Re: dioxin/cl/incineration: another study

[Ferdinand.Engelbeen@ping.be (Ferdinand Engelbeen)]

Dear dioxin-l readers,

The following information is quite technical, but responds to the main
points of the study of Thomas, V.M., and Spiro, T.G., 'An estimation of
dioxin emissions in the United States', Toxicol. and Environ., Chemistry
50:1-37 (1995), posted by Charley Cray.

>----
>and residential wood burning.  Anthropogenic emissions of
>PCDD/Fs are estimated to be an order of magnitude greater than
>emissions of PCDD/Fs from forest fires.  Dioxin emissions are
>----

Where are the forest fire emissions based on? Any references?

>----
>  Dioxin emissions are
>shown to generally increase with the chlorine content of the
>combusted material, in the absence of effective pollution
>control systems.
>----

In the absence of adequate pollution control we can see:
All figures in % for average chlorine content and
average microgram sum dioxins emitted/kg material.

material:          chlorine     dioxin

PVC at fire          45           0.4  (*)
hospital waste        7          20
hazardous waste       5.5         1
Municipal waste       0.4        10
Wood combustion       0.2         1    (*)
Coal combustion       0.02        1    (*)
Leaded gasoline       0.002       0.03
Unleaded gasoline     0.001       0.003
Heavy fuel            0.0005      0.4  (*)
Diesel Rhinebarge     n.d.        0.1  (*)

n.d. = not detectable (less than 0.0002%)
(*) figures from RIVM/TNO report 770501003, assuming sum dioxins to be
average 100 times I-TEQ figures. The other figures are from the Thomas and
Spiro report.

If you only look at the average figures from the Thomas and Spiro report,
you can see some correlation between chlorine content and dioxin emission,
but that disappears completely when more relevant data are included...

On the other hand, the use of control equipment for regulation has a
drastic effect on dioxin emission, no matter what the chlorine content of
the waste is:
The amount of dioxins emitted by hospital waste incinerators in The
Netherlands differs 4 orders (!) of magnitude between old and new
incinerators, having the same feed, but better incinerator controls...

>-----
>   While a dependence on chlorine content might seem to be a
>foregone conclusion, there has in fact been doubt on this point
> since limited data, on test-burns at municipal waste
>   incinerators, for example, have shown no correlation.
>------

more than a thousand test-burns on more than a hundred municipal waste
incinerators... limited data?

>-----
>under poorly controlled conditions (closed symbols), there is
>a clear dependence on chlorine content.  Moreover, the
>   relationship is more than proportional since the slope of the
>  log-log plot is somewhere between one and two.  Since dioxin
>molecules contain more than one chlorine atom, a higher order
>dependence is not unexpected.
>-----

Strange chemistry! Since dioxin molecules always contain 12 carbon atoms,
we can expect a very high order dependence on the carbon content of the
waste?

In fact, real correlations were found between dioxin formation and carbon
content of the fly-ash:
The Bundesministerium fuer Forschung und Technologie (German Ministery of
Research and Technology) has done a dioxin measurement program in 1985-1988
at 13 municipal waste incinerators: "Muelverbrennung und Umwelt 3", Karl J.
Thome-Kozmiensky, EF-Verlag, ISBN 3-924511-10-1, Berlin 1989. Although
there were enormous differences in type and conditions of the different
incinerators, there was no correlation between HCl in the raw offgas and
dioxin formation.
They found correlations between dioxin formation and carbon content of the
fly-ash, oxygen in the off-gas (negative), CO in the off-gas and
temperature of the e-filter.

>------
>According to the current understanding of
>dioxin formation, HCl is the chlorine source for dioxin
>formation in catalyzed reactions on fly ash, with a maximum at
>temperatures of about 400 C.  The HCl is formed during
>------

This is contrary to the results of a lot of experiments, which should be
known by the authors, because already done many years ago...
Where are the references of the authors that support this theory?

Experiments include the forementioned German report and:
Environment Canada, "The National Incinerator Testing and Evaluation
Program: Two-stage Combustion (Prince Edward Island) - Summary Report,
Report EPS 3/UP/1, Ottawa, September 1985. Here the detailed figures give a
correlation between HCl and dioxins of 0.12 (r2, no correlation), between
moisture and dioxins: 0.55 (fair), between primary air and dioxins: 0.83
(very good) and between copper content and dioxins it was 0.77 (also very
good). The amount of particulate (= fly-ash) was also important: a new
design reduced the amount of particulate a 30-fold and the dioxin emissions
reduced simultaneously by a tenfold.

>-----
>   The relationship between chlorine content and dioxin
>   emissions, demonstrated in Figure 1, provides a means to
>estimate how dioxin emissions are related to the presence of
>anthropogenic chlorinated compounds in materials that are
>burned.  With municipal and hospital waste combustion being the
> largest dioxin sources that are affected by anthropogenic
>chlorinated organic materials (see Table 2), the relationship
>of total dioxin emissions to anthropogenic chlorinated
>   compounds will depend primarily on how the emission factors
>for municipal and hospital waste combustion would change in
>the absence of chlorinated compounds.  ...
>-----

Real life tests showed that even when all PVC was omitted from waste, there
was no difference in dioxin emission...
Experiments include the forementioned German report: they made tests with
different feed: only old paper, PVC-poor, PVC-rich, the finer fractions,
etc... Only the incineration of more finer fractions did give more
dioxins... (= more fly-ash!)

Even if we assume that the chlorine input theory is right and all chlorine
industry was stopped and no anthropogenic chlorinated compounds would be
burned anymore, this would reduce the dioxin emissions not more than half,
still at least a fiftyfold too high, if we assume that anthropogenic dioxin
emissions must be at least 10 times lower than natural...

On the other hand, better emission controls can reduce dioxin emissions a
hundred- to tenthousandfold, regardless of chlorine content of the waste.


>------
>   Coal Combustion:  The average chlorine concentration in US
>coal is about 200 ppm, ranging from 20 to 8000 ppm, and coal
>combustion can be expected to produce some dioxin.
>------

With 19% of all dioxin emissions in the UK directly from coal combustion,
and a 2.6% estimate in the US, a hundred times higher than traffic, this is
a little bit underestimated... Why are the dioxin emissions of coal
combustion not included in the graph of Figure 1?

                              * * * * *

CONCLUSION:

The phase-out or ban of chlorine- and/or PVC-production, use or
incineration will have no effect on the todays dioxin load in the US or
Canada.
There is no correlation between chlorine input and dioxin formation in any
type of incineration or combustion. If you want to reduce dioxin emissions,
you must use adequate controls on every type of combustion, fire, heating,
high temperature process, etc... Or use as much as possible alternative
methods like recycling, composting (although...), thermolyses, etc...
But there will always be dioxin emissions from heating, high temperature
processes, traffic, etc..., it will never be zero...

Ferdinand Engelbeen

Ferdinand.Engelbeen@ping.be