CCUS: The Case Against the Case Against

Et tu, Naomi?

I have some regard for Naomi Oreskes. Among other things, she wrote the excellent (IMO) Merchants of Doubt, exposing how PR consultants and the ad industry have been employed, initially by the tobacco industry and later by fossil fuel companies, to sow public doubt and confusion about scientific findings that ran counter to their corporate interests. So I was disappointed and a bit saddened to read her recent piece in the March issue of Scientific American. Titled The False Promise of Carbon Capture as a Climate Solution, the piece aims to make the case against CCUS as a key element in global efforts to rein in carbon emissions.

If Oreskes were merely saying that carbon capture, by itself, can’t be a complete solution to the climate crisis, I’d be in full agreement. I might voice a snarky, “Well, DUH!” That much is pretty obvious, after all. But she’s saying more than that: “Although it might be part of the solution down the road, right now it's mostly a dangerous distraction”. A dangerous distraction is it? I’m coming to detest that phrase. The world may be full of dangerous distractions, but it seems to have become the go-to descriptor by anyone with an agenda to apply to anything that doesn't fit their agenda. As in “This is what I think we should be doing; anything else is a dangerous distraction.” Yeah, right.

Oreskes marshals familiar arguments against CCUS: it’s too expensive; the sequestered CO2 might escape; and since the captured CO2 is used mostly  for enhanced oil recovery, it increases total oil production and therefore the amount of CO2 emitted to the atmosphere. 

There are problems with each of those arguments. For starters, she backs the “too expensive” argument by picking a cost estimate of $1000 per metric tonne of CO2 for DAC.  She then multiplies that by total emissions in the US of six billion metric tonnes of CO2 per year. That yields a cost estimate of $6 trillion per year. So yes, that’s clearly “too expensive”. Except nobody in their right mind is proposing to use that form of DAC as the sole or even the main way to offset all carbon emissions currently produced in the US.

DAC could be used to help lower CO2 levels in the atmosphere after CO2 emissions have been cut to near zero by other means. But there are far more cost-effective alternatives that can be deployed long before then. One of them is capture from concentrated point sources (e.g, ethanol and biogas plants). But the “heavy lifting” of reducing emissions will necessarily be in the transition to zero-emission electricity generation and the electrification of transport, in concert with “easy” CCS from point sources.

The “might escape” argument is tedious. Being required to prove a negative – in this case, the proposition that there‘s no possible way that stored CO2 could leak from storage – is always difficult. However we needn't prove that. The short response to the “might escape” issue is “Sure, some part of the stored CO2 might ultimately escape. So what?” 

CO2 is not exactly a deadly poison. It doesn’t suddenly become one by virtue of having been captured and stored. It takes literally gigatonnes of the stuff circulating in the atmosphere to move the needle on climate effects. And the thousands of geological reservoirs that are the prime candidates for storing captured CO2 have proven their ability to store gas under high pressure by doing exactly that over the course of millions of years. If the reservoir were prone to leakage of gas and volatile hydrocarbons through the cap rock above it, it would long since have ceased to be an oil and gas reservoir. All the gas and the light hydrocarbons would be long gone.

“Ah” one might say; “but the cap rocks topping any geological reservoirs that might be used to store CO2 have necessarily been compromised by wells through them to the underlying reservoir rock. Can’t those wells, if they fail in a blowout, provide open superhighways for escape of the CO2 that was stored in the reservoir?” Well, yes, they can. And something very much  like that did happen not so long ago. But when viewed in quantitative terms, it shows the essential silliness of the CO2 leakage issue.

The incident in question was the accidental rupture of the casing in an old well into the Aliso Canyon gas field near Los Angeles. The particular well that blew out, according to the Wikipedia article on the incident, was originally installed for natural gas production in 1953. In 1973 it was reworked as an injection well after the field it served had become depleted. The field was reconfigured as a gas storage reservoir. The reworked well was not equipped with a blowout prevention valve. A valve was “not considered a priority” at the time, because the well was located far from a populated area. Anyway, a blowout from an injection well to a gas storage reservoir was thought to be unlikely. However, over the seven decades it had been in operation, the old well casing had become badly corroded by acids from bacterial growth following intrusion of groundwater. On October 23, 2013, it ruptured. In the absence of a blowout prevention valve, there was no way to stem the eruption of gas from the storage reservoir.

