Carbon Capture and Storage Explained
VOICEOVER
Welcome to Melbourne University Up Close, a fortnightly podcast of research, personalities and cultural offerings of the University of Melbourne, Australia. Up Close is available on the web at upclose.unimelb.edu.au.
SHANE HUNTINGTON
Hello, and welcome to Up Close, coming to you from Melbourne University, Australia. I’m Dr Shane Huntington. Despite significant efforts to utilise environmentally responsible energy sources, the current and future load requirements of our population necessitate the use of power generation that is greenhouse gas intensive. A reduction in the energy use seems unlikely, so it is appropriate to consider methods for capturing and storing CO2, carbon dioxide, produced by our industries. To this end significant efforts in geosequestration are currently underway. Today, on Up Close we are joined by one of Australia’s leaders in carbon capture and storage. Barry Hooper is the chief technologist of the CO2 Cooperative Research Centre at the University of Melbourne, Australia. Welcome to Up Close Barry.
BARRY HOOPER
Good morning Shane.
SHANE HUNTINGTON
Let’s start by talking about capture. What do we mean by carbon capture?
BARRY HOOPER
Well of course, CO2 is the most prevalent greenhouse gas and one of the main sources of CO2 is industry burning fossil fuels generally. One of the first aspects of carbon capture and storage is to capture, separate and purify the CO2 so that it can subsequently be sent off to storage, where it will be taken out of the atmosphere. We’re very much focusing on the separate techniques that you use for removing it from the gases, and the benchmark technique if you like is what we call solvent absorption. It is where you are absorbing CO2 into liquids and these then become rich in CO2, taking the CO2 out of the gas. And then that liquid is then put through another process, where the CO2 is liberated in a pure form, thus leaving the lean solvent as we call it to go back and continue a recycle process. So it’s an absorption of the CO2 and then stripping. So that’s the – if you like the workhorse of the industry, and the one on which we base a lot of our economics. But we’re also looking at membranes, be they either polymeric or ceramic membranes, which in the crudest form, sieves the CO2 out of gas streams. It is commercial in some applications in removing CO2 from natural gas. The third form that we look at is called adsorption, which is often confused with absorption, but it’s actually where you remove CO2 onto solids, if you like. Where you have silica gel in your camera case to remove water from the atmosphere, here you are using similar solids to take that CO2 out of a gas stream. Similarly, you then take that solid, which is laden CO2 and then you process it to liberate it in a pure form. That’s the adsorption process. Another one is where we’re looking at cryogenics and hydrates, where you actually cool down the gas stream or remove the CO2 in a form, which is either using the vapour liquid equilibrium to concentrate the CO2, or to have another – you can even use water to disrupt that and produce that we call hydrates.
SHANE HUNTINGTON
We’re talking about removing or capturing the carbon emissions, primarily in many cases I suppose where you have energy generation. I assume that these processes themselves take quite a bit of energy to actually do the job. How prohibitive is that at the moment?
BARRY HOOPER
The driver of our research in capture is to reduce the cost of capture, and one of those key aspects of that is in fact an additional amount of energy that’s required to separate those gases. The thermodynamics and the basic principles of taking a dilute gas and concentrating it, is going to take some energy. And so, whether you look at – if you say a retrofit of an existing coal fired power station, there will be if you like a parasitic load, an amount of energy that’s taken out of the actual output of that power station to achieve that. I think that’s something they have to realise, that we’re changing – we’re in a paradigm shift here. That, yes, while it might take another 20% of the energy to that power plant, but you’ve now got a situation where the power plant is now very low emission.
SHANE HUNTINGTON
With the case of power plants and so forth, the intensity of the CO2, if you will, coming out is very high, it’s very concentrated, it’s easy to locate as it were. Is it possible to use these sorts of techniques to extract CO2 directly from the atmosphere? Because we already know we have a problem with CO2. We can work on preventing greater increases in what’s in the atmosphere, but is it possible to actually reduce what’s already there using this sort of capture technology?
BARRY HOOPER
There are a number of groups who have talked about the direct removal of CO2 from the atmosphere, and certainly it’s possible. The concept of acid rain, if you like, is where various contaminants are just being absorbed into the water that’s coming down with rainfall. It’s very easy to absorb, and you can get more complex chemicals to make that more efficient. The issues around removal directly from air will also be economic, where we find it is more expensive to remove CO2 from say flue gases from power stations, which might be anyway from 4% to, let’s say, 15% carbon dioxide. To remove the lower concentrations lead to the more expensive forms, where you’re then going to say I’m going to remove it from the atmosphere, which is at 380 parts per million. That is going to be a concern. I think there are opportunities where for instance, if you had an energy source or a power station fueled by biomass, which you then removed CO2 from that emission stream, that effectively, is going to be a reduction. Considering that the biomass is renewable, we’ll take CO2 out of the atmosphere through its processes, and that’s certainly a way of getting reductions from the atmosphere.
