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About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a...  (More)

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Let's bury our CO2. What could possibly go wrong?

Uploaded: May 1, 2022

We did not act early enough on climate change, and we continue to burn through our carbon budget too fast. As a result, we are faced with the need to capture and store away increasingly large amounts of carbon dioxide (CO2). Trees are great at this but they can sequester at most a fraction of what’s needed. The International Energy Agency has estimated that we will need to capture 1.6 billion tons of CO2 by 2030 if we are to meet our climate goals, and five times that by 2050. Our plan is to bury it deep inside the planet. (1) Many people think that is pretty straight-forward, but do we know how to do it and can we do it fast enough?

We have been burying CO2 on a small scale for many years. The fossil fuel industry has been injecting CO2 into some of its less productive oil wells and coal mines in an effort to extract more oil and methane. As shown in the picture below, carbon dioxide can also be stored in saline formations, large aquifers filled with brine in sedimentary rock, that are deep enough to accommodate pressurized CO2. (2)

CO2 has been injected into coal beds and oil fields to help push out extra methane and oil. It has also been injected into saline reservoirs for storage. Source: National Energy Technology Laboratory

It turns out that we have a lot of these sedimentary basins in the US, both under land and off the coast. There appears to be more than enough room to store all of the CO2 we would ever need to store.

Sedimentary basins are common beneath the continental United States. Source: Department of Energy’s Carbon Storage Atlas (NATCARB)

How is carbon dioxide stored in one of these basins? It is compressed and injected into the earth, typically at a depth of one or more kilometers. Once down there, it spreads out through pores in the sedimentary rock (e.g., sandstone or limestone) and is trapped by a (hopefully) impermeable “capstone” above the aquifer (e.g., slate), or possibly by faults in the rock, as shown below.

Carbon dioxide (gray) seeps through sedimentary pores (dark brown) before being trapped by a capstone (light brown, top) and/or shifted impermeable layers (bottom). Source: National Energy Technology Laboratory

Over the years as the carbon dioxide stays down there, some of it becomes trapped in the pores of the rocks, where it is less likely to leak. Some of it dissolves into the saline brine. And some of it reacts with the walls of the cavities to form minerals. (3)

Carbon dioxide becomes trapped in rock pores (left), dissolved in brine (middle), and precipitated in minerals such as magnesium carbonate (right) over time. Source: National Energy Technology Laboratory

We have a fossil-trained workforce with the skills needed to evaluate the aquifers, build necessary pipelines, and drill, maintain, and monitor the wells. The cost of basic carbon storage is manageable, around $10-$20/ton, which is generally much less than the cost of capturing and transporting it. So this all seems pretty promising, right?

The crux is that we have to scale up very, very quickly. This year we are capturing about 40 Mt of CO2. We need to scale that by 40x in the next eight years to align with a pathway to net-zero by 2050. That is a massive acceleration from what at this point is still in many ways a science experiment.

To achieve net-zero, IEA estimates we need to capture this amount of CO2 globally, per source. Source: International Energy Agency Net Zero Roadmap

There is much that we don’t understand about injecting into these aquifers, and in particular injecting quickly and safely. For example, the products of the reactions that occur when the CO2 mixes with the brine and the rocks can impede the injection itself. Minerals that form can clog the openings in the porous rock and precipitate can coat the rock surfaces and make them less reactive. A large aquifer can become pretty small and/or riddled with wells if we cannot figure out how to reduce these effects so the CO2 can disperse effectively.

There are risks of contaminating our drinking water. The CO2 injections can push saltier water upwards towards the drinking water. Or the CO2 itself can mix into the drinking water, acidifying it and leaching toxins from the rock. How do we detect and prevent these issues deep underground, especially when we are developing 100+ new sites every year?

Carbon dioxide can leak up through faults or along the casing of a well to acidify the drinking water supply. Image source: Berkeley Lab

You also get the potential for earthquakes when you are putting such a large volume of fluid deep into the Earth. We have seen in places as far flung as Oklahoma, Arkansas, Illinois, and West Texas that even a very small increase in pressure in some sedimentary aquifers can lead to substantial earthquakes. The oil and gas companies have seen this when they dispose of wastewater.

Wastewater from productive wells in Oklahoma was injected into an aquifer 7000 feet below the surface. The slight resulting increase in pressure in this aquifer was transmitted through a fault in the crystalline basement below, leading to noticeable earthquakes. Source: Stanford Center for Carbon Storage webinar by Geophysicist and Stanford Professor Emeritus Mark Zoback

Slight pressure increases can be transmitted long distances to deeper and more brittle layers, which can result in larger tremors. In Oklahoma, earthquakes occurred at a depth of 6-7 km, far below where the wastewater was injected. The largest quake registered at 5.8. These tapered off only when wastewater injection was curtailed.

