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IEA Greenhouse Gas R&D Programme

Background to the Study


This report sets out accounting guidelines for measuring greenhouse gas (GHG) emissions and emissions reduction effects arising from technologies involving carbon dioxide capture, utilisation and geological storage (CCUS). 


The guidelines apply a project- and product-based approach to measure GHG emission reduction effects, based on comparing the emissions for a CCUS activity with the emissions from a comparable activity delivering the same product or service.



A modular approach is applied. Firstly, users calculate the GHG effects arising from the capture (and transport) of CO2 based on the avoided emissions from providing the same service or product as output from the CO2 source facility, but without CO2 capture.



The resulting estimate of GHG effects from CO2 capture is carried forward to the utilisation or storage step. In this subsequent step, the GHG emissions from providing the same service without using captured CO2 is estimated and compared to the GHG emissions of providing the service using captured CO2. This provides an overall estimate of the cradle-to-gate GHG effect of CCUS activities.



Additional guidance is provided on cradle-to-grave assessment, although this is not the primary focus of these guidelines – the Guidelines focus on annualised GHG emissions accounting cycles rather than whole life emissions analysis.



Specific guidance is provided on:


  • Managing system multifunctionality in carbon dioxide utilisation (CCU) activities
  • Handling functional equivalence and selecting functional units for CCUS activities
  • Managing the risk of CO2 seepage from geological storage sites.
The report is available to download.