1

RECOMMENDATIONS AND CONSIDERATIONS FOR EPA’S FORTHCOMING REVISIONS 

TO SECTION 111 STANDARDS FOR MSW LANDFILLS

Environmental Defense Fund 

 January 2, 2013 

INTRODUCTION 

This White Paper outlines EDF’s policy recommendations, and supporting research, for EPA’s 

forthcoming proposed revision of the New Source Performance Standards (NSPS) and Emission 

Guidelines (EG) for new and existing MSW landfills (40 C.F.R. Part 60, Subparts Cc and WWW). The 

recommendations below address both rigorous landfill gas (LFG) capture requirements that could be 

integrated into the existing NSPS/EG framework, as well as opportunities to reduce greenhouse gas 

(GHG) emissions at landfills that are not (or would not be) able to utilize gas capture technology. Major 

topics covered in this White Paper include: 

1. Applicability thresholds for landfill gas capture technology; 

2. Measures for controlling LFG early in the lifecycle of the landfill; 

3. Optimal design and operation of LFG collection systems; 

4. Monitoring requirements; 

5. Post-closure maintenance and monitoring; 

6. Policies to recognize and encourage organics diversion as a GHG control strategy; and 

7. Measures for landfills that are not subject to gas collection requirements. 

1. APPLICABILITY THRESHOLDS SHOULD ADDRESS METHANE DIRECTLY AND CAPTURE 

LANDFILLS THAT PRODUCE SUFFICIENT GAS TO OPERATE A FLARE

The existing NSPS and EG apply to landfills that emit 50 megagrams (Mg) per year of nonmethane organic compounds (NMOCs) and have a size at or above the design capacity threshold of 2.5 

million Mg or 2.5 million cubic meters (m3

). EPA indicated that it chose the 2.5 million Mg design 

capacity exemption because it would “exempt 90 percent of the existing landfills while losing only 15 

percent of the total NMOC reductions” and the 50 Mg/yr NMOC threshold because it would “affect less 

than 5 percent of all landfills.” 1 EPA estimated that this combined standard would “reduce NMOC 

emissions by approximately 53 percent and methane emissions by 39 percent.”2

While EPA’s existing landfill gas capture requirements have resulted in methane reductions, 

several analyses suggest that smaller landfills can effectively deploy landfill gas capture technology and 

drive further emission reductions. EDF recommends: 

 Adopting a waste-in-place (WIP) threshold rather than a design capacity threshold; 

                                                           

1

 61 Fed. Reg. at 9,111 (Mar. 12, 1996); see also U.S. EPA Office of Air and Radiation, Air Emissions from 

Municipal Solid Waste Landfills – Background Information for Final Standards and Guidelines 1-32 (1995), 

available at http://www.epa.gov/ttn/atw/landfill/bidfl.pdf. 2 Id. 
2

 Adopting a heat input applicability threshold rather than a quantitative NMOC threshold; 

 Extending applicability to landfills that accepted waste after 1977; and 

 Directly regulating methane pollution from landfills. 

Recommended Applicability Framework. When revising the NSPS applicability thresholds, EDF 

recommends that EPA focus on the parameters that most directly determine a landfill’s readiness to 

deploy LFG capture technology: the amount of methane-generating waste in place, the heat input of the 

landfill gas generated, and the surface concentration of methane at the landfill. Moreover, EPA should 

tailor each of these applicability thresholds to ensure that all landfills capable of capturing landfill gas are 

required to do so at the earliest feasible date. Below, we explain the basis for adopting each of these 

applicability thresholds. 

Waste-in-Place Threshold. Because landfill gas generation potential is determined by waste-inplace, not design capacity, a threshold based on waste-in-place is more directly predictive of methane 

generation than the current design capacity threshold.3

 Indeed, the current 2.5 million Mg design capacity 

exclusion has the perverse result of potentially excluding landfills with capacities below the threshold but 

with actual waste placements sufficient to support capture. By contrast, California’s landfill methane 

reduction rule (“California Rule”) adopts a 450,000 tons WIP threshold, regardless of the design capacity 

of the landfill, because this is the smallest quantity of waste expected to generate sufficient gas to operate 

a flare.4

 On similar grounds, a 2008 SCS Engineers report for the California Integrated Waste 

Management Board (CIWMB) on GHG management options endorses a 500,000-ton WIP applicability 

threshold.5

 Accordingly, EDF recommends that EPA adopt a WIP threshold that similarly reflects the 

minimum quantity of waste capable of sustaining a flare (understanding that this minimum quantity likely 

varies according to climatic conditions and waste composition). 

BTU Threshold. A gas heat-input threshold in British Thermal Units (BTUs) provides indication 

of when generated landfill gas is sufficient to operate a control device, and is therefore an intuitive 

benchmark for determining when a landfill should be required to install LFG capture technology.6

 A 

BTU-based applicability threshold has the further advantage of sidestepping any errors resulting from the 

application of default NMOC concentrations to estimated LFG production. In determining a landfill’s 

readiness for gas capture, the California Rule sets a threshold of 3.0 million BTUs / hour, which is based 

on the minimum gas heat-input necessary to operate a flare without utilizing supplemental gas.7

 EPA’s 

                                                           

3 See Memo from RTI to EPA, Correlations With Landfill Methane Generation and Actual Emissions (Apr. 15, 

2008) (“WIP is expected to be a much better indicator of methane generation and emissions than landfill capacity.”) 

4

 California Air Resources Board, Final Statement of Reasons for Rulemaking: Public Hearing to Consider the 

Adoption of a Regulation to Reduce Methane Emissions from Municipal Solid Waste Landfills at 11 (June 25, 

2009) (“The threshold of 450,000 tons of waste-in-place was selected because landfills with less waste-in-place are 

not expected to generate enough landfill gas to operate a gas collection and control system without supplemental 

fuel.”). 

5

 SCS Engineers, Technology and Management Options for Reducing Greenhouse Gas Emissions from Landfills 55 

(2008) (identifying 500,000 tons WIP as a BMP for installation of LFG capture but noting that this requirement 

“may not be warranted for landfills in very dry climates”). 

6 See U.S. EPA, Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from Municipal 

Solid Waste Landfills 12-13 (Apr. 2011). 

7 See ISOR at V-2. 
3

greenhouse gas reporting rule similarly defines minimum BTU values for open flares.8

 These are possible 

models that EPA should consider in defining a heat input-based threshold in the revised NSPS/EG. 

Surface Concentration Threshold. Once a landfill meets the WIP threshold and the BTU / hour 

threshold, EDF recommends that the operator be required to monitor surface methane concentrations in 

accordance with our recommendations below. A monitoring-based applicability prong provides built-in 

incentives for landfill operators to adopt one or more innovative methane avoidance or mitigation 

strategies, including organic waste diversion, oxidative landfill covers, and early landfill gas control 

measures. In addition, EDF has been informed by landfill experts that a surface concentration of 200 

parts per million (ppm) provides further empirical confirmation that a landfill is ready for installation of a 

full gas capture system. 

