JOURNAL OF GEOPHYSICAL
RESEARCH, VOL. 104, NO. D3, PAGES 3457-3470, FEBRUARY
20, 1999
Global nitrogen and sulfur inventoriesfor oceangoingships James J. Corbett Departmentof Engineeringand PublicPolicy,CarnegieMellon University,Pittsburgh,Pennsylvania
Paul S. Fischbeck Departmentsof Socialand DecisionSciences andEngineeringandPublicPolicy,CarnegieMellon University Pittsburgh,Pennsylvania
SpyrosN. Pandis Departmentsof ChemicalEngineeringand Engineeringand PublicPolicy,CarnegieMellon University,Pittsburgh Pennsylvania
Abstract. We presentgeographically resolvedglobalinventories of nitrogenandsulfur emissions frominternational maritimetransport for usein globalatmospheric models. Currentinventories of globallyresolvedsources of naturalandanthropogenic emissions do notincludethe significantcontribution of SO2or NO• fromoceangoing ships[Benkovitzet al., 1996]. We estimatetheglobalinventoryof shipemissions, usingcurrentemissiontest datafor ships[Carltonet al., 1995] anda fuel-basedapproach similarto thatusedfor automobileinventories[SingerandHarley, 1996]. This studyestimates the 1993 global
annual NOxandSO2emissions fromships tobe3.08teragrams (Tg,or1012 g)asN and4.24 Tg S, respectively.Nitrogenemissions from shipsare shownto accountfor morethan 14% of all nitrogenemissions fromfossilfuel combustion, andsulfuremissions exceed5% of sulfuremittedby all fuel combustion sourcesincludingcoal. Shipsulfuremissions correspond to about20% of biogenicdimethylsulfide (DMS) emissions.In regionsof the NorthernHemisphere,annualsulfuremissions fromshipscanbe of thesameorderof magnitudeas estimatesof the annualflux of DMS [Chinet al., 1996]. Monthlyinventories of shipsulfurandnitrogenemissions presented in thispaperaregeographically characterized
ona 2øx 2øresolution. Temporal andspatialcharacteristics of theinventory arepresented. Uncertaintyin inventoryestimates is assessed: thefifth andninety-fifthpercentilevaluesfor globalnitrogenemissions are 2.66 Tg N and4.00 Tg N, respectively; thefifth andninetyfifth percentilevaluesfor sulfuremissions are 3.29 Tg S and5.61 Tg S, respectively.We suggestthattheseinventories,availablevia the ShipEmissions Assessment (SEA) web site, be usedin modelsalongwiththeGlobalEmissions InventoryActivity(GEIA) inventories for land-based anthropogenic emissions andmodeledwithocean-biogenic inventories for DMS.
1. Introduction
Global and regionalassessment of atmosphericchemistry, air quality, and anthropogenic influenceson climatic factors (e.g., cloud formation)dependupon accurateand complete emissioninventories.Producingsuchinventorieshasbeenan important endeavorin regions where air quality concerns receivepublicattention.Regionalestimatesfor anthropogenic and biogenicemissionshave been aggregatedto assemble global inventories. However, ship emissionshave not been addressed in a coherentmannerin any existinginventoriesof SOx and NOx emissions [Benkovitz et al., 1996]. In most
sulfurand admittedly have misassigned their geographic distributions byattributing emissions fromtrade(byshipsand otherwise)to the nationsof export. National emission inventoriesexclude internationalship fuel, or bunkers [b•ternational EnergyAdtninistration (lEA), 1987]. In fact, nationsseparate inventories of fuel suppliedto international shippingwith the objectiveof removingthese fuel distributions from their domestic inventories of energy
consumption. Regional inventories typically includedomestic emissions only,admittingdifficultyin includingcommercial ship emissions[U.S. EnvironmentalProtectionAgency (EPA), 1991]. Regionalinventoriesfor ships often use methodologies that approximate emissions basedon trade
cases,methodologies to determineglobalemissionsassignall energyemissions(includingship emissions)to land masses volume;herethecomplexities of oceantradelimit thescopeto [Spiro et al., 1992]. These attempts appear to have only a few typesof cargo,thusunderestimating emissions significantlyunderestimated ship emissionsof nitrogenand [Streetset al., 1997]. The mostcomplete regionalstudiesof Copyright1999by theAmericanGeophysical Union.
international ship emissions assemble detailedinformation aboutrouteorigin and destination, ship size, powerplant
Paper number 1998JD100040.
characteristics, speed,and otherparameters, from everyport in the regionstudied[Carltonet al., 1995]. Only recently,
0148-0227/99/1998JD100040509.00
3457
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CORBET'FET AL.: GLOBALNOx AND SO2EMISSIONSFROM SHIPS
regionalstudieshavebegunto includeemissionsfrom ships as sulfur, ash, asphaltenes,and metals has increasedin residualfuels [Ewart, 1982; htternationalOrganizationfor in comparisons with globalemissions [Cooperet al., 1996]. Air pollution control of mobile sources presents a Sta•wlardization (ISO), 1987]. Residual fuel has been multidisciplinary, technicalpolicy problemfor all formsof describedas "black, thick as molassesand has an odor that's transportation, but the problemof estimatingand controlling pungentto put it politely"[Brubakerand Eley, 1992]. By air pollutionfrom oceangoingships carryinginternational contrast, "other" bunkers include marine distillate oils of cargois particularlycomplex.Currentinternational policy highergrade;however,theyoftenconsistof a blendof heavier effortsby the InternationalMaritime Organization(IMO) to fractions (residuals) with distillate oils and are not to be reduceair pollutionfromshipsystemsmarkthefirstattempts confusedwith the more highly refineddieselfuels usedin to definea policyframeworkfor addressing theseproblems. motorvehicles. Becausefuel is the greatestsingleoperating The policy implicationsof a global understanding of ship costfor a ship, commercialshipperspreferto use residual emissions inventories have been discussed [Corbett and fuels if their enginescan accommodate its poorerquality Fischbeck,1997]; this paper providesa full technical [Brubakerand Eley, 1992]. discussionof the data sets that we have developed. We suggestthat theseinventories be combinedwith the Global 1.2. Current PolicyStatusand TechnicalStudies EmissionsInventoryActivity(GEIA) inventoriesin modeling The IMO's Annex VI, Regulationsfor the Preventionof anthropogenic emissions.Scientistscan us the inventories Air Pollutionfrom ShipslIMO, 1996]addresses severalforms presented hereon bothglobaland regionalscalesto reduce of air pollutionfrom shipsincludingoxidesof nitrogenand uncertainty in existinginventories of anthropogenic emissions oxidesof sulfur. Whereaspreviousenvironmentalpolicy and to better model the effects of these emissions on actionsby IMO have focusedon protectingthe marine atmospheric chemistryandregionalair quality. environment, the motivationfor controllingshipair emissions concernspotential impact on land regions and coastal populations.IMO's NO,, controlregulationsapply to new 1.1. Ship PropulsionOverview engineinstallations and majorconversions after January1, The world'sshipsareprimarilypoweredby dieselengine 2000. SO,`controlregulations applyto all shipboard fuels systems, consisting of oneor moredieselenginesin oneof (bunkers), cappingfuelsulfurcontentat 4.5% (by weight)and threetypicalpropulsion configurations.Dieseldirect-drive outliningprovisions for SO,`EmissionControlAreas. (The engines aretypicallylarge,slow-speed dieselengines directly BalticSeais the onlyregioncurrentlydesignated by IMO to connected to the propeller;they rotateat exactlythe same be a SO,•EmissionControlArea.) Shipsoperatingwithin revolutions per minute(rpm) as the propeller(0-130 rpm), SO,, Emission Control Areas must use reduced-sulfurfuels
