Can We Remove CO2 From The Atmosphere?

October 19, 2020

Should we count on removal of CO2 from the atmosphere to meet global warming objectives? It is technically feasible to remove CO2 from the atmosphere. There are several processes under development. However, there aren’t yet any large industrial plants that could remove enough CO2 from the atmosphere to make a difference.

Even if it is technically feasible at an affordable price to remove large amounts of CO2 from the atmosphere, who would pay for the investment to build the facilities required and pay the cost of operating these facilities? To get investors to invest in carbon capture projects, there would have to be a market for the CO2 removed from the atmosphere. A carbon fee higher than the cost of removing CO2 would be required if there aren’t any large enough commercial markets for CO2.

We also have to assume that it would be feasible and economical to store the CO2 removed from the atmosphere underground forever.

What could it cost?

Let’s look at what would be required and what it might cost. For this analysis, we estimate the cost of removing enough CO2 from the atmosphere to reduce CO2 concentrations only 1.0 ppm.

A cost of $100 to $200/ton to remove CO2 is assumed based upon estimates in various reports and articles.

Removing CO2 from the atmosphere would require a very energy intensive process. An authoritative estimate is that it would take about 366kWhr of electricity to remove one ton of CO2. The pilot processes being tested also require an additional amount of energy in the form of natural gas for process heat.

The concentration of CO2 in the atmosphere is currently about 412 ppm by volume. In other words, only 1 of every 2,500 molecules in the atmosphere is CO2. Because of this low concentration of CO2 a lot of air would have to be moved through the process to capture one ton of CO2. For a process that is 50% efficient, about 3,300 tons of air would have to be pumped. Additional energy would be required to power the process for removing and capturing the CO2.

An additional cost of about $30/ton for underground storage of the CO2 removed from the atmosphere could be included in any analysis.

How much CO2 is in the atmosphere?

The total weight of the earth’s atmosphere is estimated to be 5.137 X 106 Giga metric tons. A gigaton is a billion metric tons. A metric ton is 2,204.6 pounds or 2.2 short tons, the common measure used in the U.S.

Because a molecule of CO2 (44.0095 grams/mole) is heavier than the average weight of air (28.97 grams/mole), we have to make an adjustment for this weight difference as well.

What would it cost to reduce 1ppm?

To reduce CO2 concentration by 1.0 ppm from the current concentration of about 412 ppm we’d have to remove 7.8 Gmt or 8.6 billion short tons of CO2.

A rough estimate of the potential cost is:

Amount removed Cost/ton Total cost
8.6 billion tons $100 $860 billion
8.6 billion tons $200 $1.57 trillion

So, it would take an estimated $900 billon to $1.6 trillion to remove only 1.0 ppm of CO2 from the atmosphere. It would be necessary to do this one hundred times to return the atmosphere to pre-Industrial Revolution conditions! Who would pay this expense? Wouldn’t it be cheaper to avoid putting the CO2 into the atmosphere in the first place?

Why might we want to remove CO2 from the atmosphere?

If CO2 removed from the atmosphere is combined with hydrogen to produce synthetic gaseous and liquid fuels, there could be a market for captured CO2. However, this market would not be large enough to remove the amount of CO2 being discussed in this analysis.

Any CO2 used to produce synthetic fuels would be returned to the atmosphere when these fuels are burned to produce power or heat. At best, recycling CO2 would be carbon neutral and help stabilize but not reduce the CO2 concentration in the atmosphere.

How much renewable electricity would be required?

Using 366 kWh as the estimated amount of electricity needed to remove a ton of CO2 from the atmosphere, it would take 3,148 billion kWh to remove 1.0 ppm of CO2 from the atmosphere. In 2019, the total U.S. production of electricity was about 4,118 billion kWh. So, to remove 1.0 ppm would require about 76 percent of all the electricity produced in the U.S. in a year, or about 12 percent of world electricity production. This is clearly not practical.

How should we price a carbon fee?

Ideally, a carbon fee should at least equal the cost of removing CO2 from the atmosphere. In our example, this would be $100 to $200/ton.

Note that we refer to a carbon fee, not a tax. This fee would be compensation for public health costs and environmental damage resulting from discharging greenhouse gases and other pollutants into the atmosphere. These emissions shouldn’t be free. Renewable energy is fuel-free and does not have any emissions. To the extent that fossil fuel emissions are free, this is a huge subsidy for fossil fuel use relative to renewables.

Applying this fee all at once could be too big a burden on the economy and might cause a recession. Any fee should start at a much lower number, say $40/ton and increase annually until the fee at least equals the cost of removal. Eventually, this fee would decline as fossil fuel use is reduced.

In 2019, the U.S. emitted about 4.5 Gmt (4.95 billion short tons) of CO2 from fossil fuels. A $40/ton fee applied to U.S. emissions would raise about $200 billion/year in revenues to pay for government programs to reduce global warming. This income would increase annually as the carbon fee is increased until the reduction in fossil fuel use exceeds any increase in the carbon fee. 

Impact of a $40/ton carbon fee

What would happen to some representative fuel costs if a $40/ton carbon fee was applied? According to Resources for the Future, a $40 carbon fee would increase the cost of various fossil fuels as follows:

Fuel Additional cost
Gasoline $0.33/gallon 18%
Natural gas $1.92/kcu.ft. 50%
Home heating oil $0.37/gallon 22%
Coal (Bituminous) $81/ton 173%
Jet fuel $0.35/gallon 12%

Bill Fletcher and Craig Smith

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