Benefits of More Stringent Thresholds. California’s experience in designing up-to-date landfill 

methane standards suggests that the current NSPS and EG thresholds leave significant emission 

reductions “on the table.” The California Rule’s applicability thresholds, which utilize stringent WIP, 

BTU, and surface concentration thresholds, are expected to increase the number of landfills subject to 

LFG collection by 7 percent in that State.9

 Further, the emission reductions resulting from expanded LFG 

collection account for over 25% of the total reductions expected under the California Rule. Federal 

standards set at more stringent and directly targeted thresholds would ensure all landfills capable of 

capturing and mitigating landfill methane are subject to rigorous emission standards. 

Even if EPA decides to retain applicability thresholds based on design capacity and estimated 

NMOC emissions, we recommend that the agency revise these thresholds downward to ensure they apply 

to smaller landfills capable of capturing LFG. 

Direct Regulation of Methane. Section 111 of the Clean Air Act requires the EPA Administrator 

to establish standards of performance governing the emission of air pollutants from new municipal solid 

waste landfills, and revise those standards if appropriate at least every 8 years. See 42 U.S.C. § 

7411(b)(1)(B). As part of this 8-year review, EPA has a duty to (1) make a determination whether 

standards covering methane emissions are “appropriate,” and, (2) if so, to promulgate standards. The Act 

and EPA’s implementing regulations also require EPA to issue emission guidelines covering the release 

of methane from any existing MSW landfills for which standards of performance have been issued. See 

id. § 7411(d); 40 C.F.R. § 60.22(a). 

Methane is the principal GHG emitted by landfills, and is emitted from MSW landfills in large 

quantities. In fact, EPA estimates that MSW landfills are the third largest anthropogenic source of 

methane in the United States.10 The surface concentration monitoring requirements in the current 

NSPS/EG for landfills already require the use of portable analyzers calibrated for methane. And methane 

is already a regulated constituent of GHG pollution for purposes of Prevention of Significant 

Deterioration and Title V permitting, as well as light duty and medium/heavy duty vehicle standards 

under section 202 of the CAA. Accordingly, it is appropriate for EPA to explicitly identify methane as a 

regulated pollutant from landfills under the revised NSPS and EG. 

                                                           

8 See Available and Emerging Technologies, supra note 6 at 13. 9

 ISOR at IV-2. 

10 U.S. EPA, Sources and Emissions; Methane, http://epa.gov/methane/sources.html. 
4

2. EARLY GHG CONTROL MEASURES

Landfills produce gas at varying rates over their lifetimes as biogenic material decomposes 

anaerobically to form methane. Figure 1 represents a landfill gas generation curve, with emission initially 

accelerating, peaking, and then declining as the landfill ages. 

Figure 1. Example LFG Generation Curve11

After initial installation of a landfill gas collection system, EPA’s current NSPS requires that 

owners or operators expand gas collection to active areas in which waste has been deposited for 5 years 

and to closed areas or areas at final grade within 2 years.12 EPA provided a 5-year period before 

installation of gas collection on the grounds that “[a] given area is typically active for more than 2 years” 

and wells installed within 2 years “will likely get covered over, decreasing their operational life.”13 

 There is substantial evidence that significant methane emissions occur prior to this 5-year period, 

however, and landfill gas capture, along with other proven best-management practices (BMPs), can 

reduce landfill gas emissions during this time. Moreover, these BMPs generally do not require 

installation of vertical wells and as a result, allow for early capture that does not impede eventual vertical 

well installation. Accordingly, we recommend that EPA: 

 Eliminate the 5-year / 2-year gas capture installation requirement; and 

 Adopt a requirement, similar to California, ensuring landfills meet a rigorous surface 

concentration standard everywhere but the working face as soon as a landfill meets applicability 

thresholds. 

 Evidence Indicates Significant Landfill Gas Generation Shortly After Waste Disposal. 

                                                           

11 From Barlaz et al., Controls on Landfill Gas Collection Efficiency: Instantaneous and Lifetime Performance 59 J. 

Air & Waste Mgmt. Ass’n 1399, 1403 (Dec. 2009). 

12 61 Fed. Reg. at 9911. 

13 U.S. EPA, Air Emissions from Municipal Solid Waste Landfills – Background Information for Final Standards 

and Guidelines at 1-47 (Dec. 1995). 
5

Several studies indicate that early landfill gas generation is significant, underscoring the need for 

LFG capture as early as possible in the lifecycle of the landfill. 

 U.S. EPA, Quantifying Methane Abatement at Three Municipal Solid Waste Landfills (Jan. 

2012)(“Three Landfill Study”). This study examined emissions from a landfill that had been 

accepting waste for 3 months at a new cell without landfill gas collection installed. The study 

concluded the “average methane emission factor for the summer 2010 measurement 

campaign of [the cell] was 24 ± 8.6 g/day/m2,” and characterized the finding as “important” 

given that “most models assume no methane generation for at least 6 months from initial 

waste placement.”14

 Barlaz et al, Controls on Landfill Gas Collection Efficiency: Instantaneous and Lifetime 

Performance (Dec. 2009). This study notes that landfill gas capture efficiency varies over the 

lifetime of the landfill and is a function of cover type, the extent of landfill gas capture 

system operation, and the rate of decay. At an assumed decay rate (k = 0.07), lifetime landfill 

gas collection efficiency ranges from 55 – 78 %. In other words, as much as 45% of total 

methane generated from an NSPS-compliant landfill will not be subject to gas capture, with 

approximately 30% of total methane generation emitted in the first 5 years of waste 

placement.15 Moreover, in his presentation at EPA’s October 22, 2012 Stakeholder Meeting, 

Professor Barlaz presented information indicating that the appropriate decay rate may be even 

higher (perhaps as high as 0.10), meaning methane generation occurs more quickly at 

landfills and lifetime collection efficiency may be even less than the 55 % lower bound for 

NSPS-compliant landfills.16 Barlaz (2009) emphasizes that “the early and aggressive 

collection of gas takes on increasing importance as the decay rate increases.”17 

 Green et al., Measured and Modeled Methane Emissions at MSW Landfills Prior to Gas 

Collection System Installation (2012).

18 Unlike the previous two studies, this study of two 

unidentified landfills in the Southeastern and Southwestern United States showed relatively 

low emissions (estimated using a tracer correlation approach) prior to installation of a LFG 

collection system. However, it is not clear that these sites are representative of all young 

landfills, or to what extent site-specific factors or the measurement methodology influenced 

the results. 

Early Installation of GHG Control Measures Can Substantially Reduce Methane Emissions. 

 EDF also recommends that EPA consider and take comment on requiring certain best 

management practices (BMPs) targeted at early control of GHG emissions from landfills that have met 

the applicability thresholds or are likely to do so. While we recognize that each BMP we discuss below 

                                                           

14 U.S. EPA, Three Landfill Study at 4-2. 15 Barlaz et al., Controls on Landfill Gas Collection Efficiency: Instantaneous and Lifetime Performance 59 J. Air & 

Waste Mgmt. Ass’n 1399, 1402-03 (Dec. 2009). 

