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Carbon dioxide: Acidic oceans and geosequestration
Ocean uptake of carbon dioxide: Are the oceans acidifying? – Dr Steve Widdicombe
Ocean uptake of carbon dioxide: Are the oceans acidifying?
We have got a pictorial representation here of the global carbon cycle. Our planet consists of a number of very large stores of carbon, and the carbon moves between these stores, at various rates and with various amounts, to circulate round. But of all the stores on our planet, the oceans are by far the largest. Pre-industrially – that is before 1800, before we started burning fossil fuels – it was estimated that 38,000 gigatonnes (Gt) of carbon was contained within the oceans and the organisms that lived within the oceans. I will just explain that 1 Gt is 1015 grams, which is 109 tonnes. So if you put nine zeros after the figures you see for tonnes, you will realise the vast amounts that we are talking about. The ocean contains approximately 95 per cent of all the carbon that exists on our planet, so it is an immense store. Previously it was estimated that the oceans were acting as a carbon sink and were taking up approximately 2 Gt of carbon per year.
What has been our impact on the carbon cycle? By burning fossil fuels, in essence what we are doing is releasing carbon – which would normally have been locked up in geological reservoirs – before it would have come back through normal cycling. Approximately 6 Gt of carbon is released per year into the atmosphere by human activities. And atmospheric concentrations today are higher than at any time for at least the last 420,000 years. About half of the carbon dioxide that we have produced by burning fossil fuels and in the production of cement over the last 200 years has been absorbed into the oceans. It has been calculated that between 1800 and 1994 that was a total of about 118 Gt of carbon. Obviously, 1994 was 11 years ago, and it is now estimated that that figure is nearer to 140 Gt of carbon. That represents 500 Gt of carbon dioxide.
Why is the carbon dioxide going into the oceans? Carbon dioxide is a gas, and like every gas it obeys Henry's Law with respect to passing into a solution. As you increase the atmospheric concentration of carbon dioxide, the carbon dioxide will go into the seawater. Some of it is just taken up as aqueous carbon dioxide, whilst the rest of it turns into carbonic acid H2CO3. Carbonic acid is a weak acid which easily breaks down into hydrogen ions and its constituent anions. So what we have is a distribution of the carbon dioxide between the major carbonate groups, bicarbonate HCO3 and carbonate CO3. These carbonate, bicarbonate and CO2 elements are referred to as dissolved inorganic carbon, and all of these elements are very important for ocean systems. We can see from the distributions on this slide that bicarbonate is by far the most abundant. The oceans naturally maintain a high abundance of bicarbonate, and they do that by using carbonate to buffer excess CO2 as it goes in. This is known as the 'carbonate buffer', and we perceived that this was the way in which the oceans maintained their pH. It is the way they maintained a very stable chemistry for many, many years. Our previous thoughts were that this buffer was very resilient and pH would not change. However, we are becoming aware of the fact that the carbonate buffer cannot deal with the amount of carbon dioxide that we are now putting into the oceans.
We talk a lot about pH but I think it is important to reiterate how we measure pH. pH is actually a measure of the free hydrogen ions that exist within a solution. If you imagine water, some of the constituent parts of water will actually break apart to create hydrogen ions, which are positively charged, and hydroxide ions, which are negative. The concentrations of hydrogen ions and hydroxide ions are roughly equal, about 10-7 moles per litre. This means that this is a neutral solution, with a pH of about 7. (This is where neutral pH 7 comes from.) Acid solutions are deemed to have an excess of hydrogen ions, and alkaline solutions have an excess of hydroxide ions. You may notice that this measure is actually negative logarithmic. That is, when we talk about pH change, we are talking about changes in the concentrations of hydrogen ions. And a tenfold increase in the concentration of hydrogen ions creates a decrease in pH of one unit. It is important to remember that, because when we start talking about drops in pH, the numbers that we talk about look quite small but they really equate to quite large changes in the chemistry.
Our oceans today are slightly alkaline, with a pH of 8.1, give or take 0.3 pH units depending on where you are and depending on what biological processes are going on. But the oceans are becoming more acidic as they begin to take up more carbon dioxide. The net effect of dissolving carbon dioxide in seawater is to increase the carbonic acid concentration, increase the hydrogen ions and increase the bicarbonate ions. You decrease the carbonate ions. So you are shifting the whole equation on this slide back towards the left. And when we get onto talking about the environmental impacts of this, that is a very important thing to remember, because carbonate plays a very important role in aspects of the marine ecosystem.
The figure you see here has become quite famous now. This is a piece of work done by Caldeir and Wickett, published in Nature in 2003, whereby they have been able to predict the likely pH change under a well-established emissions scenario published by the IPCC, the Intergovernmental Panel on Climate Change. They have already demonstrated that pH has already changed by 0.1 pH units since pre-industrial times. A change of 0.1 doesn't sound an awful lot until you remember that that is a 30 per cent increase in the concentration of hydrogen ions in the last 200 years. To put that into some kind of geological perspective, the rate of pH change that we are now witnessing is greater than we have seen for the last 20 million years, and we are entering an era where pH is lower than we have seen for a considerable period of time.
pH is variable in the marine system. It responds to biological processes and it responds to physical processes as well. What you see in the red area near the top of the lower figure here is an area of high productivity, when marine algae are using carbon dioxide to fuel photosynthesis. In doing so, they remove carbon dioxide from the system and we can see an increase in the pH; the water becomes more alkaline. So this is demonstrating that there is a very tight link between biological activity and pH in the water, and carbon dioxide.
We can look at this variability in marine systems and we can accept that there is a degree of variability. So then you would say, 'Well, 0.1 units change doesn't seem to be very much. How does that actually reflect what we are going to see in different parts of the ocean?' Shown here is a model which was generated for the North Sea. What I believe it shows is that by 2050, under quite a conservative estimate of atmospheric concentrations, the range of pH that the North Sea will experience will be outside the range it has experienced for the last 20 million years. We don't know how the physiological and community aspects of this system can adapt or can buffer this change. But as we are looking at a change in carbon dioxide in the atmosphere that is approximately 100 times faster than we have seen for a considerable period of time, it strikes me as being unlikely that many of the systems that operate within the marine realm today will be able to adapt quickly enough to respond.
