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GREENPEACE AGAIN: PVC AND DIOXIN EMISSIONS...

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Half truths as usual...

The newest work of Pat Costner, "Chlorine, Combustion and Dioxins", September 10, 2001, is the next attempt to discredit chlorine in general and PVC in particular. This "definitive" answer about the relationship between chlorine input and dioxin output is so far biased, that it need months of research to show all the biases and especially the omissions which prove the opposit (as far as a negative can be proven). E.g. by using very old data (when detection limits were orders of magnitude higher than nowadays) to ignore any relationship between salt in organic materials and dioxin emissions and very recent data to prove a relationship between PVC and dioxin emissions in the worst case scenarios... And if you read the original works which were used by Greenpeace, there is far more interesting information in them available than what Pat Costner has filtered out!


General

As is known from combustion in large scale facilities (household garbage incineration, hospital waste incineration, hazardous waste incineration, see the ASME report), the influence of chlorine on dioxin formation is far lower than of the incineration conditions: the three T's: Temperature, time and turbulence. That means that even large changes in chlorine content of the waste have less influence than small changes in operating conditions. Therefore the large scale facilities don't show any correlation between chlorine input and dioxin output, even not before any cleaning equipment. There are as good significant positive as negative correlations. Even Greenpeace, although using single regression statistics (in a multiple cause-and-effect case...), could not refute this. When we said that in a discussion, their graphs which showed that we were right disapeared from the Internet... but we recovered them... In the new report, Greenpeace only used data from laboratory and pilot scale combustion tests. While these can give good information about the mechanisms of dioxin formation, they have a lot of difficulties to obtain the same process conditions as can be found in large scale combustion facilities. Further, as dioxin formation is a catalytic reaction, directly related to copper content and to time and temperature, one can find any amount of dioxins with prolonged times and low temperatures (200-450 °C)...

There are special occasions, where PVC, chloride (salt), wetting and/or compacting of the waste has a serious impact on dioxin foramation. That is the case for backyard barrel burning and inadvertent fires in dumps. That is less the case for accidental fires of houses and warehouses, where incineration conditions in general are better (higher temperatures, less compacted, less wet). But even in worst case conditions, it is not the chlorine level which makes more dioxins, it is the influence of chlorine on the conditions which makes the difference. Moreover, more PVC/chlorine reduces the amount of PM(10 and 2.5), VOC's (benzene) and PAH's. The latter are far more important in carcinogenity and toxicity than dioxins...

A lot of omissions can be found in the latest Greenpeace report about the role of chlorine in dioxin formation. That will be addressed in the last part of this answer page.


Chlorine input and dioxin output in  large scale facilities.

1. Municipal waste combustors:

Original set of data: HCl content in raw waste gas (as surrogate for chlorine content in the waste) and dioxin measurements.


Partial correlation coefficients by the ASME, based on multiple regression, as is appropriate for multi-cause and effect systems like can be expected in incinerators

Single correlation coefficients according to Greenpeace for different facilities, without taking into account design (turbulence), temperature and residence time...

2. Medical waste combustors:

Original set of data: HCl content in raw waste gas (as surrogate for chlorine content in the waste) and dioxin measurements.


Partial correlation coefficients by the ASME, based on multiple regression, as is appropriate for multi-cause and effect systems like can be expected in incinerators

Single correlation coefficients according to Greenpeace for different facilities, without taking into account design (turbulence), temperature and residence time...

3. Hazardous waste combustors:

Original set of data: HCl content in raw waste gas (as surrogate for chlorine content in the waste) and dioxin measurements.

Partial correlation coefficients by the ASME, based on multiple regression, as is appropriate for multi-cause and effect systems like can be expected in incinerators

Single correlation coefficients according to Greenpeace for different facilities, without taking into account design (turbulence), temperature and residence time...

    As one can see, there is ample difference between the Greenpeace interpretation of the data of the three large scale main combustion facilities: municipal, hospital and hazardous waste incinerators. All show as good positive as negative correlations. That simply means that a small change in process conditions has a much higher influence than large changes in chlorine content...


Chlorine input and dioxin output in  backyard barrel burning.

A series of experiments where waste with different chlorine loads and different circumstances was burned in barrels, were performed by Gullet, Lemieux, et al., "PCDD/F emissions from uncontrolled, domestic waste burning" [62].

At first glance, PVC input has a tremendous impact on dioxin formation, like more copper, compressing and wetting of the waste has. But chlorine has only a secondary effect, as it lowers the burning temperature and/or augments the residence time, which results in higher dioxin releases.

