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Abstract
Carbon capture and geological storage (CCS) is a core element in the global strategy to reduce greenhouse gas (GHG) emissions. This paper characterizes and contrasts the emission quantification methods associated with CCS projects from the perspective of voluntary emission reduction initiatives and recent regulatory reporting requirements under the U.S. Environmental Protection Agency (EPA) Greenhouse Gas Reporting Program (GHGRP).

From the regulatory perspective, the U.S. EPA is addressing the mandatory GHG reporting for CO2 injection and potential geological storage, providing a different approach for facilities that supply CO2 to the market, those that inject CO2 for purposes of enhanced oil and gas recovery, and those that are engaging in long-term geological storage. Information gathered under the GHGRP will enable EPA to track the amount of CO2 supplied to the market, injected, and/or stored by U.S. facilities. In addition, where the CO2 injection facilities are also associated with other oil and gas operations, the GHGRP requires quantifying and reporting GHG emissions from those operations where the facilities meet specified regulatory thresholds. This information will be a key element in providing baseline data and activity information for the development of future emission standards and control techniques for GHG emission mitigation in the U.S.

In addition to reporting initiatives, industry is providing guidance to support voluntary GHG reduction initiatives. The American Petroleum Institute (API) and the International Petroleum Industry Environmental Conservation Association (IPIECA) have collaborated on a guideline document to promote the credible, consistent, and transparent quantification of GHG emission reductions from CCS projects (IPIECA/API, 2007). This document emphasizes that the entire range of activities associated with CCS – capture, transport, injection and storage – must be considered in quantifying emissions and emission reductions from CCS operations.

This paper will examine common aspects and notable differences between the mandatory reporting programs and voluntary GHG emission reduction activities. It will specifically emphasize collateral characteristics such as the scope of emission sources, accuracy of quantification methods, reporting and monitoring requirements.

Introduction to CCS
CCS applies established technologies to capture, transport and store CO2 emissions from large point sources. Wide deployment of CCS techniques is viewed as essential for addressing climate change, while also providing energy security, creating jobs, and economic prosperity. The International Energy Agency (IEA) states that CCS could reduce global CO2 emissions by 19%, and that without CCS, overall costs to reduce emissions to 2005 levels by 2050 would increase by 70% (IEA, 2009).

CCS refers to the chain of processes that are designed to collect or capture a CO2 gas stream, transport the CO2 to a storage location, and inject the CO2 into a geological formation1 for long-term isolation from the atmosphere (See Figure 1). CCS involves avoiding the release of CO2 emissions to the atmosphere by injecting CO2 and ultimately storing it in a geological formation. The assessment of GHG emission reductions from CCS projects should address all of these elements.