Earthquakes in northern Oklahoma, shown in green, decreased when less water was injected. Source: Stanford Center for Carbon Storage webinar by Geophysicist and Stanford Professor Emeritus Mark Zoback

West Texas is seeing an effect very much like this right now. Earlier this year the Texas regulator of oil and gas wells moved to suspend deep well water disposal in an attempt to mitigate the earthquakes, but they continue to happen, as shown in the snapshot below from a few days ago.

Source: https://earthquaketrack.com/r/western-texas/recent, April 28, 2022

It is possible to manage the pressure in these aquifers by extracting some of the brine, but processing and managing that brine is costly, and we don’t know how to do it well yet. Alternatively, it is possible to identify and bypass those aquifers with the most potential to cause fault slips. Geophysicist and Stanford Professor Emeritus Mark Zoback and his colleagues have developed a tool that does just that, but in order for it to work, faults need to be well mapped, which is not often the case.

Zoback is an expert on these aquifers, and he is concerned about the pace and scale of development that is now required. “When you start looking at the numbers, they’re mind-boggling,” he says, pointing out that we need to set up hundreds of large capture facilities in the next decade, yet each one currently takes years to analyze and permit, even when everything is going well.

He describes the Gulf Coast Sequestration project in Louisiana. A private family there owns lots of acreage, they have good seismic data and a number of drilled wells (exploratory), and a competent group of former oil and gas professionals is doing the analysis. “They are working their way through the permitting process. Everything is going well. You might call this an easy case, but it’s been four years and they are still a couple of years away.”

I asked if we could set up the wells with less analysis and then cut back the injections if there seems to be a problem, as they have done in Oklahoma and Texas. “No, no, no. Permitting and regulation is critical. Many of the sites will be okay, but without a comprehensive analysis, by the time you find out there’s a problem, you’ve spent tens or hundreds of millions of dollars. There are jobs on the line, economic implications.”

Zoback continues: “I don’t want to sound like I think the end of the world is coming. But if we don’t do it right, it will be like fracking. Everybody hates fracking. We don’t want that to happen with CO2 storage…. Saline aquifers are great. We need to characterize them and pick the right sites, and they will work in the long term. We need to remember, though, that a dot on a map showing a good location can represent a decade of work. The thing that colors my perspective on this whole topic is, how do we get moving in the next ten years?”

He recommends we look more closely at using depleted oil and gas wells. “Things that need to be done have already been done. You start with a lot more knowledge.” He added that many of them have reduced pressure because of the extraction, and so can easily support high volume injections. (In others water has flowed in and so injections may have to proceed more slowly.) Yet many people have deep concerns about using these facilities, in part because the oil and gas industry would profit from the very problem they spent decades downplaying. Zoback understands that, and adds that these depleted wells are not always in the right place. “There are no abandoned oil fields in New York City, and there are certainly lots of emitters there. This is going to be hard no matter which strategy you look at. We just have to be committed and be open to trying all options. This problem is so difficult, so hard, so big, we should not dig ourselves into any one solution.”

It is a sobering experience to speak with a scientist like Zoback, who knows what is being asked to get to net-zero and understands how difficult it is. I heard the CEO of carbon capture company Svante, Claude Letourneau, saying something similar: “I don't think people in general understand the magnitude of what needs to be done.” I wonder whether, if we all clearly understood just how difficult and even improbable the alternatives are, we would be more active in changing some of the things that are in our control, like reducing our fossil-miles, eating a more plant-based diet, buying less stuff, electrifying our homes, and championing related policies. What do you think? I’d love to hear in the comments.

Notes and References
0. Thank you very much to Stanford Professor Emeritus Mark Zoback for his generous time talking about this topic.

1. There are other ways to store carbon dioxide, for example by weathering rocks on the surface or capturing it in cement. This post focuses on underground storage because it looks to have by far the most capacity.

I should also note that this post is not about how we capture the carbon dioxide in the first place. There are many ways to capture CO2, depending in part on where it's coming from (e.g., a smoke stack at a steel factory, oil refinery, or biomass plant; a machine filtering it from the air; etc). This post assumes that the CO2 can be captured. The question then becomes -- where do we put it?

2. Carbon dioxide that is stored at this depth is “supercritical”, with the low viscosity of a gas but the high density of a liquid. More can fit in less space.

