Subpart HH—Municipal Solid Waste Landfills

§98.340 Definition of the source category.

(a) This source category applies to municipal solid waste (MSW) landfills that accepted 

waste on or after January 1, 1980, unless all three of the following conditions apply.

(1) The MSW landfill did not receive waste on or after January 1, 2013.

(2) The MSW landfill had CH4 generation as determined using Equation HH-5 and, if 

applicable, Equation HH-7 of this subpart of less than 1,190 metric tons of CH4 in the 2013 

reporting year.

(3) The owner or operator of the MSW landfill was not required to submit an annual report 

under any requirement of this part in any reporting year prior to 2013.

(b) This source category does not include Resource Conservation and Recovery Act 

(RCRA) Subtitle C or Toxic Substances Control Act (TSCA) hazardous waste landfills, 

construction and demolition waste landfills, or industrial waste landfills.

(c) This source category consists of the following sources at municipal solid waste (MSW) 

landfills: Landfills, landfill gas collection systems, and landfill gas destruction devices (including 

flares).

§98.341 Reporting threshold.

You must report GHG emissions under this subpart if your facility contains a MSW landfill 

and the facility meets the requirements of §98.2(a)(1).

§98.342 GHGs to report.

(a) You must report CH4 generation and CH4 emissions from landfills.

(b) You must report CH4 destruction resulting from landfill gas collection and combustion 

systems.
(c) You must report under subpart C of this part (General Stationary Fuel Combustion 

Sources) the emissions of CO2, CH4, and N2O from each stationary combustion unit following 

the requirements of subpart C.

§98.343 Calculating GHG emissions.

(a) For all landfills subject to the reporting requirements of this subpart, calculate annual 

modeled CH4 generation according to the applicable requirements in paragraphs (a)(1) through 

(a)(3) of this section.

(1) Calculate annual modeled CH4 generation using Equation HH-1 of this section.

Where:

GCH4 = Modeled methane generation rate in reporting year T (metric tons CH4).

x = Year in which waste was disposed.

S = Start year of calculation. Use the year 1960 or the opening year of the landfill, whichever is 

more recent.

T = Reporting year for which emissions are calculated.

WX = Quantity of waste disposed in the landfill in year × from measurement data, tipping fee 

receipts, or other company records (metric tons, as received (wet weight)).

MCF = Methane correction factor (fraction). Use the default value of 1 unless there is active 

aeration of waste within the landfill during the reporting year. If there is active aeration 

of waste within the landfill during the reporting year, use either the default value of 1 

or select an alternative value no less than 0.5 based on site-specific aeration 

parameters.
DOC = Degradable organic carbon from Table HH-1 of this subpart [fraction (metric tons 

C/metric ton waste)].

DOCF = Fraction of DOC dissimilated (fraction). Use the default value of 0.5.

F = Fraction by volume of CH4 in landfill gas from measurement data for the current reporting 

year, if available (fraction, dry basis, corrected to 0% oxygen); otherwise, use the 

default of 0.5.

k = Rate constant from Table HH-1 to this subpart (yr

−1). Select the most applicable k value for 

the majority of the past 10 years (or operating life, whichever is shorter).

(2) For years when material-specific waste quantity data are available, apply Equation HH-1 

of this section for each waste quantity type and sum the CH4 generation rates for all waste types 

to calculate the total modeled CH4 generation rate for the landfill. Use the appropriate parameter 

values for k, DOC, MCF, DOCF, and F shown in Table HH-1 of this subpart. The annual 

quantity of each type of waste disposed must be calculated as the sum of the daily quantities of 

waste (of that type) disposed. You may use the bulk waste parameters for a portion of your waste 

materials when using the material-specific modeling approach for mixed waste streams that 

cannot be designated to a specific material type. For years when waste composition data are not 

available, use the bulk waste parameter values for k and DOC in Table HH-1 to this subpart for 

the total quantity of waste disposed in those years.

(3) Beginning in the first emissions reporting year and for each year thereafter, if scales are 

in place, you must determine the annual quantity of waste (in metric tons as received, i.e., wet 

weight) disposed of in the landfill using paragraph (a)(3)(i) of this section for all containers and 

for all vehicles used to haul waste to the landfill, except for passenger cars, light duty pickup 

trucks, or waste loads that cannot be measured using the scales due to physical limitations (load 
cannot physically access or fit on the scale) and/or operational limitations of the scale (load 

exceeding the limits or sensitivity range of the scale). If scales are not in place, you must use 

paragraph (a)(3)(ii) of this section to determine the annual quantity of waste disposed. For waste 

hauled to the landfill in passenger cars or light duty pickup trucks, you may use either paragraph 

(a)(3)(i) or paragraph (a)(3)(ii) of this section to determine the annual quantity of waste disposed. 

For loads that cannot be measured using the scales due to physical and/or operational limitations 

of the scale, you must use paragraph (a)(3)(ii) of this section or similar engineering calculations 

to determine the annual quantity of waste disposed. The approach used to determine the annual 

quantity of waste disposed of must be documented in the monitoring plan.

(i) Use direct mass measurements of each individual load received at the landfill using 

either of the following methods:

(A) Weigh using mass scales each vehicle or container used to haul waste as it enters the 

landfill or disposal area; weigh using mass scales each vehicle or container after it has off-loaded 

the waste; determine the quantity of waste received from the individual load as the difference in 

the two mass measurements; and determine the annual quantity of waste received as the sum of 

all waste loads received during the year. Alternatively, you may determine annual quantity of 

waste by summing the weights of all vehicles and containers entering the landfill and subtracting 

from it the sum of all the weights of vehicles and containers after they have off-loaded the waste 

in the landfill.

(B) Weigh using mass scales each vehicle or container used to haul waste as it enters the 

landfill or disposal area; determine a representative tare weight by vehicle or container type by 

weighing no less than 5 of each type of vehicle or container after it has off-loaded the waste; 

determine the quantity of waste received from the individual load as the difference between the 
measured weight in and the tare weight determined for that container/vehicle type; and determine 

the annual quantity of waste received as the sum of all waste loads received during the year.

