Document ID: EPA-HQ-OAR-2012-0934-0120
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2013-11-13T05:00Z

September 28, 2012

Via Electronic Transmission: Shores.richard@epa.gov
Mr. Richard Shores
U.S. Environmental Protection Agency
Office of Research and Development
109 T.W. Alexander Drive (E-343-02) 
Research Triangle Park, NC  27709

Re: Quantifying Methane Abatement Efficiency at Three MSW Landfills, EPA/600/R-11/033

Dear Mr. Shores,

Thank you for providing Waste Management the opportunity to comment on and suggest revisions to the Agency's January 2012 report, Quantifying Methane Abatement Efficiency at Three Municipal Solid Waste (MSW) Landfills, EPA/600/R-11/033.  We know you have been talking to Gary Hater and Roger Green about our scientific and technical concerns with the report's research methods and conclusions.  We value the professional working relationship we have with you and Dr. Thoma and look forward to continuing cooperative research with you under the new CRADA we hope to finalize with EPA soon.  So, we very much appreciate your commitment to review our comments and make revisions to the above referenced report.

WM is a major stakeholder in any public policy debate that addresses the estimation of emissions from municipal solid waste (MSW) landfills, and the Company recognizes its obligation as an industry leader and environmental steward to accurately estimate our landfill emissions.  Towards this end, WM has invested substantial time and funding into better understanding methane emissions from landfills.  This includes conducting extensive measurement campaigns at twenty of our landfills across the country, working with the Solid Waste Industry for Climate Solutions (SWICS) on improved estimation methodologies, and working closely with EPA over the years on cooperative research.

We wanted to provide additional context for our technical and policy concerns.  After a thorough review of the report, we have concluded that the limited measurement studies undertaken do not provide data of the quality or scope required to make significant conclusions about methane abatement efficiencies at MSW landfills, nor should these data be incorporated into EPA guidance or cited as a basis for establishment of emission factors or regulatory actions. Further, we understand a Category III Quality Assurance Project Plan (QAPP) was prepared and used for this report, which, per the Agency's Quality Assurance Planning Requirements, is not sufficient to support regulatory development or regulatory guidance such as revisions to the Landfill NSPS (40 CFR Part 60 Subpart WWW) or AP-42. 

Our policy issues fall into two categories.  First, we are concerned that the limited scope of the research, summarizing five measurement campaigns at three southeastern landfills, does not provide a sound basis for the document's broad policy conclusions and proposed next steps.  Second, we have significant scientific and technical concerns about the measurement methods and physical conditions at the sites, which call into question the validity of the reported measurements.

The Limited Study Scope Does Not Support Development of Guidance, Emission Factors or Regulatory Actions

The report purports to be a comprehensive study of the use of optical remote sensing using OTM-10 to measure landfill-wide methane emissions and evaluate methane abatement efficiency.  In the conclusions chapter on page 4-3, the report states that the data provided is "considered the best available data to date" and further concludes that the data suggest "promise with the use of OTM-10 for quantifying whole landfill emissions."  In fact, this report summarizes the results of very limited field research that is not representative of landfills throughout the country.  The field research comprises merely five methane measurement campaigns performed at three landfills all located within a single climate zone during Spring and late Fall for Sites A and C and a two-week period during Summer for Site B.  Not only is the scope of the field research extremely limited, but the report provides neither a robust survey of the scientific literature on alternative landfill gas measurement technologies, nor a survey of extensive field research that has been conducted in varying climate zones and seasons.  In fact, the report's list of references is very limited, including four papers by one scientist (Hashmonay) and eleven EPA reports, seven of which were authored by the project manager of this subject report.

Our points about the very limited scope of this report and underlying reference materials are important because in the report Executive Summary and Conclusions Chapter, conclusive statements are made that are not supported by the body of the report or by any scientific citations.

The Report Minimizes the Challenges and Overstates the Performance of OTM-10 Technology
We've highlighted three additional statements from the report, two in the executive summary (p. xiii), and one in the introduction (p. 1-4):  
      Of the area source emissions, landfills are considered the most challenging because of their size, and ever changing nature due to changes in waste composition, design and operation.  Breakthroughs in technology, data analysis in allocating emissions to the entire footprint, and method development to standardize operating procedures have resulted in the ability to more accurately quantify fugitive landfill gas emissions using optical remote sensing technology. (p. xiii)
      Using the latest area source measurement techniques, a multi-week field campaign was conducted at three landfills to quantify the methane abatement efficiency. (p. xiii)
      The method has been successfully employed to characterize emissions from a variety of sources, including landfills, wastewater treatment plants ...  (p. 1-4, emphasis added)
      
