elementa 5 145 s1
Supplementary Information
Resolving m2 to km2 CH4 emissions for a complex urban source: An Indiana landfill study
Maria Obiminda L. Cambaliza1,2,3, Jean E. Bogner4, Roger B. Green5, Paul B. Shepson6, Tierney A. Harvey7,+, Kurt A. Spokas8, Brian H. Stirm9, Margaret Corcoran4,#
1
Department of Chemistry, Purdue University, Lafayette, IN, USA
2
Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City, Philippines
3
Manila Observatory, Loyola Heights, Quezon City, Philippines
4
Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA
5
Waste Management Inc., Cincinnati, OH, USA
6
Departments of Chemistry, and Earth, Atmospheric, and Planetary Sciences, Purdue University,
Lafayette, IN, USA 7
Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA US Department of Agriculture – Agricultural Research Service, St. Paul, MN, USA
8
9
School of Aviation and Transportation Technology, Purdue University, West Lafayette, IN, US
+
now with the Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK,
USA #
now with the US EPA Great Lakes National Program Office S1
Additional details on landfill cover areas Typical landfill sites in the United States include three general types of cover materials: daily, intermediate, and final cover. A brief description of the areas and their application are as follows:
(1) Daily cover: This thin soil cover or permitted alternative overlies the active filling area and is placed over compacted waste at the end of each working day. The active filling area may overlie the bottom liner/gravity drainage system in new cells, a previous daily cover, an intermediate cover, or older methanogenic waste (where a previous intermediate cover has been stripped).
(2) Intermediate cover: This thicker compacted soil cover overlies a completed cell area when a cell is filled to its designated top elevation. Intermediate covers are maintained for a period of months to years but will eventually be overlain by new cells as the landfill expands vertically.
(3) Final cover: This very thick compacted soil cover or geomembrane composite cover is placed when a group of adjacent cells reaches the final permitted grade. At closure, sites begin a 30-year period of postclosure monitoring.
S2
Additional details on the Tracer Correlation Approach (TCA) As stated in the main manuscript, each TCA measurement at the IN-1 site made use of 2 -3 cylinders of atomic absorption grade acetylene (C2H2, 99.6% purity) using either a triangular or a linear release geometry from the top of the landfill. The tracer gas is released at a known rate from the landfill surface to simulate the landfill gas emission. As mentioned in the main text, measurements of CH4 and C2H2 were conducted at sufficient distances downwind of the source to allow the respective plumes to become well-mixed. Figure 4 in Foster-Wittig et al (2015) shows an example of insufficiently mixed plumes of CH4 and C2H2 at a downwind distance of 1.3 km from the landfill where two peaks of C2H2 were observed superimposed on a single broad envelope of CH4. The whole-site CH4 emission rate was determined using both (1) the unconstrained slope of the best-fit line between CH4 and C2H2 concentrations (equation 1), and (2) the ratio of the time-integrated areas of CH4 and C2H2 (equation 2) (Foster-Wittig et al., 2015): ( )
(1)
( )
(2)
Q is the CH4 source emission rate (g min-1, eventually converted to mol s-1 in this paper), m is the unconstrained slope of the best-line line, v is the ratio of the CH4 and C2H2 areas, Qt is the known tracer (acetylene) release rate, and MCH4 and MC2H2 are the molecular weights of CH4 and C2H2, respectively. The ratio v of the CH4 and C2H2 is expressed as ∫ [ ( )
]
∫ [ ( )
]
(3)
In the relationship above, x and y are the respective CH4 and C2H2 time series, to and tf are the respective start and end time of the analysis, and x and y are the background mole fractions of CH4 and C2H2, S3
respectively. The final calculation of the whole-site CH4 emission rate was determined using the second method (equation 2), as the plume integration ratio approach resulted in lower uncertainty. It is expected that the second approach was more accurate than the linear regression method, as the areas under the curve rely on the enhancements of CH4 and C2H2 above their baselines rather than on the absolute mole fractions of both species (equation 3).
S4
Supplementary tables
Table S1. Properties of the various IN-1 landfill cover types used as inputs to CALMIM 5.4. IN-1 has a footprint of 0.7 km2 (173 acres).
Cover Type
% Area
% Gas
% Vegetation
Organic Matter
Material &
Recovery
Present
Content
Thickness
Low
See note
(growing season)
Daily
4
0
0
below* Intermediate
39
100
0
Medium
0.91m (36”) clay
Final
57
100
100
Medium
See note below+
* Two Daily covers: 0.15m (6”) clay and “extended daily cover” of 0.79m (31”) loamy sand; each 2% of area + Two Final covers: 1.2m (48”) silty clay loam (34% of area) and geomembrane composite cover (23% of area) of 0.30m (12”) loam over HDPE geomembrane over 0.61m (24”) silty clay loam.
