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Methane Emissions from Methane Emissions from

Methane Emissions from - PowerPoint Presentation

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Methane Emissions from - PPT Presentation

the US Natural Gas Infrastructure R Subramanian subucmuedu Scott Herndon Rob Roscioli Austin Mitchell Dan Zimmerle Anthony Marchese and Allen Robinson Funding data technical ID: 490624

emissions methane amp tracer methane emissions tracer amp gathering measurements flux facilities gas emission facility onsite sites natural ghgrp

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Slide1

Methane Emissions from

theUS Natural Gas Infrastructure

R Subramanian (subu@cmu.edu)Scott Herndon, Rob Roscioli, Austin Mitchell,Dan Zimmerle, Anthony Marchese, and Allen RobinsonSlide2

Funding, data, technical

input:

Environmental Defense FundKinder-MorganNiSourceTransCanadaDominionWilliamsEnableDowINGAAAnadarko

Access MidstreamSWNHessDCP*Slide3

Methane Emissions from Transmission and StorageSlide4

Transmission & Storage Sector

300,000 miles of pipelines~2000 compressor stationsOlder facilities often reciprocating compressorsPowered by gas reciprocating engines

Newer/larger units centrifugal compressorsDriven by gas turbinesSource: US EIA, http://www.eia.gov/state/maps.cfm?v=Natural%20GasSlide5

Top-down & bottom-up measurements at 45 compressor stations

 

  

Compressor Types

 

Category

Number

GHGRP reporters

Reciprocating

c

ompressors only

Centrifugal

compressor

only

Both

types

Sites with at least one

compressor running

Transmission37231221415Storage8 (10)27015Total45 (47)251921520

GHGRP reporters: facilities that emit over 25,000 MT-CO2e/year

Sixteen states, six partner companies, eleven weeks of parallel direct onsite and tracer flux

measurementsSlide6

Bottom-up: Direct Onsite Measurement of Methane EmissionsModeled on EPA GHGRP protocol, but more comprehensive

Leak detection with FLIR thermal imagingMeasure emissions with Hi-Flow, acoustic devices, turbine meters, bagsIssues:Accuracy of some techniques questionableSome leaks may not be detected due to adverse windNot all detected leaks are safely accessible

Time-consuming for comprehensive measurements and at larger sitesSlide7

“Top-Down” Downwind Dual Tracer Flux: Facility-Level Emission Rates

N2O

C2H2

CH

4Slide8

Onsite & Tracer Flux Data: Details

Reciprocating-only sites

Centrifugal-only sitesFacility-level CH4 Emissions (SCFM)Slide9

Direct Onsite vs Tracer Flux: Mostly AgreeSlide10

Onsite does not capture super-emitters

Super-emitters: Sites emitting over 300 SCFM methaneSlide11

GHGRP: NOP rod-packing venting not reported, OEL/connector emission factors lowSlide12

GHGRP emission factors not appropriate for engine exhaust methaneSlide13

The fat tail: super-emitters skew emissions distributions

Cumulative Fraction of Sites

Cumulative Methane Emissions (SCFM)Cumulative Fraction of TF Methane EmissionsSlide14

Processing Plant

Gathering Lines

Gathering Facility

Gathering pipelines were not measured as part of this study

Methane Emissions from Gathering and ProcessingSlide15

G&P Field Campaign

Tracer flux measurements at

16 processing plants

and

114 gathering facilities

(of Partner inventory of 28 & 738 facilities.)Slide16

G&P: Facility-Level Methane Emissions (kg/

hr

) & Loss Rate (% throughput)Mitchell, A.L.,

Zimmerle, D., Marchese, A.J., Robinson, A.L. et al. Measurements of Methane Emissions from Natural Gas Gathering Facilities and Processing Plants: Measurement Results.

Environ.

Sci. Technol

.,

49

(5) 3219-3227.

Median Loss Rate 0.42%

Gathering: 56 kg/

hr

/facility

Median Loss Rate 0.08%

Processing: 170 kg/

hr

/facilitySlide17

Mitchell

, A.L.,

Zimmerle, D., Marchese, A.J., Robinson, A.L. et al.

Measurements of Methane Emissions from Natural Gas Gathering Facilities and Processing Plants: Measurement Results. Environ. Sci

. Technol

.,

49

(5) 3219-3227.

25 facilities had methane loss rates > 1%

1%

9

% Emitter (660 kg/

hr

)

Mid-Size C/D Station (9.5

MMscfd

)

Three (3) 1150 HP

recipsNoticeable venting from PW TanksG&P: High-EmittersSlide18

9% Emitter (660 kg/

hr

)Mid-Size C/D Station (9.5

MMscfd) Three (3) 1150 HP

recips

Noticeable venting from PW Tanks

At 22

of the 114 sampled gathering facilities, substantial venting was observed from liquids storage

tanks

and the methane emissions from these gathering facilities was

3X compared to

facilities in which substantial

tank venting was

not

observed.

G&P: 9% emitterSlide19

Modeling Paper

Measurement Paper

From measurements to modeling

Field Campaign

Engineering Estimates

Study Onsite Estimate

Tracer Flux Measurement

GHGRP Result

Per Facility Comparison

National Model

Additional Data Sources

Additional Partner Meas.

GHGI

&

GHGRP

National ComparisonsSlide20

SummarySignificant new measurements of methane emissions from the T&S and G&P sectors

Tracer flux quantifies site-level methane emissionsIncludes* measurement of exhaust methaneQuantifies super-emittersMake EPA GHG Reporting Program comprehensiveInclude all major emission sources and sectorsUse updated emission factors, if not direct measurementsRemove the 25,000 MT-CO

2e reporting thresholdBetter identify and quantify super-emitters10% of sites => 50% of T&S emissions30% of sites => 80% of gathering emissionsSlide21

Questions?Email: subu@cmu.eduSlide22

EPA T&S methane inventory

Current:Emission factors: 1996 EPA/GRI (15 compressor stations) and 2010 ICF data

Activity factors: Pipeline miles scaled to 1990s survey, with some modificationsFuture?Can we use the GHGRP data from ~500 compressor stations?Slide23

Downwind tracer flux: Facility-level Methane Emission RatesLamb et al. (1995) used sulfur hexafluoride (SF

6) as tracerWe use nitrous oxide (N2O) and acetylene (C2

H2)Slide24

Tracer Flux: Method AssumptionsMethane and tracer(s) equivalently dispersedCheck correlation between methane and tracer(s)

Second tracer verifies assumptionAll methane sources at a site captured downwindDual tracers (up to 200m apart) encompass the siteNo other source of tracersUpwind and downwind transects with tracers off

Background-corrected methane from target siteUpwind transectsUse ethane as a signature for natural gas methaneSlide25

Ethane: Signature for natural gas emissions

Ethane lifetime ~2 months, compared to ~10 years for methanePlume dominated by natural gas ethane, not backgroundThe Aerodyne TILDAS provides mobile 1-Hz ethane measurements

Downwind Plume MeasurementsPartner-provided Gas CompositionSlide26

Tracer flux: From plume capture to methane emission rates

Uncertainty ±17% (dual tracer correlation) to ±34% (area plumes)

Methane (ppm)Ethane (ppb)

Acetylene (ppb)

N2

O (ppb)Slide27

Onsite Estimate vs Tracer Flux

1 standard ft3/min = 1.15 kg/hourSlide28

The EPA GHG Reporting Program

From 2011, mandates

reporting of CO2, CH4, N2O

Only facilities that emit over 25,000 MT-CO

2e (annualized)