U.S. Black Carbon Inventory Current and Future Activities Rebecca Lee Tooly Venkatesh Rao Office of Air Quality Planning and Standards Research Triangle Park, NC United States Environmental Protection Agency CEC Meeting October 6-7, 2010 Montreal Canada
Overview • Air quality / climate interaction • US Report to Congress • Status of U.S. black carbon inventory • Domestic emissions profile • Global issues • International BC assessment activities • Summary – main themes
Air quality / climate interaction (1 of 3) • h • Slowing atmospheric build up of CO2 is the most important long-term strategy for combating climate change • However, recent research points to the fact that shorter-lived pollutants, including BC, CH4, and troposphere O3 may collectively be responsible for as much temperature impact as CO2, especially in receptor regions like the Arctic • BC has global, regional, AND local effects • Emerging evidence that aerosol particles, and especially the BC component is a potent source of human-induced warming
Dust Elemental Carbon Possible Light Absorbing OC (for illustrative purposes) Sulfate Organic Carbon Nitrate Air quality / climate interaction (2 of 3) • Carbonaceous PM is the sum of elemental and organic carbon • Elemental carbon is the term commonly used in • Emission inventories, monitoring, and modeling • Black carbon is generally used interchangeably with elemental carbon • BC does include EC but also contains additional amounts of light absorbing carbon Terminology Example: PM2.5 monitoring data (ug/m3)
Air quality / climate interaction (3 of 3) • BC is always co-emitted with a range of other pollutants during combustion, with the most important being OC • Much of OC is likely “cooling.” However “Brown Carbon” is light-absorbing and is part of the OC spectrum • The ratio of BC/OC emissions for a given source is a potentially important metric when talking climate mitigation • BC also has health impacts since it is a component of PM2.5 (all chemical constituents of PM2.5 cause health effects)
Report to Congress on Black Carbon • Charge: • Conduct a comprehensive study on BC, due April 2011. • External review draft due end October 2010. • Report focuses on: • Characterizing nature and extent of BC issue • Identifying mitigation opportunities, comparing cost-effectiveness and considering climate/PH benefits • Limited time/scope for new analysis: mostly summarizing existing literature to provide scientific foundation for future efforts
Status of U.S. BC Inventory (1 of 4) • Currently, emissions of EC (black carbon) and other PM constituents (OC, nitrates, sulfates, crustal material) are not directly reported as part of the NEI • Chemical speciation of PM2.5 in the inventories is done via the emissions modeling process • EC emissions for most sources are estimated by matching PM2.5 emissions from the NEI to source-specific EC speciation profiles from the “SPECIATE” database • Exception on-road mobile sources - EC estimated directly through mobile models
Status of U.S. BC Inventory (2 of 4 ) • Mobile source activities….. • Mobile source portion of inventories • -New inventories for on-road using updated MOVES model • -NONROAD model used to generate nonroad inventories • -Accounting for lower EC fraction with diesel particulate filters • -Also examining commercial marine, locomotives, and aircraft • -Initial results – August 2010 • Mitigation • -New vehicles/engines: quantifying PM, OC, EC reductions from EPA regulations • -In-use engines: National Clean Diesel Campaign • -Importance of reducing fuel sulfur for PM controls • Gasoline vehicle testing • -Testing several future technology GDI vehicles for PM, PM size, and EC • -Results in late 2010
Status of U.S. BC Inventory (3 of 4 ) • Areas for improvement…. • Investigate qualitative uncertainties in how PM2.5 emissions are estimated by source category, i.e., we use these PM2.5 emissions as a starting point to convert to elemental carbon emissions in our inventories. • Understand better the source measurements that form the basis for apportioning PM to elemental carbon in the SPECIATE database. • Attempt to better understand PM composition for nonroad gasoline powered sources as well as commercial marine, i.e., current data to translate PM to elemental carbon for these sources is weak.
Status of U.S. BC Inventory (4 of 4 ) • Areas for improvement….. • Better apportion the biomass burning PM and elemental carbon emission estimates into "types of fires"---including agricultural, prescribed, wildfires. • Attempt to understand how much of organic carbon emissions are actually light-absorbing materials - "brown carbon“, measurements and sources. • Investigate temporal behavior of sources to better account for seasonality and time-of-day patterns • Particle size distributions, sulfate and OC size distributions, dust inventories, Fe content, and optical properties
EC inventory dominated by mobile source emissions • OC inventory dominated by burning About 6% of Global Total About 3% of Global Total
Mobile Source EC inventory dominated by diesel sources in 2005 (nearly 90%) • Some categories based on limited amount of EC speciation information • In the future, diesel emissions will be reduced making other categories stand out More detailed look at mobile sources • Open burning (ag, Rx, and wildfires) dominate US EC inventory • Some of burning is very seasonal • All burning categories have lots of OC, making them questionable mitigation targets for climate purposes • OC from burning could have significant amounts of light-absorbing brown carbon • In future years, fires are expected to make up much larger percentage of BC inventories (143,902 Tons) More detailed look at biomass burning sources
County based EC emission estimates allow for looking at spatial distributions. • Burning estimates show clear spatial patterns in these maps based on 2005 emissions • Overall, about 70% of EC emissions are found in urbanized counties. Some categories contribute more in urban areas than others.
