An Effortpost/Discussion about Carbon Capture and Storage

Part 1: How Is It Meant To All Work?

I wanted to write up a quick effortpost on carbon capture as someone more than a geological layperson but admittedly less than a specialist. Opinions about carbon capture range from a Muskian tech-bro belief in its emancipatory role in solving the climate crisis to a belief that it is an almost entirely failed technology that will only exacerbate emissions. It would be exceptionally boring of me to say, "Well, carbon capture is a land of contrasts…" and as such, I will show my hand immediately and say that I come down much closer to the latter belief than the former, but there is genuine nuance to understand about the technology. I hope to make the current state of things a little clearer.

I will have to simplify things for brevity and clarity; many long reports, papers, and books have been written on the subject, which adds all sorts of complications. You could (and many have) dedicated your academic and professional life to the field and its inner workings. But I hope this suffices, and I hope users arrive with more knowledge, or information to add or correct.

A Quick Explanation of the Theory

Your typical CCS project can be divided into three sections - the first is the capture of CO2; the second is the transportation; and the third is the storage - or, a not-so-secret fourth option, the utilization (such as in chemical processes or oil recovery). While the more accurate name for the process as a whole would thus be CCUS, and that acronym is what you'll see a lot of if you delve into the science, CCS works fine for our purposes.

Capture: Carbon dioxide is somehow captured or separated from other gasses, usually at a stationary source like a factory or a fossil fuel power plant. There are many technologies for this, like absorption, adsorption, and cryogenic separation, but this isn't the essay's focus. The efficiency of capturing this carbon is not (and never will be) 100%, and in some case studies I've seen figures as low as like 30%. 90% capture efficiency is an often-boasted number. In short: it depends, and as we'll see later, it's not the most burning question in the CCS debate anyway.

Transport: The carbon dioxide is liquified and then moved through pipelines. Humans have gotten pretty good at moving liquified gases through pipelines, so this is the least problematic part of the process in terms of the science. Of course, there is inevitably an environmental impact from pipeline construction and the possibility of leakages.

Storage/Utilization: This liquified carbon dioxide is injected into sinks, typically underground deposits or aquifers, or used in further processes (though this currently makes up a negligible portion of captured carbon usage - it turns out that other sources of carbon are not very hard to come by). The big argument here, and the one I was told when I was taught about it in my courses, is something along the lines of "Look - if this reservoir was able to hold this natural gas/oil for millions of years, then it can continue to hold carbon dioxide for millions of years more." While this isn't always true - seismic activity and the impact of previous oil extraction operations might produce ...interesting results down the line - the theory is relatively sound, especially with frequent monitoring.

So, this is how it's meant to work - you stick a filter of some kind on a power plant or cement factory or steelworks or something, you transport it via pipeline or perhaps other methods, and then you stick it underground where it will stay for thousands or millions of years in the same place that we got the fossil fuels from in the first place. It's an idea that is convincing in its simplicity, and - hypothetically - it requires no extra space that needs to be constructed by humans. Indeed, there are appropriate geological traps that we could put the CO2 into that didn't already have fossil fuel present due to being at the wrong depth or not having the right biological material there, so even if some reservoirs were too damaged by extraction, we could still put the carbon somewhere.

The International Energy Agency is certainly a believer in the potential of the technology, featuring it as part of its roadmap towards net zero by 2050, and has various other pieces more explicitly on the role of CCS as a technology that can both reduce emissions directly and remove CO2 already emitted from the atmosphere. The IPCC, the body dedicated to climate change at the UN, also regards carbon capture as a critical technology.

As such, CCS is increasingly finding its way into countries' and companies' climate policies. 24 out of 29 Long Term Low Emissions and Development Strategies submitted under Article 4 of the Paris Agreement have CCS as part of their strategies.

Natural Gas and Enhanced Oil Recovery

Before I discuss the problems with CCS, a brief note here on what "enhanced oil recovery" is and how CO2 and natural gas relate to it. Natural gas must be processed before it can be marketed and sold and said processing involves separating CO2 from the gas mixture. This CO2 is thus captured and sent to be used in enhanced oil recovery, which has helped boost the economic viability of natural gas extraction.

Enhanced oil recovery is the process by which you inject CO2 into existing oil and gas reservoirs to use the pressure to extract more fossil fuels, improving production rates, particularly in reservoirs in which extraction is declining. Not only are you using (typically non-renewable) energy to compress carbon dioxide into liquid form and then pump it into the rock, but the extra oil and gas you get out of the rock is being used as fuel, which worsens the climate crisis.

Part 2 here in the comments.