exceptwhenconnected tocontrollable pitchpropellers. Diesel (lessthan or equalto 1.5% by weight)or apply exhaustgas gearengines drivethepropeller indirectly, througha setof sulfur emission controls. gears,allowingenginespeedto be selected independently of Studiesbegan measuringship emissionsfrom marine propeller rpm. Dieselelectricengines drivegenerator systems dieselpropulsionenginesin the late 1980s. The most that turn the propeller;theseenginestypicallyoperateat comprehensive study to date was conductedby Lloyd's constantspeedwith electricpowerprovidingvariablepower Register of Shipping and was reportedin three phases
to the shaft. Diesel electric and diesel gear enginescan [Carltonet al., 1995;Lloyd'sRegister,1990, 1993]. Phase operateat speedsgreaterthan propellerrpm; these are one lookedat medium-and slow-speeddieselenginesand generallymedium-speed enginedesignsoperatingbetween measured steadystateemissions at variousshipengineloads 130 rpm and2000 rpm. A fourthmajorcategory of marine from approximately 60 engineson 50 vessels[Carltonet al., engine,steam-turbine systems,relies on conventionalsteam 1995]. Phase two studied transientemissions,and phase generation to drivea turbine(s)gearedto the propellershaft; threequantifiedregionalship emissions.Thesedata are the thesesystems havethermalandfuelefficiency lowerthanthat bestcurrentlyavailableto evaluateshippropulsion emissions, of modemmarinediesels[Packard,1984]. Otherpropulsion althoughthe sampleset is small in comparisonwith the systems include combustion turbines and older or approximately 86,000 registeredcommercialvessels[Lloyd's nontraditionalpropulsiondesignssuch as wind-powered Maritime b•formation Services(LMIS), 1996] and 20,000 vessels,reciprocatingsteampistons,and nuclear(for some militaryvessels[AdcockandStitt,1995]operating globally. militaryvessels). As technology for large marinediesel enginesenabledtheconsumption of lower-cost residualfuels,
2. Global Inventory of Ship Emissions
thesebecamepreferredover the steamplant technology. Dieselenginesconsume lessfuel thando otherpropulsion Our estimationof globalshipemissionsis basedon three systems [Packard,1984;Osbourne, 1943]andhavereplaced primary sources: (!) marine exhaustemissiontest data by steam-turbinesystemsthat were dominantin the 1940s [Turpinand McEwen, 1965]. Marine fuels,or bunkers,can be generallyclassifiedinto two categories:residualfuels and otherfuels. Residualfuels are a blendof variousoils obtainedfromthe highlyviscous residueof distillationor crackingafterthe lighter(andmore valuable)hydrocarbon fractionshavebeenremoved.Sincethe 1973 fuel crisis, refinerieshave used secondaryrefining technologies(known as thermal cracking)to extract the maximumquantityof refinedproducts(distillates)fromcrude oil. As a consequence theconcentration of contaminants such
Lloyd's Register [Carlton et al., 1995; Lloyd's Register, 1990] that reportsfuel-basedemissionrates for sulfur and nitrogenemissions,(2) internationalmarine fuel (bunkers) usage information reported in the Energy Information Administration's(EIA's) WorldEnergyDatabase[Malone)', 1996], and (3) engine characteristics (slow-speeddiesel, medium-speed diesel,and otherenginetypesincludingsteam turbine)for the world'sregistered shipsgreaterthanor equal to 100 grossregisteredmetrictons(t) from Lloyd'sMaritime InformationServices[LMIS, 1996]. The generalmethodology is illustratedin FigureI anddiscussed in detailbelow.
CORBETTET AL.: GLOBALNOx AND SO:EMISSIONSFROM SI-EPS Emission
Emission
Estimation
Ship Stack
Ship Registry
Emission
Data/
3459
Characterization
By Geographic
Data
Location
(ppm)
Fuel-Based Emission
By Vessel
Factor(s) (kgPollutant/
Characteristics
tonne f
(Enginetype, Vessel Type, etc,)
Global Ship Propulsion Emissions (kg Pollutant/yr)
Temporal and Spatial Resolutions
,•Annual Marine Fuel (Bunkers)
(Monthly,Seasonal, Latitudinal)
Used
(tonnes/yr)
Figure1. Generalmethodology for(a) estimation and(b) characterization of shipemissions.
2.1. Estimation Methodology
CONCAWE data for comparison with EIA data, EIA's consistencywith CONCAWE fuel This study analyzed data from Lloyd's Maritime demonstrating usages previously consideredby the Marine Environment Information Services to determine engineprofiles(Table1) for Protection Committee (MEPC), the IMO bodythat developed registeredcommercialvessels 100 gross registeredtons current language in Annex V1,Regulations for thePrevention (GRT) and greater[LM1S, 1996]. Data for naval propulsion of Air Pollution From Ships.) Fuel use data show that were providedby AMI Internationalin their Naval Main 70% to 80% of the bunkersused by Propulsion Market Overview lAdcock and Stitt, 1995]; approximately oceangoing shipsareresidualbunkers. militarysalesto world naviesby enginemanufacturers B&W, international, The Lloyd's research reported meanfuel-basedemission MAN, and Sulzer were assumedto be slow-speeddiesels, factors of 57 kg NO•/t fuel for medium-speed enginesand 87 sincethesefirms are leadingmanufacturers of suchengines. engines[Carltonet al., 1995]. The total world fleet (commercialand military) includes kg NO•/t fuel for slow-speed approximately55% slow-speeddiesel, 40% medium-speed Note that NOs emissionratesdependboth on the'type of system(because of peaktemperature profiles)and diesel, and 5% other engine types (the most common combustion to a lesser extent on the nitrogen content in the fuel. Sulfur nondieselpropulsionbeingsteamturbinetechnology). by contrast,dependsolelyon the The fuel-basedemissionsinventorywas computedfrom emissionsfrom combustion, fuel contentof sulfurand are independent of the combustion available fuel data for international marine bunkers. EIA's system (e.g., diesel engines, boilers, and gas turbines). The WorldEnergyDatabasereportsusagefor marinebunkersin Lloyd's study determined that sulfur dioxide (SO2) emissions international shipping[Malone),,1996]. This studyusedfuel follow an empirical relationship, where S% is the percent of usedatafrom the mostrecentyearsavailable,1992 and 1993. Table 2 presentsworld bunker usagefor theseyears,along sulfurcontainedin thefuel by mass[Carltonet al., 1995]: kg is simplytheresult with 1990 CONCAWE (The Oil Company's European SO2/tfuel= (20 * S%). (Thisrelationship of convening all fuel-sulfur to SO: during combustion, Organizationfor Environment,Health and Safety) reported expressed in the above units.) fuel usage data [CONCAWE, 1993]. (We include the Marine fuel specifications establishmaximumlimits for fuel sulfurcontentenablingmarineenginemanufacturers to Table 1. WorldShipEngineProfile Military Fleet
Commercial
Total Fleet
Fleet
