Natural Gas Pipeline Leaks and Emissions Andy Greenspon HEJC March 18, 2015 Natural Gas vs. CO2 • Natural gas: primarily methane CH4. • Global average atmospheric levels: – CO2 ~ 400 ppm = 400,000 ppb. – CH4 ~ 1,800 ppb = 0.45% of CO2 levels. • Lifespans: – CO2: centuries – CH4: decades (half life of 7 years in atmosphere) – Natural gas is a much more potent greenhouse gas than CO2 • ~20-‐25 Rmes more over the long term (100 years). • ~72 Rmes more over a 20 year horizon. Natural gas producRon and atmospheric methane levels. • Methane levels have steadily risen since the start of the industrial revoluRon in 1750. • Leveled off in the early 2000s. • Started rising again in the late 2000s (due to the natural gas boom??) U.S. natural gas producRon and pipelines Natural gas producRon and distribuRon compressor staRons Pipeline infrastructure is vast and distributed – companies control many different geographic regions and different types of pipes (material, age, size, miles of piping). Unaccounted for natural gas • Gas distribuRon companies in 2011 reported releasing 69 billion cubic feet of natural gas to the atmosphere. – Almost enough to meet the state of Maine’s gas needs for a year. – Equivalent to ~33.3 million metric tons of CO2. • Equivalent to CO2 emissions of ~ 6-‐7 million automobiles. – Reference: CO2 emissions in 2014: 32.3 billion metric tons • Natural gas released contributes equivalent of only ~0.1% of total CO2 emissions. • Natural gas unaccounted for in 2000-‐2011: – U.S.: 2.6 trillion cubic feet – Massachuse]s: 99 -‐ 227 billion cubic feet of natural gas – Natural gas distribuRon systems (main pipelines and smaller distribuRon networks and mains): 19% of total CH4 emissions from natural gas systems. Conversion factor assumpRons: – 1 billion cubic feet CH4 = 19,300 metric tons CH4 – 1 metric ton CH4 = 25 metric tons CO2 equivalent – 1 billion cubic feet CH4 = 482,500 metric tons CO2 equivalent newable chigan, y, Camdminisder, CO. ment of Energy bridge, eley, CA. ersity of onmen- supplere those the U.S. espond- This study presents a first effort to systematically compare published CH4 emissions estimates at scales ranging from devicelevel (>10 3 g/year) to continental-scale atmospheric studies (>1013 g/year). Studies known to us that (i) report measurementbased emissions estimates and (ii) compare those estimates with inventories or established emission factors (EFs) are shown in the first chart. Studies that measure emissions directly from devices or facilities (“bottom-up” studies) typically compare results to emissions factors (EFs; e.g., emissions per device). Large-scale inventories are created by multiplying EFs by activity factors (e.g., number of devices). Studies that estimate emissions after atmospheric mixing occurs (“atmospheric” studies) typically compare measurements to emissions inventories, such as the U.S. Envi- Atmospheric natural gas measurements vs. claimed emissions factors Brandt, et al. (2014). Ratios with common baseline (EPA GHGI) Ratios as published 1015 1014 1013 1012 12 10 1011 1010 0 1 2 3 4 5 6 7 8 109 Scale of measurement National or continental Multi-state Regional or air basin Facility Device or component 6 10 Downloaded from www.sciencemag.org on March 15, 2015 akage other techUnited mateasurenvenl CH4 ors as epenumber e for a gional ssions f typissessshow large al-to- Underestimation—Device to Continent Emissions magnitude (g CH4/year) bridge rbons carer fosstries. rming ompoG use recent e benlarge uction pheric th the • Emissions factor (EF): esRmated emissions per device. • Inventory: EF x number of devices • RaRo >1 indicates emissions are larger than expected from emissions factor or inventory claimed. Summary of studies: • Emissions are overall underesRmated. • State and regional studies predict larger Ratio: measured/inventory