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Re: Dioxins and Burning Landfill Gas

  At 11:36 PM 11/4/97 -0500, Pat Costner wrote:
  >Following are a few papers that address the issue of dioxin 
  >generation during the burning of landfill gas.  The vagaries in style 
  >of presentation of the following papers can be attributed to a span 
  >of several years and several assistants.   Any verbiage that follows 
  >a particular citation is a verbatim quote from that citation.
  Pat complained in a post that I ignored most of the information she posted,
  so here goes....
  Pat posted the following papers....
  > Lahl, U., Wilken, M., Zeschmar-Lahl, and Jager, J.  1991. PCDD/PCDF 
  >balance of different municipal waste management methods.  Chemosphere 
  >23 ( 8-10): 1481-1489 .  
  > For emission reduction, disposal gas [landfill gas] is often  
  >treated or used in thermal processes.  ... Due to our  analyses, 
  >exhaust gas after combustion of disposal gas can  contain 
  >considerable amounts of PCDD/PCDF.  We found 75-217 pg  (TE)/m3, 
  >other authors report values up to nearly 1 ng ( TE)/m3  (10).
  0.075-0.217 ng TEQ/dscm are relatively low PCDD/PCDF
  stack emission concentrations as far as combustion devices 
  are concerned.   Many other such devices of concern discharge
  not only with far higher stack gas concentrations and but also far higher
  stack exit volumetric rates..    
  I would not consider 1 ng/dscm to be a low rate.   I don't have this paper
  or quick access
  to Chemosphere, but it would be interesting to know the circumstances
  of the high number.
  > Fiedler, H. 1993. Formation and Sources of PCDD/PCDF.  Organohalogen 
  >Compounds 11: 221-228 
  >Landfill Gases 
  >  Despite the high chlorine content in landfill gases burning of  
  >these gases in muffle furnaces or internal combustion engines  
  >results in relatively low dioxin emissions in the range of 0.1  ng 
  >TEQ/m3 or lower ( HLfU 1991).
  As PCDD/PCDF stack gas emission rates go, this is relative low.   And remember
  that the environmental impact is related ,,,,not to the stack gas
  emission concentration ..... but to the product of the stack 
  emission concentration and thestack exhaust gas volume per unit of time
  (usually expressed in dry standard cubic meters per second)....ultimately
  this is the derivation of the mass emission rate........
  for inhalation toxicity purposes, the ambient concentrations downwind are
  directly proportional
  to the mass of emissions per unit time.   
  > Allen, Matthew R., Alan Braithwaite, Chris C. Hills.  1997.Trace 
  >Organic Compounds in Landfill Gas at Seven U.K. Waste Disposal  
  >Sites. Environ. Sci. Technol.  31:[4]:1054-61. 
  This articles doesn't contain any detail at all on PCDD/PCDF emissions
  from landfill gas combustion that I can see....  It does, however, mention
  that considerable chlorine contents are found in landfill gas to the point
  of potentially causing corrosive damage to landfill gas combustion
  equipment from production of HCl during burning.
  However, just because there is significant chlorine in a 
  gas being combusted doesn't necessarilymean that there will be 
  significant PCDD/PCDF emissions also.   As noted in long
  prior posts, the absolute chlorine content of PCDD/PCDF emissions even 
  from the worst dioxin sources is very, very small.   This means that 
  chlorine content of the material combusted will generally not
  be the limiting factor in the production of dioxin emissions.
  Production of 
  PCDD/PCDF in combustion systems has more to do with other
  variables, such as the temperature characteristics of the combustion
  zone and downstream combustion gas locations, the nature, type and existence 
  of particles (both metals and carbon) in the combustion gases,
  the nature, type and existence of air pollution control equipment 
  provided, and other factors.
  > Jones, K.  Comparing air emissions from landfills and WTI plants.  
  >Solid Waste Technologies. March/April 1994
  > Unlike the scant health and environmental data available from  
  >recycling facilities, there is a modest and growing data base  on 
  >landfill air emissions.  Recent state and federal  regulatory 
  >activities plus the development of dozens of  landfill gas-to-e rgy 
  >projects, have helped to build an  emissions profile.  For instance, 
  >to develop the background  for the New Source Performance Standards 
  >proposed in May 1991,  the Environmental Protection Agency compiled 
  >emissions data  for 22 landfills .  [2,3,4]  EPA's data from 13 of 
  >these  facilities includes emissions associated with using gas  
  >control systems, such as flares internal combustion engines  (ICEs), 
  >and gas turbines.  A testing program of the California  Air Resources 
  >Board (CARB) also helped to extend considerably  information on 
  >landfill gas composition. [5]
  >  To quantify dioxins emissions from landfill gas control  devices 
  >for this investigation, I used measurements reported  from flares and 
  >ICEs in Germany. [9]  The German data was used  since quantitative 
  >dioxin emissions data from controlled  landfills in the U.S. is 
  Nothing in what Pat cited from Kay Jones contains any specifics
  about numerical stack emissions or mass emission 
  rates  of PCDD/PCDF from landfill gas combustion ....