16 Wang et al., Modernizing Models and Data on Methane Production from U.S. MSW Landfills at 21 (Oct. 2012). 17 Barlaz et al. (2009), at 1403. 

18 Roger B. Green et al., Measured and Modeled Methane Emissions at MSW Landfills Prior to Gas Collection 

System Installation (Global Waste Management Symposium 2012). 
6

may not be applicable in every instance, several synthesis reports indicate that broad deployment of these 

strategies can achieve significant reductions.19 Accordingly, we urge EPA to craft a program that 

leverages deployment of technologies wherever feasible. 

Accelerated installation of horizontal landfill gas capture, along with other BMPs, can 

substantially reduce methane emissions. In contrast to the 2-5 year NSPS requirement, Barlaz notes that 

“there are landfill operators that aggressively install horizontal LFG collection systems and collect gas 

within months of refuse burial.”20 The study concludes that beginning gas collection in year 3 can boost 

lifetime collection efficiencies to between 66 and 71.9 percent,21 and aggressive gas collection beginning 

in years 1 and 2 can achieve total lifetime collection efficiencies as high as 84%.22 

Early installation of final cover systems can also reduce methane emissions. Under current 

practice, landfill operators leave intermediate cover in place for years or even decades — and as 

explained below, intermediate cover frequently applies to the majority of the landfill surface. SCS 

Engineers suggest that “[t]he sooner the final cover can be applied to a landfill the better LFG extraction 

wells will perform” and conclude “[t]he emissions from a landfill with final cover should be measurably 

less than a landfill without final cover.” Goldsmith et al.

23 and Green24 also conclude that landfills with 

final cover are associated with substantially lower methane emissions. Barlaz calculated lifetime 

collection efficiency in a landfill beginning gas collection in year 3 and incorporating improved cover 

techniques and found efficiencies between 76.3 and 87.9 percent.25

SCS Engineers also note the collecting landfill gas from the leachate collection and removal 

system can reduce methane emissions, especially early in a cell’s life: “[Collection of LFG from the 

leachate collection and removal system] has a medium to high GHG emissions reduction potential early 

in a cell’s life where the LFG preferentially moves into the LCRS, and the LCRS cleanouts continue to be 

excellent collectors of LFG in the deep portions of the landfills (subsurface migration prevention).”26 

On account of the significance of early landfill gas emissions along with the availability and 

feasibility of early gas capture installation and additional mitigation measures, EDF recommends that 

EPA require all areas of the landfill other than the working face to meet a stringent methane surface 

concentration limit. 

                                                           

19 See, e.g., SCS Engineers, Technology and Management Options supra note 6. 20 Barlaz, supra note 13 at 1399. 21 Id. at 1402-03. This assumes a K value varying between 0.02 and 0.07. 22 Id. This analysis is for a bioreactor landfill, K varying between 0.04 and 0.15, and may not be representative of 

normal landfill operations. 

23 Goldsmith et al., Methane Emissions from 20 Landfills Across the United States Using Vertical Radial Plume 

Mapping, 62 J. Air & Waste Mgmt. Ass’n 183, 197 (2012). 

24 Green, Quantifying Landfill Methane Emissions Using Novel Field Measurement Techniques at 12 (Mar. 21, 

2012). 

25 Barlaz, supra note 13 at 1402. 26 See SCS Engineers, Technologies and Management Options at 30. 
7

3. EPA SHOULD MAKE ITS METHANE SURFACE CONCENTRATION LIMIT MORE STRINGENT OR 

SUPPLEMENT THE CURRENT STANDARD WITH BMPS THAT WOULD WORK IN CONJUNCTION 

WITH MONITORING REQUIREMENTS

As discussed above, the primary measure for guaranteeing adequate performance of methane 

controls is a stringent limit on surface methane concentrations, including an integrated surface monitoring 

limit. NSPS-compliant landfills may, however, have significant methane emissions even when the 

existing 500 ppm instantaneous surface concentration is met.27 As such, we recommend that EPA tighten 

the surface concentration limit, consistent with available control strategies. As methane emissions can 

vary greatly depending on climate, we suggest EPA consider and take comment on differentiating 

methane surface concentration limits for landfills located in different climatic zones. Goldsmith et al.

measured significant differences in methane emissions across climates28 and EPA’s LandGEM model 

explicitly accounts for climate through use of different k values.29 Requiring more stringent surface 

methane concentration limits in regions with less precipitation will help to ensure all landfills are 

deploying rigorous, well-designed gas capture technology along with other available BMPs. 

Alternatively, we suggest that EPA consider additional BMPs to reduce methane emissions in 

conjunction with a surface concentration limit. Several BMPs build on those described above applicable 

to early gas collection and others are specific to ongoing landfill operations. Broad deployment of 

appropriate BMPs could achieve significant reductions.30 

Cover Improvements. As discussed above, rapid installation of final cover systems can help 

significantly reduce early LFG emissions. Equally important, many studies have shown that the type of 

final cover installed can dramatically reduce methane emissions. Spokas et al examined a landfill cell 

with a HDPE geomembrane final cover and horizontal gas collection, finding methane emissions to be 

negligible.31 The study reported that HDPE geomembranes allow only 0.0004 g CH4/m2/d to be 

transmitted through the cover.32 Similarly, Goldsmith concluded methane emissions from a closed landfill 

with synthetic final cover “generally showed atmospheric background methane levels . . . .”33 SCS 

Engineers support these findings: “[t]he use of a synthetic final cover (e.g., geomembrane) is considered a 

BMP for final cover systems since it provides the greatest degree of protection against surface emissions 

of methane.”34 

                                                           

27 U.S. EPA, Three Landfill Study at 4-1. 

28 Goldsmith et al., Methane Emissions from 20 Landfills Across the United States Using Vertical Radial Plume 

Mapping at 193 (2012). Measured emissions from intermediate soil cover varied between 3.72 g CH4/m2/d 

(semiarid) to 102.19 g CH4/m2/d (humid subtropical). 

29 U.S. EPA, Landfill Gas Emissions Model (LandGEM) Version 3.02, available at www.epa.gov/landgem-v302-

guide.pdf 

30 See, e.g., SCS Engineers, Technology and Management Options supra note 6. 31 Spokas et al., Methane Mass Balance at Three Landfill Sites: What is the Efficiency of Capture by Gas Collection 

Systems? J. Air & Waste Mgmt. Ass’n 1560 (2006) 

32 Id. at 1562. 33 Goldsmith et al., Methane Emissions from 20 Landfills Across the United States Using Vertical Radial Plume 

Mapping, 62 J. Air & Waste Mgmt. Ass’n 183, 197 (2012). 

