US EPA Perspective on Black
Carbon Emissions
Rich Mason , Tesh Rao, Rob Pinder
US Environmental Protection Agency
Office of Air Quality Planning and Standards
IPCC Expert Meeting on Short-lived Climate Forcers
Geneva, Switzerland, 28-31 May 2018

Overview of Presentation• General information on the NEI (National Emissions Inventory)• US EPA approach to quantifying PM2.5 and Black Carbon (BC/EC)
emissions in the NEI• SPECIATE database• BC data in the 2014 NEI• Sectors of interest for BC• Residential wood combustion• Agricultural burning• Mobile sources (Transportation), including marine shipping• Next steps2

National Emissions Inventory (NEI) Basics• Types of emission sources included and resolution• Point sources (facility-process for ~87,000 facilities)• Examples include electric generation and industrial facilities• Nonpoint sources (county-process)• Onroad mobile sources: exhaust, evaporative, brake and tire wear, road dust
• Nonroad mobile sources: lawnmowers, construction, farm, and mining equipment; aircraft, ships, and railroads• Biogenic soil and vegetation (county-process)• Other nonpoint sources: residential heating, gas stations, animal waste, solvents, fugitive dust• Wild and Prescribed Fires (daily-point)• States, locals and tribes (SLTs) submit CO, SOX, NOX, VOC, PM10, PM2.5, NH3 and Lead
• Hazardous Air Pollutants (HAPs) and Greenhouse Gases (GHGs) can also be voluntarily submitted• The NEI is the result of combining emission estimates from EPA with SLTs
• The full NEI is on a 3-yr cycle (e.g. 2008, 2011, 2014, 2017) and larger point sources submit annually3

Five Key NEI Goals• Complete: Includes all emissions to the atmosphere included, whether regulatedor unregulated for all counties including Puerto Rico and the Virgin Islands• Represents the year of the inventory• Uses best available information• Transparent - includes the emissions origin(who provided, factor, activity, method)• Timely4

General NEI Emission Estimation Methods• Source-specific activity and emission measurements• Source-specific emissions process models• MOVES for on-road and non-road emission estimates• SMARTFire2/BlueSky for Wildland Fires (day-specific emission estimates)• Emission Factors• Site-specific• Industry-average• See AP-42/WEBFIRE examples: https://cfpub.epa.gov/webfire/• Emissions estimated as: (EF) x (activity) x Control Factors• Mass Balance• NEI is a combination of SLT-submitted data combined with EPA estimatesused to “backfill”
5How are Black Carbon emissions developed in the NEI?
• Most of the black carbon (BC) estimates are result of applying speciation
profiles for elemental carbon (EC) to PM2.5 emissions• In the NEI, EC estimates are used to represent BC• Nearly all EC profiles are based on IMPROVE’s TOR (Thermal Optical Reflectance)
methods• On road mobile source emissions of BC come directly from the EPA model(MOVES) and represent engine test results• While BC estimates are produced as part of the process to produce species
for air quality modeling, they are also now included as a pollutant in theNEI• BC emissions reported to UN Economic Commission for Europe (UNECE)
Convention on Long-range Transboundary Air Pollution (CLRTAP)• 2012 BC Report to Congress covers details on US emissions reporting6

US Reporting to LRTAP Program• Voluntarily reported national PM2.5 emissions for over 10 years• Annual PM reporting per Gothenburg Protocol 2012 Amendments,accepted by US in 2017
• Region-level PM2.5 emissions also reported for US Pollutant Management
Area (PEMA) per Gothenburg• Voluntary BC emissions reporting began in 2014

• National estimates for year 2011
• Since then: updates to 2011 and estimates for year 20147

WHAT IS SPECIATION?
Speciation disaggregates inventory species (e.g. VOC, PM2.5)
into more detailed species

VOC

PM2.5

propaneethyleneformaldehyde
acetaldehyde
ethanoletc.
elemental (black) carbon
organic carbon
nitratesulfatealuminum
siliconironetc.
8

