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Pacific Northwest Pollution Prevention Resource Center. VOCs & Climate Change. Michelle Gaither Ken Grimm Brian Penttila 20 April 2009. UN Framework Convention on Climate Change. Annex I parties must submit:

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vocs climate change

Pacific Northwest Pollution Prevention Resource Center

VOCs & Climate Change

Michelle Gaither

Ken Grimm

Brian Penttila

20 April 2009

un framework convention on climate change
UN Framework Convention on Climate Change
  • Annex I parties must submit:
    • Inventories of anthropogenic emissions by sources andremovalsby sinks of GHGs not controlled by the Montreal Protocol
    • Six sectors: energy, industrial processes and product use, agriculture forestry and other land use, waste
  • This presentation was prepared to explore the impact of VOC emissions on climate change. From a P2 perspective, VOCs are usually of interest for their role in ground-level ozone production, due to its impact on human health. This presentation explores the further impact of VOC emissions on climate change.
3 potential voc impacts on climate
3 Potential VOC Impacts on Climate
  • Direct Radiative Forcing
    • This is the main climate effect of GHG emissions
    • Are VOCs effective at absorbing terrestrial IR, i.e., do they act like methane and CO2?
  • Indirect Radiative Forcing
    • Do VOCs affect the concentration of other GHG’s?
  • Indirect CO2
    • This expression has several uses
    • Here, we mean CO2 from the breakdown of VOCs after emission
direct radiative forcing
Direct Radiative Forcing
  • Depends on IR-absorption “Cross-Section”
    • Does the compound absorb IR and how much?
    • Where in the spectrum does absorption occur?
    • Effects compared for 1 ppbv change in conc.

Some VOCs are effective absorbers, but have very short lifetimes, so they are not important for direct forcing

From Highwood et al., 1999, Estimation of Direct Radiative Forcing due to Non-Methane Hydrocarbons.


The effectiveness of a chemicals IR absorption for warming also depends on the location of the absorption bands. Much of the spectrum is now saturated by the existing CO2 and water in the atmosphere; c.f. “atmospheric window”

direct radiative forcing1
Direct Radiative Forcing
  • Depends on a molecule’s atmospheric lifetime
    • Global Warming Potential (GWP) calculated relative to CO2
    • Effect calculate for long time periods (typ. 100-yr)
    • Short-lived compounds hard to quantify
      • VOC breakdown products quickly multiply
      • Neither reactants nor products survive long enough to be “well-mixed” (more difficult to model their effect)
  • As VOC pollution may not cross national boundaries, some emitters will claim there is no role for international regulation (“interference”)
horizontal transport time scales
Horizontal Transport Time Scales

From Mike Pilling, University of Leeds

atmospheric lifetimes of vocs
Atmospheric Lifetimes of VOCs
  • Most VOCs are very short lived

Atkinson 2000 – Atmospheric Chemistry of VOCs & NOx

direct forcing bottom line
Direct Forcing “Bottom-Line”
  • Highwood 1999
    • “The global mean radiative forcing due to anthropogenic emissions of non-methane hydrocarbons (NMHCs) is unlikely to exceed 0.015 Wm-2”
    • Mean Radiative Forcing for CO2 = 1.66, CH4 = 0.48)

Highwood, “Estimation of direct radiative forcing due to non-methane hydrocarbons,” Atmospheric Environment, 1999

indirect radiative forcing of vocs
Indirect Radiative Forcing of VOCs
  • Mechanisms from IPCC AR4:
    • Fossil carbon from non-CO2 gaseous compounds, which eventually increase CO2 in the atmosphere (from breakdown of CO, CH4, and NMVOC emissions)!
    • Changes in tropospheric ozone (from CH4, NOx, CO, and NMVOC emissions)
    • changes in OH affecting the lifetime of CH4 (from CH4, CO, NOx, and NMVOC emissions)
  • But the increased CO2 is not included in indirect forcing calculations:
    • “Following the approach taken by the SAR and the TAR, the CO2 produced from oxidation of…NMVOCs of fossil origin is not included in the GWP estimates since this carbon has been included in the national CO2 inventories.”
indirect gwp for vocs
Indirect GWP for VOCs
  • Due to impact of VOC chemical reactions on atmospheric ozone & methane concentrations
    • Calcs. from 3D atmos. transport/reaction models


