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

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

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.

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

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

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”

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”)

Horizontal Transport Time Scales From Mike Pilling, University of Leeds

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

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

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.”

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

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

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)

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

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…

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)

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.

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

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

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

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

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 GEIA (Global Emissions Inventory Activity) – Collecting data for global modelling Source:

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

Synergy Between Pollution & Climate

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