(ii) Determine the working capacity in units of mass for each type of container or vehicle 

used to haul waste to the landfill (e.g., using volumetric capacity and waste density 

measurements; direct measurement of a selected number of passenger vehicles and light duty 

pick-up trucks; or similar methods); record the number of loads received at the landfill by

vehicle/container type; calculate the annual mass per vehicle/container type as the mass product 

of the number of loads of that vehicle/container multiplied by its working capacity; and calculate 

the annual quantity of waste received as the sum of the annual mass per vehicle/container type 

across all of the vehicle/container types used to haul waste to the landfill.

(4) For years prior to the first emissions reporting year, use methods in paragraph (a)(3) of 

this section when waste disposal quantity data are readily available. When waste disposal 

quantity data are not readily available, WX shall be estimated using one of the applicable 

methods in paragraphs (a)(4)(i) through (a)(4)(iii) of this section. You must determine which 

method is most applicable to the conditions and disposal history of your facility. Historical waste 

disposal quantities should only be determined once, as part of the first annual report, and the 

same values should be used for all subsequent annual reports, supplemented by the next year's 

data on new waste disposal.

(i) Assume all prior years waste disposal quantities are the same as the waste quantity in the 

first year for which waste quantities are available.

(ii) Use the estimated population served by the landfill in each year, the values for national 

average per capita waste disposal rates found in Table HH-2 to this subpart, and calculate the 

waste quantity landfilled using Equation HH-2 of this section.
where:

WX = Quantity of waste placed in the landfill in year x (metric tons, wet basis).

POPX = Population served by the landfill in year x from city population, census data, or other 

estimates (capita).

WDRX = Average per capita waste disposal rate for year x from Table HH-2 to this subpart 

(metric tons per capita per year, wet basis; tons/cap/yr).

(iii) Use a constant average waste disposal quantity calculated using Equation HH-3 of this 

section for each year the landfill was in operation (i.e., from the first year accepting waste until 

the last year for which waste disposal data is unavailable, inclusive).

where:

WX = Quantity of waste placed in the landfill in year x (metric tons, wet basis).

LFC = Landfill capacity or, for operating landfills, capacity of the landfill used (or the total 

quantity of waste-in-place) at the end of the year prior to the year when waste disposal 

data are available from design drawings or engineering estimates (metric tons).

YrData = Year in which the landfill last received waste or, for operating landfills, the year prior 

to the first reporting year when waste disposal data is first available from company

records, or best available data.

YrOpen = Year in which the landfill first received waste from company records or best available 

data. If no data are available for estimating YrOpen for a closed landfill, use 30 years 

as the default operating life of the landfill.
(b) For landfills with gas collection systems, calculate the quantity of CH4 destroyed 

according to the requirements in paragraphs (b)(1) and (b)(2) of this section.

(1) If you continuously monitor the flow rate, CH4 concentration, temperature, pressure, 

and, if necessary, moisture content of the landfill gas that is collected and routed to a destruction 

device (before any treatment equipment) using a monitoring meter specifically for CH4 gas, as 

specified in §98.344, you must use this monitoring system and calculate the quantity of CH4

recovered for destruction using Equation HH-4 of this section. A fully integrated system that 

directly reports CH4 content requires no other calculation than summing the results of all 

monitoring periods for a given year.

where:

R = Annual quantity of recovered CH4 (metric tons CH4).

N = Total number of measurement periods in a year. Use daily averaging periods for a 

continuous monitoring system and N = 365 (or N = 366 for leap years). For monthly

sampling, as provided in paragraph (b)(2) of this section, use N=12.

n = Index for measurement period.

(V)n = Cumulative volumetric flow for the measurement period in actual cubic feet (acf). If the 

flow rate meter automatically corrects for temperature and pressure, replace 

“520°R/(T)n × (P)n/1 atm” with “1”.

(KMC)n = Moisture correction term for the measurement period, volumetric basis, as follows: 

(KMC)n = 1 when (V)n and (C)n are both measured on a dry basis or if both are 

measured on a wet basis; (KMC)n = [1-(fH2O)n] when (V)n is measured on a wet basis 
and (C)n is measured on a dry basis; and (KMC)n = 1/[1-(fH2O)n] when (V)n is measured 

on a dry basis and (C)n is measured on a wet basis.

(fH2O)n = Average moisture content of landfill gas during the measurement period, volumetric 

basis (cubic feet water per cubic feet landfill gas)

(CCH4)n = Average CH4 concentration of landfill gas for the measurement period (volume %).

0.0423 = Density of CH4 lb/cf at 520°R or 60 degrees Fahrenheit and 1 atm.

(T)n = Average temperature at which flow is measured for the measurement period (°R).

(P)n = Average pressure at which flow is measured for the measurement period (atm).

0.454/1,000 = Conversion factor (metric ton/lb).

(2) If you do not continuously monitor according to paragraph (b)(1) of this section, you 

must determine the flow rate, CH4 concentration, temperature, pressure, and moisture content of 

the landfill gas that is collected and routed to a destruction device (before any treatment 

equipment) according to the requirements in paragraphs (b)(2)(i) through (b)(2)(iii) of this 

section and calculate the quantity of CH4 recovered for destruction using Equation HH-4 of this 

section.

(i) Continuously monitor gas flow rate and determine the cumulative volume of landfill gas 

each month and the cumulative volume of landfill gas each year that is collected and routed to a 

destruction device (before any treatment equipment). Under this option, the gas flow meter is not 

required to automatically correct for temperature, pressure, or, if necessary, moisture content. If 

the gas flow meter is not equipped with automatic correction for temperature, pressure, or, if 

necessary, moisture content, you must determine these parameters as specified in paragraph 

(b)(2)(iii) of this section.
(ii) Determine the CH4 concentration in the landfill gas that is collected and routed to a 

destruction device (before any treatment equipment) in a location near or representative of the 

location of the gas flow meter at least once each calendar month; if only one measurement is 

made each calendar month, there must be at least fourteen days between measurements.

