1 

### R ECOMMENDATIONS AND 

### C ONSIDERATIONS FOR 

### EPA’ S 

### F ORTHCOMING 

### R EVISIONS
TO 

### S ECTION 

### 111 S TANDARDS FOR 

### MSW L ANDFILLS



### Environmental Defense Fund January 2, 2013

I NTRODUCTION

This White Paper outlines EDF’s policy recomme ndations, 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 framewo rk, as well as opportunities to reduce greenhouse gas (GHG) emissions at landfills that are not (or would no t 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 subj ect to gas collection requirements.

1. A PPLICABILITY T HRESHOLDS S HOULD A DDRESS M ETHANE D IRECTLY AND C APTURE L ANDFILLS THAT P RODUCE S UFFICIENT G AS TO O PERATE A F LARE

The existing NSPS and EG apply to landfills th at 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 (m 3 ). EPA indicated that it chose the 2.5 million Mg design capacity exemption because it would “exempt 90 percen t of the existing landfill s 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 require ments 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 ra ther 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/a tw/landfill/bidfl.pdf.

2 Id.2  Adopting a heat input applicability threshold ra ther 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. Be low, 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 exclud ing 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 op tions 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 fl are (understanding that this minimum quantity likely varies according to climatic c onditions and waste composition).

BTU Threshold. A gas heat-input threshold in British Th ermal Units (BTUs) provides indication of when generated landfill gas is sufficient to operat e 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 adva ntage of sidestepping any errors resulting from the application of default NMOC concentrations to es timated LFG production. In determining a landfill’s readiness for gas capture, the Califor nia Rule sets a threshold of 3.0 million BTUs / hour, which is based on the minimum gas heat-input necessary to operat e a flare without utilizing supplemental gas. 7 EPA’s

3 See Memo from RTI to EPA, Correlations With Landf ill 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, Fina l Statement of Reasons for Rulemaking : Public Hearing to Consider the Adoption of a Regulation to Reduce Methane Emissions fr om Municipal Solid Waste Landfills at 11 (June 25, 2009) (“The threshold of 450, 000 tons of waste-in-place was selected b ecause landfills with less waste-in-place are not expected to generate enough land fill 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 h eat 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 requi red to monitor surface methane concentrations in
accordance with our recommendations below. A m onitoring-based applicability prong provides built-in incentives for landfill operators to adopt one or mo re innovative methane avoidance or mitigation strategies, including organic waste diversion, oxi dative 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 conf irmation 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 N SPS and EG thresholds leave significant emission
reductions “on the table.” The California Rule’s a pplicability thresholds, which utilize stringent WIP, BTU, and surface concentration thresholds, are expect ed to increase the number of landfills subject to LFG collection by 7 percent in that State. 9 Further, the emission reduc tions 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 target ed 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 th resholds based on design capacity and estimated NMOC emissions, we recommend that the agency revi se 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 em ission 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 regul ations also require EPA to issue em ission guidelines covering the release of methane from any existing MSW landfills for wh ich 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 landf ills are the third largest anthropogenic source of
methane in the United States. 10 The surface concentration monito ring requirements in the current NSPS/EG for landfills already require the use of porta ble analyzers calibrated fo r methane. And methane is already a regulated constituent of GHG po llution 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 appr opriate 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. E ARLY GHG C ONTROL M EASURES

Landfills produce gas at varying rates over th eir 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 Curve 11

After initial installation of a landfill gas collec tion 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 meth ane emissions occur prior to this 5-year period, however, and landfill gas capture, along with othe r 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 c over 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 landf ill 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 th at 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 ma y 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 im portance 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 fact ors 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 co ntrol 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 Efficien cy: 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 Produc tion 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 synt hesis 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 insta ll 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 lifet ime 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 c over in place for years or even decades — and as explained below, intermediate c over frequently applies to the majority of the landfill surface. SCS Engineers suggest that “[t]he sooner the final cover can be applied to a landf ill 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 Green 24 also conclude that landfills with final cover are associated with substantially lowe r methane emissions. Barlaz calculated lifetime collection efficiency in a landfill beginning gas coll ection 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 ear ly 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 a dditional mitigation measures, EDF recommends that EPA require all areas of the landfill other than th e 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 be tween 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 S HOULD M AKE ITS M ETHANE S URFACE C ONCENTRATION L IMIT M ORE S TRINGENT OR S UPPLEMENT THE C URRENT S TANDARD WITH BMP S THAT W OULD W ORK IN C ONJUNCTION