or measured/EF [unitless] underesRmaRon than naRonal studies. • NaRonal studies, which average outliers be]er, suggest 1.25-‐1.75 Rmes the Inventories and emissions factors consistently underestimate actual measured CH emissions across emissions than expected from the scales. Ratios >1 indicate measured emissions are larger than expected from EFs or inventory. Main graph compares results to the EF or inventory estimate chosen by each study author. Inset compares results to green house gas inventory of the EPA. regionally scaled common (17), scaledC toH region study and (in some cases) under Challenge: adenominator ]ribuRng eofmissions to themsector ulRple 4 examination. Multiple points for each study correspond to different device classes or different cases measured in a single study. nitions of error(bar bounds vary between studies. (US,a United Can, Canada; potenRal sDefi ources anthropogenic nd States; natural). SC, South Central; Petrol. and Pet., petroleum; SoCAB, South Coast Air Basin; LA, Los Angeles; DJ, DenverAttribution Attributed to oil and gas or measured at facillity Attributed to energy indust. or not attributed 103 0.01 (6): US (5): US + Can (8): US energy (13): US energy 0.1 1.0 (6): SC-US (9): SC-US (6): SC-US, NG + Petrol. 10 (12): SoCAB I (1): UT (12): SoCAB II (7): all sources 100 1000 (2): SoCAB (2): SoCAB, NG + Pet. (10): LA county (3): DJ basin (25): DJ basin (14): Gas plants (26): Production + HF (18): Compressor (15): Gas plants (21): Gas plants, other (16): Distribution 4 Julesberg; UT, Utah; HF, hydraulic fracturing). See SM for figure construction details. Reported gas leaks in Massachuse]s Grade 1 – hazardous Grade 2 – potenRally hazardous Grade 3 – non-‐hazardous Companies ofen ignore grade 3 leaks. But in aggregate they can make significant contribuRons to CH4 emissions. To quantify the fraction of the observed ΔCH4 that was due to Nahant (NHT)] measurement stations (black points) in Boston, and the surNG emissions, we compared ratios of C2H6 and CH4 measured rounding area, overlaid on a map of the number of housing units with NG in the atmosphere and NG pipelines serving the region. Ethane per square kilometer (14). The 90-km radius circle delineates the ∼18,000is a significant component of NG, whereas microbial CH4 sources, 2 km land area for which CH4 emissions and the NG loss rate were calculated. such as landfills, sewage, and wetlands, produce little or no C2H6 The magenta and purple contours enclose 50% of the average footprint (15). Because Boston has no geologic CH4 seeps, no oil and gas (sensitivity area) of the BU and COP afternoon measurements, respectively. production or refining, and low rates of biomass burning, there The two city sites are difficult to distinguish at this scale because the horizontal distance between them is ∼2 km. The influence area is ∼80% larger are no known significant sources of C2H6 in the region other for COP than BU because the former station is higher. See SI Appendix, Table than NG. Methane concentrations in Boston were consistently elevated S2, for additional measurement site location Housing information. Measurement sites units Ethane concentrations were measured with a laser spectrom- QuanRtaRve study of gas leaks in the Boston area background (Fig. 2 and SI Appendix, Figs. S1 and S2) and • over Atmospheric CforH34 mo c(Fig. oncentraRons easured (15) at BUpattern in 3the winter of and followed aeter distinct daily A fall andand C, and SI m Ap-2012–13 1 mo in the late spring of 2014 (SI Appendix, Fig. S6). Covariances pendix, Fig. S16), associated with growth and decay of the Methane Concentrations in the Boston Atmosphere conRnuously from CSHep and2fluctuated 012 o Aug 2013 at four CH t observations planetary between boundary atmospheric layer. Concentrations over short were deAtmospheric CH concentrations