First, we note that one of the most challenging issues in using OTM-10 for whole landfill emissions (i.e., allocating emissions to the entire footprint) is characterized in the executive summary as a "breakthrough in technology" that has "resulted in the ability to more accurately quantify" emissions.  While we agree that significant fieldwork has been done by EPA and WM to better understand the use of OTM-10 in measuring whole landfill emissions, that fieldwork has identified significant challenges in the use of the technology.  We find it gravely misleading for the report to make the above referenced statement without also explaining the significant challenges and implementation uncertainties that remain to be addressed.  
Mr. Driscoll of the OAQPS Measurement Policy Group asked WM to draw from our extensive experience using OTM-10 to measure methane emissions for whole landfills and provide him our recommendations relating to the use of data obtained using OTM-10 in developing landfill emission factors.  In an August 3, 2011 letter we responded with the following concerns:
      After 72,500 measurements obtained over 50 weeks of data collection at 20 landfills, we are very concerned that only 31 percent of the data collected are usable (i.e., meet the quality assurance/quality control (QA/QC) requirements).
      Fundamentally, we do not recommend using OTM 10 with TDL for broad application as an emission measurement tool at MSW landfills.  The measurement technique is very difficult to set-up and use due to the complex topography associated with landfills and the strong influence weather (e.g., wind direction and speed, precipitation, barometric pressure) plays on the ability to obtain usable TDL readings.  The large source size, heterogeneous source area, and interference from internal or external sources of emissions (from an adjacent landfill cell outside the measurement area or a wholly separate site) can create very significant uncertainties in measuring methane flux.  
      While WM has invested significant time and resources in trying to resolve methodological uncertainties and develop best practices to make OTM 10 a practical tool for landfill emissions estimation, we simply cannot recommend its use for developing landfill emission factors at this time.  We cannot recommend using OTM 10 for regulatory compliance purposes, for calculating landfill gas collection efficiencies, or even for estimating whole landfill emission factors without first resolving these methodological problems.  
The Report Fails to Acknowledge Potentially More Effective Measurement Technologies Being Explored by EPA ORD and the Landfill Sector

Second, we are concerned with the assertion in the executive summary that OTM-10 is "the latest" measurement technique.  The report does not provide references to support these statements, and the topic is not addressed in the body of the report.  Furthermore, the report fails to acknowledge that there are other (potentially more effective) measurement techniques, such as cavity ring-down spectroscopy (CRDS), that both ORD and WM have tested and together are planning to extensively field test under a new cooperative research and development agreement (CRADA) with multiple landfill owner/operators.  As a result, a reader would conclude that OTM-10 is the best technology available and that it has been significantly improved, but the reader would not have been informed of the significant limitations and uncertainties of using the approach, or that extensive testing of another, possibly better technology is underway.

From our perspective, CRDS offers several advantages when compared to OTM 10 for determining whole landfill emission estimates.  Many of the uncertainties involving measurement error, area contributing to flux (ACF) calculation and the extrapolation emission factors are avoided as the CRDS approach can directly measure emissions from the entire landfill.  An important objective of the planned cooperative research effort with you is to develop a new OTM for the tracer correlation approach using CRDS at landfills.  We are concerned that the conclusions in this report seriously undermine the goals and objectives of this new CRADA.

The Report makes Premature and Unsupported Conclusions about the Timing of Methane Generation

The field work for the report included methane emissions measurements for two days at a new landfill cell at Landfill Site B that had accepted waste for about three months prior to the sampling.  Based on this very limited field work, the report asserts that while most models assume no methane generation for at least six months from initial waste placement, the data clearly show that for this site it would be an incorrect assumption to conclude anything other than that the methane measured had been generated by new waste (p. 4-2).  The limited nature of the sampling conducted simply does not support this conclusion.  Furthermore, based on the discussion of the sampling conducted at this site in Chapter 3, the field work did not rule out the possibility of methane flow from adjacent areas including the hog farm located only 300 meters from the landfill cell.  (See p. 3-7)  As WM described more fully in our technical comments, we have serious concerns regarding the validity of the approach used in the measurement campaigns to determine the potential for methane flow from adjacent areas.  

Based on our review of the report, WM does not find adequate support for the conclusion that the emissions measured at Landfill B can only be explained by concluding that the new waste was emitting significant quantities of methane.  The study did not sufficiently quantify the methane flow onto the cell from the nearby hog farm, nor did it account for methane flow from the inoperable gas collection system wells that were filled with water and unable to recover methane gas.  If EPA or state environment agencies accept this poorly-supported conclusion about the timing of methane generation as a fact, they might seek to require earlier installation of gas collection systems, which can greatly complicate landfill operations in new cells.  Any such decision by a permitting agency must be based on better information than that provided in this report.

The Report Fails to provide a Sound Basis for the Presented Range of Methane Abatement Efficiencies
From five measurement campaigns at three southeastern landfills, the report develops a range of methane abatement efficiencies (38% - 88%), and concludes, based on this limited field work that "the data collected does not support the use of collection efficiency values of 90 percent or greater as has been published in other studies." (p. 4-3).  We believe the dataset represented by this limited-scope effort is insufficient to call into question the research conducted at a larger universe of landfills with findings that have undergone peer review prior to publication in science journals.  Furthermore, there is far too much uncertainty in the use and interpretation of data collected using the OTM-10 approach to make such conclusive statements about collection efficiency.  Given the difficulties in measuring and interpreting results for whole landfill methane emissions, when extrapolating from the small area covered by the OTM- 10 approach, any conclusions must be based on a larger set of measurements from a representative set of landfills in a variety of climate zones.