En[tineTypes Number,%
-Slow-speed
1,289 (7%)
Number. %
56,628 (66%)
Number, %
1990
14,940 (76%)
27,758 (32%)
41,894 (40%)
1992
diesel
Steam turbine, other types Total vessels
Year
3,417 (17%)
1,820
(2%)
5,673
(5%)
1993 19,646
86.206
Data Source
58,287 (55%)
diesel
Medium-speed
Table 2. Annual World Marine fuel (Bunkers)Usage
105,854
CONCA WE
[1993] Maloney [1996] Maloney [1996]
Residual
Other Bunkers,
Bunkers,106t
106t
100
40
110
30
109
38
3460
CORBETI' ET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
designenginesthat efficiently performacrossa rangeof
studiesconsidered onlydomestic shipemissions or reliedon
marine fuel characteristics. Marine residual fuels have a
incomplete datatbr commercial shipping andthatregional
to air districtboundaries in their maximumsulfurcontentof 5% by weight;marinedistillate studieslimitedtheiranalyses fuelshavea maximum sulfurcontent of 2% by weight[ISO, scopeandignoredtransportfrom shipsoutsidetheircontrol 1987]. However, actual sulfur contentin fuels varies. In one volume(s). Theseconclusions aresupported by thegeneral studythe Fluid AnalyticalConsultancy Servicesat Lloyd's perception thatshipsoperatein theopenocean,andmoreover Registryassumedfuel sulfurcontentsof 2.7% and 0.5% for
that they are widely distributed,at distancesfar from
residualbunkersand marinedistillatefuels,respectively;populatedland regions. However, on secondlook these however,justification for these values or correlationwith "common sense"assumptions areclearlyquestionable, since actualaveragesulfurcontentwas not presented [Carltonet manyof theworld'smostpopulated regions developed along al., 1995]. In theworkpresented herewe usedtherangeof traderoutesincludingheavyshippingroutes. fuel sulfurvaluesreportedby CONCAWE andsubmitted to 2.2.1. Geographic domain.Evaluating theimportance of theIMO in 1993by the Oil Companies International Marine globalsulfuremissions to particulargeographic regions Forum [CONCA WE, 1993], as describedbelow. requiresa knowledgeof globalvessel-traffic densities.The Our global emissionscalculationsused the following Comprehensive Ocean-Atmosphere Data Set (COADS), equation to obtain the total emissionsfrom international Standardla, from the NationalCentertbr Atmospheric shipping: Research (NCAR)andtheNationalOceanic andAtmosphere Administration (NOAA), provides a source for this
Pp-' • Epi.(F.Ai)
(1)
i=1
•n...... aL.,.,nt,vuu•,tujj, 1996]. COADS is the mostextensive collectionof surface marine data available for the world ocean
over the past centuryand a half [Woodruffet al., 1993]. COADSStandardl a is a subsetof one of the longest Pp total propulsion emissions for pollutantP (either continuous climaterecordsin existence, begunin 1854 by nitrogenor sulfur); international agreementof the world maritimenations. The Ep, i fuel-based pollutant emission factorbased onengine Standardla data set summarizes on a 2ø latitudeby 2ø type(fornitrogen) or fueltype(forsulfur); longitude(2"x 2") resolution ship locationand weather where
F annualmarinefuel (bunkers)used; observations takenby merchant andnavalmariners coveting Ai percentof all vesselswith eachenginetype (for the periodof 1980-1993. By obtainingand plottingthe NO,,)or witheachfueltype(forSO2); numberof observations withineachgrid locationan estimate i forNO,,calculation: enginetype(1, slowspeed; 2, of the traffic densityof marine vesselscan be obtainedon mediumspeed;and 3, steam/other); for SO: calculation: fuel monthly,seasonal,annual,or evenmultiannuallevels. type(1, residualbunkers; 2, otherbunkers); The monthlysummaryof COADS observations for 1993 n numberof categories: threeenginetypesfor NO,, was usedhere. Global emissions(averagebestestimates) calculation; twofueltypesforSO2calculation. weredividedby thetotalannualCOADS shipobservations to Emission ratesfromLloyd'swereapplied todiesel engines. get the averageemissionsper observation.This value was A steamturbineemission rate of 8.8 kg NOx/tfuel was thenmultipliedby the numberof observations in each20 x 2ø derivedfromdatain a 1991 studyby TRC Environmentalgrid locationto map the distributionof global marine
Consultants, Inc.[Hottenstein, 1991].SincetheTRCstudy emissions. Thespatial distribution of theseemissions perunit
reportsonly hotellingemissions(emissions while at the dock areais presented, shownaloneand with the GEIA datasets, operatingat low loads),the emissionrate is considered to be a
in PlateI for sulfuremissions andin Plate2 for nitrogen lowerbound. The annualbestestimates for globalNO,, emissions.Sincethe grid sizesfor theseinventories are not emissions usedin thispaperwerecalculated byweighting the thesame,wecalculated theunitareas(whichalsovarywith yearlymarinefuelusebytheactualpercent of marineengines latitude) independently forthe2øx 2øshipsdataandthe1øx of eachtype(slow-speed diesel,medium-speed diesel,and 1oGEIAdata.Onecaneasily identify routes ofheavy trade, steamturbine)fromTablel. The average bestestimate for particularly in theNorthern Hemisphere. Thisgeographic annualnitrogen emissions is simplytheaverage of thebest analysis isbased onthefollowing assumptions: estimates foreachyear:10.12TgNO,,/yr(3.08Tg N/yr). The 1. Ship locationand meteorological observations
bestestimatesfor global SO2 from residualfuels use the summarizedin COADS representdata obtainedfrom Europeanaveragesulfurlevelof 3.3%; the bestestimates for commercial shiplog entriesvia the WorldMeteorological marinedieseloil, the mostcommonmarinedistillate,usethe
Organization's (WMO's)GlobalTelecommunication System
maximumallowablesulfurlevelof 2% [CONCAWE,1993]. (GTS)transmissions ongenerally equalintervals, ordinarily Theaverage bestestimate forSOxis 8.48Tg SO•/yr(4.24Tg every 6 hours(S.D. Woodruff,personalcommunication, S/yr). 1996). Observations madeat equalintervals allowus to assume a linearrepresentation of shipobservations withship 2.2. Characterization of ShipEmissions trafficdensity.
International shipshavebeenconsidered to bea relatively 2. COADSdatarepresent approximately 10%of the small air pollutioncontributor by most policystudies, worldfleetin number[Woodruff,1996]. We assume thatthe includingreportsby the U.S. EPA [EPA, 1991], studies COADSsummary is representative of globalmerchant and funded bystateandregional airdistricts [PortofLosAngeles navalshippingpatterns. et al., 1994], and those submitted to international bodies
3.
Global
estimates of
sulfur
emissions are
[CONCAWE,1993;Det NorskeVeritas(DNV), 1994]. The representative of actualshiptrafficprofiles(i.e., the vessel reasonstbr theselow estimatesmay includethat national types,bunkers usage,and emission profilesin eachgrid
CORBETI' ET AL.: GLOBAL NOx AND SO.,EMISSIONS FROM SHIPS
3461
Table 3 summarizesannualemissionsfrom shipsby global
Table 3. RegionalSummaryof ShipEmissions NitrogenFrom
SulfurFrom
Ships, T•/yr
Ships, Tg/yr
3.08 2.63
4.24 3.62
region. The NorthernHemisphere accounts for 85% of the world'sship emissions. The North Atlantic (including northern Europe)shiptrafficaccounts for 52% of globalship emissions; theNorthPacificregionaccounts for 27% of ship
North Atlantic a
1.61
2.22
emissions.