S5
Table S2. AMB Background CH4 mixing ratio and estimated CH4 emission rate corresponding to two downwind distances from IN-1 during the 30 August 2012 and 03 July 2014 flight experiments.
Flight Date
30 August 2012
03 July 2014
Emission Rate (mol s-1)
Downwind distance from
Background CH4
IN-1 (km)
mixing ratio (ppb)
3
1930.6 ± 8.6
18
6
1923.6 ± 7.8
16
6
1896.2 ± 1.3
7.9
4.5
1896.3 ± 1.2
6.8
S6
Table S3. Mean and Standard deviations of the TCA estimated whole-site CH4 emissions (mol s-1) from 2009 – 2012. Mean CH4 Emission
Standard deviation (1)
Measurement
Number of TCA Runs
Date 14.0
3.7
7.3 15.2
3.7
12.6 12.1
2.7
7.7 7.4
0.6
6.2
20 May 2009
12
21 July 2010
1
22 July 2010
8
17 Aug 2010
1
18 Aug 2010
6
14 Sept 2010
1
15 Sept 2010
2
11 Nov 2010
1
6.0
1.1
12 Nov 2010
3
12.5
2.5
24 Aug2011
7
8.7
1.0
25 Aug2011
4
18.3
18.2
13 Sept2011
8
7.2
2.2
14 Sept 2011
4
12.2
2.3
2 Nov 2011
7
4 Nov 2011
1
10.0 10.9
2.8
11 Dec2011
6
13.9
7.0
24 May 2012
4
9.4
3.1
25 May 2012
7
8.4
1.9
28 Aug 2012
7
8.1
0.7
31 Aug 2012
4
S7
Table S4. Comparison of upwind and downwind CH4 Mixing ratios at ground level at IN-1. Values represent first static chamber samples measured at the intermediate and extended daily covers, respectively. Upwind CH4 (column 2) refers to atmospheric mixing ratios at the ground surface obtained in May 2012 at the upland, upwind intermediate cover. Downwind CH4 (column 3) refers to the corresponding atmospheric mixing ratios at the ground surface obtained in August 2012 at the extended daily cover. The extended daily cover area was immediately adjacent to, downwind, and downslope from the active filling area.
Upwind CH4 (ppm)
Downwind CH4 (ppm)
Mean
3.99
53.5
Standard Deviation
2.20
71.1
Geometric mean
3.61
33.4
Geometric St Deviation
1.53
2.5
Max
12.02
356.9
Min
2.00
8
22
27
Count
S8
Table S5. HH-6 to Subpart HH of Part 98 - Landfill Methane Oxidation Fractions.
Use this landfill CH4 oxidation fraction:
Under these conditions:
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
C3: For landfills that do not meet the conditions in C2 above, and for which you elect not to determine CH4 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 CH4 flux rate is estimated to be 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 CH4 flux rate is estimated to be 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 landfill area containing waste and for which the CH4 flux rate is estimated to be greater than 70 g/m2/d
0.10
S9
Supplementary Figures
Figure S1. Experimental flight path as a function of altitude on 30 August 2012 for sampling the CH4 plume from IN-1. Horizontal transects were flown at 3 km and 6 km downwind distances. Winds were from the Southeast (144 ± 22) at 5.3 1.8 (1) ms-1.
S10
Figure S2. Experimental flight path as a function of altitude on 03 July 2014 at the IN-1 Landfill site. Horizontal transects were flown at 4.5 km and 6 km downwind distances. Winds were from the North Northwest (342 ± 18) at 6.2 2.0 (1) ms-1.
S11
Figure S3. Horizontal distributions of the methane plume on 30 August 2012. The raw and interpolated (kriged) CH4 plumes are shown for the 3 km (A and C) and 6 km (B and D) downwind distances corresponding to the flight path shown in Figure S2. The aircraft-based mass balance approach yielded whole landfill methane emission rates of 16 mol s-1 and 18 mol s-1 for the 3 km and 6 km twodimensional crosswind planes, respectively. The average emission rate was 17 mol s-1 (Cambaliza et al., 2014).
S12
Figure S4. Horizontal distributions of the methane plume on 3 July 2014. The raw and interpolated (kriged) CH4 plumes are shown for the 3 km (A and C) and 6 km (B and D) downwind distances corresponding to the flight path shown in Figure S3. The aircraft-based mass balance approach yielded a whole landfill methane emission flux of 7.9 mol s-1 and 6.8 mol s-1 for the 6 km and 4.5 km twodimensional crosswind planes, respectively.