were measured continuously from Fig. the daily slopes of a linear model that minimizes χ timescalestermined (SI Appendix, S1) due to small-scale atmospheric locaRons: from September 2012 through August 2013 at two locations near (16) of heterogeneous 5-min median sources afternoon dataurban (Fig. environ4 and SI Appendix, circulations and in the the urban center [Boston University (BU) and Copley Square sectionconcentrations S2.1). The median ofhigher the daily slopes of atmospheric CH ment. • Methane in winter than the Two urban cwere enters: Bless U awith nd Cseason opley (COP)] and two locations outside of Boston [Harvard Forest versus 2.6but (2.5, 2.8) varied % during the cool and 1.6 other seasons at CH bothwas sites, ΔCH season (HF) and Nahant (NHT)] (Fig. 1 and SI Appendix, Table S2 and2). The 1.7) l% during afternoon the warm season, obtained with at from BU Hdays (Fig. average annual values of B ΔCH • (1.4, Two ocaRons outside oston: arvard section S1). Background concentrations in air flowing into coefficient of determination 0.7539.3) (∼50% andthe COP awere 45.9 (37.3, 58.5) ppb and (R 30.5) > (23.6, ppb,of the days). city were estimated by randomly sampling from a range (5th to respectively (Fig.average 2), reflecting different altitudes (30 The C HN and CH sampling ratio in the NG flowing into the Forest and ahant 35th) of lower percentiles of CH measurements from two andup-215 region m, respectively; SItwo Appendix, Table measurement S2). All errorsperiods was during the atmospheric wind stations (HF or NHT, depending on the direction ofreported simthroughout thethe paper aresampling 95% confidence intervals. 2.7 ±- 0.0% in fall and winter of 2012–2013 and Random over 48 2.4h ±p0.1% eriods to ulated air trajectories; SI Appendix, section S3.1), averagedUncertainties over (Fig. 2) were calculated through a bootin spring ΔCH of in the 2014, determined from hourly gas quality data strap background af- (17, 18) (SI a 48-h moving window, to capture synoptic-scale variability andanalysis get main background concentraRons fromthat the included three pipelinesconcentrations that serve the and region 42.5 0 with NG km−2 4000 2 50 km 4 6 4 2 500 2 HF BU NHT COP 4 100 4 2 2 10 6 4 41.5 4 6 4 42.0 Latitude 43.0 43.5 Study Boundary BU 50% influence contour COP 50% influence contour 4 0 measurements ternoon hourly, daily,Figs. and seasonally CH4S2.2). remove possible influences of −70.5 small nearby sources (SI Appendix, −72.5 −71.5 Appendix, S7 and S8,averaged and section The quotient of the (SI Appendix, section S3.3). were calculated by subtracting section S3.3). Values of ΔCH C2H6 and CH4 ratios in the atmosphere and pipeline demon4 Longitude background from urban concentrations. Hourly average ΔCH4 strates that NG contributed 98 (92, 105) and 67 (59, 72) % of the Contribution of NG to Elevated CH4 Concentrations Fig. 1. data Location of aggregated two city [Boston (BU), 29-m(11–16 height; hCopley were intoUniversity daily afternoon EST, 16–21 h ΔCH4 in Boston in the cool and warm seasons, respectively. Square (COP), 215-m height] and two peripheral [Harvard Forest (HF); To on quantify theresult fraction the observed due tothe relative 4 that wasabout UTC) means to remove autocovariance and focus the analysis This is of insensitive to ΔCH assumptions Nahant (NHT)] measurement stations (black points) in Boston, and the surH and CH measured NG emissions, we compared ratios of C 2 6 4 4 contribution of the three pipelines that supply the region and of well-mixed atmospheric conditions. roundingperiods area, overlaid on a map of the number of housing units with NG in the atmosphere and NG pipelines serving the region. Ethane per square kilometer (14). The 90-km radius circle delineates the ∼18,000is a significant component of NG, whereas microbial CH4 sources, loss rate were