(iii) If the gas flow meter is not equipped with automatic correction for temperature, 

pressure, or, if necessary, moisture content:

(A) Determine the temperature and pressure in the landfill gas that is collected and routed to 

a destruction device (before any treatment equipment) in a location near or representative of the 

location of the gas flow meter at least once each calendar month; if only one measurement is 

made each calendar month, there must be at least fourteen days between measurements.

(B) If the CH4 concentration is determined on a dry basis and flow is determined on a wet 

basis or CH4 concentration is determined on a wet basis and flow is determined on a dry basis, 

and the flow meter does not automatically correct for moisture content, determine the moisture 

content in the landfill gas that is collected and routed to a destruction device (before any

treatment equipment) in a location near or representative of the location of the gas flow meter at 

least once each calendar month; if only one measurement is made each calendar month, there 

must be at least fourteen days between measurements.

(c) For all landfills, calculate CH4 generation (adjusted for oxidation in cover materials) and 

actual CH4 emissions (taking into account any CH4 recovery, and oxidation in cover materials) 

according to the applicable methods in paragraphs (c)(1) through (c)(3) of this section.

(1) Calculate CH4 generation, adjusted for oxidation, from the modeled CH4 (GCH4 from 

Equation HH-1 of this section) using Equation HH-5 of this section.
Where:

MG = Methane generation, adjusted for oxidation, from the landfill in the reporting year (metric 

tons CH4).

GCH4 = Modeled methane generation rate in reporting year from Equation HH-1 of this section 

(metric tons CH4).

OX = Oxidation fraction. Use the appropriate oxidation fraction default value from Table HH-4 

of this subpart.

(2) For landfills that do not have landfill gas collection systems, the CH4 emissions are 

equal to the CH4 generation (MG) calculated in Equation HH-5 of this section.

(3) For landfills with landfill gas collection systems, calculate CH4 emissions using the 

methodologies specified in paragraphs (c)(3)(i) and (c)(3)(ii) of this section.

(i) Calculate CH4 emissions from the modeled CH4 generation and measured CH4 recovery

using Equation HH-6 of this section.

Where:

Emissions = Methane emissions from the landfill in the reporting year (metric tons CH4).

GCH4 = Modeled methane generation rate in reporting year from Equation HH-1 of this section or 

the quantity of recovered CH4 from Equation HH-4 of this section, whichever is 

greater (metric tons CH4).

N = Number of landfill gas measurement locations (associated with a destruction device or gas 

sent off-site). If a single monitoring location is used to monitor volumetric flow and 

CH4 concentration of the recovered gas sent to one or multiple destruction devices, 

then N=1.
Rn = Quantity of recovered CH4 from Equation HH-4 of this section for the nth measurement 

location (metric tons).

OX = Oxidation fraction. Use the appropriate oxidation fraction default value from Table HH-4 

of this subpart.

DEn = Destruction efficiency (lesser of manufacturer's specified destruction efficiency and 0.99) 

for the nth measurement location. If the gas is transported off-site for destruction, use 

DE = 1. If the volumetric flow and CH4 concentration of the recovered gas is measured 

at a single location providing landfill gas to multiple destruction devices (including 

some gas destroyed on-site and some gas sent off-site for destruction), calculate DEn as 

the arithmetic average of the DE values determined for each destruction device 

associated with that measurement location.

fDest,n = Fraction of hours the destruction device associated with the nth measurement location 

was operating during active gas flow calculated as the annual operating hours for the 

destruction device divided by the annual hours flow was sent to the destruction device 

as measured at the nth measurement location. If the gas is transported off-site for 

destruction, use fDest,n= 1. If the volumetric flow and CH4 concentration of the 

recovered gas is measured at a single location providing landfill gas to multiple 

destruction devices (including some gas destroyed on-site and some gas sent off-site 

for destruction), calculate fDest,n as the arithmetic average of the fDest values determined 

for each destruction device associated with that measurement location.

(ii) Calculate CH4 generation and CH4 emissions using measured CH4 recovery and 

estimated gas collection efficiency and Equations HH-7 and HH-8 of this section.
Where:

MG = Methane generation, adjusted for oxidation, from the landfill in the reporting year (metric 

tons CH4).

Emissions = Methane emissions from the landfill in the reporting year (metric tons CH4).

N = Number of landfill gas measurement locations (associated with a destruction device or gas

sent off-site). If a single monitoring location is used to monitor volumetric flow and 

CH4 concentration of the recovered gas sent to one or multiple destruction devices, 

then N=1.

Rn = Quantity of recovered CH4 from Equation HH-4 of this section for the n

th measurement 

location (metric tons CH4).

CE = Collection efficiency estimated at landfill, taking into account system coverage, operation, 

and cover system materials from Table HH-3 of this subpart. If area by soil cover type 

information is not available, use default value of 0.75 (CE4 in table HH-3 of this 

subpart) for all areas under active influence of the collection system.

fRec,n = Fraction of hours the recovery system associated with the nth measurement location was 

operating (annual operating hours/8760 hours per year or annual operating hours/8784 

hours per year for a leap year).