WITH M ONITORING R EQUIREMENTS

As discussed above, the primary measure for guaranteeing adequate performance of methane controls is a stringent limit on surface methane concentr ations, 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 ava ilable 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 locat ed in different climatic zones. Goldsmith et al. measured significant differences in methane emissions across climates 28 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. Seve ral 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 ach ieve significant reductions. 30

Cover Improvements . As discussed above, rapid installati on of final cover systems can help significantly reduce early LFG emissions. Equally im portant, many studies have shown that the type of final cover installed can dramatically reduce methan e emissions. Spokas et al examined a landfill cell with a HDPE geomembrane final cove r 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 great est 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 th e 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 Si tes: 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 activ e 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 sy stem 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 relativel y 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 improve d 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 Landf ills 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 implemente d 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 emi ssion 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 Me thane 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 Co llection 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 S HOULD A DOPT E NHANCED S URFACE M ONITORING R EQUIREMENTS S IMILAR TO T HOSE IN THE C ALIFORNIA R ULE

As noted above, a stringent and comprehensive su rface 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 si gnificant 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, overl aid 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 rulemaki ng record as well as independent assessments. In the Initial Statement of Reasons accompanying th e proposed Landfills Rule, CARB noted that its enhanced surface monitoring requirements derive fro m 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 enhanc ed 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 signi ficantly 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 pe netrations, 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 well heads 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 st andards, the data collected by SCAMQD enabled CARB to determine that an integrated surface mon itoring limit of 25 ppm was achievable for California landfills (even landfills located in re latively 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 lim its, 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 eval uate 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 m onitoring 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 usi ng 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 sl opes are particularly prone to cover failure due to erosion and gas migration, and are susceptible to l eaks 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 camer a 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 mi ss 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 navigatio n 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 monito red 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 va lue, 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 regulator y emission reporting and compliance programs ).

To be sure, these methods currently have important limitations, including measurement uncertainty 53 and sensitivity to meteorological conditions. 54 Many of these limitations, however, can likely be remedied through additional experience in de ploying and testing these tools at a wide variety of landfills with diverse operational, climatic, and seasona l characteristics. Wider deployment will enable the development of a robust dataset on which to base new EPA-approved monitoring methodologies, and eventually establish performance standa rds that hold landfills accountable for actual emissions to the atmosphere (with potential application to other me thane-emitting sectors, such as oil and natural gas systems). To this end, EDF suggests that EPA u se both voluntary and regulatory means to aggressively ramp up deployment of OTM-10 and TCA, in partne rship with both landfill ope rators and the academic community. Such testing could be encouraged on a voluntary basis through the Landfill Methane Outreach Program and cooperative res earch 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 re quirements or reductions in enforcement penalties) for landfills that voluntarily undertake additiona l TCA or OTM-10 monitoring. Regardless of how advanced monitoring is implemented, the resulting data should be fully disclosed to the public.

5. EPA S HOULD S TRENGTHEN P OST -C LOSURE M AINTENANCE R EQUIREMENTS TO E NSURE L ONG -T ERM GHG E MISSIONS C ONTROL

Under the current NSPS and EG, a landfill’s oblig ation 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 landf ill 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 Meth ane 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 gene ral cover integrity requirement and implement a monitoring program designed to detect explosive concentrations of LFG. 55

Yet there is substantial evidence indicating that la ndfills 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 meth ane generation: approximately 30% of the lifetime methane generation potential of a landfill w ill occur 30 years after waste is disposed, 56 and approximately 15% of a landfill’s total methane generation po tential 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 co llection efficiency rates, only 36 to 48% of the
lifetime GHG emissions of a landfill would be coll ected 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 ove r time. For example, one empirical analysis of landfill waste found that leachate percolating thro ugh 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 d ecomposable waste. The large fraction of decomposables that remains untou ched by leachate could genera te 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 highlight ed 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 resp onsible 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 invo lve 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 (4 th ICLRS, June 14-16, 2006, Gallivare Sweden);

57 Scott Walker & Watson Gin, CalRecycle Review of Wa ste-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 enviro nment 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 earthqu ake event or inappropriate land use, or simply failure of equipment or containment barriers) could trigger uncontrolled production and release13 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 do cumented 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, dama ge 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 monitori ng 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 instantane ous 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-mon itor 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 surf ace 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 out come that is likely to be infeasible in this rulemaking. However, EPA should, at mini mum, 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 s hould be required to provide adeq uate financial assurances to guarantee the continued performance of NSPS a nd EG monitoring and cover maintenance activities during the post-closure period.