North Pacifict'
0.82
1.14
North Indian c
0.18
0.25
0.01 0.45
0.02 0.62
2.2.2. Vessel-typedomain. Characterizing emissions by vesseltypefollowsdirectlyfromLMIS data[LMIS, 1996], exceptfortheinclusion of militaryvessels, whicharenotpart of Lloyd's data. World military vesselquantityand propulsion characteristics wereprovided byAMI International in itsNavalMain Propulsion MarketOverview[Adcock and Stitt, 1995]. Figure2 summarizes the world fleet (both commercial andmilitary)andestimated emissions by vessel type.Thedataarepresented in percentage formatfirstforthe followingdata:(1) thepercent of totalfleetof 106,000ships, (2) the percentof totaldeadweighttonnage(DWT) in the world fleet, (3) the percentof global nitrogenemissions estimated by thisanalysis, and(4) the percentof estimated globalsulfuremissions. Thentheestimated percent of total
Globalshipemissions NorthernHemisphere
North of Russiaa SouthernHemisphere South Atlantic e
0.13
0.17
SouthPacificf
0.23
0.32
South Indian g
0.09
0.13
NorthernHemisphere watersbetweenNorthAmericaandEurope, with the Atlantic side of Central America (Gulf of Mexico) included(39øE to 97øW, IøN to 89øN).
Northern Hemisphere waters between AsiaandNorthAmerica, with the Pacificsideof CentralAmericaincluded(117øEto 89øW, 1øN to 89øN).
FromAfricato 115oE,including Indonesia waters,Northern Hemisphere.
Northernwaters(29øNto 89øN)between 4 IøEand115øE. SouthernHemisphere waters,Southern Africantip to southern tip
emissions for eachtypeof vesselis presented.
of SouthAmerica(21"E to 69øW, løS to 89øS).
The numberof vesselsand DWT in each vesseltype was
Pacific sideofSouth America to 117øE, including Australia (117øE
obtained directlyfromLloyd'sdataandAMI Intemational's to 71øW, løS to 89øS). report. To estimate theemissions contributed byeachtypeof AfricatoAustralia, Southern Hemisphere waters(115øEto vessel, brake horsepower data were used as an indicatorof 23øE,IøSto 89øS). relative fuel consumption. For commercialships this approach assumes thatall vessels operate alongsimilarengine locationare similar to the global vesseldistribution). We duty cycle profiles. This assumption was chosenbecause know of no regionswhereeconomics of tradeor otherfactors commercialships are designedto provideoptimumfuel would favor a lower-polluting,nondieselpropulsiontype in economy at somecruisingspeed.Enginesaresizedaccording commercialshipping. In heavily tradedroutes,larger ships with higher-polluting, slow-speed dieselsmaybe preferred for theirfuelefficiency; thissituationcouldadjustourdistribution slightly,althoughTable 1 showsthatslow-speed dieselpower
to a ship'sfull-loadweight. For an established cruisingspeed the fraction of rated engine RPM and engine power are relativelyconstant[MarkleandBrown,1996]. Thenumberof operatingcombinationsfor commercialships is limited, by the limited numberof duty cyclesin ISO alreadyis the dominantpropulsiontype. Thereforethis demonstrated 8178-4 [ISO, 1996]. similarityassumption appearsreasonable.
Self-Propelled Seagoing Vehicles 100%
I
I
Non-Transport 58% of Ships
Transport 42% of Ships 86% of DWT
14% of DWT
69% of NOx
31% of NOx
73% of SOx
27% of SOx
Bulk Cargo 15% of Ships
I
I
I General Cargo 23% of Ships
Passenger 4% of Ships
Fishing 23% of Ships
Service
Craft
15% of Ships
Other Military 19% of Ships Marine Craft 11% of DWT 1% of Ships
67% of DWT
18% of DWT
5% of NOx
7% of NOx
10% of NOx
13% of NOx
1% of DWT
35% of SOx
32% of SOx
6% of SOx
7% of SOx
10% of SOx
9% of SOx
1% of NOx
1% of SOx
Figure 2. World fleet of marinevehicles1996andestimatedemissions by vesseltype. Total (100%) valuesare as follows:106,000ships;771 milliondeadweighttonnage (DWT); 3.08 Tg N; 4.24 Tg S. Commercialvessels 100 grossregisteredtonsand greater[Lloyd'sMaritimeInformationServices(LMIS), 1996]; world military vesselsincludeall navalpropulsion lAdcockand Stitt, 1995].
3462
CORBET'F ET AL.: GLOBALNOxAND SO2EMISSIONSFROMSHIPS
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CORBET1r ET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
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CORBETT ET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
Military vesselpropulsion systemsare sizeddifferently 3. Comparison With Other Emission from commercial ships. They are sizedfor powerand Inventories performance definedby theirmilitarymission, notplantfuel economy.In fact, the navalshipis designedfor sustained We comparethis globalshipinventorywith otherestimates speeds in excess of theendurance (cruise)speed[Markleand in threecontexts.First, althoughour inventoriesare the first Brown,1996]. Averageenginepowercharacteristics for the to characterizefully ship emissionsglobally and by vessel U.S. Navyshowthatmilitaryshipsoperate below50% power type, we can comparethem to otherglobal or regionalship for 90% of the time that they are underway[NavalSea inventories. Second,we compareship emissionsto other SystemsCommand(NAVSEA),1994]. Moreover,military land-basedanthropogenicsources,particularly the GEIA shipsspendgreatertime in port than modemcommercial inventoriesof nitrogenand sulfur. Third, we compareship biogenicsulfuremissions, ships. Where a commercialship cannoteffectivelyearna sulfuremissionswith ocean-based, profitunless underway, militaryshipstypicallyspendasmuch namely,dimethylsulfide(DMS). as60%to 70% of theirtimein port[Westinghouse Machineo' Technology Division,1992]. A reviewof NavyNewsService 3.1. ComparisonWith Other ShipInventories Messages[NaD' Media CenterPublishing,1996]for various Ship emissionsreportedherecan be comparedto at least monthsin 1996 showsthatthe U.S. Navy deployedbetween two other global estimates (Table 4) and to two recent 29% and 57% of its fleet in any given month;typical regional estimates. On a global basis the SOx and NOx deployment ratesappearto rangebetween40% and 55% of inventoriesproducedby MARINTEK [Bremnes,1990; Kolle the fleet. For this analysisan averagemilitary vessel et al., 1989], cited by [Benkovitzet al., 1996], and produced deployment rateof 50% waschosen,althoughtheU.S. Naval by the EmissionsData for Global AtmosphericResearch deploymentrates may be greaterthan the world military (EDGAR) [Olivier et al., 1996] are significantlylower than average. To derive a fuel usefactorfor emissionsestimation, ours(Table 4). We suggestseveralreasonsfor this: (1) our inventoryused the Lloyd's registership inventoryshowing that commercial ship populationis more than 95% diesel powered[LMIS, 1996], wherepreviousstudiesassumed75% motor ships and 25% steamships;(2) the NOx emission
the military brake horsepowerwas multipliedby 22.5%, representing the productof the percentload(50% for 90% of time underway)and the percenttime deployed(50% of the time). This factor was directly applied to estimateNO,, emissionsfrom militaryships. In estimatingSO,,emissions frommilitaryvessels thefractionof militaryshipsusinghigh sulfurfuel is required.Of 154 oceannavies,up to 65% use lower-grade (higher-sulfur)fuels (G.A. Stitt, personal communication, 1996). For example,theenginemanufacturer MTU is the largestsupplierof marinedieselenginesto the worldnavies,andthecompany's enginesaredesigned to bum residualbunkerswithoutspecialfiltering(G.A. Stitt,personal communication,1996). The more developed navies, particularly NATO navies,usehigherdistillateswith verylow sulfurcontent.Applyingthisinformation, we multipliedthe militaryfuel usefactorderivedfor NO,, emissions by 65% to estimatemilitaryvesselSO,,emissions.