TC1-6: thermocouples at different heights in and above the burning waste.
TS1-4: timeframes within temperature intervals.

As you can see, chlorine sources like PVC, chlorine or HCl can be omitted out of the equation, while still obtaining a high correlation. But copper and time and/or temperature can't be omitted. That again confirms that process conditions and copper by far are the most important parameters.

Only in one series of experiments (See: barrel burning), not only dioxins were measured, but also PM, benzene, VOC's, PAH's,... From that experiments, one can learn that a higher PVC content is accompanied by lower PM, benzene, VOC and PAH emissions. With a factor 20 lower for cancerogenity for BaP than for TCDD (in some strains of rats), the emissions of high-PVC trials were less carcinogenic (as far as these contaminants are bio-available) than for low-PVC, because of much lower PM, PAH and benzene emissions. Unfortunately, VOC and PAH emissions were not measured in the new series.

Thus exchanging PVC by alternative plastics can reduce dioxin emissions in worst case scenarios, but will augment PAH emissions (already 3-4 orders of magnitude higher) in the same circumstances. Dioxins don't damage DNA and are cancer promotors only at extreme levels. PAH's break down to DNA damaging oxidized substances and thus are cancer initiators. What a choice... A good case to apply the precautionary principle? But you don't have to choose: just forbid backyard burning (and educate people to don't burn any waste - neither in barrels nor in open fire places or stoves) and let the waste go to state-of-the-art incinerators. Makes a difference of 30,000-120,000 times in emissions. No matter what you burn...


Laboratory experiments .

A lot of experiments were done in laboratoria. While these have troubles to obtain the same conditions as can be found in large scale incinerators, these can give some insight how and where dioxins are formed. This can be found at our Chemistry of dioxin formation page. Especially the influence of time, turbulence, temperature, oxygen, chlorine and metals was investigated in laboratory experiments.

While we don't have all works referenced by Pat Costner, these that we have contain very interesting information which was omitted by her. Here follows a step by step comparison. For some of the experiments that show a high correlation, nothing is mentioned about the other variables that influence dioxin formation to a much larger extent (temperature, time, turbulence and copper content). Thus not much comment can be given...

Greenpeace:
"Since every molecule of dioxin contains two or more atoms of chlorine, chlorine is an absolute necessity for dioxin formation. Therefore, when no chlorine is present, no dioxins are formed."
Omitted:
But without oxygen or carbon, no dioxins are formed either. The first is used in an alternative for incineration (thermolyses). And the second is type dependent. Carbonised organic materials are good precursors for dioxins (and PAH's), while graphite is not. And even ambient air contains hundreds to thousands times the amount of chlorine that is necessary to form dioxins found at incinerators. And any organic material contains chlorine at hundredthousands to millions of times higher levels than what is built into dioxins...

Greenpeace:
"For example, Katami et al. (2000) found less dioxin output in gaseous emissions with lower chlorine input during the combustion of newspaper with PVC or sodium chloride, as shown in figure 1".
Omitted:
The tests mentioned by Greenpeace to "prove" the relation between chlorine input and dioxin output is by Katami e.a. [63]. But in the graph they made of the testresults, they omitted one of the tests! That was a test with NaCl impregnated newspaper and PE plastic added. While the chlorine content of the fuel was reduced from 3.1% to 2.5%, the dioxin/furan emissions remained the same... Thus may we conclude that PE is a precursor for dioxin formation???

See the difference in graphs:

Further, one can give a lot of critique about the tests and the interpretation of the results:

material
% Cl2
heat content 
kcal/kg
oil 0.0036 10800
newspaper 0.0064 4420
PE 0.005 11200
PVC 35.7 6240
wood 0.028 4200
chlorine and heat content of the materials used in the tests


Materials
heavy oil newspaper wood np+NaCl np+NaCl+PE np+PVC units
54           kg oil
  55   48.45 24.57 24 kg paper
    60       kg wood
      1.55 0.79   kg NaCl
        6.4   kg PE
          4 kg PVC
54 55 60 50 31.76 28 kg total
Process conditions
36,000 64,000 280,000 31,000,000 25,000,000 51,000,000 ng/g chlorine
457 653 456 510 473 456 avg. °C chamber
378 526 435 415 434 416 avg. °C exhaust
4 4 3.67 3.9 3.33 3.33 hours
13.5 12 15 12 9.5 8.4 kg/h
87 1000 1090 1200 990 1500 avg. ppm CO exhaust (#)
583 243 252 214 180 131 Mcal total
146 61 69 55 54 39 Mcal/h
Results
0.095 0.149 0.174 25.6 18.7 30.0 ng/g PCDD total
0.651 0.783 1.99 77.8 83.2 117 ng/g PCDF total
0.746 0.932 2.164 103.4 101.9 147 ng/g PCDD/F total (*)
6.9 5.3 11.4 3.0 4.4 3.9 PCDF/PCDD ratio
n.d. n.d.   23 59 640 avg. mg/m3 HCl exhaust (#)
Material mixtures, process conditions and results of the tests by Katami e.a. [63]
(#) relative to 12% oxygen
(*) app. half the PCDD/F by weight is chlorine, to be compared with the chlorine input...