CO2 gets denser at the higher pressures at increasing depths. Source: National Energy Technology Laboratory

3. There are certain types of underground rock formations that mineralize CO2 quickly, such as those made from basalt. Researchers are beginning to explore how quickly and safely CO2 can be injected into such formations, which are relatively common in the Pacific Northwest and the Southeast. The company CarbFix has an active well in Iceland.

4. Some additional difficulties with storing CO2 at scale in underground formations are (a) ownership of those formations, which can span large areas under many properties; and (b) liability over the long-term for leaks. These are discussed some in the National Academy of Sciences report on negative emissions technologies.

5. California is in many ways an easy case for carbon storage. The aquifers are conveniently located, with a large one running down much of the center of the state.

California has sizable saline aquifers beneath much of the state. Source: Department of Energy’s Carbon Storage Atlas (NATCARB)

California’s aquifers are also pretty close to where we are emitting greenhouse gases. That makes the CO2 easier and cheaper to bury.

Emission sources shown as colored dots, are generally close to a saline aquifer. Source: Department of Energy’s Carbon Storage Atlas (NATCARB)

The formations are also promising. The lower layer of brittle rocks where the large quakes originate (the “crystalline basement”) is very low and the faults are well mapped. Stanford Professor Sally Benson, an expert in this field, is optimistic about the future of carbon storage in California. She and her colleagues have estimated that we can store about 15% of California’s emissions in underground reservoirs, at a rate of 60 Mt/year, and that we generally have the technology to do so.

They asked stakeholders why more isn’t happening already. One reason is cost. It is expensive to capture and store carbon dioxide, and state incentives are not always available or predictable. Another reason is permitting complexity. Because the process is untested in California, it’s unclear how long the process will take, which makes it harder to plan and to get funding. A 50-page paper from Lawrence Livermore Labs argues that permitting must be sped up if we are to meet our climate goals. But as Zoback suggests, it is hard to speed up permitting in a new area that is scaling up quickly and that regulators are just trying to understand.

6. The National Academy of Sciences has a lot more information on methods of sequestering carbon, and negative emissions more generally, in this report from 2019.

Current Climate Data (March 2022)
Global impacts, US impacts, CO2 metric, Climate dashboard

“An intense heat wave in mid- and late April 2022 brought temperatures 4.5 to 8.5°C (8 to 15°F) above normal in east, central, and northwest India—just weeks after the country recorded its hottest March since the country’s meteorological department began keeping records more than 120 years ago.” Source: NASA’s Earth Observatory

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Posted by Mondoman, a resident of Green Acres,
on May 1, 2022 at 1:46 pm

Mondoman is a registered user.

It seems like trying to concentrate CO2 from the general atmosphere (where it's at 400-500 parts per million) would be very difficult. Isn't the difficulty here actually getting the CO2 rather than the storage part? Maybe the idea is to process smokestack exhaust rather than general atmosphere?

Posted by WilliamR, a resident of another community,
on May 1, 2022 at 4:40 pm

WilliamR is a registered user.

Mondoman touched on one of my first thoughts when I read the column: How do you extract the CO2 from the atmosphere, especially without using more fossil fuel to do it?

Second question: Can you pump the CO2 into the ocean, with a pipe running several miles offshore? Or would it bubble up and escape back into the atmosphere?

Posted by Sherry Listgarten, a DanvilleSanRamon.com blogger,
on May 1, 2022 at 6:31 pm

Sherry Listgarten is a registered user.

Thanks for the comments! Good questions...

@Mondoman, yes, the "Capture" part of "Carbon Capture and Storage" (CCS) is generally considered to be the hard part. I'm just saying, even if we take that for granted (which of course we shouldn't), the storage part is non-trivial. That is, whether you get CO2 from a factory flue or from burning biomass or from thin air, you've got to put it somewhere. How/where do we stash 1+ gigatons of CO2 quickly and safely somewhere in the next decade?

@WilliamR: Per my comment above, this post isn't about the capture side of things, but since you asked :) Scientists are investigating ways to capture CO2 without using fossil energy. Sometimes they use waste heat from geothermal areas. They could also use waste heat from nuclear reactors. And there's renewable energy. Others are developing new "adsorbents" for the CO2 that would be more efficient. It's definitely a work in progress, though.

Re your second question, people are looking at pumping the CO2 into the ocean bed (below ground), as Equinor has been doing for a while in the North Sea. Then coastal cities can ship their (compressed) CO2 to the storage facility. I think that is happening in Europe right now to some degree.