SHANE HUNTINGTON
You’re listening to Melbourne University Up Close. I’m Dr Shane Huntington, and we’re speaking with Barry Hooper about carbon capture and storage. Barry, with regards to the CO2 once you’ve captured it, what does that look like; are we talking barrels of waste; is it solid liquid?
BARRY HOOPER
Once you’ve captured the CO2 you get it into a pure firm, and where we’re looking at then storing that in geological formations, you have to transport it from where it’s captured to where it would be stored. The generally considered option is to look for locations, which are within hundreds of kilometres, thousands of kilometres within a region, and to transport that it’s most appropriate to do it in pipelines. And the most cost effective way to do it is to take that CO2 that’s been purified, convert it from the gaseous form into a liquid or a liquid like state, which is then pumpable, can be compressed and pumped to its injection site. In the main, people are focusing on the pipeline transportation.
SHANE HUNTINGTON
How exactly is it contained once it’s in its final storage location? I assume this is deep underground and it is contained in some way?
BARRY HOOPER
The whole package if you like of carbon capture and storage is to capture it, transport it and then store it in deep geological structures. If you like, putting the carbon back where it came from in a lot of cases. In that form, the CO2 in the pipeline is very dense, it’s somewhat like a fluid. When you actually can inject that below 800 metres to a kilometre below the service, it remains in that very highly dense form. What you’re looking for, for geological storage, is a particular mix of rocks, because in reality what we’re looking at is storing it in rocks. The crust of the earth is not made up with voids or the rocks aren’t empty. They are actually full largely of water, so you get very significant increases in pressure as you go deep, effectively getting hydrostatic pressure increases. We’re looking to still find reservoirs, the sort of reservoirs that have held oil and gas and CO2, in a number of cases, for many millions of years. So, you’re looking for those reservoirs where you can inject the CO2 into the rock, into the water laden rock, and also at those depths the water is actually highly saline, probably twice the concentration of seawater. But importantly, on top of these reservoir rocks highly impervious layers of mud stone, silt stone, clay stones that actually cap off the reservoir so that the CO2 will stay in those locations. Similarly to what has happened with oil and gas and CO2 reservoirs in the past.
SHANE HUNTINGTON
It’s incredible to me that you have to have this level of knowledge of the geology of the region you’re looking at. How do you go about determining where these particular regions are?
BARRY HOOPER
This is one of the fortunate things I guess, is that a lot of the technologies, a lot of the understanding of the geology and what have you, are exactly the same sort of techniques that have been employed to find locations for oil and gas over many years. The geological surveys, the oil and gas exploration companies and so on, have techniques like seismic surveys, magnetic surveys and so on, to identify initially targets. So, once you have that, then companies go and look at physical drilling to look for cores, to get validation of the seismic and other surveys that exist.
SHANE HUNTINGTON
I suspect given what you just said, you’re also looking for locations under the oceans as well just on the land. Is that true?
BARRY HOOPER
Yes. As oil and gas production is both on-shore and off-shore, you go to where you have that sort of architecture or that positioning and adjacency of the reservoirs and the seals. In fact, one of the largest trials that has been going on since 1997 in the North Sea, associated with what’s called the Sleipner Field, where they’ve been injecting a million tonnes a year of CO2 for over 10 years.
SHANE HUNTINGTON
Let’s bring it altogether for a moment. You have the capture part, you have the storage part. Where is the primary cost occurring? Is it evenly distributed amongst those two areas, or is it all in storage?
BARRY HOOPER
The way we look at the economics is generally to come up with a cost per tonne of CO2 avoided, because at the end of the day we’re looking at reductions. On that basis the proportion of costs to capture are the largest, possibly 70 or 80 per cent, and that’s why a lot of the work, certainly in the capture area that we’re looking at, is very much looking to drive down those costs. There are still significant amounts of money in terms of the equipment for transportation, inject and so on, but once you get an economy of scale if you of collecting significant amounts of CO2, and what we term, hubbing those emissions together, they on a dollar per tonne basis come down to a smaller proportion. But certainly there are significant costs in both ends of carbon capture and storage.
