Greenhouse Gas Accounting Framework for Carbon Capture and Storage Projects
Meeting the global challenge to reduce greenhouse gas (GHG) emissions and avoid dangerous climate impacts requires deploying a portfolio of emission reduction technologies.
We must both commit to broad and deep efficiencies in the way our societies’ consume energy and to significant increases in power supplies from low carbon energy sources. At the same time, it is important to recognize that the scale of the challenge to reduce global emissions is massive, and that it will take decades for new and advanced low and zero-emissions technologies to sufficiently mature and dominate the world’s primary energy supply.
Because the use of fossil fuels – including coal – will continue to maintain a central role in powering the global economy for at least the next several decades, the portfolio of solutions to achieve the necessary GHG emissions reductions must include carbon capture and storage (CCS).
CCS refers to a suite of technologies that, when effectively combined, prevent carbon dioxide (CO2) from entering the atmosphere. The process involves capturing and compressing CO2 from power plants and other industrial facilities, transporting it to suitable storage sites, and injecting it into geologic formations for secure and permanent sequestration.
Geologic storage of CO2 emissions currently represents the only option to substantially address the greenhouse gas emissions from fossil fuel-fired power plants and large industrial facilities.
The Greenhouse Gas Accounting Framework for Carbon Capture and Storage Projects – CCS Accounting Framework – provides methods to calculate emissions reductions associated with capturing, transporting, and safely and permanently storing anthropogenic CO2 in geologic formations. It aims for consistency with the principles and procedures from ISO 14064-2:2006. Greenhouse gases – Part 2: Specification with guidance at the project level for quantification, monitoring and reporting of greenhouse gas emission reductions or removal enhancements, which represents best practice guidance for the quantification of project-based GHG emission reductions.
Ultimately, the objective of the CCS Accounting Framework is to inform and facilitate the development of a common platform to account for CO2 emissions reductions due to capturing and geologically storing CO2. It also contributes to the public discussion about the viability of CCS to serve as a feasible CO2 mitigation solution.
The emissions accounting procedures in the CCS Accounting Framework apply to multiple CO2 source types, including electric power plants – equipped with pre-combustion, post-combustion, or oxy-fired technologies – and industrial facilities (for example, natural gas production, fertilizer manufacturing, and ethanol production). For CO2 transport, the calculation methodology in this document applies only to pipelines because while other methods of transport, (e.g., truck transport) are possible, they are typically not considered viable options for large-scale CCS endeavors. With respect to the geological storage of CO2, the CCS Accounting Framework applies to saline aquifers, depleted oil and gas fields, and enhanced oil and gas recovery sites.
The CCS Accounting Framework provides a comprehensive set of GHG accounting procedures within a single methodology. The quantification approach includes equations to calculate emissions reductions by comparing baseline emissions to project emissions – the difference between the two represents the GHG reductions due to capturing and sequestering CO2, which would have otherwise entered the atmosphere.
GHG reductions from CCS project = Baseline emissions - Project emissions
Baseline emissions represent the GHG emissions that would have entered the atmosphere if not for the CCS project.
Project emissions are actual GHG emissions from CO2 capture sites, transport pipelines, and storage sites.
The quantification approach to determine baseline emissions presents two baseline options: 1) “Projection-based” and 2) “Standards-based.” In both cases, the calculation method uses data from the actual CCS project to derive baseline emissions.
Determining project emissions involves measuring CO2 captured and stored by the project and deducting CO2 emitted during capture, compression, transport, injection, and storage (and recycling of CO2 if applicable). The procedure to determine project emissions also accounts for GHG emissions from energy inputs required to operate CO2 capture, compression, transport, injection and storage equipment. Energy inputs include “direct emissions” from fossil fuel use (Scope 1 emissions) and, in case required by a program authority, “indirect emissions” from purchased and consumed electricity, steam, and heat (Scope 2 emissions).
CCS project monitoring covers large above ground industrial complexes and expansive subterranean geologic formations. In terms of emissions accounting, monitoring CO2 capture and transport involves well known technologies and practices, established over many years for compliance with federal and state permitting programs. Therefore, the monitoring program would follow generally accepted methods and should correspond with GHG monitoring requirements associated with the relevant subparts of EPA’s Greenhouse Gas Reporting Program (GHGRP) and other state-level programs.
On the other hand, monitoring geologic storage sites for the purpose of verifying the safe and permanent sequestration CO2 from the atmosphere is a relatively recent activity that may involve new techniques and technologies. While there exists no standard method or generally accepted approach to monitor CO2 storage in deep rock formations, project developers will benefit from monitoring practices deployed over the past 35 years in CO2 enhanced oil and gas recovery operations. Thus, the CCS Accounting Framework does not prescribe an approach to monitor CO2 sequestration, as geologic storage sites will vary from site to site and demand unique, fit-for-purpose monitoring plans. This approach is consistent with the monitoring, reporting and verification (MRV) procedures for geologic sequestration from subpart RR to EPA’s Greenhouse Gas Reporting Program, which overlays the monitoring requirements associated with the Underground Injection Control Program.