[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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
> 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
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::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.
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. 
> To quantify dioxins emissions from landfill gas control devices
>for this investigation, I used measurements reported from flares and
>ICEs in Germany.  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
Also, apparently vinyl chloride can be formed from
anerobic bacterial degradation of tri-chloroethylene,
according to an EPA fact sheet citing ATSDR
"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: email@example.com
Environmental Consulting and Database Systems
PO Box 39 East Lansing, MI 48826-0039
(517) 332-6971 (voice); (517) 332-8987 (fax)