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Improving Methane Emissions Estimates

Even though its methane emissions comprise a relatively small piece of the industry pie, the distribution sector of the natural gas industry is actively seeking ways to calculate and mitigate its methane emissions.

While the industry is working on technologies and approaches for mitigating emissions, it is also important to improve the way in which emissions are quantified. By establishing reasonable baselines, utilities will be able to provide more accurate reports about their emissions profiles and implement mitigation and reduction programs.

"It's important for us to help the industry better quantify its methane emissions profile and incorporate this data into an overall mitigation strategy that puts safety and the environment at the top of the priority list," says Paul Armstrong, director of business development at GTI.

GTI's Methane Emissions Project

GTI has been leading industry efforts to address the need to determine a real emissions baseline for the distribution sector. A multi-phase project launched in 2009, with sponsorship from Operations Technology Development (OTD), designed to update methane emission estimates for natural gas distribution pipelines and to provide local distribution companies (LDCs) with a user-friendly procedure for monitoring their local emission estimates, is now in its final phase. "Our research focuses on measurements from gas distribution systems—specifically, leaks from mains and service lines," says Armstrong.

"We're working to improve the accuracy of reporting methane emissions with this series of projects," says Kristine Wiley, who is leading the GTI initiative.

In the August 2011 issue of Gas Operations News ["A Better Way to Estimate Methane Emissions"], we reported on the first phase of the project, which demonstrated the applicability of using the Hi-Flow Sampler, a portable device that provides real-time measurements of gas flow rates and concentrations in a captured enclosure, for taking measurements at the surface.

Updating Emission Factors

Subsequent project phases focused on the development of a new national Emission Factor (EF). Why is this important? Traditionally, utilities have been required to use national emission factors (EFs) in their emissions reports to the EPA, which were based on a GRI-EPA study published in 1996, a study that was never intended to be used by individual companies in their reporting. Pamela Lacey, senior environmental lawyer at the American Gas Association, agrees. According to Lacey, the old study "no longer provides an accurate picture of current practice and emissions."

The second phase of the GTI testing program provided a new national EF estimate of 3.72 scf/leak-hour for plastic (PE) mains, which is significantly lower than the historic GRI-EPA EF estimate of 12.45 scf/leak-hour. In other words, the project demonstrated that the actual EF for PE pipe is about 70 percent lower than the earlier estimate (in scf/leak-year) and is much more representative of plastic distribution systems. "It is also an example of how obtaining current data and using a bottoms-up approach is very important when quantifying emissions and identifying mitigation strategies for reducing emissions," says Wiley. Subsequent phases of the project continued the field test program for cast iron and unprotected steel pipe.

The team converted the EF estimate to a mile-year basis for a direct comparison to data in the EPA GHG inventory, as shown in Table 1.

Table 1. Emissions are measured in terms of the average amount of a pollutant or material discharged into the atmosphere by a particular process or equipment (e.g.,2.28 Mscf/mile/year for PE mains).

The GTI team is currently working to develop a new methodology for implementing the revised EFs. "In addition to updating the existing EFs, we'll be working to launch a new approach that will enable operators to create utility-specific emission estimates based on their own leak data instead of the national estimates," says Wiley. "Operators would use the utility's leak database to more precisely define their emissions profiles. It’s a completely different way of looking at the issue versus the existing 'miles of pipe' approach."

GTI's focus is on developing a methodology based on the actual number of leaks in a system versus total miles of pipeline. Until now, methane emissions have been quantified by multiplying the EF (for leaks by pipe type) by a "national activity factor" (or national average of leaks per mile for the given pipe type). "Using total miles is a simpler approach for calculating emissions on a national basis, but it does not acknowledge the efforts of utilities that have implemented aggressive leak repair or rehabilitation programs," says Wiley.

The current project aims to develop utility-specific activity factors that use actual leak, repair, and duration records.

"We believe that this rigorous methodology will provide an accurate measure for baseline and incremental improvement at the utility level. Our goal is to help utilities determine the best approach for integrating these new measurement protocols into their current practices and the level of detail needed for estimating their total annual emissions," says Wiley.

Another goal of the final project phase is to garner regulatory acceptance of the new methane emissions quantification methods for use by utilities in complying with EPA reporting requirements and compliance with other emission regulations. This will include communicating with various stakeholders, such as trade organizations and environmental groups.

"Determining practical strategies for incorporating these proposed improvements in the emission estimation calculations by utilities—and attaining regulatory acceptance—is the last step in the process of helping utilities fully benefit from this research effort," says Wiley.

The future

GTI is working with industry partners to move the issue forward. One initiative is a joint conference on methane emissions that GTI will co-host with the Houston Advanced Research Center (HARC) in September. "We are also engaging with other organizations to develop smart monitoring systems for methane leaks—for both utility and residential applications," says Wiley. "And we're working to provide utilities with more real-time information to enhance safety for customers and communities."


CH4 Connections Conference September 23–24
The Woodlands, TX—Register Today

With methane emissions being an increasingly important topic to be addressed, Gas Technology Institute and Houston Advanced Research Center have developed a conference—CH4 Connections—aimed at collaborative solutions for the natural gas community. It will provide a forum for diverse interests to discuss upcoming policy decisions, the newest detection and mitigation programs and techniques, and how different facets of the community can benefit from sharing knowledge and experience with others.

As new rules to mitigate the impact of methane releases are considered, various stakeholders will come together to address important questions such as: Are new rules needed? What methods and tools are available for methane emissions detection and mitigation? What direction are policy makers going with respect to regulating the industry? How can methane emissions and their impact be accurately measured?

The conference will take place in The Woodlands, Texas—30 minutes from Bush International Airport—on September 23 and 24 and provide a broad perspective on the issues.

A variety of speakers representing gas producers, transmission pipelines, and gas distributors, plus representatives from the U.S. DOE, EPA, state agencies, and academia will be discussing policy, environmental issues, and technical challenges regarding measuring, mitigating, and weighing the impact of methane emissions in the oil and gas industry.

For more information or to register for the event visit the CH4 Connections website.


For more information contact Paul Armstrong.

Join us on
Sept. 23-24, 2014 at