Here we’re going to discuss about carbon capture and sequestration. So what is it, what kind of a technology is that? It looks almost frightening. So carbon capture and sequestration or CCS, I’m going to use the acronym a lot because otherwise it’s too long, is the capture of CO2 at large stationary point sources such as coal or gas fired power plants, oil refineries, cement plants, or steel mills.
What are the common characteristics between these different types of activities? It is that they emit exhaust gases with a relatively high concentration of CO2. And it’s an important aspect of where CCS could be feasible.
We need to have somehow a pretty high concentration of CO2 within the entire exhaust gases to be able to operate the CCS technology. That being said, there are broadly speaking, I mean of course there are many more than that, but broadly speaking there are two different types of CCS technologies. What is called pre-combustion CCS technology and post-combustion CCS technologies.
So very simply with post-combustion technologies the CO2 is captured after combustion through a chemical process that separates CO2 from the other gases. Whereas for the pre-combustion technologies the CO2 is removed from the fuels themselves through other chemical processes, but this time as the name obviously indicates, before combustion. So that’s for the capture part of carbon capture and sequestration, CCS. But what happens after that, what do we do with the CO2, because it cannot simply remain in the air once we have separated it through one of these two different techniques?
Well after the CO2 would be captured at the point source, it would be transported by pipeline to an appropriate geological site for storage under the ground. So what does that mean? I mean what could be considered as an appropriate geological site? I mean what are the conditions that must be met by these sites to safely sequester the CO2 under the ground for a very long period of time? Well as you can see on the picture in front of you there are broadly speaking again, there are more than that, but broadly speaking, three main different options for the geological sequestration of CO2.
- The first is that what is called mineable coal beds, so it’s a fancy term to speak about the coal veins that cannot be mined.
- The second type is the depleted oil or gas reserves.
So very simply the empty oil and gas fields, ones that have been exploited where you could put the CO2 back in. And the third and in fact the most important because the scale of these third categories is potentially much higher than the other two, the third type is what we call the deep saline aquifers. So types of geological grounds that are found deep under the earth’s surface.
So that was for a very general description of the different steps in the process of carbon, capture, we should add, transportation and sequestration of this CCS. So where are we in the process of developing this technology? Well CCS has not yet been proved as a whole system at a large scale. But all the individual components of CCS, so the capture, the transport, the sequestration, all of them are pretty well established technologies and they have been tested in demonstration projects. And to date there are approximately 12 CCS projects that operate under the globe at stationary point sources and most of them are projects on natural gas processing plants while some others are on fertilizer production plants.
So what is really the challenge going forward? I mean what are the obstacles that would need to be overcome if carbon capture and sequestration was to become a real option that could be deployed at scale in many countries? Well there are serious challenges, different types of challenges. One is costs. The other is scale. And finally there is an issue, an unresolved issue so far regarding the verification that carbon is really sequestered under the ground.
- So the first open question, what is the optimal power plant design to facilitate carbon capture at relatively low costs?
- Second open question, what is the best choice of geological sites for the storage of CO2 potentially at a very large scale? I mean we might be talking about tens or hundreds of billions of tons of CO2 to be sequestered during the coming decades. So where is the geological potential for that? I mean which sites would we select to do that?
- Third open question, what is the design of a reliable and economic hope infrastructure for the transport of CO2?
- And if you want a fourth question, what are the mechanisms for insuring that the CO2 that is stored remains permanently out of the atmosphere, a very important question indeed, because it determines the success of CCS eventually.
So these are important questions. There are of course other questions. All of them need good answers. But given the importance of carbon and capture and sequestration in many of the deep decarbonization scenarios, including the ones
I’m going to present when I discuss the results of the deep decarbonization pathway project, given the importance of this technology in so many of these scenarios there is really an urgent need to scale up the research, the development and the demonstration of CCS to test if it can be deployed at scale, if it can be deployed at, at scale safely.
And if it can be deployed at scale at acceptable costs, because the truth is that being able to rely on the large-scale deployment of CCS would greatly facilitate the deep Decarbonization efforts, given what we stressed many, many times now and it is the obvious very heavy dependence of the energy systems on fossil fuels today.