An assessment of options for CO₂ removal from the atmosphere

Recent work examining likely changes in global temperatures as a result of carbon dioxide (CO₂) emissions has suggested that cumulative CO ₂ emissions (i.e. total emissions over an extended period of time) could be more significant than the differences between particular emissions pathway (e.g. with different timing of emissions or peak emissions rate) in determining how the global climate might change in response to CO₂ emissions. This suggests that effective measures to mitigate the risk of dangerous climate change will need to limit cumulative emissions of CO ₂. Further, if cumulative CO₂ emissions overshoot acceptable limits, it will become necessary to remove CO₂ from the air - so-called 'negative emissions'. Technologies that effect 'negative emissions' could also be used to offset additional anthropogenic emissions from sectors where greenhouse gas emissions are difficult or impossible to reduce beyond certain, still relatively high, limits. If the prevailing carbon price for marginal abatement options rises significantly from current levels (e.g. of order up to $200/tCO₂ has been suggested by some) then a relatively wide range of options for removing CO₂ from the air may become cost-effective. Additionally, some options for removing CO₂ from the air are likely to have much lower abatement costs. This paper summarises results from research conducted to compare and contrast various options for capturing CO₂ from the air, with a particular focus on establishing the potential of these options to have a significant impact in reducing CO₂ emissions and, if so, over what timescales.