OX = Oxidation fraction. Use appropriate oxidation fraction default value from Table HH-4 of 

this subpart.
DEn = Destruction efficiency, (lesser of manufacturer's specified destruction efficiency and 0.99) 

for the nth measurement location. If the gas is transported off-site for destruction, use 

DE = 1. If the volumetric flow and CH4 concentration of the recovered gas is measured 

at a single location providing landfill gas to multiple destruction devices (including 

some gas destroyed on-site and some gas sent off-site for destruction), calculate DEn as 

the arithmetic average of the DE values determined for each destruction device 

associated with that measurement location.

fDest,n = Fraction of hours the destruction device associated with the nth measurement location 

was operating during active gas flow calculated as the annual operating hours for the 

destruction device divided by the annual hours flow was sent to the destruction device 

as measured at the nth measurement location. If the gas is transported off-site for 

destruction, use fDest,n= 1. If the volumetric flow and CH4 concentration of the 

recovered gas is measured at a single location providing landfill gas to multiple 

destruction devices (including some gas destroyed on-site and some gas sent off-site 

for destruction), calculate fDest,n as the arithmetic average of the fDest values determined 

for each destruction device associated with that measurement location.

§98.344 Monitoring and QA/QC requirements.

(a) Mass measurement equipment used to determine the quantity of waste landfilled on or 

after January 1, 2010 must meet the requirements for weighing equipment as described in 

“Specifications, Tolerances, and Other Technical Requirements For Weighing and Measuring 

Devices” NIST Handbook 44 (2009) (incorporated by reference, see §98.7).

(b) For landfills with gas collection systems, operate, maintain, and calibrate a gas 

composition monitor capable of measuring the concentration of CH4 in the recovered landfill gas 
using one of the methods specified in paragraphs (b)(1) through (b)(6) of this section or as 

specified by the manufacturer. Gas composition monitors shall be calibrated prior to the first 

reporting year and recalibrated either annually or at the minimum frequency specified by the 

manufacturer, whichever is more frequent, or whenever the error in the midrange calibration 

check exceeds ±10 percent.

(1) Method 18 at 40 CFR part 60, appendix A-6.

(2) ASTM D1945-03, Standard Test Method for Analysis of Natural Gas by Gas 

Chromatography (incorporated by reference, see §98.7).

(3) ASTM D1946-90 (Reapproved 2006), Standard Practice for Analysis of Reformed Gas 

by Gas Chromatography (incorporated by reference, see §98.7).

(4) GPA Standard 2261-00, Analysis for Natural Gas and Similar Gaseous Mixtures by Gas 

Chromatography.

(5) UOP539-97 Refinery Gas Analysis by Gas Chromatography (incorporated by reference, 

see §98.7).

(6) As an alternative to the gas chromatography methods provided in paragraphs (b)(1) 

through (b)(5) of this section, you may use total gaseous organic concentration analyzers and 

calculate the methane concentration following the requirements in paragraphs (b)(6)(i) through 

(b)(6)(iii) of this section.

(i) Use Method 25A or 25B at 40 CFR part 60, appendix A-7 to determine total gaseous 

organic concentration. You must calibrate the instrument with methane and determine the total 

gaseous organic concentration as carbon (or as methane; K=1 in Equation 25A-1 of Method 25A 

at 40 CFR part 60, appendix A-7).
(ii) Determine a non-methane organic carbon correction factor at the routine sampling 

location no less frequently than once a reporting year following the requirements in paragraphs 

(b)(6)(ii)(A) through (b)(6)(ii)(C) of this section.

(A) Take a minimum of three grab samples of the landfill gas with a minimum of 20 

minutes between samples and determine the methane composition of the landfill gas using one of 

the methods specified in paragraphs (b)(1) through (b)(5) of this section.

(B) As soon as practical after each grab sample is collected and prior to the collection of a 

subsequent grab sample, determine the total gaseous organic concentration of the landfill gas 

using either Method 25A or 25B at 40 CFR part 60, appendix A-7 as specified in paragraph 

(b)(6)(i) of this section.

(C) Determine the arithmetic average methane concentration and the arithmetic average 

total gaseous organic concentration of the samples analyzed according to paragraphs 

(b)(6)(ii)(A) and (b)(6)(ii)(B) of this section, respectively, and calculate the non-methane organic 

carbon correction factor as the ratio of the average methane concentration to the average total 

gaseous organic concentration. If the ratio exceeds 1, use 1 for the non-methane organic carbon 

correction factor.

(iii) Calculate the methane concentration as specified in Equation HH-9 of this section.

Where:

CCH4 = Methane concentration in the landfill gas (volume %) for use in Equation HH-4 of this 

subpart.
fNMOC = Non-methane organic carbon correction factor from the most recent determination of the 

non-methane organic carbon correction factor as specified in paragraph (b)(6)(ii) of 

this section (unitless).

CTGOC = Total gaseous organic carbon concentration measured using Method 25A or 25B at 40 

CFR part 60, appendix A-7 during routine monitoring of the landfill gas (volume %).

(c) For landfills with gas collection systems, install, operate, maintain, and calibrate a gas 

flow meter capable of measuring the volumetric flow rate of the recovered landfill gas using one 

of the methods specified in paragraphs (c)(1) through (c)(8) of this section or as specified by the 

manufacturer. Each gas flow meter shall be recalibrated either biennially (every 2 years) or at the 

minimum frequency specified by the manufacturer. Except as provided in §98.343(b)(2)(i), each 

gas flow meter must be capable of correcting for the temperature and pressure and, if necessary, 

moisture content.

(1) ASME MFC-3M-2004, Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and 

Venturi (incorporated by reference, see §98.7).

(2) ASME MFC-4M-1986 (Reaffirmed 1997), Measurement of Gas Flow by Turbine 

Meters (incorporated by reference, see §98.7).

(3) ASME MFC-6M-1998, Measurement of Fluid Flow in Pipes Using Vortex Flowmeters 

(incorporated by reference, see §98.7).

(4) ASME MFC-7M-1987 (Reaffirmed 1992), Measurement of Gas Flow by Means of 

Critical Flow Venturi Nozzles (incorporated by reference, see §98.7).

(5) ASME MFC-11M-2006 Measurement of Fluid Flow by Means of Coriolis Mass 

Flowmeters (incorporated by reference, see §98.7). The mass flow must be corrected to 

volumetric flow based on the measured temperature, pressure, and gas composition.
(6) ASME MFC-14M-2003 Measurement of Fluid Flow Using Small Bore Precision 

Orifice Meters (incorporated by reference, see §98.7).

