Part 3 was all about how even if everything goes well, we still have a CO2 problem, thus we have a choice to make. Today in Part 4, we’re going to scout down the business-as-usual road to a get a sense of where that option might lead.
The business-as-usual road is made of concrete and steel. That’s no surprise – it’s what we know. We can see it, and touch it, and that makes it pretty easy to understand. That also makes it quite comforting. But also expensive, and thus challenging, to scale. To understand why, it helps to understand a few basics.
We take fossil carbon out of the ground as hydrocarbon in various chain-lengths of carbon and hydrogen from a single to dozens or even hundreds of carbon atoms. By mass, crude oil is 84% carbon, 14% hydrogen, and 2% other stuff, while natural gas is 75% carbon and 25% hydrogen and pretty much nothing else.
When we burn any hydrocarbon, we start with something that weighs 14-16 grams per mol per carbon atom, and always end up always with something that weighs 44 grams per mol – the molecular weight of CO2. All of that extra weight comes from the oxygen which comes out of the air.
The implication is very significant - the thing we’re trying to get rid of, CO2, weighs roughly 3 times more than what we started with – any form of hydrocarbon. Therefore, moving that mass also requires more energy – all other things being equal, 3 times more. CO2 being a gas, it also takes up more volume – i.e. it requires more space, too. But the key point is critical – we end up with roughly 3 times as much “waste” to get rid of as the source of carbon we started with.
For now, let’s just stick with our rough 3x factor and estimate that if we start with a hydrocarbon that we take out of the ground, pipe it to a place where we then burn it, and want to put all of the resulting CO2 back into a pipe and pump it back into the ground, the pipe would have to be 3 times bigger, and we would consume 3 times more energy to get rid of the waste stream than the product we started with if we sent it back to where it came from.
Hopefully, you’re beginning to understand why the business-as-usual world might require lots of concrete and steel!
But wait, there’s more! That’s all just after the CO2 is gathered and concentrated in one place. The exhaust from a power plant contains anywhere from 5% (natural gas) to 14% (coal) CO2. Concentrating it means separating it from nitrogen, oxygen, and water, and that takes energy, too. Different technologies can do this differently, but all involve at least pumping gasses, and most often liquids. Further energy is required for the chemical separation processes most often for now involving cycles of warming and cooling liquid absorbents.
For the baseline case of “Carbon Capture and Storage” (CCS) from a power plant, the required energy is estimated to be 0.25-0.30 MWh/tCO2, or to convert into some convenient units, 0.9-1.1 GJ/tCO2. I realize that these numbers are meaningless to most folks, so to compare, I used just under 15 GJ (gigajoules = 1 billion joules) of electricity to power my home last year. Alternatively, I could have lived cold in the dark and instead used that energy to capture and store about 15 metric tons of CO2 using CCS.
But wait there’s still more! The technology family known as “direct air capture” (DAC) requires that we first extract CO2 from a much more diluted concentration in the air. CO2 exists in air at about 420 ppm (parts per million) or 0.042%. That takes a whole lot more energy as we have to move ~100x more air to handle the same amount of CO2, and spend a lot more energy moving and cycling liquids (or powering other novel processes to induce separation). As the engineering technology is still immature, we’re not sure exactly how much, but estimates range from 8.8 to 14 GJ/tCO2, or in the range of 10 times more energy than CCS.
So here’s the kicker - today we get 1 million joules (MJ) of energy for every 71 ton of CO2 from fossil energies we use, or said the other way around, we get 14 billion joules (GJ) for every ton of CO2 we release from fossil fuels.
Did you catch that? Go back two sentences and read those numbers again. With DAC, it could take up to the same amount of energy – 14 GJ/tCO2 - we produced by taking it out of the ground, to put it back.
Bloomberg recently illuminated this point when it revealed that an estimate in Shell’s newest set of scenarios was that DAC would take more energy than all of the world’s homes combined to meet the target need. I dug out that publicly available raw Shell scenario data myself to compare to my above math, and find that also in the Shell scenarios, the energy requirement for DAC in the very long term was estimated at ~12 GJ/tCO2 – very close to my above estimates.
Now if all of that energy were zero-carbon energy, one might think it could still make sense to do use zero carbon energy to do DAC, but of course only if there were no more need to displace other carbon-emitting energy sources, and we won’t run out of those for a good while. Ergo, even using renewable energy to do industrial DAC until we have a zero-carbon emissions energy system is at least partly if not completely spinning our tires.
Moreover, the industrial plants to do all of this don’t come for free. Extracting and handling all that CO2requires a whole lot of concrete and steel and that costs money, too. In some cases, we might be able to store it close to where we capture it, and in other we might pump it 100’s of miles (e.g. this project) to store it underground.
Expounding further would be a blog of its own, but estimated capital investment requirements for such facilities range from $780 to $870 per ton of CO2 annual capacity. Using our estimate from the last blog of needing at least 10 GtCO2/y capacity, that means we face a required investment of at least 8 trillion dollars. Right now, the world averages about $750 billion/y investment in oil and gas supply. Even though all the CO2 would literally come out of thin air, the money surely wouldn’t. Someone’s gonna have to pay for that.
Finally, we still need somewhere to put all of that CO2. It’s hard to get one’s mind around the scale of the storage challenge alone. 10 billion metric tons of CO2 per year is the equivalent weight of producing 10,000 new aircraft carriers every year!
Now one way to cut the costs is to store it right where you capture it, which must have been inspiration for the below scene in the Amazon series “The Peripheral” about a dystopian future which included colossal DAC-to-cement statues dotted across the landscape (image below). I guess that’s one way to cut transport and injection costs, and perhaps gain public support to fund such projects?
But see all that concrete. It’s dead. That’s carbon removed from the cycle of the processes of life to doing nothing.
Next time, we talk green where the carbon is doing the work of life. Carbon isn’t inherently evil, it’s just misunderstood. Carbon put to work in life is carbon enables even more life. That’s what we’ll talk about next in Part 5.
Co-Founder & CEO of Blue Nest Beef