Capturing carbon straight from the air: what are the costs?
Carbon capture from power plants has gained much attention as a means to decrease greenhouse gas emissions (GHGs). A recent study assesses an alternative method that directly removes carbon dioxide from the air. The findings indicate that this method is comparable in costs to the mitigation costs estimated by the IPCC and the Stern report.
Targets for reducing greenhouse gas emissions have been set at both a global and a European level. The European Union is committed to cutting its GHGs by at least 20 per cent of 1990 levels by 20201. Much focus has recently been on the capture and storage of carbon dioxide from power plants as a means of cutting GHGs.
However, the method of 'air capture' has received little attention. Air capture is the direct removal of carbon dioxide from the ambient air. Various methods have been suggested and some have been operationally tested. For example, systems have been developed using sodium hydroxide and lime to remove carbon dioxide. Since it is likely that the technology for air capture will only develop in coming years, this research examines the economics of this method.
Using predictions from the US Energy Information Agency and from the International Panel on Climate Change (IPCC), the study performs a simple calculation to estimate the amount of global carbon dioxide present in the atmosphere for the 21st century. It then estimates the costs of air capture for two different levels of CO2 stabilisation - 450 parts per million (ppm) and 550 ppm. Since estimates vary for the cost of air capture, it uses three values and expresses the costs of air capture as a percentage of global GDP.
The Stern report2 estimates the costs of mitigation in order to stabilise CO2 at 450 ppm to be about 1 per cent of global GDP in 2100. Using the report's assumptions for GDP growth of 2.5 per cent per year, the study estimates that air capture could cost from 0.5 to 2.7 per cent of global GDP, depending on the cost of the technology. Using the IPCC GDP growth projection of 2.9 per cent per year, the cost of using air capture to stabilise CO2 at 450 ppm would be 0.4 to 2.1 per cent of global GDP.
The author warns that making global cost estimates for a complex set of interrelated systems is an uncertain business. However, the analysis shows that air capture compares favourably with the cost estimates for mitigation provided in these reports if making similar assumptions to the IPCC and Stern reports. In addition, because the cost of air capture technology is likely to decrease over time it may be more financially advantageous. Although the imprecise nature of these results cannot prove air capture to be superior, they do indicate that it should receive similar levels of attention and analysis as other approaches.
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