A primaryinsightprovided by thisanalysis is thattransport shipsemitmuchgreateramounts of nitrogenandsulfurthan their numberswould suggest. Approximately 70% of the world'sship nitrogenand sulfuremissions are emittedby transport ships;however,thetotalnumberof transport shipsis
factorsused in our study are the most currentavailable [Carltonet al., 1995]; (3) we usehigherfuel sulfurvalues, moreaccuratelyreflectingtheactualaveragefuel sulfurvalues of ship fuels [CONCAWE, 1993]; and (4) the inventoryyears are different (1993 in our case), reflecting difl•rent ship profilesand/or fuel consumption, althoughwe expectthis difference to be minor or even negligible. However, comparingcarbondioxide emissionsin EDGAR with our estimatefor CO2 providesbetteragreement(Table 4). This suggests thattheoverallmethodologies areconsistent andthat usingengine-specific emissionthctorsfor nitrogenand sulfur makesan importantdifference. Two regionalstudiesof international ship emissions are
also relevantfor comparison.Lloyds,underthe Marine Exhaust EmissionsResearchProgramme,producedan
inventoryof ship emissions for the northeastern Atlantic Ocean,including theNorthSea,theNorwegian Seas,theIrish Sea,andtheEnglishChannel,equivalent to theareaof study only 42% of ships in the world fleet. Within this vessel usedby the Convention of Long-Range Transboundary Air category,bulk cargovesselshavethe highestemissions (33% Pollution, CooperativeProgrammefor Monitoring and and 35% of nitrogenand sulfur estimates,respectively), Evaluationof the LongRangeTransmission of Air Pollutants lbllowedby generalcargovessels (31% and32% of nitrogen in Europe(EMEP) [Carlton et al., 1995]. This studywas and sulfurestimates,respectively), with passenger vessels contributing only 6% of worldnitrogenand sulfurestimates. Nontransport shipsemitmuchlesstbr two primaryreasons: Table 4. Comparisonof GlobalInventories for Ship 1. Although greater in number of ships, most Emissions nontransport vessels(fishingvessels,servicecraft, and other This EDGAR [01ivier MARINTEK ShipPollutant marinecraft) havesignificantly lessbrakehorsepower than transportships.
Oxides of
Work
eta!., 1996]
3.08
0.23
1.60
2.47
2.30
2. A lowerpercent of militaryshipshavedieselengines nitrogen(as N) (83% fromTable1), andfewermilitaryshipsuseslow-speed Sulfur dioxide 4.24 dieselenginesand medium-speed enginesdesignedto bum (as S) 123.46 high-sulfurresidualbunkers(approximately 32%); in fact, Carbon NATO F-76 fuel standardsrequireuse of 1% sulfurfuels dioxide (as C) [NATOIndustrialAdvisory. Group(NIAG), 1996]. Emissionsare in Tg/yr. ,
149.92
[Bremnes, 1990]
CORBE'I'TET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS performedfor 1990, includingan estimated625,000 vessel movementswithin the region. Lloyds studiedtwo 2-week periods(in Februaryand August), obtainingship movement informationand vesselcharacteristics from all vesselsgreater than250 GRT. Using thisapproachto derivetrafficdensities, Lloyd'sappliedemissionratesto estimatesulfurand nitrogen emissionsin an approachsimilar to the onethat we haveused, exceptthat Lloyd's useda fuel sulfur value of 2.7%. When
3465
internationaltransportin the region, in addition to that considered by the Streetset al. [1997] study. Thereforewe morecompletelycaptureall shiptrafficin theregion. 3.2. Comparison With Land-Based Anthropogenic Emissions
General comparisonsof global ship emissions with emissionsof Organizationfor EconomicCooperationand area, our estimates for sulfur emissions are within 2% of Development (OECD) nations showed that sulfur and Lloyd's. Using Lloyd's fuel sulfurcontentwould reduceour nitrogenemissionsfrom shipscomparein magnitudewith the global inventory by about 13%. This agreement is largest energy-consumingnations; ships also represent encouraging, given that the methodologies for derivingtraffic significantsourcesof emissionswhen comparedwith global densities in the region were different. It may provide inventoriesof nitrogenand sulfur [Corbett and Fischbeck, justificationfor applyingour resultsto otherregionsof interest 1997]. Nitrogenemissionsfrom shipsaccounttbr 14.7% of the 21.0 Tg N emitted from all ibssil fuel combustion withoutadditionaldatagatheringeffort. Anotherstudyof internationalshipemissions, focusingon estimatedby GEIA; ship sulfuremissionsaccountor 6.5% of Asianwaters,providesanotherpointof comparison [Streetset the 65.1 Tg S estimatedby GEIA for all anthropogenic al., 1997]. This study focusedon trade volumesfor four sources[Benkovita et al., 1996]. For further context, carbon commodities:crude oil, grain, coal, and iron ore. Average dioxideemissionsfi'om shipsare only 2% of the 6,000 Tg characteristicsof the ships carrying these cargoes were carbon emitted from fossil fuel use [Khalil and Rasmussen, assumed;for example,all crudeoil was "carriedby typical 1995]. In short, ships are among the world's highest 200,000 deadweightton (DWT) tankersconsuming120 t of pollutingcombustionsourcespertonof fuel consumed. Threefurtherremarksin comparisonwith GEIA shouldbe oil perday,while travelingat 15 knots"[Streetset al., 1997]. The fuel sulfurcontentassumedin this studywas 3%. While made. First, the ratio of nitrogento sulfur emissions(N/S to theN/S theauthorsestimatethat,by usingtheirfourcargocategories, ratio)for shipsis 0.76, perhapslessbutcomparable theymayaccountfor as muchas 75% of shipemissions in the ratiosin industrializedand heavilypopulatedareas. Second, Asia region, our ship sulfur estimatesfor this region are a nearly70% of ship emissionsoccurwithin 400 km of land. factorof 2 higher. We suggestthatthiscanbe expected for at This hasbeenshownto be the fifth percentilemeantransport with an averageof 900 km leasttwo reasons:(1) Therehasbeensignificantgrowthin distancein the marinetroposphere, shippingin the Asia regionsincethe Streetset al. [1997] and a ninety-fifthpercentilevalueof 1700 km [Benkovitzet study,which used 1988 data. Accordingto Table 3 in the al., 1994]. Dependingon prevailingwind directions,thereare Review of Maritime Transport 1994 [United Nations clearimplicationsfor regionalair qualityanalyses.Third, the Conferenceon Trade and Development(UNCTAD), 1995], mostimportantissuestill to be resolvedis whetherto add the the Asia regionsaw a 0.7% increasein its shareof world ship emissiondata to GEIA without adjustment,as we have we use those values for sulfur content and focus on the same
goodsloadedanda 0.9% growthin its shareof worldgoods done in Plates 1 and 2, or whether the GEIA values should be unloaded between 1992 and 1993. With world seaborne trade
increasing about3c• duringthat 1 yearperiod,growthin the Asia regioncouldhaveaveragedasmuchas4% peryear. (2) Our inventoryis not limitedto the fourcargoesmentioned, as thetrafficdensityderivedfromCOADS doesnotdifferentiate by typeof cargo. Furthermore, our methodology capturesall
adjusteddownwardto maintain a constantglobal inventory. Approximately5% of our inventoryoverlapsthe GEIA data set, with slightly more overlapbetweenour ship inventories (which have the same spatial distributions)and GEIA's nitrogen inventory than GEIA's sulfur inventory (5.72% versus5.34%). Where overlapbetweenour ship inventories
Ship Ave ......
DMS Ave
09 '-• 0.04 '-
•
0.02
0 -90 -80 -70 -60 -50 -40 -30 -20 -10
0
10
20
30
40
50
60
70
80
90
Latitude
Figure 3. Comparisionof latitudinaldistributionof averageship sulfuremissionsand dimethylsulfide(DMS) emissions[Chin et al., 1996].