calculated. km2 land area for which CH4 emissions and the NG4 such as landfills, sewage, and wetlands, produce little or no C2H6 The magenta and purple contours enclose 50% of the average footprint (15). Because geologic CH4 seeps, no oil and gas (sensitivity area) of the BU and COP afternoon respectively. A measurements,BU B Boston has noCOP production or refining, and low rates of biomass burning, there The two city sites are difficult to distinguish at this scale because the horizontal distance between them is ∼2 km. The influence area is ∼80% larger are no known significant sources of C2H6 in the region other for COP than BU because the former station is higher. See SI Appendix, Table than NG. S2, for additional measurement site location information. Ethane concentrations were measured with a laser spectrometer (15) at BU for 3 mo in the fall and winter of 2012–13 and 1 mo in the late spring of 2014 (SI Appendix, Fig. S6). Covariances Methane Concentrations in the Boston Atmosphere between atmospheric C2H6 and CH4 observations were deAtmospheric CH4 concentrations were measured continuously termined from the daily slopes of a linear model that minimizes χ2 from September 2012 through August 2013 at two locations near (16) of 5-min median afternoon data (Fig. 4 and SI Appendix, the urban center [Boston University (BU) and Copley Square section S2.1). The median of the daily slopes of atmospheric C2H6 (COP)] and two locations outside of Boston [Harvard Forest versus CH4 was 2.6 (2.5, 2.8) % during the cool season and 1.6 SON DJF Table MAM S2 JJAand ANN SON DJF MAM JJA ANN t al. (2015). (HF) and Nahant (NHT)] (Fig. 1 and SI Appendix, (1.4, 1.7) % during the warm season, obtained McKain, from daysewith 2 sectionFig. S1). Background concentrations in air flowing into the coefficient determination (R right ) > 0.75 of and the for days). 2. Average (±95% confidence intervals) afternoon (11–16 h EST)aCH y axis) and ΔCH4 (blue; y axis)(∼50% by season the whole year at 4 (black; leftof city were randomly sampling from a range (5th to (A) estimated BU and (B) by COP. The average C2H6 and CH4 ratio in the NG flowing into the 1880 120 ∆CH4 (ppb) 100 80 20 40 60 2000 1960 CH4 (ppb) ∆CH4 (ppb) 1920 120 100 80 20 40 60 1960 1920 1880 CH4 (ppb) 2000 • Values of ΔCH calculated by subtracRng background from urban concentraRons. • Hourly average ΔCH data aggregated into daily afernoon means (11-‐16 h EST). MAM JJA ANN DJF MAM JJA ANN MAM JJA ANN SON DJF MAM JJA ANN 0 1 2 3 • Leak rate corresponds to ~300,000 m1944 etric tons of natural gas leaked over the | www.pnas.org/cgi/doi/10.1073/pnas.1416261112 2012-‐2013 year studied — about 2.7 % of all natural gas delivered to the region of study. - 7.5 million metric tons CO2 equivalent or CO2 emissions from ~1.5 million passenger vehicles. - Gas valued aANN t $90 million and could heat 200,000 homes in a year. SON DJF MAM JJA • (±95% State and intervals) federal authoriRes previous esRmate: 1.1 % obyf nsector, atural nd annual average confidence (A) optimized CH emissions in total and from NG, (B) NG consumption and (C)gas was being ed from CH concentration observations from the BU and COP sites together. (B) Consumption categories are electric power, residential lost tofo industrial, leaks fvehicle rom fuel, a rand ange oand f sources in (SIthe area, including homes, businesses, nd other, which is comprised pipeline distribution use Appendix, section 3.2.1). and electricity generaRon faciliRes. org/cgi/doi/10.1073/pnas.1416261112 et al. • If correct, Boston area would be contribuRng 9% of U.S. mMcKain ethane from natural gas – implies naRonal esRmate is also low. Nat. Gas Loss Rate (%) 200 3 Fig. 5. Seasonal and annual average (±95% confidence intervals) (A) optimized CH4 emission NG loss rates, derived from CH4 concentration observations from the BU and COP sites togeth and commercial, and other, which is comprised of industrial, vehicle fuel, and pipeline and d McKain, et al. (2015). 