More information about SPECIATE• A repository for speciated emissions profiles• A searchable Microsoft Access database and onlinedatabase• Profiles for three air pollution emission types:• Particulate Matter (PM)• Total Organic Gases (TOG)• Other Gases/pollutants [Hg, NO/NO2/HONO, semivolatile organic compounds(SVOC)]• Available on EPA Website: https://www.epa.gov/air-emissions-modeling/speciate-version-45-through-40• Nearly all SPECIATE profiles come from the literature orfrom otherwise credible source testing programs
9

The steps in PM2.5 Speciation to Black Carbon
Emissions of PM2.5 arereported for a specificSource Classification
Code (SCC)
Example:100 tons of PM2.5 fromprescribed burning
SCC: 2610000500

SPECIATE Database: AssignSpeciation Profile to the Source
Classification Code
Example:Profile Code: 91109
Composite Profile – Prescribedburning

Multiply inventory
emissions by profile
fraction to get emissionsof specific chemicalcompounds
Example:50 tons organic carbon
11 tons black carbon
35 tons non-carbon
organic matter, etc.

Note: there are thousands of SCCs in the NEI which need to bemapped to a few hundred profiles we have in the current SPECIATE
10PM2.5, Black Carbon and Organic Carbon in the 2014 NEI
PM2.5 = 5.3 MILLION TONS (4.8 TG)
Nonroad Onroad
4%
3%

Fires
33%

Miscellaneous
41%

BLACK CARBON = 431K TONS (0.4 TG)
Industrial
Processes
5%

Onroad16%

Fuel
Combustion
14%

ORGANIC CARBON= 1.5 MILLION TONS (1.4 TG)
Nonroad
3%

Fires
39%

Onroad4%

Miscellaneous
20%
Nonroad25%

Miscellaneous
10%

Industrial
Processes Fuel Combustion
1%
9%

Miscellaneous
includes all the dust
categories

Fires
53%

Industrial
Processes
2%
Fuel
Combustion
18%

11Thousands

Black Carbon Emissions (short tons) by Sector
908070605040302010012

County Distribution of Total Black Carbon in the 2014 NEI

NEI emissions are a blend of SLT andEPA data, determined primarily bycompleteness of SLT data
13

Black Carbon: Mobile (left), Residential Wood Combustion (right)

NEI emissions are a blend of SLT and EPA data,
determined primarily by completeness of SLT data14

Residential Wood Combustion (RWC) Sector• This source category includes residential wood burning devices suchas fireplaces, fireplaces with inserts (inserts), free standing
woodstoves, pellet stoves, outdoor hydronic heaters (also known asoutdoor wood boilers), indoor furnaces, and outdoor burning infirepits and chimeneas.
• EPA estimates emissions for this sector using this simple equation:
Emissions = Home Types × Appliance Fraction × Burn Rate ×
WoodDensity × Adjust Factor x Emission Factor• Black carbon emissions: 17,590 tons, 4% of total
15

Residential Wood Combustion Developments• Emission factors needs longer-term additional work for all appliancetypes• EPA/ORD is working to address the PM and VOC EF and speciation needs fromthis sector• Fledgling RWC survey to cover at least 15 states• Commission for Environmental Cooperation (CEC)-funded, results hopefully
can be used in 2017 NEI• Seeking improved characterization of appliance counts and burn rates vscurrent broad (5 Census region) approach with climate data
• Targets all appliance types and vastly-different areas to hopefully allow for
improved spatial mapping to all areas• Oversampling 6 northeast states already thinly-sampled by another survey
16Agricultural Burning Sector• This sector contains emissions from both crop residue burning as well as
grassland burning. Different crops and grasses are represented by 25 SCCs.
• Methods are based on published improvements to previous techniques of Dr.
Jessica McCarty• Activity data (acres burned) mostly obtained from satellite detects/croplanddata layer maps and SLT-based information. The biggest uncertainty in this
sector is in obtaining/computing acres burned by crop type.
• Emission factors come from the literature. Updates going on currently using inhouse (ORD) test results. Development of fire PM and compositional EFs arean active on-going research item at EPA/ORD.
• Black carbon emissions: This sector is a small contributor to the total fire totals(which includes larger Wild and Prescribed fires) in the 2014 NEI: 4% of BC.
17