34 SCS Engineers, Technology and Management Options for Reducing Greenhouse Gas Emissions from Landfills 70 

(2008); see also U.S. EPA, Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from 

Municipal Solid Waste Landfills 13 (June 2011) (“Landfills with final geomembrane covers have higher collection 

efficiencies.”) 
8

Biocovers may also help to reduce methane emissions, with several studies reporting methane 

oxidation rates of 200 g/m2/d.35 Initial research into breathing biocovers suggests that, at low flow rates, 

the biocover may come close to 100 percent oxidation.36 While long-term performance of biocovers is not 

yet established,37 these systems show promise for both active landfills seeking emission reductions in 

intermediate cover areas as well as smaller, closed landfills without landfill gas collection systems. 

Other Potential BMPs:

 Require LFG Collection from Leachate Systems. As noted above, connecting the LFG 

collection system to the leachate removal system can help to capture LFG from below the 

waste mass along the bottom of the landfill. SCS Engineers analyzed this BMP at 

California landfills, determining it was relatively low cost and would result in medium to 

high GHG reduction potential.38

 Require Systems to Avoid Waterlogged Wells. Leachate and condensate can accumulate 

in LFG wells, blocking methane capture. A study on dewatering systems installed in 

Brazilian landfills showed an average improved efficiency in LFG capture of 62 percent 

across 10 monitored wells.39 

 Require Enhanced Seals for Wellheads. As indicated by the forward-looking infrared 

(FLIR) surveys included in the Three Landfills Study, LFG wellheads and other surface 

penetrations present high potential for concentrated leaks of organic compounds. The use 

of advanced seals at wellhead help to ensure that the well can apply sufficient vacuum to 

the landfill to facilitate gas extraction. SCS recommend use of redundant systems to 

ensure seal integrity, including 2 to 3 seals made of either bentonite or clay.40 Compared 

to improperly sealed wells, this BMP is low cost and can have medium to high GHG 

mitigation potential.41 

The above-mentioned BMPs have been implemented at many landfills and are regarded by the 

industry as best practice for minimizing LFG emissions. We encourage EPA to evaluate whether these 

BMPs, in combination with a rigorous surface emission monitoring standard, can drive additional 

methane reductions. 

                                                           

35 SCS Engineers, Technology and Management Options for Reducing Greenhouse Gas Emissions from Landfills 78 

(2008); Cal Recycle, Biocovers for Landfills for Methane Emission Reduction Demonstration 70 (Oct. 2010) 

(“Results from laboratory and field tests indicated both fresh and aged green material could oxidize CH4 at high 

rates, up to 100-200 g CH4/m2/day in field tests.”). 

36 Wen-Jing Lu et al, Can a Breathing Biocover Enhance Methane Emission Reduction from a Landfill? 191 J. 

Hazardous Materials 228 (2011). 

37 See Cal Recycle, Biocovers for Landfills for Methane Emission Reduction Demonstration, supra note 27. 38 SCS Engineers, Technology and Management Options for Reducing Greenhouse Gas Emissions from Landfills 78 

(2008). 

39 David Kaminisky and Mark Varljen, Increasing LFG Collection Rates Using Gas Well Dewatering Systems (U.S. 

EPA LMOP Conference 2009), available at

http://www.epa.gov/lmop/documents/pdfs/conf/15th/22Kaminski_Final.pdf 

40 SCS Engineers, Technology and Management Options for Reducing Greenhouse Gas Emissions from Landfills 36 

(2008). 

41 Id. 
9

4. EPA SHOULD ADOPT ENHANCED SURFACE MONITORING REQUIREMENTS SIMILAR TO 

THOSE IN THE CALIFORNIA RULE

As noted above, a stringent and comprehensive surface monitoring regime is a vital element of 

the proposed revisions to the NSPS and EG. With respect to surface monitoring, EDF believes that the 

requirements in the California Rule represent a significant advance over the existing NSPS and EG. 

Accordingly, we strongly recommend that EPA adopt the key elements of CARB’s approach in the 

proposed revisions. These elements include: 

 A stringent integrated monitoring standard, overlaid with an instantaneous monitoring standard; 

 A closely-spaced walking pattern (no more than 25-foot intervals); 

 Required monitoring of all cover penetrations; and 

 Required monitoring of all LFG system components operating at positive pressure. 

Advantages of Enhanced Surface Monitoring. The value of these enhanced surface monitoring 

requirements are supported both by CARB’s rulemaking record as well as independent assessments. In 

the Initial Statement of Reasons accompanying the proposed Landfills Rule, CARB noted that its 

enhanced surface monitoring requirements derive from long-standing provisions of the South Coast Air 

Quality Management District’s (SCAMQD) Rule 1150.1.42 On the basis of SCAMQD’s experience with 

Rule 1150.1, CARB estimated enhanced monitoring under the Landfills Rule would enable facilities to 

achieve an overall gas collection efficiency of 85% — a 10 percentage point improvement over the 

assumed baseline value of 75%.43 CARB’s Final Statement of Reasons also presented data showing that 

landfills in the SCAMQD, on average, collect significantly larger quantities of LFG than landfills 

elsewhere in the state within comparable size ranges, despite the relatively arid climate in Southern 

California.44 Although CARB identified important confounding factors that could influence the reported 

discrepancy in LFG collection rates, this data is nonetheless suggestive of the efficacy of the enhanced 

monitoring requirements upon which CARB’s Landfills Rule is based. 

The need for surface monitoring at all cover penetrations, which is presently not required under 

the NSPS and EG, is also specifically highlighted in a 2008 report prepared by SCS Engineers for the 

California Integrated Waste Management Board (now known as CalRecycle). That report notes that 

effective seals around landfill wellheads are critical for both minimizing surface emissions and optimizing 

the vacuum that can be applied to the LFG extraction system.45 Monitoring around cover penetrations, as 

required in CARB’s Landfills Rule, is an important means for identifying which wellheads or other 

protrusions should be outfitted with enhanced seals — a BMP that SCS Engineers rated as having 

“medium” to “high” GHG reduction potential for improperly sealed wells.46 The importance of 

monitoring wellheads is also underscored by EPA’s recent Three Landfills Study, which identified 

significant VOC emissions at improperly sealed wellheads using a forward-looking infrared (FLIR) 

camera. 47 

                                                           

42 Landfills Rule ISOR, at IV-5. 

43 Id. at IV-6. 44 FSOR at 25. 

45 SCS Engineers, Technologies and Management Options at 35-36. 

46 Id. 47 Three Landfills Study, at 3-9. 
10

Likewise, CARB elected to require leak testing of LFG collection system components in order to 

ensure that there are no significant point sources of LFG emissions in areas of the collection system that 

are under positive pressure. 48 Although there is little data on leaks of LFG from collection system 

components, EDF notes that this requirement mirrors the leak detection and repair (LDAR) requirements 

that EPA and many states have long imposed on owners and operators of natural gas processing plants, 

chemical facilities, and other installations handling regulated materials under pressure. CARB’s 

component leak monitoring requirement is a logical and precautionary extension of this time-tested 

technique to similar sectors. In addition, component leak monitoring would yield useful information on 

the prevalence of leaks from above-ground components of the LFG collection system. 

