AIR QUALITY AND ETHANOL

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AIR QUALITY AND ETHANOL

• Gary Z. Whitten

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INTRODUCTION

• Ethanol impacts both positive and negative
• Ethanol similar to but not MTBE
• Trade-offs can be complex
• Not readily acceptable due to
• Regulations
• Agencies
• Oil companies
• And sometimes environmental groups

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Carbon Monoxide, Ozone, Toxics, and PM

• CO makes ozone
• Toxics are closely regulated and adjusted in RFG
• PM needs more recognition

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Carbon monoxide makes ozone

• 1974 paper just CO and NOx might exceed ozone
  standard.
• 1988 testimony 1 pound waiver mainly due to CO
  reduction by ethanol.
• 1998 NRC study credit for CO reduction should be
  in RFG.

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Toxics are closely regulated in RFG

• Ethanol can reduce benzene by 30 percent
• Dilution
• Octane substitute for aromatics
• Cleaner burning
• Refiners often can adjust benzene for RFG
• Acetaldehyde increased by ethanol, but several
  studies show this is not a problem

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PM needs more recognition

• Science of PM rapidly emerging
• PM can be primary or secondary
• Ethanol significantly reduces both
• Secondary (man-made)may be essentially all from
  aromatics
• Ethanol impact similar to benzene

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Ozone Trade-offs

• CO reduction equal to at least 3 of VOC
• This is for RFG going from 2 to 3.5 oxygen
• For non-oxy the full credit could be 7
• Aggressive driving, high emitters, old cars, and
  off-road engines also show VOC benefits
• Unfortunately, regulations based mainly on data
  from low-emitting vehicles show much VOC benefit

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Trade-offs (Cont.)

• Recent data (1999) show 63 of CO and 47 of VOC
  coming from 10 of vehicles
• ARB tests show aggressive driving (REP05)
• Ethanol (vs MTBE) showed 3 benefit in normal
  driving (FTP) but 10 when REP05 data included.
• Complex Model for RFG and ARB model both all
  based on FTP (no REP05 data)

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Trade-offs (cont.)

• EPA tests on 36 vehicle fleet (half higher
  emitters) show 6 CO reduction and 4 VOC
  reduction with ethanol (vs, MTBE), but all the
  benefits came from the higher emitters.
• Note only FTP data here (no REP05)
• Grid model tests show
• CO major (33 of ozone) impact
• Exhaust VOC more important than evaps.