(7) ASME MFC-18M-2001 Measurement of Fluid Flow using Variable Area Meters 

(incorporated by reference, see §98.7).

(8) Method 2A or 2D at 40 CFR part 60, appendix A-1.

(d) All temperature, pressure, and if necessary, moisture content monitors must be 

calibrated using the procedures and frequencies specified by the manufacturer.

(e) For landfills electing to measure the fraction by volume of CH4 in landfill gas (F), 

follow the requirements in paragraphs (e)(1) and (2) of this section. (1) Use a gas composition 

monitor capable of measuring the concentration of CH4 on a dry basis that is properly operated, 

calibrated, and maintained according to the requirements specified in paragraph (b) of this 

section. You must either use a gas composition monitor that is also capable of measuring the O2

concentration correcting for excess (infiltration) air or you must operate, maintain, and calibrate 

a second monitor capable of measuring the O2 concentration on a dry basis according to the 

manufacturer's specifications.

(2) Use Equation HH-10 of this section to correct the measured CH4 concentration to 0% 

oxygen. If multiple CH4 concentration measurements are made during the reporting year, 

determine F separately for each measurement made during the reporting year, and use the results 

to determine the arithmetic average value of F for use in Equation HH-1 of this part.

Where:

F = Fraction by volume of CH4 in landfill gas (fraction, dry basis, corrected to 0% oxygen).

CCH4 = Measured CH4 concentration in landfill gas (volume %, dry basis).
20.9c = Defined O2 correction basis, (volume %, dry basis).

20.9 = O2 concentration in air (volume %, dry basis).

%O2 = Measured O2 concentration in landfill gas (volume %, dry basis).

(f) The owner or operator shall document the procedures used to ensure the accuracy of the 

estimates of disposal quantities and, if applicable, gas flow rate, gas composition, temperature, 

pressure, and moisture content measurements. These procedures include, but are not limited to, 

calibration of weighing equipment, fuel flow meters, and other measurement devices. The 

estimated accuracy of measurements made with these devices, and the technical basis for these 

estimates shall be recorded.

§98.345 Procedures for estimating missing data.

A complete record of all measured parameters used in the GHG emissions calculations is 

required. Therefore, whenever a quality-assured value of a required parameter is unavailable 

(e.g., if a meter malfunctions during unit operation or if a required fuel sample is not taken), a 

substitute data value for the missing parameter shall be used in the calculations, according to the 

requirements in paragraphs (a) through (c) of this section.

(a) For each missing value of the CH4 content, the substitute data value shall be the 

arithmetic average of the quality-assured values of that parameter immediately preceding and 

immediately following the missing data incident. If the “after” value is not obtained by the end 

of the reporting year, you may use the “before” value for the missing data substitution. If, for a 

particular parameter, no quality-assured data are available prior to the missing data incident, the 

substitute data value shall be the first quality-assured value obtained after the missing data 

period.
(b) For missing gas flow rates, the substitute data value shall be the arithmetic average of 

the quality-assured values of that parameter immediately preceding and immediately following 

the missing data incident. If the “after” value is not obtained by the end of the reporting year, you 

may use the “before” value for the missing data substitution. If, for a particular parameter, no 

quality-assured data are available prior to the missing data incident, the substitute data value 

shall be the first quality-assured value obtained after the missing data period.

(c) For missing daily waste disposal quantity data for disposal in the reporting year, the 

substitute value shall be the average daily waste disposal quantity for that day of the week as 

measured on the week before and week after the missing daily data.

§98.346 Data reporting requirements.

In addition to the information required by §98.3(c), each annual report must contain the 

following information for each landfill.

(a) A classification of the landfill as “open” (actively received waste in the reporting year) 

or “closed” (no longer receiving waste), the year in which the landfill first started accepting 

waste for disposal, the last year the landfill accepted waste (for open landfills, enter the estimated 

year of landfill closure), the capacity (in metric tons) of the landfill, an indication of whether 

leachate recirculation is used during the reporting year and its typical frequency of use over the 

past 10 years (e.g., used several times a year for the past 10 years, used at least once a year for 

the past 10 years, used occasionally but not every year over the past 10 years, not used), an 

indication as to whether scales are present at the landfill, and the waste disposal quantity for each 

year of landfilling required to be included when using Equation HH-1 of this subpart (in metric 

tons, wet weight).
(b) Method for estimating reporting year and historical waste disposal quantities, reason for 

its selection, and the range of years it is applied. For years when waste quantity data are 

determined using the methods in §98.343(a)(3), report separately the quantity of waste 

determined using the methods in §98.343(a)(3)(i) and the quantity of waste determined using the 

methods in §98.343(a)(3)(ii). For historical waste disposal quantities that were not determined 

using the methods in §98.343(a)(3), provide the population served by the landfill for each year 

the Equation HH-2 of this subpart is applied, if applicable, or, for open landfills using Equation 

HH-3 of this subpart, provide the value of landfill capacity (LFC) used in the calculation.

(c) Waste composition for each year required for Equation HH-1 of this subpart, in 

percentage by weight, for each waste category listed in Table HH-1 to this subpart that is used in 

Equation HH-1 of this subpart to calculate the annual modeled CH4 generation.

(d) For each waste type used to calculate CH4 generation using Equation HH-1 of this 

subpart, you must report:

(1) Degradable organic carbon (DOC) and fraction of DOC dissimilated (DOCF) values 

used in the calculations.

(2) Decay rate (k) value used in the calculations.

(e) Fraction of CH4 in landfill gas (F), an indication of whether the fraction of CH4 was 

determined based on measured values or the default value, and the methane correction factor 

(MCF) used in the calculations. If an MCF other than the default of 1 is used, provide an 

indication of whether active aeration of the waste in the landfill was conducted during the 

reporting year, a description of the aeration system, including aeration blower capacity, the 

fraction of the landfill containing waste affected by aeration, the total number of hours during the 
year the aeration blower was operated, and other factors used as a basis for the selected MCF 

value.

