Evaluation of MTBE as a Component of Reformulated Gasoline Catherine P. Koshland Donald Lucas Robert F. Sawyer Pamela M. Franklin University of California, Berkeley EPA Blue Ribbon Panel Sacramento, CA March 25, 1999 Good afternoon. My name is Pamela Franklin. Today I’d like to describe research conducted at the University of California, Berkeley, with Professors Cathy Koshland and Robert Sawyer and Dr. Donald Lucas at the Lawrence Berkeley National Laboratory. We conducted this research as part of a University of California - wide, comprehensive evaluation funded by state legislation to investigate the effects of MTBE, including health effects, effects of groundwater and surface water, remediation techniques, and overall costs and benefits. The purpose of this research was intended to provide the Governor with input to make a decision about MTBE in California. While our research included a lot of technical data, today I’d like to provide you with an overview of the context in which we conducted this study and some of the political / policy implications for this research.

Objectives Evaluate published literature of vehicle emissions from conventional fuels, oxygenated fuels, and reformulated fuels Laboratory studies Vehicle dynamometer studies On-road studies Evaluate Auto/Oil database Conduct experimental laboratory reactor study to identify combustion byproducts Our effort focused on an evaluation of the effects of MTBE on automotive combustion byproducts. To this end, we performed three tasks: 1. we conducted an extensive investigation into the existing literature on laboratory, vehicle, and on-road studies, ranging from pure MTBE reaction at ambient and elevated temperatures, to vehicle dynamometer testing with selected fuel formulations, to real-world vehicles and complex fuel mixtures. 2. we also evaluated an extensive database compiled by the Auto/Oil study, a collaborative effort of 14 oil companies and 3 domestic auto manufacturers, which speciated over 150 hydrocarbon emissions (engine out + exhaust) for different vehicle technologies and fuel formulations. 3. Finally, we conducted original laboratory experiments in a flow reactor in order to simulate “worst-case” automotive engine-out emissions, to fill in data gaps we identified, to better identify contribution of MTBE to specific combustion byproducts.

Gasolines Conventional fuel = hydrocarbons “Oxyfuel” = conventional fuel + oxygenate Goal: reduce CO emissions Reformulated gasoline (RFG) Goal: reduce ozone precursors, toxic emissions Federal RFG (1995): Requires minimum 2.0 wt% oxygen California Phase 1 RFG (1992) Eliminated lead, reduced vapor pressure, required detergents California Phase 2 RFG (1996) More stringent than Federal RFG requirements Limits eight fuel parameters Requires 1.8 - 2.2 wt% oxygen unless predictive model used It’s helpful to begin by describing some of the different “flavors” of gasoline. Different gasoline formulations are regulated by federal statute under the 1990 Clean Air Act. California also has special privilege to make its own fuel regulations. Conventional fuel may have low levels of oxygenates (2-3 vol%), primarily as octane booster. Oxyfuels and RFGs - do not mandate any particular oxygenate. MTBE is the refiners’ “oxygenate of choice” - technical, economic reasons.

MTBE combustion byproducts Laboratory reactor measurements Increase in MTBE emissions, byproduct emissions (especially isobutylene, formaldehyde) when MTBE is a component of reformulated gasoline Methanol (pure MTBE byproduct) not observed as byproduct of MTBE-fuel at elevated temperatures TBF (pure MTBE byproduct under atmospheric conditions) not observed at elevated temperatures Observed combustion byproducts consistent Laboratory studies of pure MTBE Vehicle and on-road studies of gasoline with MTBE Our experimental studies concur with other laboratory studies in flow reactors at elevated temperatures.

California Phase 2 RFG vs California Phase 2 RFG vs. Conventional Gasoline Vehicle and tunnel measurements Reduces hydrocarbons: 12 - 27% Reduces CO: 21 - 28% Reduces NOx: 7 - 16% Reduces benzene: 34 - 47% Increases aldehydes when oxygenates are included in fuel formulation These results encapsulate a wide range of vehicle dynamometer and on-road studies comparing exhaust emissions from reformulated fuel (typically with 11 vol% MTBE) and conventional gasoline.

Impact of fuel formulations on automotive emissions Oxyfuel vs. conventional gasoline Reduces CO exhaust emissions Reduces emissions of total hydrocarbons, benzene, and aromatics by dilution effect RFG vs. conventional gasoline Reduces ozone-forming potential of emissions Larger emission reductions of total hydrocarbons, benzene, and aromatics Reduces evaporative emissions Improves effectiveness of catalytic converter CaRFG2 with MTBE vs. non-oxygenated CaRFG2 Produce similar reductions in ozone-forming potential and mass emissions of total hydrocarbons, benzene, and aromatics MTBE-fuel increases direct (exhaust) formaldehyde emissions Similarly, these broad-stroke comparisons of the impact of different fuel types on vehicle emissions are based on vehicle dynamometer and on-road studies.