4 4 SO 2 0 SON DJF 1 600 400 200 0 DJF C Nat. Gas Loss Rate (%) 800 Nat. Gas Consumption (g CH4 m−2 yr−1) 15 10 0 SON 4 C Elec Power Res & Com Other RaRo of C2H6 to CH4 determines proporRon of natural gas contribuRon to CH4 emissions 20 25 30 B Total Nat Gas 5 CH4 Emissions (g m−2 yr−1) A SON 4 0 5 QuanRtaRve study of gas leaks in the Boston area 0 10 Nat. Gas Consu (23). Emissions of NG in our study area are equal to ∼8% of US emissions attributed to distribution, transport, and storage, and ∼23% of national emissions from distribution alone, a notably higher fraction than the ∼3% of US residential and commercial CH4 Emiss nalysis makes no assumptions about the relative emissions of specific NG-consuming sectors or ses (SI Appendix, section S3.2.1), which could e very different loss rates than the aggregate Primary cause of natural gas leaks – old infrastructure • Cast iron and bare steel: – Leak 18 Rmes more gas than plasRc pipes. – Leak 57 Rmes more gas than protected steel. • In 2012, Massachuse]s had: – 5,482 miles of leak-‐prone mains. – 194,326 miles of leak-‐prone service lines. 2013 MassachuseAs State Rank for Pipeline Material Rank Item 2 Most miles of cast iron service lines 3 Most miles of cast iron mains 4 Most miles of bare steel service lines 9 Most miles of bare steel mains 6 Most miles of pipeline from cast iron and bare steel New England Gas Main Milesb New England Gas Service Linesb 17 -1% -1% -1% -2% -3% -3% 8% -4% 185 -5,637 -2% -5% -2% -11% -13% -19% 448% -5% 8,813 Nstar Gas Main Miles 145 -3% -2% -2% -2% -3% -2% -3% -3% 716 -4% Lack of incenRves to repair “minor” leaks Table 6: Replacement rates for leak-prone pipeline in Massachusetts, by company, 2004-2012 17 Nstar Gas Service Lines Wakefield Municipal Gas & Light Main Miles Wakefield Municipal Gas & Light Service Lines Westfield Gas & Electric Main Miles Westfield Gas & Electric Service Company Name Lines • 9,303 -2% -4% -2% -3% -4% -4% -5% 26,514 11 Leakprone 529 Pipeline Replaced 15 Since 2004 493 -1% -3% -4% -1% -1% -9% rate -4% Replacement -3% 37 0% -4% -4% -1% -4% -7% -8% -2% -4% -2% -2% -2% -5% -4% -1% -10% 2005 14% 2006 -7% 2007 -6% 2008 -8% 2009 -6% 2010 -4% 2011 -4% 2012 -5% Leak1,463 prone Pipeline 42 Remaining in 2012 1,543 Massachusetts - Main Miles Berkshire Gas - Main Miles Massachusetts - Service Berkshire Gas - Service Lines Lines Blackstone Gas - Miles Main Miles National- Main 1,293 23 -3% -2% -3% -73% 0% 251% -2% -2% -2% -2% -3% -2% -3% -3% -4% -4% 5,571 115 1,088 28,419 220,944 -3% -2% 0% -5% -3% -4% 0% -3% -3% -2% 0% -3% -2% -3% 0% -2% -2% -4% 0% -4% -4% -3% 0% 3% -2% 0% 100% -4% -5% -4% 0% -3% 3,864 194,326 093,705 Blackstone Gas - Service Lines National- Services 02,036,032 0% -10% 0% 4% 0% -2% 0% -2% 0% -4% 0% -35% 0% -4% 0% -12% 02,568,279 Source: Staff analysis of PHMSA’s Cast and Wrought Iron and Bare Steel Pipeline Inventory, available at: http://opsweb.phmsa.dot.gov/pipeline_replacement/cast_iron_inventory.asp and http://opsweb.phmsa.dot.gov/pipeline_replacement/bare_steel_inventory.asp respectively. Boston Gas - Main Milesa,b 496 -1% -2% -1% -1% -2% -3% -2% -3% 2,997 Notes: According to PHMSA officials, changes in replacement rates are generally due to three factors: (1) pipeline replacement, (2) acquisition of or selling off part of a distribution pipeline, or (3) changes in pipeline classification due to updated information or recordkeeping. a,b BostonbyGas - Service Lines 6,609 -2%in 2010. 13% -1% -2% -3% -5% -3% -3% 90,523 a Owned National Grid. Essex Gas was merged into Boston Gas b Participating in Massachusetts’ Targeted Infrastructure Replacement Program. Fitchburg Gas & Electric applied in 2011. In many states, gas companies pass on the cost of lost gas to customers. 