Before I go into some examples of how pH change and CO2 change are going to impact on specific organisms, I would like to recap some important information about calcium carbonate. A lot of organisms – molluscs and corals and echinoderms – produce calcium carbonate, and the way in which they do it is to take the calcium ions and combine it with bicarbonate ions. You may say, 'Well, we've seen that bicarbonate ions are actually increasing, so surely all this carbon dioxide in the water will help them.' It will help them to calcify, but what actually happens is that the production of calcium carbonate also generates more CO2 and water molecules. We know that carbon dioxide and water molecules combine very easily to form carbonic acid. And the carbonic acid combines with carbonate ions to produce more bicarbonate ions. So if we have a lot of carbonate ions we can actually follow this whole process through and calcification works fine. If we are lacking in carbonate ions – and remember that that is what is happening, the carbonate ions are being used up because of the carbonate buffer – these ions are unavailable and the whole process is shunted backwards. So because carbonate ions are becoming scarcer, there is an inhibition of calcium carbonate formation. To summarise: marine organisms that construct calcium carbonate structures are dependent on the presence of carbonate. Calcium carbonate will dissolve unless there is a sufficiently high concentration of carbonate ions. And calcium carbonate becomes more soluble with decreasing temperature and increasing pressure. This is another very important aspect of calcium carbonate chemistry to remember: the colder the water is, the more likely calcium carbonate is to dissolve, and the deeper the water is, again the more likely it is to dissolve. That means it is more difficult to operate as a calcifying organism if you are in cold, deep water. So polar regions are particularly difficult to calcify in. What you will now have, because there is a depth and temperature relationship with the solubility of calcium carbonate, is that there will come a point in any ocean where, in the top surface layers, you will be able to calcify and lay down calcium carbonate, but as you go deeper you will get to a depth or a temperature where calcium carbonate dissolves. The boundary between these two states of water is called the carbonate 'saturation horizon'. Carbonate comes in two forms, as calcite and as aragonite. Different marine groups utilise different types of carbonate. Foraminifera, which are small microorganisms; coccolithophores, which are marine algae; echinoderms, the starfish and urchins; molluscs, the seashells; and macroalgae all use calcite, which is much less soluble than aragonite. So the saturation horizon for this form of calcium carbonate is generally deeper than it is for aragonite. So we would expect that organisms that use aragonite – corals, pteropod molluscs and some other macroalgae – will probably be more susceptible to changes in ocean pH than the organisms that use calcite. I have highlighted coccolithophores and corals in this table because I am going to go on to talk a little bit about those organisms in more detail. So what does a change in pH mean for the oceans and the organisms that live in them?
First of all, let's talk about the effects on microorganisms. You may think: why are plankton important, why are the small plants that float around our oceans important? Well, it is because they produce 50 per cent of the global primary productivity. All the rainforests and all the temperate forests add up to only the same amount of carbon production, of primary productivity, as all the small microorganisms in the ocean. So on a global scale these plants are very important. Carbon dioxide and pH change could influence a whole host of different processes. With regard to photosynthesis, you would think that if you increased carbon dioxide for a plant, photosynthesis would increase. But marine plants evolved in a time when carbon dioxide levels were much lower than they are today, and many species have developed specific enzymes, called Rubisco enzymes, which act to concentrate carbon dioxide. So what we have is marine plants which are not limited by carbon dioxide. We will only see small increases in photosynthesis, because most of the organisms are limited by other factors such as temperature, light or nutrients. That impacts again on growth and composition: there is little effect. Most of the effect will be due to changes in nutrients. These organisms, as well, are limited by trace metals. We know that pH has a very strong relationship with the speciation of metals, but as yet very little work has been done to look at the exact impact of metal speciation on microalgae growth. What I will go on to talk about next is the nutrient speciation element, which probably contains most of the research that has been done to date, and most of the knowledge.
This is quite a complicated diagram – please don't be fazed by it – but there are certain key messages to take home from it. One is that as pH changes, the relative balances between the species of key nutrients also changes. Nitrogen, in particular: there is a balance between ammonia and ammonium which is pH dependent, with the concentrations of ammonia actually decreasing as pH declines. Inorganic phosphate, as well: there are particular species of inorganic phosphate that are utilised by marine plankton. (We have here a picture of some diatoms, some typical marine plankton.) These organisms take specific species. So any changes in the species or the distribution of nutrients is going to be important for their wellbeing. Changes in the relative proportions of phosphorus, nitrogen and trace metals may have an effect on plankton diversity.
There are also bacterial processes which are inhibited by pH. Shown here is a very important process called nitrification and denitrification. This bacterial breakdown of ammonia/ammonium to nitrite/nitrate and eventually to nitrogen gas has now been experimentally demonstrated to be negatively impacted by reduction in pH. So there is a very important biological process, controlled by bacteria, which is going to change.
This process doesn't happen in the same way in the same place. There is a great deal of environmental heterogeneity; a lot of spatial changes occur. And again – excuse me for using the North Sea because it is an area that we are familiar with and I didn't have any examples from around the Australian coast – what we have here is a shallow ocean where denitrification in the sediments is very important. We have a model simulation here of the rates of denitrification in the year 2000, and then the forecast rates with respect to a worst case scenario simulation. We can see from these figures that there are actually hot spots, where the differences and the impacts are going to be felt most. So it is not a general, across-the-board impact; there are going to be places that are very badly hit and some that are hardly hit at all. But our model is also very conservative, in that although the denitrification here has been parameterised for sandy sediments, a lot of the sediments are muddy and denitrification is much more important in muddy sediments. So what you see here is a best case scenario for what will happen, and even so a 10 per cent decrease in denitrification will be consistent across this domain. Denitrification is a very important process in removing excess nitrate from the system, so the implications here for things like eutrophication are quite serious.
There is a whole suite of effects on larger organisms that we could go through, but we don't have time today. Scientists are only beginning to get a handle on a lot of these impacts; the evidence is being amassed day by day and is still very much in its infancy.
However, some examples of the effects are shown here, for instance on zooplankton. If you don't want to consider zooplankton as important in their own right, then you can consider them as the food of fish. There is evidence that not only does reduction in pH cause mortality in zooplankton but it also causes a reduction in fertility. So if they don't die, they will at least be unable to reproduce at the present rate. The organism at the lower left of this slide is very important. This is a pteropod mollusc, and as you might remember from a previous slide, pteropod molluscs are dependent on aragonite. They are also exceptionally important organisms for the Southern Ocean. In the Southern Ocean, these organisms can occur in numbers of 1000 per m3 of water; they provide an awful lot of food for higher trophic species. So if you consider where they live – the Southern Ocean, high latitudes, cold waters, areas where the aragonite saturation depth is rapidly approaching the surface – you can see that they are going to find it increasingly difficult to lay down their calcium carbonate shells. We may even see the disappearance of the pteropod from the Southern Ocean over the next 100 years. This has huge implications for the whole ecosystem. Organisms will search for other prey; this may well have an impact on juvenile fish. As yet we are not sure what the exact ecosystem effects will be, but there will be effects.
Large organisms which have very high oxygen demands, such as squid, are very susceptible to changes in pH. In fact, a recent study has shown that a decrease of pH by 0.25 units will cause a reduction in their oxygen-carrying capacity of 50 per cent. That is quite a heavy metabolic load to be carrying, and several papers have indicated that squid are seriously under threat now. A piece of research which has come to light just recently, and which I haven't had time to include on the slide, is that fish create calcium carbonate in their guts as a mechanism for their osmoregulation. They swallow seawater, and they deposit calcium carbonate granules in their guts. They maintain their guts at quite an alkaline level in order to do this. Research is now going on to see what kind of impact the surrounding seawater pH is going to have on this effect. Obviously, if it takes more energy to calcify and to maintain your osmoregulatory balance, that energy is going to have to come from somewhere, and either it will come from growth or it will come from reproduction. Squids and fish are obviously important food resources for humans, whales et cetera. So losing these organisms would have knock-on effects up the ecosystem.