3466
CORBETT ET AL.' GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
Table 5. Ratioof ShipSulfurto DMS Sulfur
ShipSulfur to DMSRatio 0 0.25 0.50 0.75 1 10 100 1,000 10,000
Frequency (usin•4x5[•ridcells)
layer atmospheric chemistrymodelsoften underpredict
Percent ofGlobal Surface Area
678 1276 199 94 61 246 167 39 3
24.5 46.2 7.2 3.4 2.2 8.9 6.0 1.4 0.1
systematically the SO2concentrations measured overremote ocean areas, particularlyin the Northern Hemisphere [Capaldo andPandis,1997]. Untilnowthisunderprediction has been attributedto persistentcontinentalpollutionor uncertainty in the DMS chemistry; however,highership trafficdensities in the NorthernHemisphere oceansmay provideanalternateexplanation.
4. Characteristics of the ShipEmissions Inventories
The semiempiricalmethodthat we usedto derivetraffic
densities and calculate internationalship emissions and GEIA's anthropogenic inventoriesdid occur,we plot the maximumvaluefor that location. The overlapin the Northern Hemisphere is about3.2 timesas greatas the overlapin the SouthernHemisphere;this discrepancymay be primarily a functionof the EMEP area, which explicitlyincludessome internationalshippingemissions.
inventories results
in
inventories with
characteristics
important to thoseusingthedatasetin atmospheric modeling or otherstudies.Becausethe COADS datasetis provided with monthly resolution,we are able analyze these characteristics temporally andspatially. 4.1. Variation by Month and Season
3.3. Comparisonof Ship Sulfur EmissionsWith DMS
The variationof ship emissions by seasonis drivenby routing and navigationconcernswith a strongseasonal of ship traffic. Becauseshipsare uniqueamonganthropogenic sources in influencein both quantityand distribution maybeimportant toconsider in modeling the that they occuron the world's oceansand are a significant Thesevariations sourceof SO2emissions, theircomparison with oceanDMS is seasonality of emissions in globalchemicaltransport models important.We compareglobalDMS estimatesfrom Chin et or in regionalanalyses. Figure 4 showsmonthlyship al. [1996] with our inventory. While this is a modeled emissions asa percentage of annualshipemissions. Globally, inventory forDMS, usinga 4øby 5øresolution, thisdepiction ship transportappearsnearlyconstantduringmuchof the of theglobalDMS sourceof 22 Tg S/yrappearsto be thebest year, with a minimum in December. This may be due to influences,such as winter holidays,or to available geographicallyresolveddata set. Ship sulfur socioeconomic emissionsequal about 20% of global DMS emissions; weather.The influenceof weatheron navigation canbe seen however,as shownin Figure3, averageshipsulfuremissions more dramaticallyin Figure 5, where ship traffic in the duringnon-winter canequalor exceedaverageDMS emissions in the Northern northernlatitudesoccursalmostexclusively Hemisphere midlatitudes. Table5 indicates thattheratioof months; during winter months (December, January, shipsulfuremissionsto DMS flux is greaterthan unityover February), ship traffic in the southernlatitudes is most prevalent. about16% of theglobalsurface.
Emissions
3.4. Qualitative ComparisonWith SO2Observations
4.2. VariationWith Latitudeand Longitude
Plates2 and3 show,theshipemissions flux in manyareas Qualitativeagreement with empiricaldatacanbe foundin oceancampaignsthat measuredsulfurdioxideconcentrations (particularlythe NorthernHemisphere)can be of the same anthropogenic emissions.Ship in remote areas (i.e., ocean regions far from !and). orderasflux fromland-based can be comparable sources of nitrogenand sulfur Measurements of atmosphericconcentrations in the North and emissions in someregionsof importance, for example,in SouthPacific Oceansshow higher "background"levelsfor emissions aged marine air in the Northern Pacific than the Southern northernEurope, South Asia, and the West Coast of the Pacific [Gregor)' et al., 1996]. Moreover,marine boundary United States. However, on averagethey are about5% and
9.0%
....
8.5%
8.0% 7.5% 7.0%
6.5%,
,
,'.......... , .......... ,..... , ....... 1............... l-'
Month
Figure 4. Monthlyvariationin shipemissions (aspercentof annual).
CORBETF ET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
3467
0.012 .... •nt•rr 0.01
0.006
----summer, .... '
I/
,,,
40
50
i,
•
o.oo. 0.002 -90-80-70-60-50-40-30-20-10
0
10 20
30
60
70
80
90
Latitude
Figure5, Seasonality of latitudinaldistribution of shipsulfuremissions.
10% of totalanthropogenic emissions of sulfurandnitrogen, and AMI International. However, each of the values usedin shipemissions is uncertain to somedegree. An respectively. The latitudinal distribution of shipemissions is estimating depicted by usingaverage emission fluxesin Figures6a and uncertaintyanalysiswas performedfor global estimates 6b; these can be directly comparedto the latitudinal (Figure7) and for the vesseltypedomain(Table6) using distributions of land-based anthropogenic emissions presented MonteCarlo simulation.The fifth and ninety-fifthpercentile valuesfor globalnitrogenemissions are2.66 Tg N and4.00 byBenkovitz et al. [1996]in theirFigure3. Tg N, respectively. Thefifthandninety-fifth percentile values forsulfuremissions are3.29Tg S and5.61Tg S, respectively. Uncertainty Uncertainty in the followinginputvariablessignificantly (listedin orderof importance): The emissionsreportedabovewere calculatedby using affectedthe globalestimates (1) mean emission rates reported by Lloyd's Register;the meanvaluesfrom Lloyd'semissions research,reportedfuel analysisappliedthe NOx statistical distribution usefromtheEIA, anddirectanalysisof shipdatafromI3,IIS uncertainty
•
0.04
,• 0.035 ß-
•
0.03
,
•31
•
0.02
0.01
0.005 -90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
Latitude
o•
0.03
o
(n
b)
0.025
E u,i
A
o
E
0.02 0.015
Z •
0.01
0.005
•
-90-80-70-60-50-40-30-20-10
0 Latitude
Figure6, Latitudinal distribution of average (a) sulfurand(b) nitrogen emission flux.
3468
CORBETTET AL.: GLOBALNOxAND SO2EMISSIONSFROMSHIPS 1.2
0.8
•e•-•::"•';•:•rl'otal
NOx from
Ships (as N)
0,2
Total SOxfrom Ships (as S)
0.0
2.01 2.31 2.62 2.92 3.23 3.53 3.84 4.14 4.45 4.76 5.06 5.37 5.67 5.98
Ship PropulsionEmissions(Tg/yr)
Figure 7. Resultsof uncertainty analysisfor globalshipemissions.
data from Lloyd's tests (A.A. Wright, personalHowever,it alsoidentifiesthe potentialvalueof assessing communication, 1996);and(2) fuel sulfurcontentfor bunkers. globalemissions frommilitaryvessels morerigorously. This
Residualfuel sulfurvalueswere assigned a triangle work has beendoneratherthoroughly by the U.S. Navy distribution, allowing thesulfurcontent tovarybetween a low [NAVSEA, 1994], and estimates have been made for other of 2%, a modeof 3.3%,anda highof 5%, andotherbunkers NATO navies[NIAG, 1996]. Thesestudiesaccurately wereassigneda uniformdistributionbetween0.5% and 2.5% demonstrate that modernnavalpropulsion, with a greater sulfur.