SHANE HUNTINGTON
You’re listening to Melbourne University Up Close. I’m Dr Shane Huntington, and we’re speaking with Barry Hooper about carbon capture and storage. Barry, let’s move on now to the issue of power generation. Take us through an example of a typical coal fired power station and the types of overall modifications and additional costs in generating power, that we will start to see, should this technology be widely adopted.
BARRY HOOPER
The traditional coal fired power station for instance, and I start there because the fossil fuel industry is really where carbon capture and storage is most applicable, and around the world coal still constitutes a significant proportion of electricity generated, and even more so in the developing countries. And certainly the growth in China and India is going to result in new power stations. So traditionally, the pulverised fuel power stations will require those that exist today, potentials for retrofit, where we’re looking at the different types of separation techniques, the potential is that you could just take that gas that’s coming from the power station, put it through a process, almost like an add on process. And the integrations really come in how you integrate the energy usage from the existing power station to the capture plant, and there will be integrations in terms of it’s largely heat exchange between some of the higher heat sources and the lower heat users for the carbon capture process. And there’ll be integrations around turbines and so on. That’s all engineering revisions and technology changes, which are being addressed and understood. One of the interesting aspects of this is a significant focus on new types of power generation technology, and particularly gasification, where the fossil fuel source, say coal, is partially oxidised. You don’t actually burn it as you do in a pulverised power station. You partially oxidise the solid fuel, and produce what we call a synthesis gas, which is a gas that contains carbon monoxide, carbon dioxide, hydrogen and some other contaminants. But largely you are converting solid fuels to a gas. It’s at high temperature and high pressure, and then you actually burn those gases through a turbine, somewhat similar to that used for natural gas combined cycle production of energy. There are slightly different applications of the different separation techniques in what we call pre-combustion - the gasification where you remove the CO2 prior to the final combustion of those gases. And so the integration of those largely bringing these in as a new build to power stations, is an interesting new feature of the carbon capture and power generation components of CCS.
SHANE HUNTINGTON
Now the CO2 Cooperative Research Centre programme has a number of industry groups it’s interacting with, and presumably a number of field trials. Tell us a bit about these industries that you’re working with, and the sorts of I guess real life scenarios that are going on.
BARRY HOOPER
We have the involvement of large international companies in the oil and gas and the resources industries, as well as generators and other associated organisations who really see this as an issue that needs to be addressed, both for their industries and also for the community. Where we’re looking at research activities around capture and storage, the other component is very much on demonstrations. Because at the end of the day while all these techniques have been used and are applied in various forms at various sizes, where we’re looking at it for large scale and deep cuts of CO2, we really have to go to put together some equipment that’s larger than has been done. And this form of new industry effectively has to be developed, and so it’s about getting ever increasingly sized demonstrations in place. Where the capture issue as I mentioned was around cost, around the storage, is to demonstrate that both from a regulatory perspective and a technical perspective, to give confidence to the communities and to governments about this as a technique. We’ve been involved in some demonstrations of storage. Most recently a project we call the CO2CRC Otway Project, which is injection of 100,000 tonnes of CO2 into a region in Western Victoria here in Australia. We’ve found that it’s taken several years to put this project together, and there are two main aspects of it. Firstly, to bring along governments and legislators to understand how you need to put together the protocols, etc for this new industry. But from as technical perspective also to look at monitoring and verifying that the CO2 is staying where it should and that as we expect it will, to raise that level of confidence.
SHANE HUNTINGTON
Barry Hooper, chief technologist of the CO2 Cooperative Research Centre here at the University of Melbourne, Australia, thank you for being our guest today on Up Close.
BARRY HOOPER
Thanks Shane.
SHANE HUNTINGTON
Relative links, a full transcript and more info on this episode can be found on our website at upclose.unimelb.edu.au. We also invite you to leave your comments or feedback on this or any episode of Up Close. Simply click on the add new comments link at the bottom of the episode page. Melbourne University Up Close is brought to you by the Marketing and Communications Division in association with Asia Institute of the University of Melbourne, Australia.
Our producers for this episode were Kelvin Param and Eric Van Bemmel. Audio recording by Craig McArthur. Theme music performed by Sergio Ercole. Melbourne University Up Close is created by Eric Van Bemmel and Kelvin Param. I’m Dr Shane Huntington. Until next time goodbye.
VOICEOVER
You’ve been listening to Melbourne University Up Close, a fortnightly podcast of research, personalities and cultural offerings of the University of Melbourne, Australia. Up Close is available on the web at upclose.unimelb.edu.au. Copyright 2008, University of Melbourne.
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