(f) The surface area of the landfill containing waste (in square meters), identification of the 

type(s) of cover material used (as either organic cover, clay cover, sand cover, or other soil 

mixtures). 

(g) The modeled annual methane generation rate for the reporting year (metric tons CH4) 

calculated using Equation HH-1 of this subpart.

(h) For landfills without gas collection systems, the annual methane emissions (i.e., the 

methane generation, adjusted for oxidation, calculated using Equation HH-5 of this subpart), 

reported in metric tons CH4, the oxidation fraction used in the calculation, and an indication of 

whether passive vents and/or passive flares (vents or flares that are not considered part of the gas 

collection system as defined in §98.6) are present at this landfill.

(i) For landfills with gas collection systems, you must report:

(1) Total volumetric flow of landfill gas collected for destruction for the reporting year 

(cubic feet at 520 °R or 60 degrees Fahrenheit and 1 atm).

(2) Annual average CH4 concentration of landfill gas collected for destruction (percent by 

volume).

(3) Monthly average temperature and pressure for each month at which flow is measured for 

landfill gas collected for destruction, or statement that temperature and/or pressure is 

incorporated into internal calculations run by the monitoring equipment.

(4) An indication as to whether flow was measured on a wet or dry basis, an indication as to 

whether CH4 concentration was measured on a wet or dry basis, and if required for Equation 
HH-4 of this subpart, monthly average moisture content for each month at which flow is 

measured for landfill gas collected for destruction.

(5) An indication of whether destruction occurs at the landfill facility, off-site, or both. If 

destruction occurs at the landfill facility, also report for each measurement location:

(i) The number of destruction devices associated with the measurement location.

(ii) The annual operating hours of the gas collection system associated with the

measurement location,

(iii) For each destruction device associated with the measurement location, report:

(A) The destruction efficiency (decimal).

(B) The annual operating hours where active gas flow was sent to the destruction device.

(6) Annual quantity of recovered CH4 (metric tons CH4) calculated using Equation HH-4 of 

this subpart for each measurement location.

(7) A description of the gas collection system (manufacturer, capacity, and number of 

wells), the surface area (square meters) and estimated waste depth (meters) for each area 

specified in Table HH-3 to this subpart, the estimated gas collection system efficiency for 

landfills with this gas collection system and an indication of whether the gas collection efficiency

was determined on an area-weighted average basis (Option 1) or a volume-weighted average 

basis (Option 2), and an indication of whether passive vents and/or passive flares (vents or flares 

that are not considered part of the gas collection system as defined in §98.6) are present at the 

landfill.

(8) Methane generation corrected for oxidation calculated using Equation HH-5 of this 

subpart, reported in metric tons CH4, and the oxidation fraction used in the calculation.
(9) Methane generation (GCH4) value used as an input to Equation HH-6 of this subpart. 

Specify whether the value is modeled (GCH4 from HH-1 of this subpart) or measured (R from 

Equation HH-4 of this subpart).

(10) Methane generation corrected for oxidation calculated using Equation HH-7 of this 

subpart, reported in metric tons CH4, and the oxidation fraction used in the calculation.

(11) Methane emissions calculated using Equation HH-6 of this subpart, reported in metric 

tons CH4, and the oxidation fraction used in the calculation.

(12) Methane emissions calculated using Equation HH-8 of this subpart, reported in metric 

tons CH4, and the oxidation fraction used in the calculation.

(13) Methane emissions for the landfill (i.e., the subpart HH total methane emissions). 

Choose the methane emissions from either Equation HH-6 of this subpart or Equation HH-8 of 

this subpart that best represents the emissions from the landfill. If the quantity of recovered CH4

from Equation HH-4 of this subpart is used as the value of GCH4 in Equation HH-6 of this 

subpart, use the methane emissions calculated using Equation HH-8 of this subpart as the 

methane emissions for the landfill.

§98.347 Records that must be retained.

In addition to the information required by §98.3(g), you must retain the calibration records 

for all monitoring equipment, including the method or manufacturer's specification used for 

calibration. You must retain records of all measurements made to determine tare weights and 

working capacities by vehicle/container type if these are used to determine the annual waste 

quantities.

§98.348 Definitions.
Except as specified in this section, all terms used in this subpart have the same meaning 

given in the Clean Air Act and subpart A of this part.

Active venting means a pipe or a system of pipes used with a fan or similar mechanical draft 

equipment (forced convection) used to actively assist the flow of landfill gas to the surface of the 

landfill where the landfill gas is discharged either directly to the atmosphere or to a noncombustion control device (such as a carbon absorber) and then to the atmosphere.

Alternative final cover means materials, other than soil, used at a landfill that meets final 

closure regulations of the competent federal, state, or local authority. Alternative final covers 

may include, but are not limited to, evapotranspiration covers, capillary barrier covers, asphalt 

covers, or concrete covers. The state, local, or other agency responsible for permitting the

landfill determines whether an alternative final cover meets the applicable regulatory

requirements and has been shown to adequately protect human health and the environment. 

Construction and demolition (C&D) waste landfill means a solid waste disposal facility

subject to the requirements of part 257, subparts A or B of this chapter that receives construction 

and demolition waste and does not receive hazardous waste (defined in §261.3 of this chapter) or 

industrial solid waste (defined in §258.2 of this chapter) or municipal solid waste (as defined in 

§98.6) other than residential lead-based paint waste. A C&D waste landfill typically receives any 

one or more of the following types of solid wastes: Roadwork material, excavated material, 

demolition waste, construction/renovation waste, and site clearance waste.