We mentioned calcification, so I am going to talk a little bit about two calcifying organisms – the coccolithophores, these marine algae, and also the corals. But please bear in mind that these aren't the only calcifying organisms; there are a lot of organisms that could be affected.
So why are coccolithophores important? They represent the largest current producer of calcite on the Earth. You may have seen pictures of the White Cliffs of Dover, in the southeast of England. All those cliffs are made up of the dead bodies of coccolithophores. They create enormous blooms. The panel at the top right here shows the UK, with a single coccolithophore bloom as seen on a satellite image. It covers hundreds of thousands of square kilometres. They play an important role in the global carbon cycle, because they actually transport calcium carbonate to deeper waters and the sediments. They are an organism that is responsible for removing the carbon from the system through what we call the 'biological pump'. Coccolithophores are also major producers of dimethyl sulphide. Some of you may of heard of this; it is an important greenhouse gas, and it is thought to be very important in the formation of clouds, so providing a negative feedback to climate change. By losing coccolithophores we are losing this important negative feedback. And, of course, a reduction in coccolithophores would cause a change in the composition and the diversity of plankton communities, and a change in biogeochemistry.
Does CO2 actually damage coccolithophores? Here you can see some work done by Ulf Riebesell, which was published in Nature in 2000. He looked at several species of coccolithophores. At the top we have organisms which were grown under conditions of approximately 300 ppm, which represents a situation that would have been at the beginning of the Industrial Revolution. If we contrast that with the state of the organisms grown under conditions which simulate 780–850 ppm atmospheric concentrations, we can see that there is a definite impact on these organisms. Their calcification is being markedly affected.
Coccolithophores are relatively easy to model. They respond very predictably to physical responses, stratification and mixing, so we have got quite an accurate model. Here we can see how we can model differences between a very strong bloom in one year and a weak bloom in another. And that is all linked in to the physical parameters of the model. What happens if we put pH and carbon dioxide into these models?
As you can see here, in the year 2000 we still see the usual nice big strong blooms – differences from year to year, granted, but still a bloom every year. As the scenarios approach higher and higher levels of atmospheric carbon dioxide concentrations, you can see that the blooms decrease until eventually, in a worst case scenario in the year 2100, approximately 1000 ppm carbon dioxide concentrations, the blooms have all but disappeared. Not only is it the case that the organisms themselves are becoming abundant, but the number of liths – the calcium carbonate plates which grow on them – are actually being reduced per organism. This will have an enormous impact on the biological pump and also on the pelagic ecosystem.
What about warm water corals? We know that they only occupy approximately 1.3 million square kilometres, which is less than 1.2 per cent of the world's continental shelf area. Despite that small amount of area covered, millions of people directly depend on healthy coral reefs for tourism and fisheries. These are also highly diverse ecosystems. And they occur mostly in the warm, alkaline, sunlit waters where there is high aragonite saturation.
Many of you would know all this, but I think it is important to recap what exactly a coral is. A coral is an organism that forms a powerful mutualistic symbiosis with an alga. That is how corals obtain their energy: the algae catch the energy from the sun and provide nutrients to the corals in order to allow them to grow.
So what is the fate of corals? Almost 30 per cent of warm water corals have now disappeared since the beginning of the 1980s. This has largely been attributed to increased frequency of warm seawater periods, as shown on the graph here, moving above a threshold and causing a phenomenon called bleaching, in which the algae within the corals die.
But high atmospheric CO2 is compounding this problem by lowering the aragonite saturation state of seawater. Various models have now predicted that we can actually estimate the amount of aragonite, or the aragonite saturation state, within the Pacific Ocean during the pre-industrial time. Here we can see a lot of green colour. If you think that corals need approximately 3.28–4.06 saturation level to be able to grow and to calcify, that corresponds to the green area. The predictions we are making for 2060 are that the green area will have pretty much disappeared, so corals are going to find it very, very difficult to calcify. Experiments have also shown that merely by doubling the atmospheric CO2 concentrations, calcification rates could decrease by 10–30 per cent, and some studies have even shown that to go up to 54 per cent.
What does it matter? Apart from the fact that we are losing a very diverse ecosystem, what does it matter in money? Globally, corals support millions of people through subsistence food gathering and tourism. So far, studies have been based primarily on warming and have not considered the changes in ocean chemistry; therefore, the predictions made by these models are very conservative. In a recent study on the Great Barrier Reef, where the area of coastal Queensland was split into five regions, scientists tried to estimate the value of the coral reef to the gross regional product of that area. They came up with a figure of $A1.4 billion, which is approximately 60 per cent of the entire gross regional product for coastal Queensland. The most dependent region was north Queensland. Of the $A900 million in tourist revenue, $A800 million was actually directly associated with having a healthy coral reef.
They then went on to look at what the effects would be if the reef became degraded and lost some of its appeal to the tourists. They used in their calculations very realistic scenarios which had been generated by the IPCC, the Intergovernmental Panel on Climate Change. They estimated that the sort of reef degradation they would expect to see with an atmospheric concentration of 600 ppm by 2100 would cost local economics a minimum of $250 billion over the 19 years between 2001 and 2020. And if CO2 was much higher, which it is not unrealistic to expect, financial costs could be as high as $14 billion.
This problem is not limited to Australia. Caribbean reefs provide annual benefits in the region of $US3.1 billion to $US4.6 billion, and by 2015 the loss of income due to reef degradation is estimated to be several hundred million dollars per year. Hawaii is the same – $US364 million is attributed to having coral reefs around Hawaii. A lot of that is linked in to the snorkelling and diving tourism industry, but there are also things like property, where people are prepared to pay more money because their house is near a nice coral reef. 'Non-use' represents what people are prepared to pay in order to have the knowledge that the coral reef exists, and $US2.5 million is on fisheries. These are just financial costs and do not actually include any of the ecological costs that may go along with provision of the reef, for example protection of other habitats such as seagrasses and mangroves. These are much more difficult to attach financial values to, but please bear in mind that they are also services that the reef provides but that have not been costed in.
Warm water corals are not the only corals. Often referred to as 'deep water' corals, the species shown here exist at depths between 10 metres and over 1000 metres. Their distribution is probably controlled by temperature. Unlike warm water corals, these organisms are non-photosynthetic, and rely on organic matter from above. They are found all over the world, and they have only recently been discovered. The exact area that these corals cover is unknown, but it is estimated that it could equal or even exceed that of the warm water corals. They are long lived and slow growing. Colonies have been radiocarbon dated to be up to 8000 years old, and fossil records show they have been around for millions of years. Now, we have only just found these ecosystems, and they are already under pressure. They support a diverse ecosystem.