6. T HE R EVISED NSPS S HOULD E XPLICITLY A CKNOWLEDGE O RGANICS D IVERSION AS A C OMPLIANCE P ATHWAY FOR M ITIGATION OF GHG E MISSIONS

The diversion and composting or recycling of organic wastes is an economical and environmentally effective approach to mitigati ng landfill methane emissions, and we urge EPA to consider and take comment on various options for explicitly encouraging orga nics diversion through the
revisions to the NSPS and EG.

of landfill gas and leachate . . . . The st ate of the science thus indicates that municipal solid waste landfills will in many cases pose a significant threat to the environmen t 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.33-3414 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 re mote sensing techniques indicates that even landfills with operating LFG collection systems still emit signifi cant quantities of methane, especially when using
intermediate cover — which is the variety of cover that is often most prevalent on an active landfill 62 and which can remain in place for year s or even decades. For example, the 20-landfill study carried out by
Goldsmith et al. found that landfills with interm ediate cover and operati ng LFG collection systems emitted as much as 140.96 grams methane per square meter per day (g/m 2 -d). At this emission rate, a 100-acre landfill would emit nearly 21,000 metric tons of methane (or approximately 521,000 metric tons
CO 2 -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 likel y to occur early in the lifecycle of a landfill — before LFG collection systems ar e 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-re lated emissions of methane and CO 2 . In addition, composting yields important ancillary benefits such as enhanced storag e of carbon in the soil and avoided use of synthetic
fertilizer. 65 Recognizing the efficacy of composting in a voiding 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 prop ortional to the quantity of waste generation. 66 Similarly, the documentation underlying EPA’s Waste Reduc tion 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/m 2 -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/m 2 -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/m 2 -d to 76 g/m 2 -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 13 th 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 diversi on with composting as a GHG mitigation strategy, more than 97% of food waste, over 42% of yard w aste, 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 succe ssful 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 s ite-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 pr oposing one or more specific mechanisms for encouraging voluntary organics diversion in the re vised NSPS. Such mechanisms could include:

 The revised NSPS could explicitly recognize comple te or near-complete organics diversion as an alternative compliance pathway to traditional LFG collection. Under this alternative compliance pathway, a landfill that verifiably demonstrates th at 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 adoptimplementation plans pursuant to section 111(d) of the Clean Air Act that include communityspecific or statewide composting and recycling in itiatives. 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 es timated 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 Un iversal 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 gui dance should be developed in consultation with states, municipal authorities, civil society, and industry.

 For landfills that achieve less than total dive rsion 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 potentia l 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 S HOULD E VALUATE M ETHANE C ONTROL O PTIONS FOR MSW L ANDFILLS N OT S UBJECT TO LFG C OLLECTION

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 meth ane emissions from landfills that are presently not subject to LFG collection requirements — either becau se 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 landf ills subject to the NSPS and EG account for only 36%
of total GHG emissions from the landfill sector – and fo r 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 la ndfills 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 “pro vided the best correlation . . . to sites that account for the majority of the contribution to the na tionwide 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 ab sence 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 all 78 – older or smaller landfills, and that othe r 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, in cluding but not limited to biocovers; 79

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

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

 Use of solar spark flares 81 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 ru le 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 CO 2 -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 surf ace, and stating that “This control t echnology does not require extensive retrofit and is applicable to all landfills, including uncontr olled 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 woul d 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 landf ills 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 prio r to the methane entering the atmos phere.”); 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. E NVTL

. E NGINEERING 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 , W ASTE M GMT . 26: 399-407 (2006) (reporting results of field tests of biofilters at a passively vented landfill, finding oxidation rates of 80 g/m 3 /h and estimating that the biofiltration system was capable of destroying 62% of th e 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 invest igation by EPA and should also be proposed and subject to public comment as part of a proposed re vision to Subparts Cc and WWW. EPA should also broadly solicit public comment on the technical a nd economic feasibility of other GHG control options
for landfills that are too old or too small for LFG co llection under the limited protections of the current standards. By doing so, EPA may obtain valuab le information from vendors, landfill operators, academics, and other stakeholders on the optimal regul atory approaches for this important segment of the landfill GHG inventory.