“Air capture” refers to the direct removal of carbon dioxide from the atmosphere. Leading work on this technology has been done by David Keith at the University of Calgary, his recent Ph.D. student Joshua Stolaroff, and separately by Klaus Lackner at Columbia University. Motivated by recent discussions on this site about the Massachusetts vs. EPA lawsuit, I wondered what the costs would be of neutralizing the carbon dioxide emissions of U.S. autos via air capture, and indeed all of U.S. emissions. Here is what I have come up with.


Air capture is a compelling technology because it requires no government regulation, no change in behavior, no international negotiations, and, most importantly from the standpoint of political action, no changes in energy production or use. Politically, it is therefore as simple and straightforward an approach as can be imagined. It is a top down technology in the sense that it can be used to “tune” the atmosphere to a desired concentration level. The downside is that it is expensive, but still far cheaper than the damages projected, for instance, in the recent Stern Review. Its ease in implementation and political simplicity more than offset its higher costs than other approaches to reducing carbon emissions.

In his recent dissertation (of which I have a copy but I am unaware if it is available online), Dr. Stolaroff suggests (his lower realistic estimate) that air capture technologies can remove carbon dioxide at a cost of $140/ton of carbon dioxide (or about $500/ton of carbon). In an interview with PBS earlier this year, Prof. Lackner suggested that the costs of direct air capture might eventually be as low as $30/ton of carbon dioxide (or about $100/ton of carbon). In the thought experiment below I’ll use both $100/ton and $500/ton.

1. US Auto CO2 Emissions

U.S. auto emissions are responsible for about 6% of total global emissions. The U.S. EIA estimates (XLS) total global carbon emissions in 2006 to be 7.45 GtC. Six percent of this is 0.45 GtC. The total costs of air capture to remove this amount of carbon from the atmosphere is $45 billion (at $100/ton) and $224 billion (at $500/ton). There are approximately 250 million passenger vehicles in the United States. The annual cost of air capture per auto is therefore $179 (at $100/ton) and $895 (at $500/ton). By contrast, this web site suggests that drivers can offset their auto emissions for $30-$80 per year per auto.

2. All U.S. CO2 Emissions

By extension, all U.S. carbon dioxide emissions could be offset by air capture for a per capita cost of $600 (at $100/ton) and $3,000 (at $500 per ton). At current use of gasoline (approximately 150 billion gallons per year) this could be achieved with a gas tax of $1.09 per gallon (at $100/ton) or $5.43 per gallon (at $500/ton). This level of taxation is comparable to gas taxes in European countries. If demand decreases as a result of the tax, as it probably would, then the tax would of course have to increase proportionately.

If the policy goal is to reduce total U.S. emissions by 40% then this could be achieved with a gas tax of $0.43 ($2.17). A gas tax of $1.00 would probably be more than enough to get this process started, including the costs of developing the air capture technology. The tax level could certainly be modified in future years based on experience with the actual costs of air capture technology and U.S. fuel usage.

This solution is so simple and straightforward, I wonder why those concerned with global warming aren’t trumpeting it as a solution in the United States? Instead, the focus is on complicated and politically intractable approaches with dubious chances for success. Air capture is easy (compared to other solutions that have been proposed) to implement and politically requires only enough motivation to win a $1.00/gallon gas tax. If global warming is indeed going to cost us 5-20% of global GDP, how can we not pursue air capture?

What have I missed?