All together, one can conclude that no conclusion can be drawn from this tests, as different process conditions with a known high influence on dioxin formation were not kept constant. That is as well as for temperature as for time, but probably also for turbulence, as different load conditions also can introduce changes in air flows...
 

Greenpeace:
Numerous studies of laboratory- and pilot-scale combustion systems have found that dioxin formation decreases with reduced chlorine input. The U.S. Environmental Protection Agency (2000) acknowledged this to be the case in their recent review of such studies:
“[R]eview of experimental data clearly indicates an association between chlorine content of feed/fuels and … synthesis of CDDs and CDFs.”
Omitted:
The above statement is true, but what was omitted is how much the chlorine content influences chlorinated organics formation, compared to other influences. As seen in experiments on laboratory and pilot scale (see laboratory experiments), those that show a correlation, have a two-fold increase of PCDD/F with a 12-fold increase in chlorine. Others show a 30% reduction with a tenfold decrease in chlorine content. That is within the variation of measurements of one dioxin sample within one laboratory (+- 30-50%) or between laboratories (up to a five-fold!). Or far within the variation between series with identical experiments (a 3- to 10-fold)...
The U.S. EPA also stated that for large scale combustors:

As the latter is the a way of combustion that can have significance in dioxin releases, that is addressed in this page: backyard barrel burning.
And the USEPA about the attack by Pat Costner on the ASME report on large scale combustors, which found no relationship between chlorine and dioxins: Greenpeace:
…Plastifyed linoleum gave more abundant yield of PCDD/PCDFs than mechanical mixture of PVC with plastifyer.
Omitted:
The relevant amount of chlorine in plastified linoleum (a few tenths of a %?) vs. the chlorine content of plastified PVC (>30%)???

Greenpeace:
Samples with a higher chlorine content give a higher CP [note: chlorophenols as surrogate for dioxin] emission but tend to reach a plateau value. ... [W]ith added HCl .. it appears that the CP emission increases quite regularly if not linearly with [HCl].” and
"Lowering the chlorine load – by leaving out compostables and PVC -, lowers the CP-level."
Omitted:
The complete work of Kanters and Louw has something more to say: complete elimination of PVC out of the feed had no effect on total CP formation, neither had the complete elimination of the compostables fraction. Only when both were reduced, resulting in a tenfold decrease in chlorine content, a 30% reduction was obtained. That was within the variability of CP measurements (30%) and far within the variability of two series of identical experiments (a 3-fold).

Greenpeace:
“… PCDD/F yields do in fact increase with increasing Cl radicals. … the presence of Cl radicals could be a critical influencing factor on
chlorination and PCDD/F formation.”
Omitted:
Cl *radicals* have no correlation with chlorine in the feed, neither in particulate or gases as they are formed by catalytic oxidation from chloride ions (either salt or HCl) by copper and oxygen. Thus copper and oxygen are the limiting factors, not chlorine...

Greenpeace:
"In another series of laboratory experiments, Wikstrom et al. (1996) varied the chlorine content of an artificial waste by spiking it with PVC or calcium chloride, obtaining the results illustrated in Figure 2." and
"Some scientists who agree that dioxin formation correlates with chlorine input nonetheless oppose policies restricting chlorine input. They contend that, even though restricting chlorine input reduces dioxin formation, other factors have far greater influence. For example, while Wikstrom and Marklund (2001) found a positive chlorine/dioxin relationship, they concluded that “the most important variable for changes in the PCDDs/Fs [dioxins] … formation was disturbance in the combustion condition and not the variation in chlorine content of the fuel“.
Then follows a ridiculous explanation why chlorine input still is important.
Omitted:
Wikström et al. [64], performed far more work than was mentioned by Greenpeace.  The graph shown by Greenpeace is outdated, as more experiments by Wikström et al. were done:

Wikström et al. performed 13 experiments with eight fuels, containing 0.28-1.1% chlorine. The results: Major Conclusions of a lot more experiments by Wikström et al.: The de novo synthesis mentioned here is about the non to low-chlorinated carbon skeletons, which are mainly formed at temperatures > 650 degr.C, together with the other PAH's, while (further) chlorination is performed below 650 degr.C.