S13
Resolving m2 to km2 CH4 emissions for a complex urban source: An Indiana landfill study
Maria Obiminda L. Cambaliza1,2,3, Jean E. Bogner4, Roger B. Green5, Paul B. Shepson6, Tierney A. Harvey7,+, Kurt A. Spokas8, Brian H. Stirm9, Margaret Corcoran4,#
1
Department of Chemistry, Purdue University, Lafayette, IN, USA
2
Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City, Philippines
3
Manila Observatory, Loyola Heights, Quezon City, Philippines
4
Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA
5
Waste Management Inc., Cincinnati, OH, USA
6
Departments of Chemistry, and Earth, Atmospheric, and Planetary Sciences, Purdue University,
Lafayette, IN, USA 7
Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA US Department of Agriculture – Agricultural Research Service, St. Paul, MN, USA
8
9
School of Aviation and Transportation Technology, Purdue University, West Lafayette, IN, US
+
now with the Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK,
USA #
now with the US EPA Great Lakes National Program Office S1
Additional details on landfill cover areas Typical landfill sites in the United States include three general types of cover materials: daily, intermediate, and final cover. A brief description of the areas and their application are as follows:
(1) Daily cover: This thin soil cover or permitted alternative overlies the active filling area and is placed over compacted waste at the end of each working day. The active filling area may overlie the bottom liner/gravity drainage system in new cells, a previous daily cover, an intermediate cover, or older methanogenic waste (where a previous intermediate cover has been stripped).
(2) Intermediate cover: This thicker compacted soil cover overlies a completed cell area when a cell is filled to its designated top elevation. Intermediate covers are maintained for a period of months to years but will eventually be overlain by new cells as the landfill expands vertically.
(3) Final cover: This very thick compacted soil cover or geomembrane composite cover is placed when a group of adjacent cells reaches the final permitted grade. At closure, sites begin a 30-year period of postclosure monitoring.
S2
Additional details on the Tracer Correlation Approach (TCA) As stated in the main manuscript, each TCA measurement at the IN-1 site made use of 2 -3 cylinders of atomic absorption grade acetylene (C2H2, 99.6% purity) using either a triangular or a linear release geometry from the top of the landfill. The tracer gas is released at a known rate from the landfill surface to simulate the landfill gas emission. As mentioned in the main text, measurements of CH4 and C2H2 were conducted at sufficient distances downwind of the source to allow the respective plumes to become well-mixed. Figure 4 in Foster-Wittig et al (2015) shows an example of insufficiently mixed plumes of CH4 and C2H2 at a downwind distance of 1.3 km from the landfill where two peaks of C2H2 were observed superimposed on a single broad envelope of CH4. The whole-site CH4 emission rate was determined using both (1) the unconstrained slope of the best-fit line between CH4 and C2H2 concentrations (equation 1), and (2) the ratio of the time-integrated areas of CH4 and C2H2 (equation 2) (Foster-Wittig et al., 2015): ( )
(1)
( )
(2)
Q is the CH4 source emission rate (g min-1, eventually converted to mol s-1 in this paper), m is the unconstrained slope of the best-line line, v is the ratio of the CH4 and C2H2 areas, Qt is the known tracer (acetylene) release rate, and MCH4 and MC2H2 are the molecular weights of CH4 and C2H2, respectively. The ratio v of the CH4 and C2H2 is expressed as ∫ [ ( )
]
∫ [ ( )
]
(3)
In the relationship above, x and y are the respective CH4 and C2H2 time series, to and tf are the respective start and end time of the analysis, and x and y are the background mole fractions of CH4 and C2H2, S3
respectively. The final calculation of the whole-site CH4 emission rate was determined using the second method (equation 2), as the plume integration ratio approach resulted in lower uncertainty. It is expected that the second approach was more accurate than the linear regression method, as the areas under the curve rely on the enhancements of CH4 and C2H2 above their baselines rather than on the absolute mole fractions of both species (equation 3).
S4
Supplementary tables
Table S1. Properties of the various IN-1 landfill cover types used as inputs to CALMIM 5.4. IN-1 has a footprint of 0.7 km2 (173 acres).
Cover Type
% Area
% Gas
% Vegetation
Organic Matter
Material &
Recovery
Present
Content
Thickness
Low
See note
(growing season)
Daily
4
0
0
below* Intermediate
39
100
0
Medium
0.91m (36”) clay
Final
57
100
100
Medium
See note below+
* Two Daily covers: 0.15m (6”) clay and “extended daily cover” of 0.79m (31”) loamy sand; each 2% of area + Two Final covers: 1.2m (48”) silty clay loam (34% of area) and geomembrane composite cover (23% of area) of 0.30m (12”) loam over HDPE geomembrane over 0.61m (24”) silty clay loam.
