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Re: another question

  I have worked for several years in estimating emissions from and permitting
  landfill gas vents and flares. In all the literature (from EPA, EPA
  contractors, and various researchers and permitting agencies) I have read
  on the subject of landfill gas, I have never seen any reference to dioxin
  emissions, either measured, estimated or otherwise. I would not expect to
  find any appreciable concentrations of dioxins in landfill gas, as dioxins
  have fairly low vapor pressures over the range of temperatures typically
  encountered in landfill gas. Also, minimal particulate matter is emitted
  from a typical vent, so that emissions of dioxins adsorbed on particulate
  matter should not be a consideration. 
  Dioxins could be present in measurable quantities in emissions from LFG
  flares, but again I doubt the typical flare would be a concern. EPA rules
  require most flares to operate under conditions of time and temperature
  which are unfavorable for to the production of dioxins. EPA rules require
  monitoring and recording of flare operating parameters, so there is a means
  of assuring compliance. Since there is little if any fly ash generated in
  the flare, and there are no downstream air pollution control devices, there
  is almost no chance of de novo dioxin formation. I am assuming that there
  are traces (few ppm) of chlorinated hydrocarbons in the LFG. Sometimes
  there are no measureable chlorinated hydrocarbons, sometimes there are
  relatively high levels.
  LFG is also frequently burned in large internal combustion engines and
  boilers. I would expect similar dioxin emissions (if any) from these
  devices. Landfills designated as Superfund sites (of which there are many)
  are probably the ones most likely to have any dioxin emissions.
  Bottom line, I would be much more concerned about other emissions from LFG
  or LFG control devices than dioxins. Methane migration (underground) is a
  documented health and safety problem in areas surrounding landfills.
  Hydrogen sulfide has been a documented health and safety (not to mention
  nuisance) problem in certain landfills (without flares), particularly those
  which accepted a lot of sheet rock, animal hides, etc. Chlorinated
  hydrocarbons and other air toxics are last on the list of my concerns, and
  could be a consideration at industrial landfills and landfills with
  histories of significant hazardous waste disposal.
  I hope the above information is helpful and not excessive. Feel free to
  email me with more explicit questions.
  John Wilcox
  > From: CCHW <cchw@essential.org>
  > To: Multiple recipients of list <dioxin-l@essential.org>
  > Subject: another question
  > Date: Tuesday, November 04, 1997 11:42 AM
  > Another question:  Does anyone have information on dioxin in landfill
  > gases - when they are vented or flared?
  > thanks.
  > CCHW  Center for Health, Environment and Justice
  >       P.O. Box 6806  Falls Church, VA 22040
  >       (703) 237-2249   (703) 237-8389 (fax)