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VOCs & Climate Change Michelle Gaither Ken Grimm Brian Penttila 20 April 2009 Pacific Northwest Pollution Prevention Resource Center.

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Presentation on theme: "VOCs & Climate Change Michelle Gaither Ken Grimm Brian Penttila 20 April 2009 Pacific Northwest Pollution Prevention Resource Center."— Presentation transcript:

1 VOCs & Climate Change Michelle Gaither Ken Grimm Brian Penttila 20 April 2009 Pacific Northwest Pollution Prevention Resource Center

2 UN Framework Convention on Climate Change Annex I parties must submit: – Inventories of anthropogenic emissions by sources and removals by sinks of GHGs not controlled by the Montreal Protocol – Six sectors: energy, industrial processes and product use, agriculture forestry and other land use, waste

3 Objective 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.

4 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 CO 2 ? Indirect Radiative Forcing – Do VOCs affect the concentration of other GHG’s? Indirect CO 2 – This expression has several uses – Here, we mean CO 2 from the breakdown of VOCs after emission

5 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. From Highwood et al., 1999, Estimation of Direct Radiative Forcing due to Non-Methane Hydrocarbons. Some VOCs are effective absorbers, but have very short lifetimes, so they are not important for direct forcing

6 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 CO 2 and water in the atmosphere; c.f. “atmospheric window”

7 Direct Radiative Forcing Depends on a molecule’s atmospheric lifetime – Global Warming Potential (GWP) calculated relative to CO 2 – 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”)

8 Horizontal Transport Time Scales From Mike Pilling, University of Leeds

9 Atmospheric Lifetimes of VOCs Most VOCs are very short lived Atkinson 2000 – Atmospheric Chemistry of VOCs & NO x

10 Direct Forcing “Bottom-Line” Highwood 1999 – “The global mean radiative forcing due to anthropogenic emissions of non-methane hydrocarbons (NMHCs) is unlikely to exceed Wm -2 ” – Mean Radiative Forcing for CO 2 = 1.66, CH 4 = 0.48) Highwood, “Estimation of direct radiative forcing due to non- methane hydrocarbons,” Atmospheric Environment, 1999

11 Indirect Radiative Forcing of VOCs Mechanisms from IPCC AR4: – Fossil carbon from non-CO 2 gaseous compounds, which eventually increase CO 2 in the atmosphere (from breakdown of CO, CH 4, and NMVOC emissions)! – Changes in tropospheric ozone (from CH 4, NO x, CO, and NMVOC emissions) – changes in OH affecting the lifetime of CH 4 (from CH4, CO, NO x, and NMVOC emissions) But the increased CO 2 is not included in indirect forcing calculations: – “Following the approach taken by the SAR and the TAR, the CO 2 produced from oxidation of…NMVOCs of fossil origin is not included in the GWP estimates since this carbon has been included in the national CO 2 inventories.”

12 Indirect GWP for VOCs Due to impact of VOC chemical reactions on atmospheric ozone & methane concentrations – Calcs. from 3D atmos. transport/reaction models From IPCC AR4

13 Radiative Forcing for Emissions Impact of non- methane VOCs is indirect, via effect on CO 2, O 3 and CH 4

14 Indirect CO 2 & GHG Inventories Confusion 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 CO 2 emissions associated with Life Cycle Assessment (LCA) approaches. (And different from “indirect forcing,” the change in forcing due to impact on other GHGs)

15 GHG Accounting - Fossil Fuel Revised 1996 IPCC Guidelines - Energy – When fuels are burned, most carbon is emitted as CO 2 immediately during the combustion process. Some carbon is released as…[NMVOCs], which oxidize to CO 2 in the atmosphere within a period from a few days to years. The IPCC methodology accounts for all the carbon from these emissions in the total for CO 2 emissions. – Calculated through emission factors

16 GHG Accounting - Solvent Use Revised 1996 IPCC Guidelines – Solvent – 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…

17 Indirect CO 2 from VOCs Protocols Differ Fossil Fuel Combustion: indirect CO 2 included – Emission factors for fossil fuel combustion assume all carbon is oxidized to CO 2, except for solids. Fossil Fuel Production – Fugitive emissions: indirect CO 2 NOT included Industrial Processes – Indirect CO 2 may or may not be included Non-Energy Use – Indirect CO 2 may or may not be included Waste – Indirect CO 2 NOT included (biogenic origin) Some confusion as 2006 Guidelines have changed versus 1996 Guidelines (Kyoto process)

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19 Gillenwater 2008 Assume all CH 4, CO & NMVOC from fossil fuel fugitives and industrial processes ends up as CO 2 Est. change in percentage of national GHG emissions: May be some double-counting here Good for some parties, worse for others Country/party Russian Federation1.2%1.5% United States0.9%0.6% European Comm.0.6%0.4% From: Gillenwater, “Forgotten carbon: indirect CO2 in greenhouse gas emission inventories,” Environmental Science & Policy, 2008.

20 Summary 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 CO 2

21 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 vs NO x -limited Weather Little hope to calculate individual “emission” factors All have diurnal and seasonal variation

22 Background Slides Additional information on atmospheric breakdown of VOCs Characterization of VOC reactivity: MIR, POCP Global modeling and monitoring activities US vs EU terminology

23 Example: Fate of Octane Reactions are complex From: Burrows, ACCENT Conference, 2007.

24 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

25 Global Monitoring of VOC’s GEIA (Global Emissions Inventory Activity) – Collecting data for global modelling Source:

26 Modelling Approaches EPA Multipollutant – Detroit test case EU “GAINS” – Greenhouse Gas-Air Pollution Interactions & Synergies –

27 Synergy Between Pollution & Climate

28 VOC’s – What’s In? What’s Out? USEPA – "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: 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 kPa. Includes HFCs, HCFCs? AKA Non-Methane Hydrocarbons (NMHCs) or NMVOCs


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