But I don't think anyone today is looking to pump CO2 into the ocean itself, in part because the ocean is already absorbing 30-50% of our anthropogenic CO2 emissions and getting quite acidic as a result. (Hence the coral reefs dying, marine animals having trouble building shells, etc.) They are looking at *removing* CO2 from the ocean (carbon capture may be easier in the ocean than in the air because it's more concentrated there), and that would let the ocean absorb more CO2 naturally from the air.

I should do a post or two on the capture side of things. What was interesting to me here, though, is that even the "easy" part of CCS (Carbon Capture and Storage) is really hard when you consider the scale and pace that is now required because we are taking so frigging long to ramp down our emissions.

Posted by BruceS, a resident of Greenmeadow,
on May 2, 2022 at 5:21 pm

BruceS is a registered user.

Good timing! Specifics on storing CO2 at the bottom of the ocean. I just read this article in National Geographic. I believe they let non-members read a few articles a month. If not, let me know and I'll at least send you the text:

Web Link

Posted by David Coale, a resident of Barron Park,
on May 2, 2022 at 5:44 pm

David Coale is a registered user.

What is clear from the enormity of the climate change problem is that there is no silver bullet solution to the problem and that we will need many many different solutions to both CO2 reduction and sequestration. On the sequestration side, as you have pointed out, even if we could capture CO2 cost effectively, there are still issues with permitting etc, such that this is not the final solution and can not be put in place in time. We will need all kinds of sequestration, including reforestation, regenerative agriculture, mineralization and ocean fertilization to name a few. We must be careful not to think that CO2 sequestration will save the day and give us a license to emit more CO2 now, and technology will save the day later. It is all solutions on deck and full speed ahead if we are going to save our planet and I am afraid that most people don't understand this.

Posted by Matt Passell, a resident of Charleston Meadows,
on May 2, 2022 at 6:20 pm

Matt Passell is a registered user.

We certainly need many solutions as there is no silver bullet. There is a climate simulator (EN-ROADS) that people may find interesting at Climate Interactive. It visually demonstrates how much each type of solution would impact average global temperature from now through 2100. It also offers background information and technical details.

Posted by ArtL, a resident of Barron Park,
on May 2, 2022 at 8:34 pm

ArtL is a registered user.

This is a brilliant survey of the technology and of some of the many geological problems that need to be evaluated and understood. While the author describes this as the 'easy' part of CCS, the economics turn out not to be so easy to resolve either. The costs are substantial, and the question is who pays. The only way for CCS to make sense is for the government to put a price or a tax on carbon. Our government does not seem to have the will to create the policies that would enable this technology to succeed. Without such a strong economic incentive, the likelihood is that the great potential of CCS to store CO2 emissions will remain unfulfilled. For example, NRG's $1 billion Petra Nova plant in Houston, touted by carbon capture advocates as an example of a successful project stopped operating because of mechanical problems and because it was uneconomic to sell carbon dioxide to boost oil drilling operations

Posted by martin m, a resident of another community,
on May 4, 2022 at 5:06 am

martin m is a registered user.

.......'Our government does not seem to have the will to create the policies that would enable this technology to succeed. Without such a strong economic incentive, the likelihood is that the great potential of CCS to store CO2 emissions will remain unfulfilled'...... Well..!!!... a lot of stuff will remain unfulfilled. I write from Ireland and wondered whether I had any right to contribute to climate discussion so far away and then the penny (cent) dropped, we are all in this together !! I am responding to the relatively minor issue of your use of the expression 'net-zero' in the blog! I work as an architect, and it is very clear to me that we have continually set our sights and aspirations too low in virtually all spheres of energy reduction and in particular, building zero energy buildings, The low aspirations are usually with a view to meeting the needs of the market at the (low ) level it is at. All given with the blessing of 'Cost optimality'. We need ramping up, NOW. I reference a book newly published your side of the pond....Ending Fossil Fuels, Why Net Zero Is Not Enough' (Holly Jean Buck, (Univ. Buffalo, NY)). Net-Zero is too close to assuaging people to believing that we have all of this under control, and we don't....HELP..!. Net-zero as an expression is part of this problem. Lets just start defining and using ZERO and difficult as it is.....try and meet it. Our politicians world wide need to start practicing giving bad news!....future pain/energy use restraint is inevitable.
The blogs are wonderful and responses really insightful......

Posted by Ptown Baseball Dad , a resident of Birdland,
on May 4, 2022 at 6:32 pm

Ptown Baseball Dad is a registered user.

How do we in the west get major mostly unfiltered carbon polluters like China and India on board? Both nations refuse to align with western nations on this most important issue.

