Page 1 of 39

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.
Page 2 of 39

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.
Page 3 of 39

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, 
Page 4 of 39

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 
Page 5 of 39

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 offloaded 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; 
Page 6 of 39

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 
Page 7 of 39

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 
Page 8 of 39

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.
Page 9 of 39

(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.

   

 

 

 

1,000

0.454

1atm

P

T

520 R

0.0423

100%

C

R V

N

n 1

n

n

CH4 n  n



















 



     K MC n

(Eq. HH-4)

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)nand (C)nare both measured on a dry 

basis or if both are measured on a wet basis; 

(KMC)n= [1-(fH2O)n] when (V)nis measured on a wet 
Page 10 of 39

basis and (C)nis measured on a dry basis; and 

(KMC)n= 1/[1-(fH2O)n] when (V)nis measured on a 

dry basis and (C)nis 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 
Page 11 of 39

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 
Page 12 of 39

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.
Page 13 of 39

(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.

     











     











    

N

n

N

n 1

n n Dest,n

1

CH4 n Emissions G - R 1 OX R 1 DE f (Eq. HH-6)

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).
Page 14 of 39

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.

(1- OX)

f

R

CE

1 MG

1 Rec,n

n 

















 

N

n

(Eq. HH-7)
Page 15 of 39

     

















     



















































      

N

n

N

n

N

n 1

n n Dest,n

1

n

1 Rec,n

n R 1 OX R 1 DE f

f

R

CE

1

Emissions (Eq. HH-8)

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 nth 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 
Page 16 of 39

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 
Page 17 of 39

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.
Page 18 of 39

(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 
Page 19 of 39

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 nonmethane 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 
Page 20 of 39

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.
Page 21 of 39

(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 (e)(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.

 























2

4

20.9 %

20.9

100% O

C

F

CH c

(Eq. HH-10)
Page 22 of 39

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 accuracy 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, 
Page 23 of 39

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 
Page 24 of 39

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 
Page 25 of 39

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 
Page 26 of 39

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 of cover material 

used (as either organic cover, clay cover, sand cover, or other 

soil mixtures). If multiple cover types are used, the surface 

area associated with each cover type.

(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.
Page 27 of 39

(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

the number of destruction devices associated with that 

measurement location and the annual operating hours and the 
Page 28 of 39

destruction efficiency (percent) for each destruction device 

associated with that measurement location.

(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, the annual operating hours of the gas 

collection system for each measurement location, 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).
Page 29 of 39

(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.

§ 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.

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 
Page 30 of 39

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.

Solid waste has the meaning established by the 

Administrator pursuant to the Solid Waste Disposal Act (42 

U.S.C.A. 6901 et seq.).
Page 31 of 39

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 prewetting of the waste, direct discharge into the working face, 

spraying, infiltration ponds, vertical injection wells, 

horizontal gravity distribution systems, and pressure 

distribution systems.

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 

roll-off 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.
Page 32 of 39

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 0.057b yr−1

k (inerts, e.g., glass, 

plastics, metal, concrete)

0.00 yr−1

k (C&D waste) 0.02 to 0.04b yr−1

DOC and k values—Waste composition option

DOC (food waste) 0.15 Weight 

fraction, wet 
Page 33 of 39

Factor Default value Units

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 0.185c yr−1

k (garden) 0.05 to 0.10c yr−1

k (paper) 0.04 to 0.06c yr−1

k (wood and straw) 0.02 to 0.03c yr−1

k (textiles) 0.04 to 0.06c yr−1

k (diapers) 0.05 to 0.10c yr−1

k (sewage sludge) 0.06 to 0.185c yr−1

k (inerts e.g., glass, 

plastics, metal, concrete)

0.00 yr−1
Page 34 of 39

Factor Default value Units

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
Page 35 of 39

Year

Waste per capita

ton/cap/yr

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
Page 36 of 39

Year

Waste per capita

ton/cap/yr

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 and/or 

geomembrane cover system and active 

gas collection

CE5: 95%.

Area weighted average collection CEave1 = (A2*CE2 + A3*CE3 + 
Page 37 of 39

Description

Landfill Gas Collection 

Efficiency

efficiency for landfills A4*CE4 + 

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

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 a 

geomembrane (synthetic) cover with 

less than 12 inches of cover soil for 

the majority 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

0.10

C4: For landfills that do not meet the 

conditions in C2 above and that do not have 

a soil cover of at least 24 inches for a 

majority of the landfill area containing 

waste

0.10

C5: For landfills that have a soil cover of 

at least 24 inches for a majority of the 

landfill area containing waste and for which 

the methane flux rate is less than 10 grams 

per square meter per day (g/m2/d)

0.35

C6: For landfills that have a soil cover of 

at least 24 inches for a majority of the 

landfill area containing waste and for which 

the methane flux rate is 10 to 70 g/m2/d

0.25

C7: For landfills that have a soil cover of 

at least 24 inches for a majority of the 

0.10
Page 38 of 39

landfill area containing waste and for which 

the methane flux rate is greater than 70 

g/m2/d

aMethane 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: 

For Equation HH-5 of this subpart, or for Equation TT-6 of 

subpart TT of this part,

MF K G SArea   CH4

For Equation HH-6 of this subpart,

MF K G - R SArea

1

CH4 n













  

N

n

For Equations HH-7 of this subpart,

SArea

f

R

CE

1 MF K

1 Rec,n

n

































  

N

n

For Equation HH-8 of this subpart,

R SArea

f

R

CE

1 MF K

1

n

1 Rec,n

n



















































     

N

n

N

n

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, 

m

2). 

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 
Page 39 of 39

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 offsite). 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).