Conclusions: MTBE’s role as a fuel component MTBE (as well as other oxygenates) helps reduce automotive CO emissions in older cars and increases formaldehyde emissions from all vehicles RFG - with or without MTBE - has significant air quality benefits In newer vehicles, non-oxygenated CaRFG2 provides essentially the same emissions benefits as CaRFG2 with MTBE Fully-compliant CaRFG2 can be produced without MTBE Fuel formulation changes are one dimension of a comprehensive strategy to reduce auto emissions in California Here are some of the conclusions / policy implications we’ve drawn from our review of the available information and our own study, in terms of how these results impact policy decisions.

Response to reviewer comments: Scientific support for conclusions “Based only on Auto/Oil study” Conclusions based on totality of evidence Auto/Oil study results compelling “Does not directly compare two fuels identical except for MTBE” Impossible to compare identical CaRFG2 formulations with and without MTBE California is the only place where “RFG” is not synonymous with “oxygenated RFG” Auto/Oil study: CaRFG2 with 11 vol% MTBE vs. a non-oxygenated CaRFG2 “Advanced technology,” 1983-85 MY; 1989 MY; Federal Tier I (1993 California, 1994-96 rest of US) published Auto/Oil study; also database few studies: tunnel studies (e.g., Kirchstetter et al.) haven’t tested CaRFG2 without MTBE as a comparison! impossible to compare two “identical” RFGs with and without MTBE: - differences in octane number

“MTBE plays an important role in reducing CO emissions” Response to reviewer comments: MTBE’s contribution to reduced vehicle emissions “MTBE plays an important role in reducing CO emissions” Oxygenates lower tailpipe CO by 2 - 10% per wt% oxygen Wide variation: vehicle technology, ambient temperature “Conclusion ignores the contribution of CO to reduced ozone-forming potential” CO has low reactivity, but is emitted at higher levels than most HCs California predictive model does not include OFP per se Auto/Oil urban airshed ozone models do include the impact of reduced CO emissions “MTBE reduces toxic emissions via ‘dilution effect’ ” True for “oxy-fuels” (conventional gas + oxygenate) Not accurate description of oxygenated RFG Reduced CO emissions: 2 - 10% per wt % oxygen varies widely depending on vehicle technology uncertain effects at low temperatures ambient CO - confounding factors: meteorology, fleet turnover not really an issue in California anymore CO and OFP: CO has low MIR compared to other HCs but is emitted at higher levels: uncertainty about net contribution: 10-20% of HC OFP? California predictive model doesn’t include OFP per se Auto/Oil: urban airshed model projects peak ozone formation - includes impact of reduced CO emissions Reduction in toxic emissions via “dilution effect” accurate description of “oxyfuels” = conv. gas + oxygenate not at all accurate for RFGs - “match blended” We concur with ARB’s comment: “Oxygenates do provide value in that they have blending properties that facilitate meeting the overall specifications for CaRFG2 …. We believe it is more accurate to conclude that oxygenates are effective in making gasoline with lower emitting properties but that alternative gasoline formulations that are equally effective and do not use oxygenates are also feasible to produce.”

“Evaluation of other hydrocarbon species not considered” Response to reviewer comments: Benzene vs. other automotive toxic emissions “Evaluation of other hydrocarbon species not considered” Incorrect. We evaluated numerous hydrocarbon byproducts, including: Formaldehyde Direct emissions Secondary atmospheric formation important Acetaldehyde 1,3-butadiene US EPA: “US EPA does not believe that decreases in other toxic compounds should be ignored on the basis of their statistical significance.”

Response to reviewer comments: Advanced Technology Vehicles “ ‘Advanced Technology’ vehicles (Auto/Oil study) not defined” Mid-1990s prototypes at time of study 3-way catalysts, exhaust gas recirculation, sequential or port fuel injection “ ‘Advanced Technology’ vehicles represent only a small fraction of California fleet” Growing proportion of on-road fleet Vehicle turnover important Significant fraction of vehicle miles traveled and mobile source emissions

“Evaporative emissions not considered” Response to reviewer comments: Extrapolation of studies to the real world “Vehicle dynamometer studies have limitations and should not be extrapolated to real-world” Evaluated wide range of studies, including on-road Auto/Oil study included older vehicles, high-emitting vehicles “Evaporative emissions not considered” Evaluated in Auto/Oil study; incorporated in their conclusions “High-emitting vehicles and ‘gross polluters’ not considered” Relatively few vehicles contribute disproportionately to automotive pollution Fuel formulation may not be the most effective way to address this aspect of auto pollution

Response to reviewer comments: Role of oxygenated fuels in reducing automotive CO emissions “Relying on fleet turnover is insufficient to reduce CO emissions and ensure compliance with CO standards” Compliance with NAAQS for CO a decreasing problem in California Vast improvements in vehicle technology are having an important effect “Oxygenates are needed to reduce emissions from high-emitting vehicles” Fuel formulation changes are one way to address this problem, but may not be the most effective way to reduce emissions from gross polluters, malfunctioning vehicles

Response to reviewer comments: Other benefits from oxygenated fuels “Reduced particulate matter (PM) emissions benefits ignored” Increasing concern over ultra-fine particulate emissions Few data are available High aromatic fuel content may be important precursor “Emission reduction benefits in off-road vehicles ignored” Contribution to mobile source emissions varies according to pollutant type As on-road fleet turns over, new vehicle technology, off-road sources will become increasingly important