Greenpeace:
"Delayed release of dioxins. The 'memory effect', which has been documented in a number of studies (e.g., Gullett et al. (2000) ; Blumenstock et al. (2000) ; Zimmerman et al. (2001) ; Hunsinger et al. (2000) occurs when dioxins are adsorbed onto the walls of incinerator stacks, ducts, etc., and then slowly released. This results in underestimation of the dioxin emissions that might otherwise correlate with a specific rate of chlorine input."
Omitted:
As was clearly stated at the dioxin seminar in Bruges, November 18-20, 2001 , the "memory effect" is indeed important, especially with upsets. But with upsets it is mainly soot/PAH's which precipitate on the walls. Further incineration again forms dioxins from the soot/PAH's. Thus again by catalytic chlorination from carbon sources... That means that you have to wait a long time after such an incident, before one can take conclusions of experiments. But that has nothing to do with the chlorine content of the waste...

Greenpeace:
"In a more specific example, the U.S. Environmental Protection Agency attributed reduced dioxin releases from lead smelters to the phase-out of PVC separators in lead batteries which are processed in such smelters"
Omitted:
The USEPA attributed 1 g I-TEQ dioxins per year to secondary lead smelters in 1987, 1.63 g I-TEQ/a in 1995, both very unimportant (but rising?) quantities. Quantities are from the UNEP world-wide dioxin inventory [60].

Greenpeace:
"For example, Gullett et al. (2000) carried out a series of experiments in which simulated domestic waste with varied quantities of PVC was burned in open barrels and, in one case, in a waste pile. As illustrated in Figure 4, dioxin formation decreased with lower PVC content. In the one test with a waste pile, they found considerably lower dioxin formation than with the open barrel burns."
Omitted:
The latter confirms that burning conditions are far more important than composition...
Further is omitted that the series of experiments included experiments where salt was added (more dioxins), the waste was wetted (more dioxins). Copper was added (more dioxins) and the waste was compacted (more dioxins)...
Further, the researchers tried to make correlations between one or more factors and dioxin formation. The results show that high correlations can be obtained WITHOUT chlorine, PVC or HCl in the equation. The only constant factor was copper, together with time and/or temperature of the incineration. See the results of backyard barrel burning on this page.
That leads us to one possible explanation of why higher dioxins are found with more PVC/chloride/water/compacting in these circumstances: all these factors hinders the incineration, changing the burning temperature and/or time. But that is more than compensated by the reduction of VOC's, benzene and PAH's at lower temperatures.
Only in one series of experiments by Lemieux e.a.[54], not only dioxins were measured, but also PM, benzene, VOC's, PAH's,... From that experiments, one can learn that a higher PVC content is accompanied by lower benzene, VOC and PAH emissions. With a factor 20 lower for cancerogenity for BaP than for TCDD (in some strains of rats), the emissions of high-PVC trials were less carcinogenic (as far as these contaminants are bio-available) than for low-PVC, because of much lower PM, PAH and benzene emissions. Unfortunately, VOC and PAH emissions were not measured in the new series.
That is confirmed by Wikström et al. [64]:

Thus exchanging PVC by alternative plastics can reduce dioxin emissions in worst case scenarios, but will augment PAH emissions (already 3-4 orders of magnitude higher) in the same circumstances. Dioxins don't damage DNA and are cancer promotors only at extreme levels. PAH's break down to DNA damaging oxidized substances and thus are cancer initiators. What a choice... A good case to apply the precautionary principle? But you don't have to choose: just forbid backyard burning (the government just started a campaign in Flanders to educate people to don't burn waste - neither in barrels nor in open fire places or stoves) and let the waste go to state-of-the-art incinerators. Makes a difference of 30,000-120,000 times in emissions. All kinds of emissions. No matter what you burn...

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Conclusion:

As usual, Greenpeace only mentions (parts of) these works which support their prejudiced opinion. That is their normal strategy, which is a political one and that has nothing to do with science (except the science of manipulation of the public opinion, for which they are unbeatable). This is - again - clearly the case for this work of Pat Costner who has read several works that are mentioned here, but - in our opinion deliberately - left out relevant information. As more examples of omissions will be found, this page will be updated...

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Created: November 22, 2001.
Last update: January 1, 2002.

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