16 – MassachuseAs customers lost $640 million to $1.5 billion from 2000-‐2011 due to leaked gas. • Replacing old pipes significant capital. 189 requires -1% -2% -2% upfront -3% -3% -5% Colonial Gas - Main Milesa,b cColumbia Gas is a subsidiary of NiSource. -19% -17% 253 – 33 states, including Massachuse]s, have infrastructure replacement programs. 1,078 26% 1% -6% -8% -6% -3% -10% -10% 4,466 – But sRll li]le incenRve to accelerate pipeline replacement so long as companies can sRll pass b,c Columbia Gas - Main 344 -5%lost gas. -5% -4% -4% -3% -2% -4% -4% 979 costs oMiles n to customers for Colonial Gas - Service Linesa,b • -3% -3% -3% established -3% -3% limits -3% on -4% Only two states, P13,907 ennsylvania a-4% nd Texas, have the a46,622 mount companies can charge customers for l-1% ost gas. Essex Gas - Main Miles 23 -2% -4% -1% -3% -6% 1% -3% 111 Columbia Gas - Service Linesb,c a,b • – GasTexas: 2010 to 2533 012 gas -1% companies their o-2% f leak-‐prone service lines a,b Essex - Service Lines 4% reduced -2% -2% inventory -3% -3% -3% 4,433 by 55 percent ( 101,790 l ines). Fitchburg Gas & Electric - Main b Miles– 21 period, -83% 433% -3% -3% -3% reduced -3% -3% leak-‐prone -4% 66 service In this same Rme gas companies in Massachuse]s their Fitchburg Gas & Electric lines by just 4 p-490 ercent (8,278 lines). -8% Service Linesb -6% -14% -9% -8% 119% -6% -8% 3,379 As of 2013, only fi6 ve states a0% ll non-‐hazardous leaks t-2% o be repaired 0% required -2% -3% -3% 0% 0% 58 within a certain Rmeframe. City of Holyoke Service Lines 1,127 -2% -4% -2% -2% -5% -3% -7% -10% 2,557 City of Holyoke Main Miles Methods to detect and reduce pipeline leaks • Include all emissions sources in inventory for possible leaks, including: – downstream of customer meters – industrial faciliRes – residenRal and commercial serngs. • Improve sampling protocols and develop more comprehensive leak surveys. – negaRve unaccounted for gas volumes by companies indicate calculaRng or reporRng errors – infrequent high emission events are under-‐sampled. – small leaks require more sensiRve equipment to detect • Replace old mains and service lines sooner rather than later. New MA law to promote repair of pipeline infrastructure • Passed in July 2014: An act relaRve to natural gas leaks – Grade 1 (hazardous) leaks must be repaired unRl hazard is eliminated. – Grade 2 (potenRally hazardous) leaks required to be repaired within a year. – Grade 3 (non-‐hazardous) leaks must be reevaluated. – Gas companies accountable for plans to remove leak-‐prone infrastructure. • What’s sRll missing: – Ratepayers sRll pay the cost of lost gas. – Grade 3 leaks don’t actually have to be repaired on any Rmetable. – No requirement to acRvely replace old cast iron and bare steel pipes without leaks. OpRmism for the future? • Based on EPA assumpRons, Massachuse]s residents stand to realize $156 million in net benefits over 10 years from the companies parRcipaRng in MA infrastructure replacement program. • State law requires Massachuse]s to reduce GHG emissions to 25 percent below 1990 levels by 2020. • By 2010, Massachuse]s had already succeeded in reducing methane emissions from the natural gas distribuRon system by 14 percent below 1990 levels. New pipeline proposal through MA/NH – 2018? • Capacity to transport up to 2.2 billion cubic feet of natural gas per day from wells in Pennsylvania to markets in the Northeast. • Co-‐locaRng with exisRng right of way uRlity corridors. • 65 and 90 % of affected landowners in MA and NH respecRvely have not granted permission to enter their land for surveying purposes. - Possible eminent domain authority to pursue access to those denied properRes if pipeline wins a cerRficate from federal regulators. QuesRons?
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