Posted by Mondoman, a resident of Green Acres,
on May 4, 2022 at 8:36 pm

Mondoman is a registered user.

@Ptown I would think that imposing high tariffs on imports made using high-emissions power and infrastructure (e.g. from China or Vietnam) would be a way of influencing those countries' emissions via a purely domestic policy. Perhaps even 100% or 200% tariffs?

Posted by Sherry Listgarten, a DanvilleSanRamon.com blogger,
on May 4, 2022 at 9:15 pm

Sherry Listgarten is a registered user.

Thanks all for the really interesting comments!

@Bruce, thanks for the link, and it's great that you recognized the topic! Miraculously enough, I link to Project Vesta in footnote 1. My understanding is that it's definitely worth pursuing -- it's a good way to capture and store in one process -- but it's tough to scale to the degree that saline aquifer storage can scale, in part because it requires transporting rock (harder than piping a fluid), and in part because you need the appropriate coastlines (not too far from olivine sources). But again, I think it has proven to work at a small scale, so worth deploying where it makes sense. FWIW, a conference on this stuff ("enhanced weathering" aka "surficial mineralization") just wrapped up. Hopefully the video will be available soon. (Here is the video of last year's.)

@David, I agree. What gets me is that the behavioral changes, if we could pull them off, seem to be the fastest and simplest and cheapest. If Europeans would turn down their winter thermostat by just 1-2 degrees (Celsius), it would reduce Russian oil use by 10% and save everyone money. And that would be instantaneous. Why aren't we all on board with this kind of change? Is it a lack of understanding or a lack of will or a "them first" or "wait until I have to" or ...

@Matt, thanks for the pointer. I think those interactive models can be really informative when done in a group/game situation. Maybe we'll host a local one one of these days...

@ArtL: There are some credits available for sequestering CO2, but not always, or as much, when it's coupled with "enhanced recovery" to extract yet more fossil fuel. There is an understandable aversion to paying companies to keep extracting the fuel that is creating the problem we're trying to solve. A better bet imo if you want to be remunerated is to sequester the CO2 on its own and leave the fossil in the ground.

I also understand that the "enhanced recovery" process can be adjusted to prioritize sequestering CO2, which it does not right now. (Sequestering is secondary to extraction.)

I personally really struggle with this idea of rewarding fossil companies for helping to fix the problem that they downplayed for decades, to our grave detriment. We need all of the skills of the workers, but I would prefer for them to leave and start new companies that haven't already been the source of so much misinformation and harm, because "progress moves at the speed of trust". WDYT?

@Martin, I think it's great that you wrote in because as you say we are all in this together. I agree that "net zero" can really muddy what action is most needed, sort of like "reduce, reuse, recycle", when recycling doesn't really work but it's mostly what people do. We are misled. Offsets also are often questionable. (New report out.) The worry is we do something that adds up to zero in our calculations but the climate itself doesn't see it that way.

@Ptown, I wouldn't say that China isn't working on this. Here is one graph showing the scale of investment they are making in wind and solar. They already have 3x what we have, and they are planning to double it by 2025. CarbonBrief estimates that with this level of investment, they can start reducing their emissions by as early as 2025. And certainly they are heavily invested in the climate tech market. They also stopped investing in coal outside of China, which was really important for the possibility of clean development in developing countries. So FWIW I am hopeful that climate can be an area of meaningful alignment between our countries and Europe because of the interest in mutual trade vs border adjustment fees. (And @Mondoman just said the same thing.) But I should read more on this...

Source: CarbonBrief, May 2022

Thanks again for these really insightful questions and comments...

Posted by Dirk Svensen, a resident of Country Fair,
on May 9, 2022 at 9:57 am

Dirk Svensen is a registered user.

You have noted that "They already have 3x what we have". While technically true, this bar chart really makes the wrong comparison in the wind and solar category. Would a more appropriate comparison be gigawatts per million population? This would then yield 0.37 for China and 0.51 for the US. Thus, the US currently has 38% more than China based on population.

Posted by Sherry Listgarten, a DanvilleSanRamon.com blogger,
on May 9, 2022 at 10:23 am

Sherry Listgarten is a registered user.

@Dirk: It's a good question. I think that China would argue to do it based on GDP or per-capita GDP or even per-capita land. (We have these same debates about how to count emissions.) So I just went with the blanket number. Either way, the amount they are planning to build is impressive imo and should do a lot to move the (their) industry forward.

Posted by John, a resident of California Somerset,
on Jul 4, 2022 at 8:22 am

John is a registered user.

This seems like a great solution for carbon capture, using it within battery storage:
Web Link

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