numberof gas turbineand otherlow-emissionalternatives to
Theimpactof uncertainty in thesevariables ontheglobal dieselenginesandspecifying verylow sulfurfuels,emitsfar estimates is 2 ordersof magnitude greaterthanotheruncertain lessthanmodern commercial marine dieselpropulsion. inputs,including EIA fuelaccuracy [Heppner andFrench, We believethattheuncertainty in ourestimates forship 1996]anduncertainty in fleetenginedistributions (Table1). emissions is smallerthantheuncertainty in overallglobal
Although Lloyd's Marine Exhaust EmissionsResearch anthropogenic emissions.For example,our estimatefor Programmeprovidesthe best availabledata, furtherstack nitrogen emissions fromshipshas loweruncertainty than testingand improvedfuel sulfur data are recommended to land-based combustion systems, because nearlyall ship
reduce uncertainty in globalestimates andto identifytrends emissions arefromsimilardieselengines usingsimilarfuel, thatmayaccount forvariability.Evenso,shipemissions still whereas land-based combustion sources are not as appearto be importantif one considered only the fifth homogenous in process or fueltype. Globalsulfurinventories percentileestimates. havelessuncertainty thanglobalnitrogeninventories, since Uncertainty in the contribution to ship emissions by sulfuremissions arefueldependent, whilenitrogen emissions differentvesseltypesdepends on estimates for military are process dependentand more variable. However, vessels.As wediscussed above,theengineoperating profile international shipsuseonlytwoprimary fueltypesandpay for militaryvessels is muchdifferentfromthatfor commercial close attention to fuel sulfur content as a matter of routine
vessels, andnavalshipsspendlesstimeunderway thando operation;thereforewe believe that we have characterized othervesseltypes.MonteCarlosimulation wasperformed,shipsulfurestimates with loweruncertainty thanland-based allowing thepercent ofglobalemissions frommilitary vessels sourceinventories.This findingagainraisesthe question to vary accordingto a triangledistributionwith low of 9%, posed in section 3.2aboutwhether to addtheshipinventories mode(bestestimate) of 23%,andhighof 100%of totalbrake presented hereto theGEIA inventory or makeadjustments to horsepower capacity. (The100%valuetreats militaryvesselskeepthe totalinventory constant.If someadjustments are thesamewayas commercial vesselemissions.)As Table6 indicated, wesuggest (onthebasisof theuncertainty analysis shows, theuncertainty in emissions contribution fortransportdiscussed here)that the GEIA inventories be modified by ships(bulkcargo,generalcargo,andpassenger) is much using some appropriateschemeto remove international lowerthanthatfor nontransport ships(fishing,service craft, maritimetradeemissionsfrom nationalemissions.However,
military,andothermarinecraft). Thisfindingis expected,where national inventoriesdo not include theseemissions, because uncertainty in militaryvesselemissions directly littleadjustment maybeneeded.Perhaps anoverallreduction affectsnontransport emissionestimates(see Figure 2). in uncertainty of the GEIA emissions maybe achieved by accounting forshipemissions.
Table6. Uncertainty Bounds forVesselTypeEmissions
Contribution (5thand95thPercentile) Vessel Type Bulk cargo Generalcargo Passenger Nontransport
NO,, Emissions
SO,,Emissions
Contribution, %
Contribution, %
27.1-36.8 25.5-34.8 5.7-9.5 30.5-50.1
30.2-37.7 28.4-35.7 6.0-9.5 27.4-43.4
Uncertainty in theglobaldistribution of shipsmustalsobe considered.As we statedin section2.2.1, the COADS data set includesobservations from about 10% of the world fleet.
Weassumed thatthissample isstatistically representative and showed thatourmethod yieldscloseagreement withthemore directmethodusedby Lloyds[Carltonet al., 1995]. This indicates thatourapproach maybe equivalently accurate to morecomplicated methodologies usedat the regionallevel. Thetrafficdensities thatwe derivedshouldbe confirmed by
CORBETTET AL.: GLOBALNOx AND SO2EMISSIONSFROM SHIPS
3469
additional studies usingmethods ascomprehensive asthose of Brubaker, N., and G.D. Eley, Marine Fuels: Burning Crude's Lloyds; additionally, theapproach takenherecanberepeated Leftovers,Surveyor,23(2), 2-7, 1992. Capaldo,K., and S. Pandis,Dimethylsulfide chemistry in the remote byusing therecently released 1øx1øversion ofCOADS. marineatmosphere: Evaluationand sensitivity analysisof available 6. Conclusions
International shipnitrogen andsulfuremissions arelarger thantheywerepreviously considered tobe,withestimates of the orderof the largestnations'domestic emissions; this findingis confirmed by analysisof uncertainty in input variables. These emissionsare characterizedaccordingto whereandwhentheyoccurgeographically andwhichtypesof vessels produce them. When these emissions are characterized geographically, they are shownto be largerin the NorthernHemisphere,particularlyalong heavily traded routes. Nearly 70% of ship emissionsoccurwithin potential transportdistance of land regions, dependingon wind direction. In allocatingemissionsby vesseltype, transport vessels(bulk cargo,generalcargo,and passenger) accountfor nearly70% of emissions fromships.
mechanisms, J. Geophys.Res.,102(D19), 23,251-23,267, 1997. Carlton, J.S., S.D. Danton, R.W. Gawen, K.A. Lavender, N.M. Mathieson,A.G. Newell, G.L. Reynolds,A.D. Webster,C.M.R. Wills, and A.A. Wright, Marine Exhaust EmissionsResearch Programme,Lloyd'sRegist.Eng. Serv.,London,1995. Chin, M., D.J. Jacob, G.M. Gardner, M.S. Foreman-Fowler, P.A.
Spiro, and D.L. Savoie,A global three-dimensional model of tropospheric sulfate,J. Geophys.Res., 101(D13), 18,667-18,690, 1996.
CONCAWE, The Europeanenvironmentaland refiningimplications of reducing the sulphur content of marine bunker fuels, CONCAWE Air Qual. Manage.Group,Brussels,Belgium,1993. Cooper,D.A., K. Peterson,and D. Simpson,Hydrocarbon, PAH and PCB emissionsfrom ferries: A case study in the SkagerakKattegatt-Oresund region,A,nos. Environ., 30(14), 2463-2473, 1996.
Corbett, J.J., and P.S. Fischbeck,Emissionsfrom ships, Science, 278(5339), 823-824, 1997.
Der Norske Veritas (DNV), The North Sea as a SpecialArea, Det NorskeVeritasIndustryAS, Hovik, Norway, 1994.