As to the level of the surface concentration standards, the data collected by SCAMQD enabled 

CARB to determine that an integrated surface monitoring limit of 25 ppm was achievable for California 

landfills (even landfills located in relatively humid areas of the state).49 Given the diversity of climates in 

California, EDF believes that the 25 ppm limit in the California Rule would be a presumptively 

reasonable starting point for a similar requirement in the proposed revisions to the NSPS and EG. With 

respect to the instantaneous surface concentration limits, EDF notes that CARB is collecting data on the 

frequency of instantaneous surface readings in the range of 200 ppm to 500 ppm.50 EDF recommends 

that EPA request this data from CARB, and evaluate whether a downward revision in the current 

NSPS/EG surface concentration limit of 500 ppm is achievable. 

Areas for Proposal and Additional Comment. EDF also asks EPA to propose, and take comment 

on, two potential enhancements to CARB’s surface monitoring requirements — both intended to address 

common criticisms of the monitoring methods prescribed by both CARB and EPA. First, one limitation 

of traditional surface monitoring techniques is that certain steep or inaccessible areas of the landfill, 

especially the side slopes, cannot be monitored using handheld analyzers and are therefore exempt from 

monitoring under the California Rule and the current NSPS/EG. This represents an important blind spot 

in the traditional monitoring regime, given that side slopes are particularly prone to cover failure due to 

erosion and gas migration, and are susceptible to leaks due to the relatively high horizontal permeability 

of landfill waste.51 At this time, EDF is aware of at least two technologies that can potentially be used to 

detect emissions from side slopes: vertical radial plume mapping (VRPM) using OTM-10 and, in some 

situations, optical gas imaging (OGI) using a FLIR camera or similar instrument. Although it is not clear 

that either of these technologies are routinely used to monitor side slope emissions at landfills, it is 

important that EPA at least take comment on best demonstrated methods for monitoring this often 

overlooked area of a landfill. 

Second, the “serpentine” walking path can easily miss smaller fissures and penetrations in the 

landfill surface, even when a relatively tight spacing is utilized.52 One partial solution to this problem is 

to explicitly require that the walking path vary with each quarterly monitoring survey – a practice that can 

potentially be verified using GPS or similar navigation technologies. Although such a requirement would 

                                                           

48 ISOR at V-6. 

49 FSOR at 28. 

50 FSOR at 30. 

51 See SCS Engineers, GHG Management Techniques at 20. 52 See id. at 61 (showing that a serpentine walking pattern with 30-meter spacing leaves substantial portions of 

landfill surface unmonitored). 
11

not ensure that all potential leaking locations are monitored with each survey, it would ensure that a large 

proportion of the landfill surface is eventually monitored over time. EDF recommends that EPA consider 

and take comment on this option. 

 EDF Supports Continued Refinement of Advanced Remote Sensing Techniques. As a final note, 

EDF emphasizes the importance of EPA’s efforts to advance the deployment of sophisticated tools for 

directly measuring fugitive methane emissions from landfills, including OTM-10 and the tracer 

correlation approach (TCA). These methods are of potentially immense value, because they yield actual

emission rates rather than calculated rates based on modeling assumptions – allowing for empirical 

confirmation of the effectiveness of methane controls at all landfills, including landfills not currently 

undertaking LFG collection. For this reason, we strongly support the continued refinement of these 

methods for eventual incorporation into regulatory emission reporting and compliance programs ). 

To be sure, these methods currently have important limitations, including measurement 

uncertainty53 and sensitivity to meteorological conditions.54 Many of these limitations, however, can 

likely be remedied through additional experience in deploying and testing these tools at a wide variety of 

landfills with diverse operational, climatic, and seasonal characteristics. Wider deployment will enable 

the development of a robust dataset on which to base new EPA-approved monitoring methodologies, and 

eventually establish performance standards that hold landfills accountable for actual emissions to the 

atmosphere (with potential application to other methane-emitting sectors, such as oil and natural gas 

systems). To this end, EDF suggests that EPA use both voluntary and regulatory means to aggressively 

ramp up deployment of OTM-10 and TCA, in partnership with both landfill operators and the academic 

community. Such testing could be encouraged on a voluntary basis through the Landfill Methane 

Outreach Program and cooperative research and development agreements, or required at a sample of 

landfills through Section 114 orders or through amendments to Subpart HH of the Mandatory Reporting 

Rule. EPA might also consider adding certain compliance flexibilities to the revised NSPS and EG (for 

example, somewhat less frequent surface monitoring requirements or reductions in enforcement penalties) 

for landfills that voluntarily undertake additional TCA or OTM-10 monitoring. Regardless of how 

advanced monitoring is implemented, the resulting data should be fully disclosed to the public. 

5. EPA SHOULD STRENGTHEN POST-CLOSURE MAINTENANCE REQUIREMENTS TO ENSURE 

LONG-TERM GHG EMISSIONS CONTROL 

Under the current NSPS and EG, a landfill’s obligation to control GHG emissions begins and 

ends with the installation and eventual removal of a LFG collection system. Landfills face no continuing 

requirements to maintain the integrity of the landfill after the removal of the LFG collection system, 

beyond the basic post-closure obligations set forth in EPA’s Resource Conservation and Recovery Act 

(RCRA) regulations (40 C.F.R. Part 258). Those regulations are not designed for minimization of GHG 

                                                           

53 See Gary Hater et al., Results From Six Years of Emission Studies on U.S. Landfills at 6 (presented at Global 

Waste Management Symposium 2012) (citing Babilotte A., R. Green, G. Hater, T. Watermolen, B. Staley. 2009. 

Field Intercomparison of Methods to Measure Fugitive Methane Emissions. Sardinia Solid International Solid Waste 

Symposium). 

54 See, e.g., Three Landfills Study at 3-4 to 3-9; Liukang Xu et al, Impact of Changes in Barometric Pressure on 

Landfill Methane Emission (Global Waste Mgmt Symposium 2012); Swan, Landfill Methane Emission Variability 

on Time Scales (Global Waste Mgmt Symposium 2012). 
12

emissions, requiring only that landfills meet a general cover integrity requirement and implement a 

monitoring program designed to detect explosive concentrations of LFG.55 

Yet there is substantial evidence indicating that landfills have the potential to generate significant 

quantities of methane long after they are closed and the LFG collection system has ceased to operate. 