Destruction device means a flare, thermal oxidizer, boiler, turbine, internal combustion 

engine, or any other combustion unit used to destroy or oxidize methane contained in landfill 

gas.
Industrial waste landfill means any landfill other than a municipal solid waste landfill, a 

RCRA Subtitle C hazardous waste landfill, or a TSCA hazardous waste landfill, in which 

industrial solid waste, such a RCRA Subtitle D wastes (nonhazardous industrial solid waste, 

defined in §257.2 of this chapter), commercial solid wastes, or conditionally exempt small 

quantity generator wastes, is placed. An industrial waste landfill includes all disposal areas at the 

facility.

Intermediate or interim cover means the placement of material over waste in a landfill for a 

period of time prior to the disposal of additional waste and/or final closure as defined by state 

regulation, permit, guidance or written plan, or state accepted best management practice. 

Landfill capacity means the maximum amount of solid waste a landfill can accept. For the 

purposes of this subpart, for landfills that have a permit, the landfill capacity can be determined 

in terms of volume or mass in the most recent permit issued by the state, local, or Tribal agency

responsible for regulating the landfill, plus any in-place waste not accounted for in the most 

recent permit. If the owner or operator chooses to convert from volume to mass to determine its 

capacity, the calculation must include a site-specific density.

Leachate recirculation means the practice of taking the leachate collected from the landfill 

and reapplying it to the landfill by any of one of a variety of methods, including pre-wetting of 

the waste, direct discharge into the working face, spraying, infiltration ponds, vertical injection 

wells, horizontal gravity distribution systems, and pressure distribution systems.

Passive vent means a pipe or a system of pipes that allows landfill gas to flow naturally, 

without the use of a fan or similar mechanical draft equipment, to the surface of the landfill 

where an opening or pipe (vent) allows for the free flow of landfill gas to the atmosphere or to a 

passive vent flare without diffusion through the top layer of surface soil.
Solid waste has the meaning established by the Administrator pursuant to the Solid Waste 

Disposal Act (42 U.S.C.A. 6901 et seq.).

Working capacity means the maximum volume or mass of waste that is actually placed in 

the landfill from an individual or representative type of container (such as a tank, truck, or rolloff bin) used to convey wastes to the landfill, taking into account that the container may not be 

able to be 100 percent filled and/or 100 percent emptied for each load.

[75 FR 66473, Oct. 28, 2010, as amended at 78 FR 71970, Nov. 29, 2013]

Table HH-1 to Subpart HH of Part 98—Emissions Factors, Oxidation Factors and 

Methods

Factor Default value Units

DOC and k values—Bulk waste option

DOC (bulk waste) 0.20 Weight fraction, wet 

basis.

k (precipitation plus recirculated leachatea<20 

inches/year)

0.02 yr−1

k (precipitation plus recirculated leachatea20-40 

inches/year)

0.038 yr−1

k (precipitation plus recirculated leachatea>40 

inches/year)

0.057 yr−1

DOC and k values—Modified bulk MSW option

DOC (bulk MSW, excluding inerts and C&D 

waste)

0.31 Weight fraction, wet 

basis.

DOC (inerts, e.g., glass, plastics, metal, 

concrete)

0.00 Weight fraction, wet 

basis.

DOC (C&D waste) 0.08 Weight fraction, wet 

basis.

k (bulk MSW, excluding inerts and C&D waste) 0.02 to 0.057byr−1

k (inerts, e.g., glass, plastics, metal, concrete) 0.00 yr−1

k (C&D waste) 0.02 to 0.04byr−1

DOC and k values—Waste composition option

DOC (food waste) 0.15 Weight fraction, wet 
basis.

DOC (garden) 0.2 Weight fraction, wet 

basis.

DOC (paper) 0.4 Weight fraction, wet 

basis.

DOC (wood and straw) 0.43 Weight fraction, wet 

basis.

DOC (textiles) 0.24 Weight fraction, wet 

basis.

DOC (diapers) 0.24 Weight fraction, wet 

basis.

DOC (sewage sludge) 0.05 Weight fraction, wet 

basis.

DOC (inerts, e.g., glass, plastics, metal, cement) 0.00 Weight fraction, wet 

basis.

k (food waste) 0.06 to 0.185cyr−1

k (garden) 0.05 to 0.10cyr−1

k (paper) 0.04 to 0.06cyr−1

k (wood and straw) 0.02 to 0.03cyr−1

k (textiles) 0.04 to 0.06cyr−1

k (diapers) 0.05 to 0.10cyr−1

k (sewage sludge) 0.06 to 0.185cyr−1

k (inerts e.g., glass, plastics, metal, concrete) 0.00 yr−1

Other parameters—All MSW landfills

MCF 1.

DOCF 0.5

F 0.5

OX See Table HH-4 of this 

subpart

DE 0.99

aRecirculated leachate (in inches/year) is the total volume of leachate recirculated from 

company records or engineering estimates divided by the area of the portion of the landfill 

containing waste with appropriate unit conversions. Alternatively, landfills that use leachate 
recirculation can elect to use the k value of 0.057 rather than calculating the recirculated leachate 

rate.

bUse the lesser value when precipitation plus recirculated leachate is less than 20 

inches/year. Use the greater value when precipitation plus recirculated leachate is greater than 40 

inches/year. Use the average of the range of values when precipitation plus recirculated leachate 

is 20 to 40 inches/year (inclusive). Alternatively, landfills that use leachate recirculation can 

elect to use the greater value rather than calculating the recirculated leachate rate.

cUse the lesser value when the potential evapotranspiration rate exceeds the mean annual 

precipitation rate plus recirculated leachate. Use the greater value when the potential 

evapotranspiration rate does not exceed the mean annual precipitation rate plus recirculated 

leachate. Alternatively, landfills that use leachate recirculation can elect to use the greater value 

rather than assessing the potential evapotranspiration rate or recirculated leachate rate.