Recent oil exploration off the shelf around the UK has turned up hundreds and hundreds of reefs of cold water coral. (This particular species is Lophelia pertusa.) Remember that the shallowing of the aragonite saturation horizon will have a serious impact on these ecosystems.
What I hope to get across with this slide is the fact that the marine ecosystem is a very complex thing. If you start impacting one area, that is going to have indirect effects on another. We have only just begun to look at the various different effects in the different parts of this ecosystem, and wherever we look we seem to find detrimental effects with pH and CO2, all of which are linked in together and exacerbating each other. It is a very complex and intricate ecosystem, and quite vulnerable.
In summary, the oceans are absorbing much more of the CO2 we produce and are becoming more acidic as a result. Almost half of all the human-derived carbon dioxide produced in the last 200 years is now in the oceans, and they currently take up 1 tonne of human-derived CO2 per year for each person on the planet. Ocean acidification is a predictable response, probably more so than global warming. Ocean pH has already changed by 0.1 pH units since 1800. (That is a 30 per cent increase in hydrogen ions.) pH also looks likely to decrease by at least another 0.5 units by 2100. The rate of change in ocean pH is at least 100 times greater than the world has experienced for millions of years. Ocean acidification and global warming are intrinsically linked. A warmer ocean absorbs less carbon dioxide.
So ecosystems will be affected. Seawater pH and carbonate concentrations are critical in marine systems, and the best scientific information suggests that corals (both warm water and cold water) will be adversely affected, along with the communities they support – not just the marine communities they support but also the human communities they support. Many other marine creatures depend on calcification, and they will also be affected. Non-calcifying organisms may be affected too, through physiological stress, reduced reproductive success and also reduced resistance to infection. Ecosystem functions such as nitrogen cycling and dealing with eutrophication will be affected. We believe that ecosystems will survive, but one of the key questions is: will they actually contain the organisms that we want them to contain or that we need them to contain? What can we do about it ? I will quickly whip through a number of the suggested ways in which we could possibly address this issue.
You may have heard of some of these solutions. The first, obviously, is to drastically reduce the release of industrial CO2. I don't think anyone will disagree with that. The others are a concept called ocean fertilisation, ocean sequestration, and geological sequestration.
Ocean fertilisation works on the principle that there are areas of our planet, such as the Southern Ocean, where there are lots of nutrients kicking around but very little productivity. Something is limiting the plankton growth, and that something is found to be iron.
A number of experiments have been done where iron has been added to the ocean, to see if we can increase the rate at which the plankton grow and take up the CO2, and basically increase the biological pump. So what happens?
In these regions, if you add iron you do stimulate plankton growth. The ecosystem is transformed from a low-particulate-export to a high-particulate-export system, which basically means it increases the rain of organics down to the sea floor. But there is a depletion of the inorganic nutrients and the dissolved CO2 in the surface. Depending on where the fertilisation is done, this depletion can have serious downstream effects, with an impact on global carbon fixation. Also, even though the nutrients were not being used in the Southern Ocean, they were going to be used somewhere else. So if you use them in the Southern Ocean, it means they are not available somewhere else to be used. It has been shown that on a global scale, rather than just a regional scale, fertilisation actually decreases the amount of carbon that the oceans can absorb. And the enhanced sinking flux leads to lower oxygen concentrations below the thermocline, and potentially nitrous oxide production. (Nitrous oxide is another potent greenhouse gas.) So, whilst fertilisation was thought to be a possible answer early on, I think it has been pretty much shown to be not the answer we had hoped for.
Ocean sequestration is the dumping of CO2 actually in the water on the seabed.
Experiments are currently under way in America and Japan to look at the environmental effects. So far, these experiments have shown that the environmental consequences of putting CO2 on the sea floor are catastrophic.
That leads us on to geological sequestration. From my point of view, and the area of work that I am particularly interested in, it is not the technology of getting it under there, it is just to bear in mind that we still don't know what the potential environmental impacts would be if facilities like this were to leak. But I think that, as scientists, what we need to do now is to not rule out any possibilities, but to research the science so that we can actually understand the full implications of any policy decision that is made.
What I would like to leave you with is a picture of a sunset over a warming ocean which now is 0.1 pH units lower than pre-industrial, and now contains over 500 Gt of fossil fuel. What I would say to you is that ocean acidification is surely another argument for the control of CO2 emissions. Discussion Question – Steve, you present a scenario where a decrease in pH will cause a collapse of the marine ecosystem. You present pH going back 25 million years, but if you go back further, about 100 million years, in the last greenhouse world we had good ocean productivity and a lot of preservation of organic matter. So what inherently is the difference there? And is there evidence going back that far that maybe pH levels were lower in that time of greenhouse gas, and organisms could still survive? Steve Widdicombe – Yes, you're right. We did have an ecosystem there which functioned, which was the point that I made towards the end. But the ecosystem that existed then was not the ecosystems that we have now. I have no doubt that presumably organisms will survive, and an ecosystem will come out at the end of this that will enable the whole system to keep functioning. I don't think the ecosystem will collapse; I think it will change. If we are happy to let it change, then we have no problem. But if we want to maintain the ecosystem as it is now, or if we want to maintain it with specific attributes that we feel we need as a species to survive, then I think it is important that we address these issues. There has been an example in Chesapeake Bay, in the United States, where eutrophication has actually altered the ecosystem in Chesapeake Bay to such an extent that where there was once a flourishing fishery for high-quality fish, the ecosystem is now dominated by bacteria and jellyfish. As far as the ecosystem is concerned, that is back in the Cambrian. So it is still functioning – it is still processing nutrients, it is still processing organic material – but is it an ecosystem that we are happy to live with?
Geological storage of carbon dioxide: How long can we keep it out of the atmosphere? I would like to acknowledge my co-authors, Chris Boreham and Frank la Pedalina, who were involved in some of the early work that we did looking at CO2 storage, especially in terms of how long we can keep CO2 out of the atmosphere.
I would also like to acknowledge quite a number of people that I have worked with over recent years, at Geoscience Australia, at CSIRO and at the Australian School of Petroleum, and also the support I have had from the CO2CRC and the Department of Industry, Tourism and Resources (DITR).
You see here an outline of what I am going to talk about today. We will have a very brief review of what geological storage is; what the nature of the problem is in terms of world emissions; whether we are looking at temporary or permanent storage; and how we get at storage times in terms of geological storage. And to do that I have to describe what a petroleum system is, and the sort of analysis that we do in petroleum exploration work. I will also pose the question, at the end, of how long is long enough.