Indeed, the First Order Decay models used by EPA and the IPCC to estimate LFG generation over time 

indicate that landfills exhibit a “long tail” of methane generation: approximately 30% of the lifetime 

methane generation potential of a landfill will occur 30 years after waste is disposed,56 and approximately 

15% of a landfill’s total methane generation potential remains even 100 years after disposal.57 One 

landfill GHG study prepared by Covanta Energy and submitted to CARB found that, using the First Order 

Decay model and standard assumptions regarding LFG collection efficiency rates, only 36 to 48% of the 

lifetime GHG emissions of a landfill would be collected even assuming a LFG collection period ranging 

from 30 to 45 years.58 

Furthermore, the First Order Decay model may well underestimate long-term methane 

generation, because it does not take into account the unusual fluid dynamics that develop within landfill 

cells and likely influence methane generation rates over time. For example, one empirical analysis of 

landfill waste found that leachate percolating through a landfill tends to follow preferred “channels” 

rather than distributing evenly through the waste.59 As a result, the study found, moisture in a sealed 

landfill only reaches approximately 28% of the decomposable waste. The large fraction of 

decomposables that remains untouched by leachate could generate a significant “second wave” of 

methane, even years after the landfill is closed, if the final cover fails and allows precipitation to infiltrate 

the waste. This possibility was most recently highlighted in a 2012 report co-authored by Scott Walker of 

CalRecycle, which warned that 

If dry tomb landfill containment is breached . . . gas generation and emissions may increase when 

there are no financial assurances or viable responsible parties. . . . The potential increase in 

emissions from risk of default for long-term postclosure maintenance and corrective action from 

dry tomb landfills is a significant policy consideration for greenhouse gas emissions.60

                                                           

55 See 40 C.F.R. § 258.61(a)(1), (4). The precise procedures used in such methane monitoring programs apparently 

vary from landfill to landfill, but usually involve soil sampling around the site perimeter. See U.S. Department of 

Health and Human Services, Agency for Toxic Substances and Disease Registry, Landfill Gas Primer at 34-35 

(2001). 

56 Don Augenstein & John Benemann, Landfill Methane Capture Via Permeable Layers (4th ICLRS, June 14-16, 

2006, Gallivare Sweden); 

57 Scott Walker & Watson Gin, CalRecycle Review of Waste-to-Energy and Avoided Landfill Methane Emissions 

(July 3, 2012). 

58 Comments of Covanta Energy on CARB’s Proposed Regulation to Implement the California Cap-and-Trade 

Program (Aug. 11, 2011). 

59 Christopher Zeiss & Wade Major, Moisture Flow Through Municipal Solid Waste: Patterns and Characteristics, 

J. Envtl. Sys. 22:211 (1993/1994). 

60 Walker & Gin, supra note 60 at 10. See also California Integrated Waste Management Board, Discussion Paper 

Regarding Postclosure Maintenance Beyond the Initial 30 Years and Financial Assurance Demonstrations 4 (Dec. 

6, 2004) (“some landfills may remain a threat to the environment for longer than 30 years. . . . stakeholders have 

reported to Board staff that landfill gas control systems have had to be installed at landfills that had not operated for 

up to 60 years. Dry tomb landfills (favored by Subtitle D and 27 CCR) indefinitely suspend and/or retard the 

decomposition process such that a breach in containment (e.g. extreme climate or earthquake event or inappropriate 

land use, or simply failure of equipment or containment barriers) could trigger uncontrolled production and release 
13

EPA’s own Office of Inspector General (OIG) has also found that landfill cover failure is not a 

matter of idle speculation, but is a real and documented phenomenon that has been shown to occur 

frequently within the initial 30 years following landfill closure. A 2001 report by the OIG, for example, 

found several instances in a nine-state sample of landfills in which landfill cover integrity was 

compromised due to erosion, vegetation growth, damage caused by wild animals or human intruders, and 

other diverse causes. According to the OIG, “Most of the states in our sample reported animal or 

weather-related damage at their sites.” 61 

 As a result, long-term, post-closure monitoring and maintenance is an important subject to 

address in the proposed revisions to the NSPS and EG. EDF suggests that the following specific 

requirements be included in the proposal and made available for public comment: 

 Regular monitoring of integrated and instantaneous surface concentrations of methane, on the 

same schedule and using the same techniques as during the period of active LFG collection, 

should be required during the post-closure period. As described above, these leak surveys should 

be comprehensive and should include targeted monitoring of all cover penetrations and aboveground components of the LFG collection system (if present and still in use). Also as noted 

above, EPA should take comment on the feasibility of using OGI to monitor for significant leaks 

on side slopes and other difficult-to-monitor locations on the landfill surface. 

 Just as during the period of active LFG collection, prompt remediation of any cover defects found 

during these monitoring surveys should be required. EPA should require that such repairs be 

verified using rigorous surface concentration monitoring. 

 The duration of the post-closure monitoring and maintenance period should be as long as 

practicable. Indeed, the evidence cited above suggests that post-closure monitoring and 

maintenance should continue indefinitely — an outcome that is likely to be infeasible in this 

rulemaking. However, EPA should, at minimum, consider adopting the same 30-year postclosure period that is required under Part 258 of RCRA regulations. 

 As required in Part 258, Subpart G of EPA’s RCRA regulations for other aspects of post-closure 

maintenance, landfill operators should be required to provide adequate financial assurances to 

guarantee the continued performance of NSPS and EG monitoring and cover maintenance 

activities during the post-closure period. 

 

6. THE REVISED NSPS SHOULD EXPLICITLY ACKNOWLEDGE ORGANICS DIVERSION AS A 

COMPLIANCE PATHWAY FOR MITIGATION OF GHG EMISSIONS

The diversion and composting or recycling of organic wastes is an economical and 

environmentally effective approach to mitigating landfill methane emissions, and we urge EPA to 

consider and take comment on various options for explicitly encouraging organics diversion through the 

revisions to the NSPS and EG. 

                                                                                                                                                                                               

of landfill gas and leachate . . . . The state of the science thus indicates that municipal solid waste landfills will in 

many cases pose a significant threat to the environment well beyond the conventional 30-year PCM period.”). 61 Office of the Inspector General, RCRA Financial Assurance for Closure and Post-Closure (2001-P-007) 

(March 30, 2001), at pp.33-34 
14

Although LFG collection effectively mitigates most landfill GHG emissions occurring while the 

collection system is installed, no collection system is capable of eliminating LFG emissions. To the 

contrary, empirical data obtained using advanced remote sensing techniques indicates that even landfills 

with operating LFG collection systems still emit significant quantities of methane, especially when using 

intermediate cover — which is the variety of cover that is often most prevalent on an active landfill62 and 

which can remain in place for years or even decades. For example, the 20-landfill study carried out by 

Goldsmith et al. found that landfills with intermediate cover and operating LFG collection systems 

emitted as much as 140.96 grams methane per square meter per day (g/m2

-d). At this emission rate, a 

100-acre landfill would emit nearly 21,000 metric tons of methane (or approximately 521,000 metric tons 

