The Role of Top-Down Technologies in the Proposed Changes to Subpart W
Author: Dave Levy
Proposed amendments to subpart W of the GHGRP will address gaps in methane emissions reporting.
Data from some top-down technologies, in combination with other empirical data, could be used to calculate total emissions from large emission events.
Continuous monitoring systems can help operators reduce regulatory exposure under the proposed rules in subpart W.
The EPA recently released proposed revisions to the Greenhouse Gas Reporting Program (GHGRP) for the oil and gas sector. This article summarizes the proposed revisions and the role that top-down technologies can play to meet potential new reporting requirements.
Background
The Clean Air Act (CAA) established the GHGRP. The program requires reporting of GHG data from certain large GHG emission sources, fuel and industrial gas suppliers, and CO2 injection sites.
The GHGRP requirements cover emissions from different aspects of the oil and gas industry through several of its subparts. At issue now are changes to subpart W of the GHGRP, which consists of emission sources in four segments of the petroleum and natural gas industry: pipeline transport of natural gas, natural gas distribution facilities, crude petroleum extraction, and natural gas extraction.
The Purpose of Amendments to Subpart W
The proposed amendments to subpart W will address gaps in the total methane emissions reported by facilities by adding new covered sources which include nitrogen removal units, produced water tanks, mud degassing, crankcase venting, and combustion slips. It also proposes to add a new emissions source, referred to as “other large release events”, which would capture abnormal methane emission events that may not be accurately accounted for using existing methods in subpart W.
The EPA is proposing new calculation methodologies and requirements to report GHG emissions from these sources. The changes would also add new or revise existing calculation methodologies to improve the accuracy of reported emissions data; to collect data at a more granular level to improve data transparency; and to include the use of new technologies such as remote sensing for quantifying emissions from other large release events.
The Proposal References Subparts OOOOb and OOOOc
Included with proposed changes to subpart W are references to subparts OOOOb and OOOOc.
Under the new proposal, subpart OOOOb will increase the number of equipment categories that must be inspected at a source level for facilities that were constructed, modified, or reconstructed after 11/15/2021.
Subpart OOOOc will require states to to establish performance standards for emissions control for existing sources. OOOOc impacts any site put into production on or before 11/15/2021. It is expected that most OOOOc standards will align with proposed standards in OOOOb.
Among the proposed changes, OOOOb/c will require operators to conduct a root cause analysis and take corrective actions for super-emitter events and require ongoing fugitive emissions monitoring at all well sites until the site has been closed. OOOOb/c will also expand LDAR requirements and double the number of required inspections.
The EPA Outlines the Role of Top-Down Tech in the New Reporting Rules
The EPA expects that under the proposed methodology for “other large release events” in this proposal, data from some top-down approaches, in combination with other empirical data, could be used to calculate the total emissions from these events and/or estimate the duration of such an event.
The EPA states that top-down monitoring approaches which have demonstrated their accuracy and ability to identify such events may be used to comply with the new reporting requirements. The rule also proposes to use top-down methods to supplement other requirements for periodic measurement and calculation of annual emissions.
The EPA notes that top-down data may also help identify areas where there is a large gap between the bottom-up CH4 emissions estimates and the top-down measurement data, requiring facilities to revise emission estimates.
Subpart W, OOOOb/c, and Continuous Monitoring
Continuous monitoring (CM) is an essential emissions management tool for operators under current and potential federal regulatory programs.
CM is well-suited for new measurement and reporting requirements under subpart W because it can detect leaks immediately, which can lead to faster remediation and help operators reduce regulatory exposure to super-emitter events. CM systems are easy to implement and scale, enabling operators to cost-effectively monitor an expanding list of regulated assets.
The supplemental proposal would explicitly give upstream operators the option to use continuous monitoring technologies to comply with OOOOb. Since it is expected that requirements for states to develop performance standards for emissions control under OOOOc will closely match performance standards proposed under OOOOb, operators which implement CM for the federal use-case will likely be in compliance with future state regulations, and will likely not need to take additional action upon enactment.
Continuous Monitoring and Compliance at the State Level
CM can also help operators satisfy a range of state and territory rules concerning emissions management, reporting, and LDAR.
Continuous monitoring is arguably the best tool for meeting Colorado’s Regulation 7, which requires operators to monitor air quality during pre-production and early production phases using systems that are capable of reporting at a frequency of at least every fifteen minutes.
Under California’s anticipated enactment of SB 1137, LDAR plans must include “a continuously operating emissions detection system designed to provide for rapid detection of target chemical constituents to identify leaks before emissions impact the surrounding communities.”
In New Mexico, operators that successfully isolate and repair leaks using an approved Advanced Leak and Repair Monitoring technology (ALARM), such as continuous monitoring, may apply for offset credits against their annual volume of lost gas.
In Canada, operators can apply to use continuous monitoring technologies as an alternative to OGI and OVA under the Alternative Fugitive Emissions Management Program (Alt-FEMP) to comply with Directive 060.
Conclusion
Although updates to subpart W and the GHGRP have not been finalized, it is clear that operators will need to employ new approaches to meet increasingly stringent emissions regulations. Whatever the final rules, continuous monitoring remains one of the best tools for finding and fixing leaks fast, keeping gas in the pipe for sale, and cost-effectively achieving commercial and environmental goals.