So what is geological storage? Essentially, it is where you can capture and separate the CO2 at some sort of processing plant or power station. At the moment we can do that, but the issue is the cost. At gas locations with high CO2 that is a sunk cost, so it is not as big an issue, but at a coal-fired power station they are talking of around $40 to $70 a tonne. Then you need to compress and transport the CO2 to a storage site. That is not an issue; we have been doing that for decades in the oil and gas industry for methane. Then you might need to compress the CO2 again and inject that into your target formation. The CO2 will migrate away from that injection point and then you will monitor the movement of that. Now, we think that is okay, but there is still quite a bit of research to be done. Finally, we hope the CO2 will be permanently trapped – depending on how you define permanent. There are a number of trapping styles that I will go through, in terms of what we describe as a hydrodynamic or a solution-style trap, whether it is mineralogical trapping or structural trapping. I will give you an example of some of those.
Often you will hear people talk about supercritical CO2. This relates to the depth, pressure and temperature at which you can inject CO2 so it will be supercritical – at supercritical state it will be about 500 times denser than it is at the surface. This is good, because you can get a lot of CO2 into a small space. Depending on the geothermal gradient in the Earth, this will be at around 800 metres sub-surface.
There is a variety of options that have often been put forward for geological storage. Starting on the right-hand side of this slide and working to the left, we are talking about enhanced coal bed methane, where you can inject the CO2 and get an economic benefit by getting methane out; you can inject potentially into coal seams, or into depleted oil and gas reservoirs; you can use enhanced oil recovery (EOR), as the CO2 acts as a solvent and drives out oil that is still remaining in the reservoirs, and therefore you can get that benefit; and finally you can use deep saline reservoirs, which are reservoirs deep in the sub-surface, full of water which is highly saline. This is really where most of the capacity is.
We will just look at this example. This is a typical sort of thing that you might have for an anticline – the dome feature across this oilfield – or a depleted field, or some sort of structural trap.
If you inject the CO2, you will see it in cross section as well as in plan coming up to the base of the seal and migrating out and filling up that structure. Note the scale here: we are talking about one to 10 kilometres.
The beauty of these types of sites is that they have got proven seal potential. Within Australia there is not a lot of opportunity, but in places like the US and Canada there is substantial opportunity. Of the total capacity it is a relatively small percentage, but because it is over an oilfield you have a known data set in terms of wells and seismic data.
Some of the issues are that you might have to identify spill points, such as out on the edges of the field; where you have got existing well penetrations, they are potential leak points; and in production of the field there will be effects such as geomechanics and pressure depletion aspects. Also, if you have other hydrocarbons in the region, you could potentially compromise those resources.
A second style of trap is this hydrodynamic or solution-style trap, and here we have changed scale to tens to hundreds of kilometres. So these are large regional structures.
And again if you inject, the CO2 will migrate along the base of the seal. As it migrates, it will start to dissolve into the formation water within the reservoir. At that point, the CO2 will become more dense than the surrounding formation water, and work done at CSIRO has shown that this will then migrate the CO2 back into the deeper centre of the basin – which is a really good outcome.
These are very large structures; they have enormous total capacity. There are many opportunities around Australia and around the world in what we call 'passive continental margins', such as the North West Shelf, but they do rely on this long-term dissolution and this long time frame for migration. But that scenario actually might work for us.
Some of the issues are that there is a lot of research required on these types of traps, and we need to get pilots under way to understand them; as you migrate away from known data points such as wells, how continuous your reservoirs and seals might be will be an issue; and if they migrate a long way up-dip, then there might be issues in contaminating shallow groundwater horizons.
We have been involved in a major study that we did between 1999 and early 2002, looking at over 100 sites around Australia. We term these things ESSCI, which is a good Australian play on the term 'Esky' but stands for a potential 'environmentally sustainable site for CO2 injection'. In the study we looked at over 100 sites across a huge range of different trap types here – in depleted fields, dry structures and coal bed methane – but essentially when we looked at all these different trap types we found that most of the volume is sitting in the hydrodynamic traps.
We extended this study out to the world, to look at storage opportunities and at where might be prospective for CO2 injection. This is not a map of where CO2 potentially exists but of where you might begin to look. So you can see there are many opportunities around the world, potentially.
If you overlay the emissions for the world, you can see the major issues that exist in China and certainly Japan, and in parts of India, through Europe, and the USA.
But then if you put a buffer around that – some sort of economic limit in terms of the pipeline length, say of 300 km – it starts to focus the mind as to where you really should start concentrating in terms of doing a regional analysis, such as we have done in Australia, to understand what the storage opportunities might be.
All that work has clearly identified to us that there is an important issue. Each one of these sites is so complex in terms of the geology, you have to deal with it on the site specifics, and come and do that detailed work. And this is a theme which carries through with all the geological work, that you can't just say, 'Oh yes, this is what the average leak rate may be, or the quality of the geological setting.' You need to understand each individual province.
I have put this in terms of oil industry lingo, and I apologise to people for jumping out of the metric system here. I have put it in terms of trillions of cubic feet (TCF), on the right-hand side of the slide. One TCF – I use this because it is a nice easy term – is what we would consider a very large gas field. And it might produce over a 10- to 20-year time period. So that is how quickly you could get it out of the ground. Australia's total emissions nowadays are about 500 million tonnes, or 10 TCF. Emissions coming from large stationary point sources, such as power stations, where we could potentially capture the CO2, are about half of that, or 5 TCF. Emissions in the Chicago district alone are greater than the entire emissions in Australia, and in the US they are around 40 TCF just from power stations. For the world, the CO2 emissions total, in CO2 equivalents, is around 410 trillion cubic feet of CO2 per year. That's an awful lot of pore space to have to find in those rocks, especially when you realise that you have got to keep doing that on an annual basis. To look at it in terms of production of gas, which is the analogy that I am making back to the gas industry: Australia produces about 1 TCF of gas a year; the US, about 22 TCF; and the world, about 100 TCF. If you look at the total reserves and produced gas for the world, you see that it is around 6500 trillion cubic feet. So you are starting to get an idea of the magnitude of the problem. What does it mean?
It means that in terms of the emission rate that we have right now, versus the gas production industry, it is about four to 10 times bigger. And if you could access that space created by producing that gas, you would probably have around 15 to 25 years of capacity, just out of gas fields.
This is an image from space showing nitrous oxide emissions. This is not a direct link to power stations, because the transport industry is involved as well, but it is a good guide. You can see these huge 'bushfires', so to speak, in China, through Europe, and also through the USA. You can even see shipping transport coming across from the Middle East to Asia. You have got to remember that over the next 50 years, 50 per cent of all the new power stations are going to be in China and India, and currently China is adding about 1 GW capacity per week, which is something like 40 or 50 times bigger than Australia's requirements.
So the volume of emissions is massive. Let's not hide that fact. And I put this up to remind myself that I recently gave a talk like this in Brisbane to the oil industry, and I said, 'Look, guys, go and sit out on the headland at Stradbroke Island, look out over that ocean, and think to yourselves what you need to do to change the pH of that mass of water. That's when you come to a realisation of the size of this issue.'