CO2-e, using a GWP for methane of 25) over the course of a single year.63 As discussed above, research 

by Prof. Barlaz has shown that significant emissions of methane are also likely to occur early in the 

lifecycle of a landfill — before LFG collection systems are typically installed. As a result, Prof. Barlaz 

has estimated that the lifetime collection efficiency of a landfill is only 61-70% when assuming a 

reasonable range of decay rates (k values ranging from 0.04 to 0.12) and reasonable phase-in schedules 

for LFG collection.64 

 Composting of organic waste, by contrast, avoids generation of landfill methane altogether and 

results in relatively little process-related emissions of methane and CO2. In addition, composting yields 

important ancillary benefits such as enhanced storage of carbon in the soil and avoided use of synthetic 

fertilizer.65 Recognizing the efficacy of composting in avoiding GHG emissions, EPA’s 2010 white paper 

on best available control technologies for GHGs from MSW landfills explicitly identifies organic waste 

diversion as a control option. The white paper also notes that organic waste diversion from landfills 

“prevents CH4 generation” by an amount proportional to the quantity of waste generation.66 Similarly, 

the documentation underlying EPA’s Waste Reduction Model (WARM) notes that organic wastes 

deposited in landfills have significant net GHG emissions even after taking into account the non-degraded 

fraction of organic wastes that is “sequestered” in landfills, as well as avoided GHGs resulting from LFGto-energy projects.67 These EPA assessments are backed by academic research; Prof. Barlaz, for 

example, estimated in a 2010 journal article that a reasonably ambitious organics diversion program 

(removing 50% of food waste and 90% of yard waste) would reduce a typical landfill’s peak methane 

                                                           

62 See, e.g., Goldsmith et al., supra note 24 at 194 (noting that “intermediate soil covers . . . often constitute the 

majority of the landfill cover.”). 

63 Although 140.96 g/m2

-d was the highest emission rate measured by Goldsmith et al. for intermediate soil covers, 

other landfills surveyed in the same study were also found to have very high methane emissions. Two other landfills 

emitted in excess of 100 g/m2

-d, and most of the landfills located in humid subtropical or humid continental climates 

(typical for most of the United States) had emission rates ranging from approximately 43 g/m2

-d to 76 g/m2-d. 64 See Morton A. Barlaz, Jeff P. Chanton, & Roger B. Green, Controls on Landfill Gas Collection Efficiency: 

Instantaneous and Lifetime Performance, J. Air & Waste Mgmt. Ass’n 59:1399-1404 (2009); Morton A. Barlaz and 

Florentina de la Cruz, Landfill Gas Modeling: Estimation of Landfill Gas Decay Rate Constants and Yields for 

Individual Waste Components (presented at 13th Annual LMOP Conference, Jan. 13, 2010). 65 EPA, “Composting,” Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste 

Reduction Model (WARM) Version 12, at 2 (Feb. 2012). 

66 EPA White Paper at 21. 

67 EPA, “Landfilling,” Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste 

Reduction Model (WARM) Version 12, at 1 (Feb. 2012). 
15

production rate by 25%.68 Removing all yard and food waste would yield an even more significant peak 

reduction of 45%.69

 Despite the advantages of organics diversion with composting as a GHG mitigation strategy, 

more than 97% of food waste, over 42% of yard waste, and nearly 40% of paper and paperboard are 

currently being landfilled.70 Moreover, the structure of the current NSPS and EG does little to encourage 

higher rates of organics diversion. Not only do the NSPS and EG neglect to acknowledge organics 

diversion as a control strategy (warranting not even a mention in the final rule), but the First Order Decay 

model used to determine whether a landfill emits 50 Mg/year of NMOC relies on default waste 

composition values that do not take into account successful organics diversion programs. Operators that 

wish to depart from the default FOD parameters may do so only by measuring site-specific NMOC 

concentrations and decay rates (k values), using complex procedures set forth in appendices to the NSPS 

and EG. For landfills that elect not to make such site-specific measurements, the applicability of Subparts 

WWW and Cc is triggered mechanically by reaching a certain volume of waste-in-place, regardless of the 

actual composition of that waste. 

 For the revised NSPS, EPA should consider proposing one or more specific mechanisms for 

encouraging voluntary organics diversion in the revised NSPS. Such mechanisms could include: 

 The revised NSPS could explicitly recognize complete or near-complete organics diversion as an 

alternative compliance pathway to traditional LFG collection. Under this alternative compliance 

pathway, a landfill that verifiably demonstrates that it accepts no or virtually no organic waste, 

and has thereby effectively avoided the generation of methane, would not be required to install a 

LFG collection system. Such a pathway could be appealing for states and communities that are 

taking leadership to reduce landfilling of organic wastes,71 and would provide an incentive for 

additional communities to adopt such measures. Note that the California Rule provides the 

functional equivalent of such an alternative compliance pathway by exempting landfills that 

contain only inert or non-decomposable waste.72 

 For existing landfills that are subject to the EG, EPA should provide a pathway for states to adopt 

implementation plans pursuant to section 111(d) of the Clean Air Act that include communityspecific or statewide composting and recycling initiatives. Such encouragement should include 

guidance on types of measures that EPA believes will achieve a satisfactory level of organics 

diversion, as well as methods that states can employ to demonstrate the effectiveness of proposed 

                                                           

68 See Barlaz and de la Cruz (Jan. 13, 2010), supra note ___ at 27; Florentina de la Cruz & Morton Barlaz, 

Estimation of waste component-specific landfill decay rates using laboratory-scale decomposition data, Envtl. Sci. 

Tech. 44(12):4722-8 (2010). 

69 Id. In principle, complete diversion of organic waste would virtually eliminate methane emissions from a landfill. 

See EPA White Paper at 21. Presumably, the remaining 55% of methane emissions estimated in Prof. Barlaz’s 

model derive from other forms of undiverted organic waste (such as office paper, drywall, or mixed MSW). 

70 See EPA, Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 

2010 at 5 (Dec. 2011). 

71 For example, the state of Vermont’s Universal Recycling Act requires all yard waste to be separated and recycled 

by 2015, and all food waste to be separated and recycled by 2020. See 10 V.S.A. §§ 6605, 6605k. Similarly, in 

furtherance of a municipal goal of achieving “Zero Waste” by 2020, San Francisco’s Environment Code mandates 

universal separation and collection of compostables and recycles from other MSW. San Francisco Envt. Code § 

1903. 

72 Cal. Code Regs. tit. 17, § 95462. 
16

or adopted organics diversion programs. This guidance should be developed in consultation with 

states, municipal authorities, civil society, and industry. 

 For landfills that achieve less than total diversion of organic waste, EPA should consider 

modifying the First Order Decay model (which would still be needed to calculate BTU heat 

inputs under the applicability framework outlined above) to allow landfills to substitute sitespecific waste composition data. As a result of this modification, landfills that achieve higher 

rates of organic waste diversion would be able to defer the installation of LFG collection systems 

until the quantity of LFG generated is sufficient to sustain such systems. This modification to the 

First Order Decay model would remove a potential regulatory disincentive to implementation of 

organics diversion requirements, and could – at the margin – encourage some landfills to 

undertake additional diversion of organic waste. 

