The oil giant Saudi Aramco recently published an article on Carbon Capture which got my attention. Is Carbon Capture the holy grail to solve the climate crisis?

The fossil fuel industry is pushing carbon capture as a panacea to our greenhouse gas emission problems. Fossil fuels are wonderful and essential to our way of life, they say. There’s just one problem. Burning fossil fuels produces an unwanted byproduct called carbon dioxide (CO₂) that is rapidly destroying our planet. If only we can suck CO₂ out of smokestacks, or even out of thin air, and store it away some place, we can happily continue to drive our gas guzzling SUVs and sleep well at night. And maybe we can even find some good use for the captured CO₂. Who needs an energy transition? Drill, baby, drill!

Fossil fuel interests successfully built funding for Carbon Capture into President Biden’s signature climate legislation, the Inflation Reduction Act (IRA). They have also funded professors at prestigious universities to initiate Carbon Capture research projects.

Welcome to the murky world of “Carbon Capture,” full of smoke and mirrors, where a little bit of digging shows that nothing is as it seems!

First, a bit of terminology.

Carbon Capture means what it says, the capture of unwanted carbon. As expected, the most efficient way to do this is at the point of production of CO₂, i.e., in the smokestack of a fossil fuel combusting furnace, factory or power plant.

Direct Air Capture (DAC) means capturing carbon directly from the air. The argument goes that even if we achieve “net zero,” we will have to suck a lot of carbon out of the air to make up for past sins and bring the concentration of CO₂ in the atmosphere back to a safe level of 350 parts per million (ppm). Today, we are already at an extremely dangerous level of 426 ppm, which will certainly go up before it ultimately may come down.

Carbon Capture, Use and Sequestration (CCUS) tries to answer the question of what we will do with the CO₂, assuming we are successful in capturing it. We will either use it for something useful or salt it away somewhere where it won’t cause harm. The most common reuse of CO₂ is “enhanced oil recovery” whereby the gas is pumped into existing oil and gas wells. This action makes the oil lighter and brings it to the surface, thus increasing the productivity of the well. The most common sequestration (or “salt away”) method is to trap the CO₂ at high pressure in some material and bury that material deep underground, hopefully never to be seen again. Saline aquifers, underground caverns and depleted oil wells have all been proposed as burial grounds. All of these plans are somewhat reminiscent of our one-time hopes for dealing with spent nuclear rods.

Now that we understand the basics of CCUS, let’s get to some obvious pros and cons.

As always, we’ll start with economics. Consider electricity generation from fossil fuels (e.g., a fracked gas turbine). Capturing CO₂ out of the smokestack has a 25% energy overhead (to say nothing of water needs). What does this mean? If we produce 100 units of electrical energy from a gas turbine, it will cost 25 units of energy to capture the CO₂ from the smokestack. Yes, it takes energy to capture CO₂! If those additional 25 units of energy are produced from fossil fuels, capturing that carbon will cost more energy. Leaving aside one-time capital cost, the operational cost of carbon capture makes energy 33% more expensive. See here and here for layman’s summaries of the above-referenced technical paper.

DAC has a higher overhead of 75%. Example: it will cost 75 kWhr of energy to suck out of the atmosphere the emissions from producing 100 kWhr of electricity from fossil fuels. CO₂ is at a high concentration in a smokestack compared to the open atmosphere, so it stands to reason that it is harder to recover CO₂ directly from the air.

Predictably, this makes energy production with carbon capture uncompetitive. Already, a combination of solar and batteries delivers “firm” electricity (i.e., electricity when we want it rather than when the sun shines) less expensively than fossil fuel sources. The 33% overhead makes it an economic non-starter. Proponents of CCUS argue that this carbon capture research is a worthwhile endeavor. They say, “Costs are high now, but will perhaps come down over time. Maybe someone will come up with a better way to capture carbon.” The only problem is that even if the overhead of carbon capture comes down to 0%, fossil fuels lose the economic battle to clean green renewables!

Even if it’s expensive, there is something to be said for a near-100% clean gas turbine power plant or industrial smokestack. Let’s tackle the next question: does CO₂ actually get captured? The sad answer is, “No, not usually.”