This brings me to some work done at Princeton by Rob Socolow and Steve Pacala. They have the concept, which many of you may have heard of, of the need to reduce 7 Gt of carbon, in this instance, over this period of time, so that by the time we get to 2050 there are 7 Gt of carbon not getting to the atmosphere.
What they have done is to break the stabilisation triangle up into seven little triangles of 1 Gt, and it has produced this chart that I will go through with you. What I want you to do is to mentally think that of these eight technologies, we need to choose seven that are going to work and that we can implement.
Coal-fired power stations: what we would need with carbon capture and storage would be 800 of those. And this is for 1 Gt. Nuclear power stations: we would need 700 of those, or twice what we currently have. Wind power: we would need 2 million 1 MW power stations, or we would have to have 120 per cent of Queensland occupied by wind power. Solar: we would need 2000 times what we currently have. Hydrogen fuel: we would need a billion hydrogen cars. Vehicle efficiency: we would need to double the fuel efficiency of 2 billion gasoline or diesel cars, which is four times the current car fleet. If we looked at just geological storage, the volume of injection would equate to 100 million barrels per day of fluid, which is probably okay. And in terms of biomass, we would need to have one-third of the world's cropland being used to produce the biomass. Now remember, I said this is 1 Gt. We need to look at 6 to 7 Gt. So it is quite daunting. And what this is telling you is that no single technology is going to be able to address this problem, and we need a portfolio approach. So, to get to the real topic of what I am talking about, can we keep the CO2 out of the atmosphere, and what are the first questions we get? The first question is obviously, 'Won't it leak?' Then, 'How long can we keep it down there?' and, 'Will it be temporary or permanent?'
I am going to apologise beforehand to any professions that I belittle here in a minute, but basically I believe that the answer to the question of whether it will be temporary or permanent is Yes and Yes. It really depends on the site, getting back to the project-specific sites – the geology, the operations, the regulations, the safeguards that are all put in place.
So what is our Temporary or Permanent definition? For a politician, Temporary is till the next day, basically, for a headline. And Permanent might be till the next election, which might be several years away. For an economist, Temporary will be till the next interest rate announcement, and the long time period might be the net present value period, which might be 30 years. And for us that is an issue. The economists cannot model out to a million years, because NPVs zero out after about 30 or 40 years. Engineers will just say, 'What would you like it to be?' The climatologist will say, 'Till the next glaciation' – and, to look at the data, basically that is overdue. Maybe we've been staving off the climate change. The public don't know. They're asking for technical answers from groups like this. But what they do tell us is, 'Don't alter my lifestyle.' And the geologist, which is the point that I am trying to get to, and it depends on who you are really talking to, will say that maybe 1000 years would be Temporary, and Permanent would obviously be over something like a million.
So how should a geoscientist respond to these questions? They should tell you, 'Yes, it could leak – if you choose an inappropriate site.' And to come back to the oil and gas industry, we know that you can look at accumulations which have been in the deep sub-surface for millions of years. So let's look at these accumulations. We have had thousands of billions of barrels of hydrocarbons which have been stored in the sub-surface, along with CO2 that has been co-produced with those hydrocarbons, and they have been stored there for tens to hundreds of millions of years. But where is this proof? Is this just us geologists saying, 'It's safe, it's okay. Just trust us'? Well, the truth is in the petroleum systems.
What I am going to show you now is a series of petroleum provinces around the world, looking at the storage times in terms of millions of years and also in terms of volumes, in billions of barrels of oil equivalent. I have selected five simple systems geographically around the world, showing you that we have got nearly 200 billion barrels of oil equivalents in parts of Arabia which have been stored for 25 million years, and some of these areas have nearly 100 million years of storage of really substantial volumes of hydrocarbons.
If we look at Australia, again we can come into a number of provinces and see storage times of 40 million, 80 million and 10 million years. But, importantly, up on the North West Shelf we have got areas where we have had co-produced and co-stored CO2 volumes of 280 million and 100 million tonnes of CO2 in there with the hydrocarbons. So this is good news. And in just these provinces, together, we have about 100 Gt of storage space.
So what is a petroleum system? I will give you a very brief review of what it is, so you can understand how we have got to these determinations. Basically, it is a source rock, be it an organic-rich shale or a coal, which produces hydrocarbons and all the accumulations produced from that. So that will contain the source, a reservoir – such as a sandstone – and some sort of seal, which might be a clay or a shale. You need a trap, to actually store the hydrocarbons, and you need the process of generation and migration of those hydrocarbons. And then you need to preserve it. (The preservation is where we come up with our storage time.) And the list goes on. But when you look at petroleum systems, the critical issue is one of timing, the sequencing of events. If you get them out of order, such as having your trap form after the generation, you are obviously not going to trap hydrocarbons.
So what elements do we have in a system? We normally have a map, cross-sections, an event chart – which we will look at in a little bit of detail – and a burial history chart, which is what a geochemist puts together. But when you look round the world, you see that all of these petroleum systems have been documented and all this information is publicly available. And event charts are really the critical things to any analysis.
Here we are looking at a geological cross-section dated about 250 million years ago. What we are looking at is the brown section at the bottom, which is the underlying sequence of this sedimentary basin. We then have our source rock, in the green, which might be a marine organic-rich shale. We then have our reservoirs, in yellow, which might be a sandstone, and a seal, in blue, which could be a clay or a shale. Then we often have a very thick sequence of overburden, which has buried this basin very deeply. As you go deeper down through the basin, temperature in the rocks increases, and you will get to an area where the source rocks actually generate oil. And as you go down deeper still, you will come out of the oil window and come into what we call the gas window, where you generate gas.
If we consider the picture from 250 million years ago as 'before', we can now look at a present-day view for the 'after', when we have actually formed structures where the oil and gas are trapped. You can see here where our oil comes out, migrates up through the reservoirs, and is caught up in the traps.
This is an event chart building up all of the aspects we have been looking at. At the top we have our time scale, going back to 400 million years; then we have our petroleum system events, including our elements and also our processes, and all the critical components of the evolution of that sedimentary basin.
This slide is to remind me that we are not just talking hydrocarbons, we are talking CO2 as well, in these systems.
We will build up this event chart so you understand how we get to these numbers. What we will do is actually generate the storage time out of this system. We start with our geological time scale. This represents the entire rock sequence we are looking at in the basin. We start with a basin – a virgin basin, shall we call it. We bring in our source rock. That will probably be down in the deep marine sections of the basin. We then add our reservoir rock, as it comes in from streams and beaches and along the near shore of the coastal environments. Then we will bring in our seal, where we have a major sea level rise – yes, they did occur in the past – and it will flood all the way back up over the onshore sections. Then we will bring in the overburden, which will rapidly bury this section and push these rocks down through the oil window and into the gas window. And you need to have these in the right order for all this to work. Finally, we will have our trap formation, which will occur at the end of this yellow arrow, and we generate our trap ready to produce our hydrocarbons. So then we will generate the hydrocarbons and they will migrate up out of the source, up into the trap. That then gives us our preservation time, after the trap is formed.
