Carbon Capture is a hot topic in climate policy Find out why it’s all about how we do the math.
I once had a job selling swimming pool supplies, including chemicals. We would test samples of people’s pool water to help them manage the chemical balance. We noticed that the water kept becoming more acidic than it had been in the past.
That was because the urgent environmental issue in those years was acid rain. Although there were skeptics, for the most part, countries responded quickly to the threat. Within a decade, they brought the pollutants that caused acid rain under control.
Acid rain came from emissions of sulphur dioxide from burning fossil fuels, especially coal. One of the ways these emissions were curbed was through the introduction of devices called scrubbers. They’re now standard equipment.
Within a decade, they brought acid rain under control
These systems work by spraying an agent like wet limestone, into a chamber in the flue of the smokestack. This removes the sulphur dioxide from the exhaust gas. Sulphur dioxide is a useful chemical. In some cases, such as some steel plants, they can reuse the sulphur dioxide captured in their production processes, saving money.
It seems like everything old is new again. This week, three news items arose about doing something similar about carbon emissions. Carbon capture is a hot topic these days. Some see it as a possible alternative to cutting the emissions that cause the climate crisis.
Carbon capture reduces only a small fraction of carbon emissions
At Stanford University, Professor Mark Z. Jacobsen cast a wet blanket over the idea of carbon capture in a study published in the journal Energy and Environmental Science. In his words, “All sorts of scenarios have been developed under the assumption that carbon capture actually reduces substantial amounts of carbon. However, this research finds that it reduces only a small fraction of carbon emissions, and it usually increases air pollution.”
Proponents of carbon capture claim that they can reduce fossil fuel emissions at power plants by 80-90%. Jacobsen responds that they are not looking at the whole picture. He studied published information about two plants. One plant was a generating station that had installed equipment to remove the carbon from its emissions. The other was a plant built to remove C02 directly from the air around it.
Jacobsen looked at the emissions released by the whole supply chain needed to generate the electricity consumed by carbon capture devices. He found that, when we look at it that way, the new gear captured only 10-11 percent of the emissions they produced over 20 years. In the end, Jacobsen reaffirmed the expert consensus that the best approach is to replace fossil fuels with renewable energy like solar and wind.
A new approach to carbon capture
In that same issue of Energy and Environmental Science, engineers Sahag Voskian and T. Alan Hatton from MIT announced a new approach to carbon capture. Their method doesn’t have to be applied to high concentrations of CO2 like in smokestacks. They can remove it from the air even at concentrations as low as 400 ppm. That’s the level in the C02 laden air we all breathe these days.
In their research paper, they describe a technique in which they pass the air through a stack of charged electrochemical plates. It works like a battery, absorbing C02 while it charges and releasing that same C02 as it discharges. It works at room temperature with normal air pressure. That means it uses far less power than current carbon capture technology.
Scientists describe the equipment as binary because it is strongly attracted to C02 while it charges and is absolutely unattracted while it discharges. Factories could use the released C02 to carbonate soft drinks, for example. The system uses about one gigajoule of energy per ton of carbon dioxide captured. Techniques like those studied by Professor Jacobsen can use up to ten gigajoules per ton. The MIT proposal might be a game-changer.
A big part of the debate is how we do the math
As you can see, a big part of the debate around carbon capture is about how we do the math. That was the subject of yet another article published this week.
In a policy brief for the journal Frontiers in Climate, researchers led by Duncan T. McLaren from Lancaster University called for better accounting in measuring emission goals and results. They believe that so-called “negative emissions,” where C02 is taken out of the air, should be accounted for entirely separately from “emissions reduction” where we don’t release the C02 in the first place.
Politicians brag about reducing their carbon emissions to “net-zero.” They are usually combining the effects of stopping emissions and those of future technologies for sucking C02 out of the air in that zero number. The researchers argue that, instead, policymakers should set these goals separately, with specific numbers for each.
Governments use “negative emissions targets” to justify fossil fuels
The reason they think this is important is that their evidence shows that governments try to use negative emissions targets to justify staying in the fossil fuel business. In their minds, any benefits from carbon capture should be looked at as a bonus.
When politicians promise to reduce emissions, they shouldn’t get to fudge the numbers. They should stick to their reduction targets by rapidly cutting carbon emissions at the source. Anything governments accomplish through carbon capture should be measured on top of the principal goal of emission reduction.
Figures don’t lie, but liars can figure
They say that “figures don’t lie, but liars can figure.” We, as a global society, need to get a better handle on what we can accomplish through carbon capture and how to measure the benefits. As it stands, we don’t have time to wait until we know the answers to these questions and have feasible carbon capture devices.
We need to get on with reducing emissions right now. As we discover more about when and how to apply negative emission technology, we can add that to the mix. As readers can see, that debate is far from settled.
We always have more to learn if we dare to know.
The health and climate impacts of carbon capture and direct air capture
Massachusetts Institute of Technology
Faradaic electro-swing reactive adsorption for CO2 capture.
Beyond “Net-Zero”: A Case for Separate Targets for Emissions Reduction and Negative Emissions