radiative forcing for emissions
Radiative Forcing for Emissions

Impact of non-methane VOCs is indirect, via effect on CO2, O3 and CH4

indirect co 2 ghg inventories confusion in terms
Indirect CO2 & GHG InventoriesConfusion in Terms
  • Indirect emissions – National Inventory Reporting
    • National Inventory Reporting uses the term “indirect emissions” to refer specifically to those greenhouse gas emissions which arise from the breakdown of another substance in the environment.
    • NOT to be confused with “Indirect emissions” found in other sources, e.g., Safeguarding the Ozone Layer 2003
      • Here “Indirect emissions” refers to energy-related CO2 emissions associated with Life Cycle Assessment (LCA) approaches.
  • (And different from “indirect forcing,” the change in forcing due to impact on other GHGs)
ghg accounting fossil fuel
GHG Accounting - Fossil Fuel
  • Revised 1996 IPCC Guidelines - Energy 1.4.1
    • When fuels are burned, most carbon is emitted as CO2 immediately during the combustion process. Some carbon is released as…[NMVOCs], which oxidize to CO2 in the atmosphere within a period from a few days to 10-11 years. The IPCC methodology accounts for all the carbon from these emissions in the total for CO2 emissions.
    • Calculated through emission factors
ghg accounting solvent use
GHG Accounting - Solvent Use
  • Revised 1996 IPCC Guidelines – Solvent 1.4.1
    • 24% of US NMVOC emissions
    • NMVOC “is a greenhouse gas (actually a class of gases) covered under the programme, but it has been assigned a lower priority…”
    • “…already under heavy scrutiny…”
    • Reported separately as NMVOC emissions.
  • Skipping other categories for now…
indirect co 2 from vocs protocols differ
Indirect CO2 from VOCsProtocols Differ
  • Fossil Fuel Combustion: indirect CO2 included
    • Emission factors for fossil fuel combustion assume all carbon is oxidized to CO2, except for solids.
  • Fossil Fuel Production
    • Fugitive emissions: indirect CO2NOT included
  • Industrial Processes
    • Indirect CO2may or may not be included
  • Non-Energy Use
    • Indirect CO2may or may not be included
  • Waste
    • Indirect CO2NOT included (biogenic origin)
  • Some confusion as 2006 Guidelines have changed versus 1996 Guidelines (Kyoto process)
gillenwater 2008
Gillenwater 2008
  • Assume all CH4, CO & NMVOC from fossil fuel fugitives and industrial processes ends up as CO2
  • Est. change in percentage of national GHG emissions:
  • May be some double-counting here
  • Good for some parties, worse for others

From: Gillenwater, “Forgotten carbon: indirect CO2 in greenhouse gas emission inventories,” Environmental Science & Policy, 2008.

  • IPCC practice is to ignore the Direct Forcing effect of VOCs
  • IPCC guidelines incorporate the effect of VOC emissions on atmospheric chemistry-induced changes in other GHGs (ozone, methane), aka Indirect Forcing
  • 1996 & 2006 GHG inventory calculations include at least some sources of Indirect CO2
fate of voc s
Fate of VOC’s
  • Sinks include:
    • Chemical reaction
    • Physical removal
      • Aerosol formation (wet and dry deposition)
    • Rates dependent on:
      • Temperature and light
      • Local concentration
        • e.g., for ozone, VOC-limited vsNOx-limited
      • Weather
  • Little hope to calculate individual “emission” factors

All have diurnal and seasonal variation

background slides
Background Slides
  • Additional information on atmospheric breakdown of VOCs
  • Characterization of VOC reactivity: MIR, POCP
  • Global modeling and monitoring activities
  • US vsEU terminology
example fate of octane
Example: Fate of Octane
  • Reactions are complex

From: Burrows, ACCENT Conference, 2007.

characterization of vocs
Characterization of VOCs
  • Reactivity based on individual compounds
    • Lab results on individual reactants/reactions
      • Atkinson at UC-Riverside is the guru
    • Structure-based (QSAR) models (Gramatica 2004)
      • e.g., alkanes more stable than alkenes
    • MIR (Maximum Incremental Reactivity)
    • POCP (photochemical ozone creation potential)
  • Results from global/regional models
    • POCP response to “pulse” of given compound or source
    • More realistic/comprehensive view of indirect effect
global monitoring of voc s
Global Monitoring of VOC’s
  • GEIA (Global Emissions Inventory Activity)
    • Collecting data for global modelling

Source: http://www.geiacenter.org/

modelling approaches
Modelling Approaches
  • EPA Multipollutant – Detroit test case
  • EU “GAINS” – Greenhouse Gas-Air Pollution Interactions & Synergies
    • http://www.iiasa.ac.at/rains/index.html?sb=1
voc s what s in what s out
VOC’s – What’s In? What’s Out?
    • "Volatile organic compounds (VOC)" means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.
    • Other excluded chemicals include: methane, ethane, acetone, Montreal gases (methylene chloride, CFCs, HFCs, HCFCs, etc.), etc.
    • List at: http://www.epa.gov/ttn/naaqs/ozone/ozonetech/def_voc.htm
  • EU
    • A VOC is any organic compound having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa. Includes HFCs, HCFCs?
  • AKA Non-Methane Hydrocarbons (NMHCs) or NMVOCs