CO₂ Capture and Storage

9. How could emission reductions be quantified?

An important aspect of CO₂ capture and storage is the development and application of methods to estimate and report the quantities in which greenhouse gas emissions are reduced, avoided, or removed from the atmosphere.

This requires:

• the estimation and reporting of actual emissions for national greenhouse gas inventories, and
• accounting for CO₂ capture and storage under international agreements to limit net emissions.

In the absence of international agreements, it is not clear whether the various forms of CO₂ capture and storage will be treated as reductions in emissions or as removals from the atmosphere. CO₂ capture and storage is markedly different in many ways from CO₂ sequestration in biological carbon sinks (forests, soil etc), and the different forms of carbon capture and storage are markedly different from one another. While one tonne of CO₂ permanently stored has the same benefit in terms of atmospheric CO₂ concentrations as one tonne of CO₂ not emitted, one tonne of CO₂ temporarily stored has less benefit. This difference should be reflected in any system of accounting for reductions in net greenhouse gas emissions. Currently, there are no methods available within the UNFCCC framework for monitoring, measuring or accounting for physical leakage from storage sites.

Table TS.12. Global potential contribution of CCS as part of a mitigation portfolio

Although methods currently available for national emissions inventories can either accommodate CO₂ capture and storage systems or be revised to do so, accounting for stored CO₂ raises questions about the acceptance and transfer of responsibility for stored emissions. Such issues may be addressed through national and international political processes. More...