So that is how, for all these petroleum systems round the world, we can document these storage times. It is very simple, actually, in many aspects.
But what about round Australia and the rest of the world where we don't have active petroleum systems, or we have less 'prolific' ones? Why don't we have oil and gas everywhere? Surely it fails? Or does it leak? And can we learn anything from it?
These are just a number of provinces round Australia that we are well aware of in the oil and gas industry, and we can understand why some of these provinces are less perfect than others, whether it is to do with the seal quality or the reservoir quality or a timing issue.
But the bottom line with this information, I am trying to tell you, is that there is a vast data set and knowledge base in the oil and gas industry that can be applied to this CO2 storage technology.
What about leakage? Well yes, some fields in the past have been destroyed in what you could call catastrophic release, and these operate on geological time. But often these are related to major plate tectonic events. If you have got significant escape from a trap, it is going to be episodic; it is not going to be constant, otherwise you basically will not trap and store any hydrocarbons. And often we have re-migration out of a trap into a secondary trap. Leakage does occur naturally, and we do a lot of work on that in the CO2 business, looking at natural analogues. But these are not a good analogue for storage, because they are very leaky systems. We do use seeps – I will admit this – as clues to actually explore for effective source rocks in some basins.
This is an example of seismic from the Timor Sea, on the North West Shelf. You can see that we have got a fault going through the trap.
If you look at detail on the seismic you can see an anomaly which we call a hydrocarbon-related diagenetic zone. What has happened in the past is that hydrocarbons have migrated through this sequence and there has been cementation in this section. Effectively, it has been trapped. But it has produced this anomaly. How does this happen? Some of this would have leaked to the surface but also caused chemical change in the rocks.
Let's go back and look in this region. Say we go back about 5 million years, when Eurasia collided with Australia and actually formed the island of Timor.
Basically, Timor came in from the northwest and collided with the Australian plate, and set off reactions which spilled hydrocarbons to the surface. Why did that happen?
Well, some faults were in a northeast–southwest orientation, and therefore were under compression as we had the collision.
And those faults in the northwest–southeast direction were actually under extension and opened up and caused this leakage. It is a well-understood phenomenon, and it is the way that people often explore in this part of the world to see if they will have hydrocarbons in these traps.
What about very high leakage rates? I really don't think they are part of a storage time at all, because if you have got high leakage rates you haven't got storage. So it is not viable. If you have a long storage time that we have shown you in nature, it means that leakage at a viable site is insignificant. Just do the maths on storing hydrocarbons for hundreds of millions of years. What percentage leakage rate do you need per year to store the volumes that we have been talking about? And many of the fields that you go to are actually filled to spill. Even when you look at some of the 'poor' storage sites, there is good work which is suggesting that you could retain CO2 for thousands of years before you would get any leakage to the surface in a very poorly described site.
But this is natural leakage I have been talking about, not well leakage. Well leakage is really an engineering issue and it needs to be put in perspective. You can remediate it, you can plan for it, and it is really not a major cost in the total cost of these sorts of projects.
Are there going to be implementation issues? I do have concerns, when I look at the magnitude of the problem that we are looking at, whether we are going to have issues with depleted versus original pressures and with pressure build-ups across basins, and issues once we go from our first-tier to our second-tier to our third-tier sites, as economics and volume actually push it to those sites. Basically, what I am saying is that there are some aspects of this where the jury is out but we do need to do more work. And over the longer time period? Well, that is the question that we are trying to answer. There is a tool kit in the geosciences by which we can address that. The sorts of things we are doing are to look at rocks in terms of microscopic work and basin work and seismic and flow vectors and the whole range of remote sensing data that we have at hand, to look at the seal analysis and the cores and the well logs and the geomechanical analysis, the data sets and Mohr circles – for those that know what they are – and permeability and palaeogeography and core, and finally to come down and do the source sink matching work. So there are a whole lot of things we can apply to this problem. But do we need to ask ourselves, at the end of the day, how long is long enough?
If you look down at Lake Vostok, in Antarctica, at the ice cores, you see some very interesting results coming out of there.
Basically, it is saying that over the last 800,000 years we have had eight glacial/interglacial cycles. So if 100,000 years is good enough, if the answer to that question is yes, then I would say that petroleum systems will be able to provide significant storage times, provided we go to appropriately located sites – and probably much longer than these 100,000 years. So now what? This basically comes down to three questions, which I have put back to a number of audiences. First, we can hope that we have got all the models wrong. But I don't think that is the case. And for global warming, people have in the past argued that it might take 50 years to prove it, but governments have accepted it. And basically the ocean acidification issue, I believe, is bigger than global warming, and it is here and now. The second option is that we take on this heroic effort – and it will be a heroic engineering effort – and that we need a portfolio of options. One thing that does concern me is the range of 'new' technology based things that we have to implement. And the third option is the very simple option of a simpler lifestyle. The issue with that is that there are a lot of people out there in the world who have got the simpler lifestyle and don't want to have the simpler lifestyle. They want to have our lifestyle. Discussion Question – The politicians lead when the people lead. I think both the talks have really conveyed the magnitude of the problem. I knew it was big, but it didn't realise it was that big, yet I have got a science background, an engineering background, and have been following these issues for years. I know a lot of people who do not, though, and I would say that is true of the majority of the public. (I hope that is not an arrogant statement on my part.) How do you get the message across to people? The scientists are clearly failing at the moment, in the way I can see it, because if the public was convinced then I assume the politicians would be acting. And they're not. Steve Widdicombe – From a UK perspective, we have actually had quite a lot of success in the last year in getting the media to be interested in ocean acidification. There have been a number of BBC news items at prime time exploring the issues of acidification, and we have actually managed to get recognition from the Prime Minister's chief scientific adviser that ocean acidification is one of the key environmental issues. And we have actually been able to contribute information to the G8 discussions which have lately been going on. So in the UK we have managed to do quite well, but it has been a long slog even to get the media to take it on. I don't really know what the situation is here in Australia. John Bradshaw – I will answer it in two ways, one with my government hat on and one without. I have been on the road for quite a long time over the last two years, as my two kids will attest. At a recent talk that I gave to the oil industry, my old exploration manager from the company I used to work with came up to me and basically said what you have just said. He asked, 'Why wasn't I told?' And I said, 'Because you haven't been paying attention.' But, having said that, and coming back in my government position, where I am providing technical advice back into the policy sections of DITR, I would say there has been a mammoth amount of work happening over the last two years. Prior to that there was four solid years of work done in the GEODIS program – which then flowed into the CO2CRC program – which has allowed us the time to do our homework and to get the answers to a lot of the questions that we as scientists were posing to ourselves, so that we now can stand up and give the authoritative responses to some of the issues like 'Will it