VOX explores the basic idea behind carbon capture and utilization (CCU), one of the hottest topics in clean energy these days.
David Roberts, reporting for VOX. This is part three of a four-part series on carbon capture and utilization (CCU), the growing industry dedicated to using carbon dioxide captured from the atmosphere to fight climate change. Part one introduces CCU and its basic forms, and part two is about enhanced oil recovery, the largest current use of CO2. The fourth post considers how policymakers should approach CCU technologies.
It is well understood at this point that carbon dioxide is a deadly pollutant that is heating the atmosphere. What’s less well understood is that CO2 is also a useful feedstock, an input into a variety of industrial processes. From plastics to concrete, CO2 is a basic industrial building block — a valuable commodity.
To many climate campaigners, this suggests that maybe we should use more of it. Maybe, if the industries that use CO2 could be incentivized to increase their use, we could use enough to substantially decrease the amount we emit into the atmosphere.
Use more; emit less. That is the basic idea behind carbon capture and utilization (CCU), one of the hottest topics in clean energy these days.
In my first post in this series, I introduced the concept of CCU and its basic forms. In the second, I took a close look at what is currently the most common industrial use of CO2, namely enhanced oil recovery (EOR), whereby CO2 is injected in spent wells to squeeze out more oil and gas. (It’s complicated.)
In this post, we’re going to take a look at the other industrial uses of CO2 to try to get a sense of how viable they are, what their total potential might be, and whether they might play a significant role in the fight against climate change. Fun times!
One important note: For the purposes of this post, I’m looking at industrial processes. They involve pulling CO2 out of the air — either out of the flue gases of industrial facilities, via traditional carbon capture, or out of the ambient air, via direct air capture (DAC) — concentrating it, and using it as industrial feedstock.
There are also a number of natural ways of gathering more CO2, from planting more forests to sequestering more carbon in the soil. They are interesting and of potentially significant scale, but they deserve their own post. This post is about machines.
Before we get into the various forms of CCU, let’s keep in mind three important questions we need to be asking about all of them as we take their measure.
The questions are drawn from a giant literature review on CCU, recently released in the journal Nature, which assessed over 11,000 papers and was accompanied by an expert opinion survey. It helps bring into clear focus the key metrics involved in appraising these technologies.
The first question is, does the CCU technology produce a climate benefit? Does it reduce carbon emissions, and if so, how much? Does it sequester carbon, and if so, for how long?
There are a few overlapping concepts here that are often conflated in popular dialogue, so it’s worth distinguishing them. Here’s how the Nature paper does it:
CO2u: utilization of CO2
CO2ρ: reduction in CO2 emissions relative to baseline
CO2r: removal of CO2 from the atmosphere
CO2s: storage of CO2