  It would have been nice to have the German data which 
  was mentioned but not articulated specifically.
  Kay Jones, but the way, came to our state in the mid-1980's
  to tell us all that electrostatic precipitators with no stack 
  scrubbing constituted state-of-the-art emission control
  for the Detroit Incinerator, one of the worlds largest.   Ultimately, however,
  the operators of that plant were ordered to install baghouse/dryscrubbers
  and to rip out the ESPs at a cost of tens of millions of dollars.
  > PCDD/PCDF releases from various waste management strategies   
  >[undated, draft for publication]- 
  > GH Eduljee, ERM P Dyke, ETSU, AEA Technology PW Cains, Technical 
  >Products Division, AEA Technology
  > In reality, the presence of PCDD/Fs in collected, untreated bulk 
  >refuse and in the various waste fractions will result in their 
  >transfer to downstream recycling and resource recovery options. 
  >PCDD/Fs have been measured in compost, landfill gas and leachate, and 
  >in gases and residues from metals recycling operations.
  >  The maximum quantity of landfill gas generated is 120-240m3 per 
  >tonne of MSW. Fifty percent of the landfill gas leaves the landfill 
  >site as an uncontrolled fugitive emission. Fifty percent of the 
  >landfill gas is collected for energy recovery in a gas engine. The 
  >generation of flue gas is 10 m3/m3 of raw gas (flue gas at 11% 
  >oxygen). Emission factors are 0. 32-0.36 ng I-TEQ/m3 of fugitive gas, 
  >and 0.1-1 ng I-TEQ/m3 of flue gas.
  > P Dyke, ETSU, AEA Technology, B154, Harwell, Oxon OX11 0RA, UK Fax: 
  >(Intl +44) (0)1235 433 981
  Looking at this paper on the net, the author explicitly states 
  that the numbers quoted here as "assumptions," not actual test conditions.
  Eduljee is the author that tries to argue that recycling is worse
  than incineration.
  Also, apparently vinyl chloride can be formed from 
  anerobic bacterial degradation of tri-chloroethylene,
  according to an EPA fact sheet citing ATSDR
  reports at 
  "Vinyl chloride is a microbial degradation product of 
  trichloroethylene in groundwater; 100 percent transformation to [SIC]
  trichloroethylene was obtained after 10 days under anaerobic conditions."
  -3.Agency for Toxic Substances and Disease Registry (ATSDR).
  Toxicological Profile for Trichloroethylene.
  U.S. Public Health Service, U.S. Department of Health 
  and Human Services, Atlanta, GA. 1992. 
  So landfill-related vinyl chloride can occur without having to assume
  that it is generated in significant quantities by off-gassing
  of PVC in the absence of heat and UV in the middle of 
  Finally, as to the combustion of landfill gases and an overall 
  If you do not collect and burn such gases, the resulting fugitive emissions
  from landfills will cause....
  ...much greater community odors
  ...fugitive emissions of methane as a greenhouse gas
  ...fugitive emissions of volatile organic compounds that result in ozone
  ...fugitive emissions of any toxic organic compounds that may be present
  ...the potential for migration of explosive landfill gases through
  underground strata that
     can ultimately lead to explosions.
  As long as we have MSW landfills in place, which have to be the worst form of 
  waste disposal ever invented, we (as a society) still have to deal with the
  problems which are serious.   And any collection system will only 
  be getting a portion of the gas.
  Burning collected gases with a torch/flare means poor combustion and
  destruction of the
  gases, particularly at the edges of the flame zone and particularly during
  high wind conditions.
  Burning with a dedicated combustor with burners and a stack means that
  at least you are doing a relatively better job of combusting the gases
  and limiting ambient concentrations downwind.
  Burning with internal combustion or turbine engines means that you can
  get rid of the landfill gas and generate electricity at the same time and
  lower use of other fossil fuels.
  Alex J. Sagady & Associates        Email:  asagady@sojourn.com
  Environmental Consulting and Database Systems
  PO Box 39  East Lansing, MI  48826-0039  
  (517) 332-6971 (voice); (517) 332-8987 (fax)