leak?' and 'How long will it stay down there?' I think you are right, the public are not engaged as much as they could be, but I believe that the ocean issue will start to engage them – because it is here and now, and it is our future in terms of our young kids who will actually be wearing that within the next 50 years. It is not a two- or three-degree temperature change in 200 years' time, such that people who live in Canberra or Siberia will say, 'That's great. I'm looking forward to it.' So it is a matter of bringing the immediacy of the problem up in front of people. I think that at the government level, across the science as well as the policy sections of the government, people really are aware of this issue and that is why you are seeing many of the things that government has put in place over the last 12 months or so. Steve Widdicombe – And ocean acidification is still a fledgling issue. It is incredible to think that it has had the publicity it has had, considering that four or five years ago the majority of the scientific community would have still sworn that pH will not change. John Bradshaw – The other thing I should mention is that since 2001 there have been 100 scientists in the world involved in the Intergovernmental Panel on Climate Change Special Report on Carbon Capture and Storage. That will be coming out on 25 September, through the UN, to all the governments. It is a definitive volume on the state of the art for carbon capture and storage, which will be in the hands of governments. Additionally to that, over 12 months ago there were something like 16 countries involved with the Carbon Sequestration Leadership Forum, which is a government-to-government initiative putting together ranges of opportunities, including capability building through the Third World to ensure that we got transfer of technology into places like China and India, to actually implement some of the things that we are talking about. So I think we are right on the cusp of major changes. But, of course, the big issue as you look around the world is a market. Once you put a dollar value on CO2 in parts of the world, with a lot of these things the industry will be able to come in and look at it. And there are parts of the world, such as in Norway, where there is a $50 a tonne tax on CO2 emissions, and as a result a field called Sleitner has been successfully injecting a million tonnes of CO2 per year since 1986. So it is a matter for all those things, which are now starting to line up, to take effect. Question – Here is a question for Dr Bradshaw. I would like to get calibrated on the scale required for geosequestration to achieve one of the Pacala and Socolow stabilisation wedges. So could you calibrate me either towards all capital investment in the oil and gas sector, or maybe towards the rate of investment that you mentioned, 1 GW a week in China? How would the size of the effort required to store safely one gigatonne by 2050 in geosequestration compare with either or both of those two efforts? John Bradshaw – I can try and address that several ways. At Sleitner, in the North Sea, which is a Statoil operation, the first commercial geosequestration project, they are injecting a million tonnes of CO2 every year. In some ways that is a unique setting, but it is a good example. You would need 3500 Sleitners to solve the entire problem. So I suppose we could divide that by seven, to get the number we would need to have up and running by 2050. There are operations with enhanced oil recovery in places like Wayburn, but they are being largely driven by economic benefit, and where a Sleitner will store something of the order of 20 million tonnes, that EOR operation will store a similar volume of CO2 but over a three- or four-year period. We have got operations on the North West Shelf at Gorgon, a high-CO2 gas field, which are looking at storing something of the order of 150 million tonnes of CO2 in that location. I quoted at the bottom of a slide the figure of 100 million barrels of fluid per year, or something like that. That is about the order of magnitude of production for the world from oil and gas. So it is the right sort of order of magnitude. But it will be a substantial effort, and if you can think of something as big as the gas industry up and running within 50 years, that is what we need to look at. Question – I think this relates very much to the last question, but perhaps in a different order. At the moment we have $60 oil, and one of the reasons it is $60 is that the oil business is desperately trying to do enough activity to keep the supply up with demand. So at the moment the oil industry is short of drilling rig capacity, engineering capacity et cetera. How big is the effort we would need on sequestration, compared with the ongoing effort on adding supply to meet demand? Can we do it, or does it mean very substantial further increases in oil costs? John Bradshaw – I suppose again there are several ways to answer that question. Without wanting to be rude, I look round this room and see the number of grey hairs in here. The oil and gas industry is like all the science institutes in that respect – I think the average age in the oil industry is over 50 now. And anyone who knows anything about the oil and gas industry is in there working and earning a very large wage at the moment. So there is an issue on the human resource side. But what I have seen with the very large number of young people coming through, many of whom we have employed at Geoscience Australia, is that they have a passion and a fervour to get involved with their science. We have also got a number of people who are getting towards the end of their career and who are wanting to come back and get involved in their science, so I think we can probably tackle that. But there is a human resource issue to actually do that. In terms of drilling rig capacity and things like that, one of the issues is that, say, in the North Sea, they have recently decommissioned six offshore platforms, and there is a whole range of them in Australia, as well as in the North Sea, which are soon coming up for decommissioning. And so issues need to be looked at to actually access those sites before they are decommissioned and to use them for storage. It will take some very smart policy setting to do that. But in the main there is a lot of smart drilling technology, such as horizontal wells and lateral wells, which can increase injection rate. I don't really think that that will be an issue, because I don't think people will be out there using offshore drilling rigs, going looking for new provinces for CO2 storage. In the main, they will be going into areas which are well known and well understood, and often with wells already in there. You might wind up drilling one or two new wells, but I can't see it like a big new frontier such as we had back in the late 1960s into offshore areas because we had the technology. But it will be an issue, I do grant that. Question – If we get specific and start looking at areas where we are producing most of the CO2 from power stations around southeastern Australia, let alone Chicago and so on, are there real specific options there that will have the features that are required for the long-term sequestration? John Bradshaw – The bottom line is yes. That is the short answer, I suppose. But it will be in the complexity of the sites. As you would know well, the areas where you have got your coal basins are not always necessarily the best locations for CO2 storage. Often you want locations in the passive continental margin, which in Australia are all on the west coast, whereas all our coal is on the east coast. It is a similar setting in South Africa. In the US they have got a Mid-Cretaceous continental seaway which is ideally placed for storage without having to take the CO2 very far. But at the end of the day, depending on what the market is, I don't see that as a big issue. I will give you an example. We did the work in the Sydney region, and the Sydney–Hawkesbury sandstone that forms those lovely cliffs is great for building stone but not ideal for storage. When we did the work we said, 'Okay, this is going to be tough in this region. We might find opportunities.' But just as an exercise we built a ring pipeline around the entire set of power stations in Sydney, did the modelling on it, and ran down the pipeline route to the Gippsland basin, where we have got wonderful reservoirs in the offshore region. Now, we would have thought that would be extremely expensive – which it was in capital costs – but because the volumes of CO2 involved in the Sydney regions are so huge, economies of scale kicked in and those sites wound up being one of the cheapest on a basis of dollars per tonne of CO2. So if you haven't got ideal solutions locally, if you have got a hub-type economy and some way of bringing all that CO2 to one location, then I really don't think that in the long term it will be an issue. For instance, in Russia, we have just got a 3000-kilometre pipeline for gas. Why not have one for CO2?
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