Table HH-2 to Subpart HH of Part 98—U.S. Per Capita Waste Disposal Rates

Year

Waste per capita

ton/cap/yr

1950 0.63

1951 0.63

1952 0.63

1953 0.63

1954 0.63

1955 0.63

1956 0.63

1957 0.63

1958 0.63

1959 0.63

1960 0.63

1961 0.64

1962 0.64

1963 0.65

1964 0.65

1965 0.66

1966 0.66

1967 0.67

1968 0.68
1969 0.68

1970 0.69

1971 0.69

1972 0.70

1973 0.71

1974 0.71

1975 0.72

1976 0.73

1977 0.73

1978 0.74

1979 0.75

1980 0.75

1981 0.76

1982 0.77

1983 0.77

1984 0.78

1985 0.79

1986 0.79

1987 0.80

1988 0.80

1989 0.83

1990 0.82

1991 0.76

1992 0.74

1993 0.76

1994 0.75

1995 0.70

1996 0.68

1997 0.69

1998 0.75
1999 0.75

2000 0.80

2001 0.91

2002 1.02

2003 1.02

2004 1.01

2005 0.98

2006 0.95

2007 0.95

2008 0.95

2009 and all later years 0.95

Table HH-3 to Subpart HH of Part 98—Landfill Gas Collection Efficiencies

Description Landfill Gas Collection Efficiency

A1: Area with no waste in-place Not applicable; do not use this area in 

the calculation.

A2: Area without active gas collection, regardless of 

cover type

CE2: 0%.

A3: Area with daily soil cover and active gas collection CE3: 60%.

A4: Area with an intermediate soil cover, or a final soil 

cover not meeting the criteria for A5 below, and active 

gas collection

CE4: 75%.

A5: Area with a final soil cover of 3 feet or thicker of 

clay or alternative final cover (as approved by the 

relevant agency) and/or geomembrane cover system and 

active gas collection

CE5: 95%.

Weighted average collection efficiency for landfills:

Option 1: Area weighted average collection efficiency

for landfills

CEave1 = (A2*CE2 + A3*CE3 + 

A4*CE4 + A5*CE5) / (A2 + A3 + A4 

+ A5).

Option 2: Volume weighted average collection 

efficiency for landfills, where D2, D3, D4 and D5 are the 

waste depths for areas A2, A3, A4 and A5, respectively,

as described above. 

CEave1 = (A2*D2*CE2 + 

A3*D3*CE3 + A4*D4*CE4 + 

A5*D5*CE5) / (A2*D2 + A3*D3 + 

A4*D4 + A5*D5).
Table HH-4 to Subpart HH of Part 98—Landfill Methane Oxidation Fractions

Under these conditions:

Use this 

landfill 

methane 

oxidation

fraction:

I. For all reporting years prior to the 2013 reporting year

C1: For all landfills regardless of cover type or methane flux 0.10

II. For the 2013 reporting year and all subsequent years

C2: For landfills that have an alternative final cover (approved by the relevant 

agency) and/or a geomembrane (synthetic) cover with less than 12 inches of 

cover soil for greater than 50% of the landfill area containing waste

0.0

C3: For landfills that do not meet the conditions in C2 above and for which you 

elect not to determine methane flux, or for landfills with passive vents/passive 

flares that service greater than 50% of the landfill area containing waste, or for 

landfills with only passive vents/passive flares or active venting

0.10

C4: For landfills that do not meet the conditions in C2 above and that do not 

have intermediate or interim coverafor greater than 50% of the landfill area 

containing waste

0.10

C5: For landfills that have intermediate or interim coverafor greater than 50%

of the landfill area containing waste and for which the methane flux ratebis less 

than 10 grams per square meter per day (g/m2/d)

0.35

C6: For landfills that have intermediate or interim coverafor greater than 50% of 

the landfill area containing waste and for which the methane flux ratebis 10 to 

70 g/m2/d

0.25

C7: For landfills that have intermediate or interim coverafor greater than 50% of 

the landfill area containing waste and for which the methane flux ratebis greater 

than 70 g/m2/d

0.10

aWhere a landfill is located in a state that does not have an intermediate or interim cover 

requirement, the landfill must have soil cover of 12 inches or greater in order to use an oxidation 

fraction of 0.25 or 0.35.

bMethane flux rate (in grams per square meter per day; g/m2

/d) is the mass flow rate of 

methane per unit area at the bottom of the surface soil prior to any oxidation and is calculated as 

follows:
Where:

MF = Methane flux rate from the landfill in the reporting year (grams per square meter per day, 

g/m2/d).

K = unit conversion factor = 106/365 (g/metric ton per days/year) or 106/366 for a leap year.

SArea = The surface area of the landfill containing waste at the beginning of the reporting year 

(square meters, m2).

GCH4 = Modeled methane generation rate in reporting year from Equation HH-1 of this subpart 

or Equation TT-1 of subpart TT of this part, as applicable, except for application with 

Equation HH-6 of this subpart (metric tons CH4). For application with Equation HH-6 

of this subpart, the greater of the modeled methane generation rate in reporting year 

from Equation HH-1 of this subpart or Equation TT-1 of this part, as applicable, and 

the quantity of recovered CH4 from Equation HH-4 of this subpart (metric tons CH4).

CE = Collection efficiency estimated at landfill, taking into account system coverage, operation, 

and cover system materials from Table HH-3 of this subpart. If area by soil cover type 
information is not available, use default value of 0.75 (CE4 in table HH-3 of this 

subpart) for all areas under active influence of the collection system.

N = Number of landfill gas measurement locations (associated with a destruction device or gas 

sent off-site). If a single monitoring location is used to monitor volumetric flow and 

CH4 concentration of the recovered gas sent to one or multiple destruction devices, 

then N=1.

Rn = Quantity of recovered CH4 from Equation HH-4 of this subpart for the nth measurement 

location (metric tons).

fRec,n = Fraction of hours the recovery system associated with the nth measurement location was 

operating (annual operating hours/8760 hours per year or annual operating hours/8784 

hours per year for a leap year).