carbon capture and storage is seen as a key 'bridging' technology that could help the emergence of a hydrogen energy economy, which may eventually replace today's largely carbon-based energy system. This is because, although hydrogen is expected to be produced in the long term from carbon-free renewable energy sources (e.g. via hydrolysis), in the shorter term it will probably be produced mainly from fossil fuels, generating carbon dioxide as part of the production process. Professor Tohidi stresses that carbon storage is only a short to medium-term solution. He says: "It should not be considered a limitless option but rather a stop-gap means to facilitate a smooth transition from fossil fuels to clean energy resources."

As well as contributing to climate change, carbon dioxide could pose a serious threat to marine life if it escaped from sub-seabed storage in significant quantities.

Source: Engineering and Physical Sciences Research Council

Explore further: Drought's lasting impact on forests

Related Stories

Drought's lasting impact on forests

July 30, 2015

In the virtual worlds of climate modeling, forests and other vegetation are assumed to bounce back quickly from extreme drought. But that assumption is far off the mark, according to a new study of drought impacts at forest ...

'Carbon sink' detected underneath world's deserts

July 28, 2015

The world's deserts may be storing some of the climate-changing carbon dioxide emitted by human activities, a new study suggests. Massive aquifers underneath deserts could hold more carbon than all the plants on land, according ...

Where is solar power headed?

July 22, 2015

Most experts agree that to have a shot at curbing the worst impacts of climate change, we need to extricate our society from fossil fuels and ramp up our use of renewable energy.

Recommended for you

Quantum matter stuck in unrest

July 31, 2015

Using ultracold atoms trapped in light crystals, scientists from the MPQ, LMU, and the Weizmann Institute observe a novel state of matter that never thermalizes.

Out of the lamplight

July 31, 2015

The human body is governed by complex biochemical circuits. Chemical inputs spur chain reactions that generate new outputs. Understanding how these circuits work—how their components interact to enable life—is critical ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.