CO2 storage in deep rock formations is a safe strategy to fight global warming

The Paris Agreement sets the commitment of limiting the maximum global average temperature rise in 2 ºC to fight climate change. Photo: IPCC
The Paris Agreement sets the commitment of limiting the maximum global average temperature rise in 2 ºC to fight climate change. Photo: IPCC
Research
(13/06/2018)

Carbon dioxide or CO₂ ─the main cause of the greenhouse effect and global warming─ can be safely stored in sub-seafloors for thousands of years, according to a study published in the journal Nature Communications with Juan Alcalde, doctor in Earth Sciences by the University of Barcelona and expert from the University of Aberdeen (Scotland) as its first author. The new study, in which the researcher Xènia Ogaya, from the Faculty of Earth Sciences and the Geomodels Research Institute of the University of Barcelona has participated, reinforces the trust on the use of capture technology and geological storage of this gas at a large scale to reduce the impact of CO₂ atmospheric emissions, generated by human activity.

The Paris Agreement sets the commitment of limiting the maximum global average temperature rise in 2 ºC to fight climate change. Photo: IPCC
The Paris Agreement sets the commitment of limiting the maximum global average temperature rise in 2 ºC to fight climate change. Photo: IPCC
Research
13/06/2018

Carbon dioxide or CO₂ ─the main cause of the greenhouse effect and global warming─ can be safely stored in sub-seafloors for thousands of years, according to a study published in the journal Nature Communications with Juan Alcalde, doctor in Earth Sciences by the University of Barcelona and expert from the University of Aberdeen (Scotland) as its first author. The new study, in which the researcher Xènia Ogaya, from the Faculty of Earth Sciences and the Geomodels Research Institute of the University of Barcelona has participated, reinforces the trust on the use of capture technology and geological storage of this gas at a large scale to reduce the impact of CO₂ atmospheric emissions, generated by human activity.

 

Anthropocene: human footprint all over the planet

The United Nations Climate Change Conference (COP21), held in Paris in 2015, is a worldwide model regarding the fight against climate change. The Paris Agreement -ratified in Spain in 2016- renews the terms of the Kyoto Protocol and sets the commitment of limiting the maximum global average temperature rise in 2 ºC to fight climate change. This agreement forces the 195 signing countries to reduce CO₂ emissions into the atmosphere derived from industrial activity, electric energy, heating and transport.

Capturing the excess of CO₂ emissions and guaranteeing its secure storage in deep geological formations is a fundamental strategy to limit the greenhouse effect and stop global warming. According to Juan Alcalde, “we are not going to reach our objectives on reducing the CO₂ emissions unless we implement this and other technologies, and increase the production and work on renewable energies”.

The geological reservoirs that enable CO₂ storage “have to be porous and permeable rocks -covered by other non-porous and impermeable rocks to act as a seal- so that the injected CO₂ stays in the sub-seafloors and does not go back to the surface”, says researcher Xènia Ogaya, from the Department of Earth and Ocean Dynamics of the UB. “In general, we select rocks in sedimentary formations that are already storing other fluids (such as hydrocarbon or water) so we are more certain the seal is functional, since they have been storing these fluids for thousands or even millions of years. Lately, the storing in basalts has been studied as well, in Iceland, but project is still being worked on. 


What happens when CO₂ is injected in the sub-seafloor?


The authors of the new study, in which experts of the University of Edinburgh (United Kingdom) take part, have added an outstanding volume of data at a global scale on natural CO₂ and methane (CH₄) storing, projects of gas storing and activity of the hydrocarbon industry (natural gas storing, injection sounding and laboratory experiments).

“This is a complex database, which took us almost four years to complete and which enables us to understand what happens with CO₂ when it is injected in the sub-seafloor”, points out Juan Alcalde.
In the study, researchers created a CO₂ geological storing model, which enabled them to work on simulations of predictions on the behaviour of stored has for the next 10,000 years. As scientific fresh news, this study gathers all the available information on the factors and processes that take part in gas storage: for instance, the natural trapping of CO₂ inside the rocks through microscopic bubbles, or its dissolution in the water which occurs inside some rocky formations in the subfloor. 

“The security of CO₂ storage is an understandable concern for citizens and governments. Our job shows subfloor storage of this gas is secure on the long run, and therefore, it is a fundamental tool to fight climate change”, notes Alcalde.

“The obtained predictions offer valuable information on the security and efficiency related to different storage projects”, highlights researcher Xènia Ogaya, who collaborated in the development of the mathematical models that enabled the researchers to make the predictions on the behaviour of CO₂ in subfloors once it was injected”.

Researcher Stephanie Flude (University of Edinburgh), who co-leads the research study, notes that “the selected inputs to build our models are conservative but realistic. It is important to highlight that those simulations that were made out of data from areas with a strict regulation of the hydrocarbon industry activity -like the North Sea- retained more than 90 % of the injected carbon dioxide after 10,000 years in 95 % of the cases”.