We have over 300 urban/rural monitors that measure EC in the ambient air • We are currently trying use these data for time-series analysis as well as in conjunction with emissions data to QA the EC inventory and better characterize sources that emit EC.
Deposition of BC onto snow and ice in the Arctic causes warming and melting of the ice. (OC also has “warming” effects in these areas…) • Emissions north of the 40th parallel have been shown to particularly effect Arctic/Greenland impacts • In the US, there are about 1180 counties (about 38% of total) north of the 40th parallel. • When arrayed against the national EC emissions piechart, this graph shows mobile sources to have even more of a contribution to EC emissions north of 40 in the United States.
“Current” Year mobile sources • Diesel mobile sources dominate current EC inventories… • Mobile Source diesel regulations significantly reduce EC emissions from those categories as we move into future (numbers will be available in RtC) • Bottom chart is conceptual depiction of how 2030 EC may look based on expected mobile source reductions. • All other categories’ emissions kept at 2005 levels. “Current” Year All Sources Conceptual Future, All Sources
Globally, biomass burning and residential sources make more than 2/3rds of the total BC. Biomass burning contributes to nearly 3/4th of total global OC emissions. • Global OC emissions are about 4 times higher than EC emissions (OC:EC in EPA inventories is about 2:1) • There are uncertainties in these emission estimates. Studies indicate that emissions estimates from all sources maybe off by a factor of 2, on average. For specific nations and sectors, inventories maybe considerably more uncertain. • Note that these estimates are for year 1996 while domestic emissions are for year 2005 • All global inventory information in RtC comes directly from peer-reviewed literature Streets, D. G., Bond, T. C., Lee, T., and Jang, C.: On the future of carbonaceous aerosol emissions, J. Geophys. Res., 109, doi:10.1029/2004JD004902
One of the very important contributors to BC emissions in developing countries is the residential sector. This sector contributes 27% of EC emissions globally. • In developing countries, most of these emissions come from cookstoves (for which there is a separate mitigation section in RtC). In the US, it is likely heating contributes more to this sector than cooking • Cookstoves burn different fuels, but all produce thick clouds of soot that coat houses, cause human health problems, leads to mortality, and damages glaciers thosands of miles away. • China, India, and Africa contribute nearly 2/3rds of total BC emissions from this key global sector.
We have some global EC (in red) and BC (in black) monitoring data to work with • Obtainable data shows highest concentrations exist in China/India. • Can explore how ambient measurements compare with global inventories…have begun to do some of that with RtC work…lots of measurement types of issues to work out… Chapter 2, RtC, Frank, Tikvart, et al.
Future Work--Global inventories • Understand methods used to estimate emissions • Better understand uncertainties in emission estimates, by region and sector • Agreement on consistent measurement methods • Better characterization of small emission sources that have high BC EFs • Better engagement of international scientists, governments, and regulatory agencies in collaborations of technology assessments • Innovative ways to assess regional emission rates and emissions: • source apportionment type tools • ambient and remote sensing data, as well as model output
Other international BC assessments • Canada & U.S. • CA BC profile indicates emissions dominated by fires, key OC contribution • Information and technology transfer with CA: • how we estimate emissions from biomass burning /fires • ambient monitoring to better understand the models for estimating EC/OC • UN-ECE LRTAP • UNEP BC and Ozone assessment – mitigation focus • Arctic Council TF SLCFs – emissions, impacts, mitigation • India / China self-assessments
Some Main Themes • Areas of Focus on BC in US: • Legislation • Report to Congress • New research • Applied science and tool development • Current major BC source in US: mobile sources • As future mobile reduction programs are realized, burning activities will be major contribution • Reduction of BC provides air quality health co-benefit for all • BC has greatest impact globally / regionally
Black carbon – Different in a number of ways from GHGs • Definitional uncertainties and lack of standardized measurement techniques • Short-lived in atmosphere (not well mixed like GHGs) • Location matters more (e.g., proximity to Arctic can lead to additional effects) • Causes precipitation, “dimming”, and snow albedo effects not directly associated with GHGs • Co-emitted with other aerosols including organic carbon which has cooling effects (different sectors have different BC:OC ratios) • Number and size of particles can matter (not just mass); aging processes in the atmosphere • Estimates of common metric ‘radiative forcing’ more uncertain compared to well-mixed GHGs