S5
Table S2. AMB Background CH4 mixing ratio and estimated CH4 emission rate corresponding to two downwind distances from IN-1 during the 30 August 2012 and 03 July 2014 flight experiments.
Flight Date
30 August 2012
03 July 2014
Emission Rate (mol s-1)
Downwind distance from
Background CH4
IN-1 (km)
mixing ratio (ppb)
3
1930.6 ± 8.6
18
6
1923.6 ± 7.8
16
6
1896.2 ± 1.3
7.9
4.5
1896.3 ± 1.2
6.8
S6
Table S3. Mean and Standard deviations of the TCA estimated whole-site CH4 emissions (mol s-1) from 2009 – 2012. Mean CH4 Emission
Standard deviation (1)
Measurement
Number of TCA Runs
Date 14.0
3.7
7.3 15.2
3.7
12.6 12.1
2.7
7.7 7.4
0.6
6.2
20 May 2009
12
21 July 2010
1
22 July 2010
8
17 Aug 2010
1
18 Aug 2010
6
14 Sept 2010
1
15 Sept 2010
2
11 Nov 2010
1
6.0
1.1
12 Nov 2010
3
12.5
2.5
24 Aug2011
7
8.7
1.0
25 Aug2011
4
18.3
18.2
13 Sept2011
8
7.2
2.2
14 Sept 2011
4
12.2
2.3
2 Nov 2011
7
4 Nov 2011
1
10.0 10.9
2.8
11 Dec2011
6
13.9
7.0
24 May 2012
4
9.4
3.1
25 May 2012
7
8.4
1.9
28 Aug 2012
7
8.1
0.7
31 Aug 2012
4
S7
Table S4. Comparison of upwind and downwind CH4 Mixing ratios at ground level at IN-1. Values represent first static chamber samples measured at the intermediate and extended daily covers, respectively. Upwind CH4 (column 2) refers to atmospheric mixing ratios at the ground surface obtained in May 2012 at the upland, upwind intermediate cover. Downwind CH4 (column 3) refers to the corresponding atmospheric mixing ratios at the ground surface obtained in August 2012 at the extended daily cover. The extended daily cover area was immediately adjacent to, downwind, and downslope from the active filling area.
Upwind CH4 (ppm)
Downwind CH4 (ppm)
Mean
3.99
53.5
Standard Deviation
2.20
71.1
Geometric mean
3.61
33.4
Geometric St Deviation
1.53
2.5
Max
12.02
356.9
Min
2.00
8
22
27
Count
S8
Table S5. HH-6 to Subpart HH of Part 98 - Landfill Methane Oxidation Fractions.
Use this landfill CH4 oxidation fraction:
Under these conditions:
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
C3: For landfills that do not meet the conditions in C2 above, and for which you elect not to determine CH4 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 CH4 flux rate is estimated to be 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 CH4 flux rate is estimated to be 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 landfill area containing waste and for which the CH4 flux rate is estimated to be greater than 70 g/m2/d
0.10
S9
Supplementary Figures
Figure S1. Experimental flight path as a function of altitude on 30 August 2012 for sampling the CH4 plume from IN-1. Horizontal transects were flown at 3 km and 6 km downwind distances. Winds were from the Southeast (144 ± 22) at 5.3 1.8 (1) ms-1.
S10
Figure S2. Experimental flight path as a function of altitude on 03 July 2014 at the IN-1 Landfill site. Horizontal transects were flown at 4.5 km and 6 km downwind distances. Winds were from the North Northwest (342 ± 18) at 6.2 2.0 (1) ms-1.
S11
Figure S3. Horizontal distributions of the methane plume on 30 August 2012. The raw and interpolated (kriged) CH4 plumes are shown for the 3 km (A and C) and 6 km (B and D) downwind distances corresponding to the flight path shown in Figure S2. The aircraft-based mass balance approach yielded whole landfill methane emission rates of 16 mol s-1 and 18 mol s-1 for the 3 km and 6 km twodimensional crosswind planes, respectively. The average emission rate was 17 mol s-1 (Cambaliza et al., 2014).
S12
Figure S4. Horizontal distributions of the methane plume on 3 July 2014. The raw and interpolated (kriged) CH4 plumes are shown for the 3 km (A and C) and 6 km (B and D) downwind distances corresponding to the flight path shown in Figure S3. The aircraft-based mass balance approach yielded a whole landfill methane emission flux of 7.9 mol s-1 and 6.8 mol s-1 for the 6 km and 4.5 km twodimensional crosswind planes, respectively.
S13