Commercial Marine Vessels (CMV) Sector• The CMV sector includes boats and ships used either directly or indirectly in theconduct of commerce or military activity. The majority of vessels in this category
are powered by diesel engines that are either fueled with distillate or residual
fuel oil blends. For the purpose of this inventory, we assume that Category 3 (C3)vessels primarily use residual blends while Category 1 and 2 (C1 and C2) vessels
typically used distillate fuels• Black Carbon: 12,950 tons, 3% of total. Note that BC>OC for this sector.
• For C1 and C2 vessels “HDDV” profile is applied since they are diesel engines. C3
vessels which run on residual type fuels, are assigned a 0.5% BC fraction. Thus,
there is a large discrepancy of how much of the emitted PM2.5 is BC based onthese profiles, which are fuel specific.
• Future work will need to look at obtaining better PM speciation profiles for bothtypes of CMV vessels
182014 NEI Mobile Source PM2.5, BC & OC (thousands, short tons)
On-Road non-Diesel Light Duty Vehicles
On-Road non-Diesel Heavy Duty Vehicles
On-Road Diesel Light Duty Vehicles
On-Road Diesel Heavy Duty Vehicles
Non-Road Equipment - Other
Non-Road Equipment - Gasoline
Non-Road Equipment - Diesel
Locomotives
Commercial Marine Vessels
Aircraft
0102030

OC40

EC

5060

708090100PM2.5• HDDV (diesel profile) of 77% BC applied to all diesel sources, is a critical future need for research and possible revision• Totals for Mobile Sources: PM2.5 = 0.33 Tg, BC = 0.16 Tg, OC = 0.09 Tg (note OC < EC), due to diesels operations 19

Ongoing research at EPA for speciation• Wild and Prescribed Fires (Open Burn TestFacility)• By combustion phase• By differing fuels representing differentregions• By fire intensity changes• Field measurements of agricultural andwildland fire emissions• Possibly also investigate brown carbon• Residential wood combustion• Contact: Dr. Amara Holder(holder.amara@epa.gov)
20Conclusions and next steps• US Black Carbon is currently about 7-8% of global totals• Biomass burning and diesel-powered engines are the top sources forBC emissions in the US inventory• Speciation profiles need to be continually updated to best represent
both black carbon and organic carbon emissions• We have completed an analysis in house looking at SPECIATE andaddressing which profiles need updating in a priority fashion. The“HDDV” profile is top priority to research and revise. We will publish
this work soon.
21Questions?
Acknowledgements: NEI Team (Rich Mason, Tesh Rao, Laurel Driver,Jennifer Snyder, Ron Ryan, Madeleine Strum, Sally Dombrowski,
Rhonda Thompson), Amara Holder, Rob Pinder, Marcus Sarofim(EPA/OAP)
mason.rich@epa.gov
22Appendix

23

BC Science• Formed during incomplete combustion• Contributes to warming by directly absorbing sunlight and darkening ice and snow
• Immediate climate benefits are possible due to BC’s short atmospheric lifetime(compared say to carbon dioxide)• Influence is regional and global• BC’s warming effect is offset somewhat by cooling from light-scattering pollutants (OC,SO4, etc.)• Traditional diesel exhaust is mostly BC• Residential wood combustion is mostly OC• The ratio of non-BC (conveniently stated to be OC) to BC is a simple, yet useful number• Programs to reduce PM2.5 will also reduce BC. Since BC has been implicated in adverse
health effects, programs that reduce PM2.5 (and BC) will lead to health effect benefits.
24

PM2.5 Speciation Profile Example, PrescribedBurning, # 91109
pollutant species• The Profilesof PMspecies
weightfractions
are specificto particle
size ranges

PM2_5PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5
PM2_5

POC
PEC
PSO4
PNO3
PNH4
PAL
PCA
PCL
PFE
PK
PMN
PMOTHR
PNA
PNCOM
PSI
PTI

massfrac

0.50190.10930.00330.01070.00340.00050.00070.00240.00040.00140.00010.01250.00140.35130.00010.0007

POC, PEC = Carbon
PSO4, PNO3, PNH4 =inorganic ions
PNCOM = NonCarbon Organic Mass(computed)
PAL, PCA, PCL, PFE,
PK, PMN, PNA, PSI,PTI = Trace Elements
PMOTHR = what’s left
over25