Direct Air Carbon Capture and Storage: Go hard or go home?

With the exception of BECCs, the majority of geoengineering methods have focused on enhancing or replicating a natural process to remove atmospheric carbon. These ‘natural’ processes require global implementation, which has resulted in the issue of ‘planetary scale’ cropping up almost every week. As a result, I find myself consistently remarking on the environmental issues surrounding this large scale and concluding that they could be useful on a smaller scale. However, small scale solutions won’t bring the 400ppm of CO₂ down to pre-industrial levels. So maybe a more direct approach is necessary? This brings me to the last carbon capture method on the list; Direct Air Carbon Capture and Storage (DACs). 

Direct Carbon Capture and Storage does exactly what it says on the tin. Technology is used to remove atmospheric carbon. A system driven by renewable energy removes CO₂ from air when it makes contact with a recycled sorbent  e.g. calcium hydroxide Ca(OH)₂ (the ‘slaked’ lime in last week’s post). The resultant CO₂ is then compressed and transferred to the storage location or used for industrial purposes.  

(The DACs process (Rapp, 2011))

At present, this technology is still in the pilot stage, but it could be scaled up or down to sequester the required amounts of CO₂. DACs can be used anywhere because it is not restricted to an energy production plant (e.g. BECCS) or a certain area of land (e.g. Afforestation). Therefore, DACs could offset power plants, or be scaled down and incorporated into residential housing. However, if a personal DAC machine removed the equivalent emissions of 10 trees per year, this would still fall short of the total household’s emissions (see previous blog: Afforestation and Reforestation ). Although, if all UK households installed a device it would offset a notable portion of emissions. This method particularly opens up the moral issue of geoengineering methods. Realistically, if you knew your emissions were being offset by a machine in your garden, even partially, would you be more likely or less likely to change your lifestyle? Probably less likely.

(How a household DACs machine may look (Chiara, 2014))

Goeppert et al. (2012) provided an assessment of DACs and concluded the main limitations on the potential scale are those imposed by the economy. In theory, it could be rolled out globally, but in reality large investment into the industry and surrounding infrastructure would be needed to make it feasible. Goeppert et al. (2012) suggested costs of US$20-1000 per ton of CO₂, although they note there is ongoing research into cheaper processes and different sorbent materials. Furthermore, it is likely the associated costs with geoengineering technologies will reduce over time as they become more commonplace, but this is very difficult to quantify.

The major issue facing all CDR methods (Nichols, 2011)

From my personal experience, I believe DACs would be met with less suspicion than other CDR methods. We are used to building a direct solution to a problem and inherently want to reduce the impact to us and the environment. If DACs were successfully implemented I think it is likely less effort would be put into mitigating climate change, but it could be a useful stepping stone to a renewable world.