Summary of Technical Issues with the Report

1. Concerns regarding the installation of the Open Path Tunable Diode Laser 
We are concerned with the researchers' methods for quantification of methane flow from adjacent sources of methane (e.g., the hog farm near Landfill B), as well as readily apparent errors in setting up the TDL measurement equipment (as indicated in Figure 3-3).  The TDL reflectors were placed either adjacent to or downwind of gas wells.  Therefore, the measurements bias toward the high side under these field conditions.
We are also concerned with the high variability in daily measurements observed at several sites, because the report indicates that the authors were not able determine the cause(s).  It is possible that the variability was related to methane flow from adjacent areas, but a more thorough investigation is necessary to confirm this.  Until the issue of adjacent flow is resolved, EPA cannot assure the validity of these data for the purpose of determining methane abatement efficiencies.
We recommend that EPA conduct a thorough review of these issues (potentially with the input of external reviewers), and that EPA includes appropriate caveats and/or additional explanatory material in the report to ensure that the procedures followed and validity of the results can be properly assessed.  Until the quality of the results is better understood, the data should not be used for policy or regulatory purposes, or incorporated into OTM-10.  As previously stated, EPA prepared and used a Category III QAPP for this report, which is not sufficient to support regulatory development or regulatory guidance such as revisions to the Landfill NSPS (40 CFR Part 60 Subpart WWW) or AP-42.      

2. Use of measurements from Landfill B should not have been included in the study because its gas collection system was not representative of modern landfills at the time of the study. 
Although the report states in two places (pp. xiii and 4-3) that the three landfills had gas collection and control systems in place "as required by the Clean Air Act New Source Performance Standards and Emission Guidelines for municipal solid waste landfills," this was not the case at Landfill B at the time of the field work.  Although that landfill had a gas collection system in place, it could not pass the NSPS serpentine compliance test at the time of the measurement study.
The report notes that shortly after the measurement campaign, Landfill B installed a new gas collection system, and states that "it would be helpful to re-test to see what level of reduction occurred as a result of the improvements..."  (p. 4-3)
We agree that Landfill B should be retested.  We further believe that EPA should not have included the initial results from Landfill B in the study, which is the source of the low-end abatement efficiency of 38 percent. 

3. Concerns regarding the approach used to estimate NMOC and mercury emissions 
Our concerns regarding non-methane organic compound (NMOC) emissions focus on two issues: (1) the use of the NMOC to methane ratio in the landfill gas collection header system as a proxy for the NMOC: methane ratio in the atmosphere above the landfill, and (2) the need to incorporate recent research on biological degradation of NMOC as it moves through the landfill cover into the estimation methodology. 
This is an issue of significant regulatory importance, because NMOC emissions are the trigger for NSPS applicability.  The fact that EPA is currently working on an NSPS update and has not yet seriously engaged in the new science on NMOC emissions is a serious concern to us.   
WM contracted with Doctors Paul Imhoff, Jeffrey Chanton and Morton Barlaz to evaluate the validity of estimating NMOC emission rates by measuring NMOC concentrations in header gas.  We provided their analysis with our technical comments on the subject report.  Drs. Imhoff, Chanton and Barlaz concluded that because concentrations of NMOC in landfills are spatially variable, and that NMOC can be readily attenuated in landfill covers by biodegradation, landfill header gas concentrations are not representative of NMOC concentrations in landfill gas emitted to the atmosphere.  We have concerns about the approach used in the report and do not believe the report's conclusions should be used in development of emission factors or for other regulatory purposes.  We thus request that EPA review these issues as part of its re-examination of this report and take steps to better incorporate recent scientific findings into ongoing regulatory developments.
WM provided comments on the mercury emissions factors developed from similar analyses in the draft update of the MSW Landfill AP-42 emissions factors.  We believe the calibration data and QA/QC data from the mercury analysis should also be thoroughly reviewed by internal and external experts and appropriate revisions made to the report.
We appreciate the opportunity to share our comments and recommendations with you.  Both of us will be in RTP for the October 22 NSPS Stakeholder meeting.  If it would be helpful to discuss with you these comments and your planned report revisions, we would be happy to do so after the stakeholder meeting or on the 23[rd].  Again, thank you for your careful consideration of our policy and technical concerns and recommended report revisions. 

Sincerely,

 				
Kerry Kelly, Director					Amy Van Kolken Banister, Sr. Director
Federal Regulatory Affairs				Corporate Air  Programs
Cc:  	Eben Thoma
	Steve Fruh
	David Cozzie
	Hillary Ward
      Tom Driscoll