Key Domestic BC Source Categories • Mobile Source BC • Primarily diesel engines • Biomass burning • Primarily wildfires, agricultural & prescribed burning and residential wood combustion • Stationary fossil fuel combustion • Primarily natural gas combustion, coal combustion, and stationary diesel engines • Bottom pie indicates future increased role of biomass burning and stationary fossil fuel combustion after implementation of mobile diesel controls • (NOTE: Revision of domestic inventories currently underway) Domestic BC Emissions 2005 Domestic BC Emissions 2030
Relying completely on literature for global characterizations Relying on Streets, Bond paper(s) for most of the information on global BC/OC emissions Combining fuel composition data and assumptions of combustion technologies and emissions controls Similar to earlier work done in the literature (Klimont, 2002). Emissions for a fuel/sector combination are calculated as an aggregate of the contributions of all technologies within that sector. The total emissions for each country, in turn, are the sum across all fuel/sector combinations These are “sub micron” inventories…inventories in PM2.5 range maybe 10-15% higher See Bond et al. 2004 for more information… Global BC/OC Methods
US Emissions compared to US part of Bond EC and OC inventories • EPA EC emission estimates are, in sum, are about 7% higher • However, some sectors don’t match well (Ag burning, for example) • US part of global inventories show much more OC than we estimate in EPA inventories (impacts OC:EC ratios, for example) • Similar very preliminary comparisons between EPA and IIASA BC inventories for US show EPA estimates to be much higher (x2) • Comparison issue(s) needs to be explored further (which inventories are used to represent regions in global models, what the sensitivities are, etc.) Future work includes better understanding global methods for estimating emissions…
Analytical Tool Development • Health and climate impacts • Future scenario development • Stand alone radiative transfer model • New research
EC/PM2.5 Emissions Reductions • Mobile Rules most important • e.g., Onroad, nonroad, locomotive/marine • Largest reductions come from diesel engines: regulations projected to reduce diesel EC emissions by 82% from 2005 levels by 2030 • Other regulations affecting PM2.5 (and EC) • 2006 national ambient air quality standards for PM (PM NAAQS) • Toxic Rules • e.g. incinerators, boilers, other MACT standards • Consent Decrees and Legal Settlements • e.g., refineries • Plant Closures • As the mobile reductions occur, other source categories will become a larger % of total U.S. EC emissions
Work In Progress:Global Health and Climate Impacts of BC Emissions Reductions Objective: Calculate change in PM2.5 concentration and premature mortality that could be achieved by reducing BC emissions Health impact function Step 3a: Estimate health benefits (Δ PM2.5-related mortality) • Step 1: Model BC emissions reductions • Global • Regional • Sectoral Step 2: Estimate Δ in PM2.5 concentrations Step 3b: Estimate climate benefits (Δ Direct Radiative Forcing) Global chemical transport model Radiative transfer model 33
Work In Progress:GLIMPSE • A framework for connecting: • atmospheric chemistry • radiative forcing • energy-economy models • Rapidly understand the integrated air quality and climate change impacts of US emission scenarios.
Impact of SO42- (top) and BC (bottom) on regional radiative forcing (RF) Work in ProgressStand alone radiative transfer model Answer Policy-Relevant Questions, for example: • What are the effects of US AQ-focused regulations on climate? • How can existing AQ management be adapted to maximize climate benefits while continuing to protect AQ-related health/welfare concerns?
$7 million Research Initiative • What improvements can be developed and demonstrated in understanding sources, source sectors, chemical composition, physical properties, and quantities of BC, related co-pollutants, and other SLCFs in the global to regional scale emission inventories? • How can modeling tools quantify and evaluate regional scale climate and air quality effects of BC, related co-pollutants and other SLCFs? Can the modeling tools quantify these effects and their uncertainties by source sector and geographic locale? • What are the impacts of long range transport of BC, related co-pollutants and other SLCFs on air quality and regional climate forcing? What sources or source sectors contribute to those impacts? How does the uncertainty in the global inventory of these species affect the calculated impacts? • What metrics can be used to simultaneously evaluate short term climate and air quality impacts of BC, related co-pollutants, and other SLCFs? How can these metrics be used to compare SLCFs amongst themselves and/or SLCFS to LLGHG in the climate and air quality contexts? Open until September 22 at http://epa.gov/ncer/rfa/2010/2010_star_blackcarbon.html