The shipinventories presented herearelargerthanprevious Ewart,W.D., Bunkers,72 pp., FairplayPubl.Ltd., Surrey,England, 1982. globalshipinventories but areconsistent with regionalefforts Gregory, G.L., A.S. Bachmeier,D.R. Blake, B.G. Heikes, D.C. and improveupon other methodologies.The ship sulfur Thornton,A.R. Bandy,J.D. Bradshaw,and Y. Kondo,Chemical inventoryequalsabout20% of oceanDMS flux (as S) and signaturesof aged Pacific marine air: Mixed layer and free exceedslocal DMS flux in morethan 15% of globalsurface troposphere as measuredduringPEM-WestA, J. Geophys.Res, 101(D1), 1727-1742, 1996. area. Seasonalcharacteristics for ship traffic represent supplydata, significantvariability in overall volume and in latitudinal Heppner,T.G., andC.L. French,Accuracyof petroleum in Pet. Suppl. Mon., DOE•IA 0109(96/09), 1996. distribution. Average latitudinal distributionis generally similar to land-basedanthropogenicemissions,equaling Hottenstein,L.N., Ship EmissionsControl Studyfor the Ports of Long Beach and Los Angeles:Marine VesselEmissionsWhile about5% of sulfuremissionsand 10% of nitrogenemissions Hotelling in Port and Evaluation of Alternative NO• Control from land-basedsources.Becauseship propulsionis more Technologies, TRC Environ.Consult.,Inc., MissionViejo, Calif., 1991. homogeneousthan land-based combustion systems, the EnergyAgency(IEA), EnergyStatistics1970-1985and uncertaintyin the globalinventoriespresented hereis smaller International Main Seriesfrom 1960, 513 pp., Org. for Econ.Coop.and Der., than that for land-based globalinventories; the uncertainty in Paris, France, 1987. shipemissions maybe lowerthansomenationalinventories. InternationalMaritime Organization(IMO), Draft text of the Annex The inventories presented hereshouldbe usedalongwith the Vl to MARPOL 73/78 for Preventionof Air PollutionFromShips, editedby Marine Environ.Protect.Comm. (MEPC) 39/6, London, GEIA inventoriesto representanthropogenic emissionsin 1996. atmosphericanalysesof NOx, SOx, and their severalrelated International Organizationfor Standardization(ISO), International products(e.g., ozoneand sulfate). The nitrogenand sulfur Standard.PetroleumProducts- Fuels(classF) - Specifications of inventoriesare availableat the Ship EmissionsAssessment Marine Fuels, Geneva, Switzerland, 1987. (SEA) web site at Carnegie Mellon University ISO, ReciprocatingInternal Combustion Engines:ExhaustEmission (http://www.andrew.cmu.edu/--jcorbett/SEA.html). Measurement, Part 4, Test Cycles for Different Engine Acknowledgments. The work was supportedby NSF grant SBR9521914, EPA STAR Fellowship U-915180-01-0, and by academicfundsof the Departmentof Engineeringand PublicPolicy, CarnegieMellon University,Pittsburgh,Pennsylvania.
Applications,Geneva,Switzerland,1996. Khalil. M.A.K., and R.A. Rasmussen, The changingcomposition of the Earth'satmosphere,in Composition,Chemistr3,, and Climate of the Atmosphere,editedby FI.B. Singh,chapter3, pp. 50-87, Van Nostrand Reinhold, New York, 1995.
Kolle, F., O. Melhus, and K. Bremnes, NO• emissionsfrom
References Adcock, L.E., and G.A. Stitt, AMI International's Naval Main
Propulsion,VlarketOverview,AM1 Int., Bremerton, Wash.,1995. Benkovitz, C.M., C.M. Berkowitz, R.C. Easter, S. Nemesure, R.
internationalsea transport,MARINTEK, Sintel Group, Norw. Mar. Technol. Res. Inst., Oslo, 1989.
Lloyd'sMaritimeInformation Services (LMIS),Datasetof Ships100 GRT or Greater, Stamford, Conn., 1996.
Lloyd'sRegisterof Shipping,Marine ExhaustEmissionsResearch Programme:Stead)' State Operation (includingSlow Speed
Wagener,and S.E. Schwartz,Sulfateover the north atlanticand Addendum), London, 1990. adjacentcontinentalregions:Evaluationfor OctoberandNovember Lloyd'sRegisterof Shipping,Marine ExhaustEmissionsResearch 1986 using a three-dimensional model driven by observationProgramme: Transient Emissions and Air Quality Impact derivedmeteorology, J. Geophys.Res.,99(D10), 20,725-20,756, Evaluation, London, 1993. 1994.
Benkovitz,C.M., M.T. Scholtz,J. Pacyna,L. Tarfason,J. Dignon, Maloney, M.J., World Energy Database, Energy Inform. Admin. (EIA), Washington,D.C., 1996. E.C. Voldner, P.A. Spiro, J.A. Logan, and T.E. Graedel,Global gridded inventoriesof anthropogenic emissionsof sulfur and Markle, S.P., and A.J. Brown,Naval ship engineexhaustemission characterization, Nay. Eng.J., 108(5), 37-47, 1996. nitrogen, J. Geophys. Res.,101(D22),29,239-29,253,1996. Bremnes,C.P.K., Exhaustgas emissions from international marine NATO IndustrialAdvisoryGroup(NIAG), PrefeasibiliryStud),on a NATOEnvironmentally SoundShipof the21st Century,Brussels, transport:Global distributionof NO,• and SO2 methodsof Belgium,1996. calculation,MARINTEK, SintefGroup,Norw. Mar. Technol.Res. Inst., Oslo, 1990. Naval Sea SystemsCommand(NAVSEA), U.S. Navy marinediesel
3470
CORBETT ET AL.: GLOBAL NOx AND SO2EMISSIONS FROM SHIPS
United Nations Conferenceon Trade and Development(LINCTAD), Reviewof Maritime Transport1994, New York, 1995. Navy Media Center Publishing,Navy News Service Message, U.S. EnvironmentalProtectionAgency(EPA), Washington,Nonroad engineand vehicleemissionstudy- report,D.C., 1991. Washington,D.C., 1996. MachineryTechnologyDivision,Internal Combustion Olivier, J.G.J., A.F. Bouwman, C.W.M. Van der Maas, J.J.M. Westinghouse (Gas Turbine and Diesel) Engine Exhaust Emission Study, Berdowski,C. Veldt, J.P.J. Bloos, A.J.H. Visschedijk,P.Y.J. Pittsburgh,Pa., 1992. Zandveld,and J.L. Haveflag,Envion.Databasefor Glob. Atmos. Res.(EDGAR),Rep.771060002, Nat.Inst.onPubl.Healthand Woodruff,S., ComprehensiveOceanAtmosphereData Set(COADS), Nat. Oceanic and Atmos. Admin., and Nat. Cent. for Atmos. Res., Environ.(RIVM), Bilthoven,Netherlands,1996. Boulder, Colo., 1996. Osbourne,A., Modern Marine Engineer'sManual, Cornell Mar. Woodruff, S.D., S.J. Lubker, K. Wolter, S.J. Worley, and J.D. Elms, Press, Centreville, Md., 1943. Comprehensive Ocean-Atmosphere Data Set(COADS) Releasel a: Packard,W.V., Sea-Trading:The Ships, 136 pp., FairplayPubl., 1980-92, Earth Syst.Monit., 4(1), 1993. Surrey,England, 1984.
engineand gas turbineexhaustemissions, Washington,D.C., 1994.
Portof LosAngeles et al.,Controlof shipemission in theSouthCoast air basin:Assessment of the proposed federalimplementation plan J. J. Corbettand P.S. Fischbeck, Department of Engineering and shipfeeemission feeprogram, LosAngeles, Calif.,1994. PublicPolicy,CarnegieMellonUniversity, Pittsburgh, PA 15213. Singer,B.C., and R.A. Harley,A fuel-based motorvehicleemission (
[email protected];Paul_S_Fischbeck @andrew.cmu.edu) inventory, J. Air WasteManage.Assoc.,46(6), 581-593, 1996. of Chemical Engineering, Carnegie Mellon Spiro,P.A., D.J. Jacob,andJ.A. Logan,Globalinventory of sulfur S. N. Pandis,Department emissions with 1ø x 1ø resolution, J. Geophys.Res.,97(D5), 6023University,Pittsburgh, PA 15213. (
[email protected]) 6036, 1992.
Streets, D.G., G.R. Carmichael, and R.L. Arndt, Sulfur dioxide
emissionsand sulfur depositionfrom internationalshippingin Asian waters,Atmos. Environ., 31(10), 1573-1582, 1997.
Turpin, E.A., and W.A. McEwen, Merchant Marine Officer's (ReceivedApril 14, 1998;revisedAugust17, 1998; Handbook, Cornell Mar. Press, Centreville, Md., 1965.
acceptedAugust26, 1998.)