That was a worst-case scenario for leakage of gas from a geological storage reservoir. It corresponded to a full core meltdown from a nuclear reactor. So what was the damage? The outflow from the blown well continued for over three months before an emergency well drilled by SoCalGas intersected the blown well at its base and was able to seal off the flow. In the first few days after the blowout, the outflow of methane, ethane, and bits of volatile hydrocarbons brought up with the escaping gas amounted to several thousand tons per day. In the days after that initial eruption, the outflow slowed, as the stored gas had further to migrate through the porous reservoir rock before reaching the open well. In total, over the three plus months it took before the well was finally sealed, roughly 100,000 tonnes of methane and light hydrocarbons escaped from the reservoir. 

CO2 is heavier than methane, and had the reservoir been storing CO2 instead of natural gas, the leaked tonnage would have been higher. It might have been 250,000 tonnes. That sounds bad, until one learns that it’s no more than is released by a modest forest fire burning 5 square miles. Large forest fires can release a good deal more. In fact, between 2018 and 2023, ten extreme forest fires each released more than 600 million tonnes of CO2 into the atmosphere [q.v.]. That’s 2,500 times worse than the potential leakage from a worst-case blowout from a geological storage reservoir for CO2. The loss of that much CO2 from storage in a worst-case accident would be unfortunate, but it would be a very tiny blip on a graph of overall carbon emissions and storage.

The non-problem of EOR

That brings us to the most serious of the arguments that Oreskes lays out: the assertion that use of captured CO2 for enhanced oil recovery (EOR) would result in higher emissions of CO2 by increasing supplies of fossil fuels. This is a dangerous argument in that, while it’s dead wrong, it sounds plausible. It’s easy to be taken in by it. Reality, however, is that it’s the successful blocking of the use of CO2 for EOR that would result in more use of fossil fuels and higher emissions of CO2. The reason can be understood by considering the nature of supply and demand for fossil fuels.

Fossil fuels have what economists refer to as a “low price elasticity of demand”. Demand for fuels, in the short term, is insensitive to market price. Buyers generally buy what they need and no more, regardless of price. Very little of the overall demand for oil is discretionary; most of the demand is “locked in” by the nature of existing commercial, industrial, and residential infrastructure and by the state of the economy. Demand for oil can be reduced by a serious economic recession. Oil suppliers are careful to maintain supply at a high enough level to keep prices within a range that won’t crush their customers' economies.

Given this situation, the ability to extract more oil and gas from mature fields has virtually no effect on net end-user demand. It does, however, have a major effect on gross demand.  A barrel of oil extracted from a mature field through the use of EOR is a barrel of oil that doesn’t have to be extracted from a new well somewhere else. That’s good, because new wells are expensive in both monetary and energy terms. A recent study found that for new oil production, 15.5% of gross production was needed to offset the oil consumed in production, refining, and distribution of the remaining 84.5% of the oil produced. Indeed, considering that the lion’s share of new oil and gas production is now coming from fracked wells in US shale plays, and considering the energy costs of mining and transporting fracking sand and of fracking operations themselves, it’s remarkable that the energy toll for new production is only 15.5%. But whatever the actual toll is, EOR from mature oil fields avoids most of it.

This is the way the oil age ends

Former Saudi oil minister Sheik Ahmed Zaki Yamani is known for an incisive observation: “The stone age did not end for lack of stone, and the oil age will not end for lack of oil.” Consumption of oil and other fossil fuels will continue for as long as there is demand; it will end when demand ends. Demand will end when there are alternatives that consumers find more attractive. 

If they want to help bring down carbon emissions, climate activists need to focus their campaign efforts more on policies that will encourage development and deployment of more attractive alternatives to unmitigated burning of fossil fuels. There’s been plenty of focus on policies promoting wind and solar energy and adoption of electric vehicles. Those are well and good, but they aren’t the only options for zero-carbon power generation. Nor are they necessarily the best. They can be deployed quickly, which is a telling advantage. However, they come with large embodied carbon footprints. Ancillary infrastructure – batteries, long distance transmission lines, and backup generation resources – needed to deal with intermittency drives up the overall cost of electricity. Other options that might possibly work out better for displacing fossil fuels include advanced nuclear, enhanced geothermal systems (EGS) (here and here), CO2 plume geothermal (here), and supercritical Brayton cycle heat engines (here).

Most of these other options are still being refined / developed, implemented in demonstration projects, or only in early stages of commercial deployment. They all hold promise, and none are intermittent. They don’t depend on the weather. We’ll have to see how they ultimately pan out. In the meantime, CCUS from point sources – especially those that inherently capture 100% of CO2 emissions – offers the quickest path to significant reductions of carbon emissions. And if the captured CO2 can be used for enhanced oil recovery from mature oil and gas fields, so much the better!