7. EPA SHOULD EVALUATE METHANE CONTROL OPTIONS FOR MSW LANDFILLS NOT 

SUBJECT TO LFG COLLECTION

Lastly, the imminent revision of the NSPS and EG for MSW landfills is an important opportunity 

for EPA to consider whether and how to address methane emissions from landfills that are presently not 

subject to LFG collection requirements — either because they are too small or too old to fall within the 

scope of the present NSPS and EG. 

The available evidence indicates that substantial quantities of methane are emitted by such 

landfills. In the Technical Support Document (TSD) accompanying Subpart HH of the Mandatory 

Reporting Rule, for example, EPA stated that landfills subject to the NSPS and EG account for only 36% 

of total GHG emissions from the landfill sector – and for that reason, rejected comments urging that 

Subpart HH apply only to landfills covered by the NSPS and EG.73 The preamble to the final Mandatory 

Reporting Rule further notes that closed MSW landfills are responsible for “approximately half” of all 

methane emissions from the nation’s landfills.74 There, EPA explained that closed landfills account for a 

large share of overall MSW landfill emissions “because landfills can continue to emit for decades after 

they are closed and because these landfills are older, and less likely to have been required to add landfill 

gas collection systems.”75 Lastly, in the documentation underlying the most recent version of EPA’s 

Waste Reduction Model (WARM), EPA states that landfills without LFG recovery account for 

approximately 28% of total GHG emissions from MSW landfills.76 

 To be sure, these statistics are only indicative of the scale of GHG emissions from landfills that 

are too old or too small to trigger the NSPS and EG. For example, the TSD for Subpart HH does not 

                                                           

73 EPA Office of Air and Radiation, Technical Support Document for the Landfill Sector: Proposed Rule for 

Mandatory Reporting of Greenhouse Gases (Feb. 4, 2009). 

74 Mandatory Reporting of Greenhouse Gases, 74 Fed. Reg. 56,260, 56,335 (Oct. 30, 2009). 

75 Id. For this reason, EPA declined to exclude closed landfills from the scope of the MSW landfill reporting 

requirements in 40 C.F.R. Part 98, Subpart HH, despite comments from industry that such requirements would be 

unjustifiably burdensome and costly. Rather, EPA required reporting from all MSW landfills that accepted waste on 

or after January 1, 1980, explaining that this criterion “provided the best correlation . . . to sites that account for the 

majority of the contribution to the nationwide GHG emissions from landfills.” Id. (citing ‘‘Correlations with 

Landfill Methane Generation and Actual Emissions,” document number EPA– HQ–OAR–2008–0508–2165). 

76 EPA, “Landfilling,” Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste 

Reduction Model (WARM) Version 12, at 1 (Feb. 2012). 
17

make clear what fraction of the GHG emissions from landfills not covered by the NSPS or the EG is 

attributable to relatively new landfills that are likely to be required to install LFG collection in the near 

future. Similarly, the WARM documentation simply reports emissions from landfills that do not have 

LFG collection systems, without explaining whether the absence of such systems is due to age or size. To 

the extent that significant GHG emissions derive from newer landfills that are not (yet) subject to the 

NSPS or EG, EDF believes it is critical that the revisions to Subparts WWW and Cc incentivize early 

installation of LFG collection as well as other appropriate BMPs.77 Nevertheless, the data assembled by 

EPA strongly suggest that closed landfills, and potentially small landfills, are also an important part of the 

overall problem of GHG emissions from landfills. 

 EDF recognizes that installation of LFG collection systems will be technically infeasible at 

some– but not all78 – older or smaller landfills, and that other methane control options for such landfills 

may be limited. However, EDF is aware of several potential technologies that have been employed to at 

least partially control methane from landfills that are poor candidates for LFG collection. These 

technologies include: 

 Installation of an oxidative cover, including but not limited to biocovers;79

 Routing of passively vented LFG to a biofiltration cell;80

 Upgrades to final covers coupled with vigilant maintenance of cover integrity; and 

 Use of solar spark flares81 or other methane destruction devices that require low heat input and 

can operate intermittently. 

                                                           

77 See section III, supra. 78 CARB, for example, has estimated that its landfills rule will cause the number of landfills with LFG collection 

systems to increase from 204 to 218 (an increase of approximately 7%), with a corresponding GHG emission 

reduction of approximately 0.4 million metric tons CO2-e in 2020 (a reduction of 5.2% in baseline emissions for 

2020). See Landfill Rule, ISOR, at ES-2. 79 See EPA Landfills BACT White Paper at 17 (Stating that biocovers are capable of oxidizing approximately 32% 

of methane emitted from a landfill’s surface, and stating that “This control technology does not require extensive 

retrofit and is applicable to all landfills, including uncontrolled and older landfills with passive or active collection 

systems.”) (citing Abichou, Field Performance of Biocells, Biocovers, and Biofilters to Mitigate Greenhouse Gas 

Emissions from Landfills, Florida Center for Solid and Hazardous Waste Management (Mar. 2006)); Ramin Yazdani 

& Paul Imhoff, Biocovers at Landfills for Methane Emissions Reduction Demonstration 8 (CalRecycle, Oct. 2010) 

(“California has many small, closed landfills which would benefit from installing a biocover to mitigate fugitive 

methane as an alternative to installing a comprehensive gas collection system”); SCS, Technologies and Mgmt 

Options at 79 (“California has many small, closed landfills which might benefit from installing a biocover to 

mitigate fugitive methane which may not be available in sufficient quantities to justify a gas collection system, but 

should be captured or treated prior to the methane entering the atmosphere.”); URS Corp., Greenhouse Gas 

Mitigation: Landfill Gas and Industrial, Institutional, and Commercial Boilers, Steam Generators and Process 

Heaters 3-7 to 3-8 (Apr. 2008). 

80 See Abichou et al., Mitigating methane emissions from passive landfill vents: a viable option for older closed 

landfills, J. ENVTL. ENGINEERING 3:284-87 (2011) (reporting oxidation rates of 20% and higher using a radial 

biofilter at a passively vented landfill); Gebert and Grongroft, Performance of a passively vented field scale biofilter 

for the microbial oxidation of landfill methane, WASTE MGMT. 26: 399-407 (2006) (reporting results of field tests of 

biofilters at a passively vented landfill, finding oxidation rates of 80 g/m3

/h and estimating that the biofiltration 

system was capable of destroying 62% of the landfill’s fugitive methane emisisons). 81 Aklilu Tesfamichael & Ronald S. Johnson, Air Sparging and Solar Spark Vent Flares – Low Cost LFG Mitigation 

for Slow LFG Migration (Presented at Global Waste Management Symposium 2012). 
18

EDF believes these options are worthy of initial investigation by EPA and should also be proposed and 

subject to public comment as part of a proposed revision to Subparts Cc and WWW. EPA should also 

broadly solicit public comment on the technical and economic feasibility of other GHG control options 

for landfills that are too old or too small for LFG collection under the limited protections of the current 

standards. By doing so, EPA may obtain valuable information from vendors, landfill operators, 

academics, and other stakeholders on the optimal regulatory approaches for this important segment of the 

landfill GHG inventory.