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The top of Bloom’s ladder

Dear Reader,

The other day I was looking at a web site devoted to PVC, it is written by some people who are strongly opposed to Greenpeace’s opinion on chlorine chemicals. Greenpeace is strongly opposed to the use of organic chlorine compounds (including PVC) while the chlorophiles say that PVC is great and good for the environment.

One of Greenpeaces’s claims that adding chlorine compounds like PVC to incinerators will lead to the formation of dioxin, and that PVC under the conditions in a landfill forms vinyl chloride. While I do not have an infinite amount of time I will have to choose to only deal with the second point.

However there is a little bit of a problem which was pointed out by the chlorophiles, they claim that bacteria in the landfills are forming the vinyl chloride from waste which is not related to PVC.

I took a look in the literature T.E. Mattes et. al. in FEMS Microbiology Reviews, 2010, 34, pages 445-475 writes at length about how bacteria can degrade polychloroethylenes (tetrachloroethylene, trichloroethylene and dichloroethylene) into vinyl chloride (chloroethylene) and then ethylene. Now while in hindsight things always look very clear and simple, I choose not to fall into the trap of assuming that Greenpeace had a crystal ball which allowed them to see the future. While some elements in the Green movement want industry to have a crystal ball to allow them to see every future effect of their activities (regardless of how unexpected these effects might be) I think it is unreasonable to expect either the “Greens” or the “Chemical Industry” to have these crystal balls.

If any of my readers know where I can get one from them please drop me a line as I think I would find it very useful in both my professional life and in my private life. I am not holding my breath waiting as I do not think such crystal balls exist !

But I then looked further back into the past, when I looked in the academic literature for “Biodegradation” and “Chloroethenes” I found back in 1995 a paper by J. Gerritse et. al. in Applied Microbiology and Biotechnology,  1995, 43 (5), pages 920-928. In this paper it reported that under anoxic conditions that “PCE was converted mainly into cis-1,2-dichloroethene, small amounts of TCE and chloroethene, and chloride”.

It is interesting to note that J. Gerritse has published more on this subject since the paper in 1995, (for example J. Gerritse et. al. Archives of MicroBiology, 1996, 165, pages 132-140) in which the abstract reports

“A strictly anaerobic bacterium, strain PCE1, was isolated from a tetrachloroethene-dechlorinating enrichment culture. Cells of the bacterium were motile curved rods, with approximately four lateral flagella. They possessed a gram-positive type of cell wall and contained cytochrome c. Optimum growth occurred at pH 7.2-7.8 and 34-38 degrees C. The organism grew with L-lactate, pyruvate, butyrate, formate, succinate, or ethanol as electron donors, using either tetrachloroethene, 2-chlorophenol, 2,4,6-trichlorophenol, 3-chloro-4-hydroxy-phenylacetate, sulfite, thiosulfate, or fumarate as electron accepters. Strain PCE1 also grew fermentatively with pyruvate as the sole substrate. L-Lactate and pyruvate were oxidized to acetate. Tetrachloroethene was reductively dechlorinated to trichloroethene and small amounts (< 5%) of cis-1,2-dichloroethene and trans-1,2-dichloroethene. Chlorinated phenolic compounds were dechlorinated specifically at the ol-tho-position. On the basis of 16S rRNA sequence analysis, the organism was identified as a species within the genus Desulfitobacterium, which until now only contained the chlorophenol-dechlorinating bacterium, Desulfitobacterium dehalogenans.”

Looking at the reference list for the 1995 paper I quickly found papers published around about 1990 on how bacteria reduce the more chlorinated ethylenes into less chlorine rich ethylenes. The reduction of these chlorine rich solvents (which have nothing to do with PVC) is a more reasonable source of vinyl chloride in landfill gas. PVC does not degrade into vinyl chloride, when it is heated it forms hydrochloric acid and a black tar which is rich in benzene, styrene, napthalene and soot. While the thermal degradation products of PVC are not nice, they are clearly not the same as vinyl chloride.

Now I would like to point out that chemicals like perchloroethylene (PCE, perc or tetrachloroethylene) and trichloroethylene (TCE or trike) should never have been added to a land fill but I think to blame one industry for the deeds of another is not fair. Blaming one industry for the misdeeds of another is as unreasonable as a policeman arresting a person at random so that he has someone to blame for a crime !

I think that Greenpeace should have devoted more time to reading the literature on vinyl chloride and landfills, as they have a team of full time people who incloude some people who have a background in science then I do not think it would be too hard for them to have found the papers on bacteria and vinyl chloride. I would also suggest to them that they take care to avoid the pitfalls of “groupthink” and other forms of tunnel vision which can lead to some very poor choices.

In British chemistry we have an ironic joke about people who dash into the lab becuase they do not want to spend time reading boring books becuase they want to do exciting chemistry, the joke is

“Why waste a week in the library when you can waste a month in the lab”

I would suggest to Greenpeace that they should adopt an altered version of this joke,

“Why waste a week in the library when you can expose yourself to ridicule, lose credibility and look silly while making an ill advised protest or pressrelease”

While the environment does need a friend, right now the claims which Greenpeace has made about the evils of PVC being added to landfills have caused them to lose credibility in my eyes. Now some of you might ask what is Bloom’s ladder and what is at the top of it. Bloom’s ladder is a series of levels of learning, at the top is the ability to compare and judge the worthyness of one source compared with another. Looking at a single item on the chlorophiles site, it does appear that they are more trustworthy than Greenpeace. This is becuase the science which the chlorophiles site is based on is better.

Now I imagine that I may have enraged some of my readers (If I have enraged you then sorry but people do not come to my blog to be pandered to) but I suggest that anyone who is enraged by my disection of a small part of Greenpeaces antiPVC campaign should go through the chlorophiles website with great care. If they can find any science which they doubt there, then please contact me and I will make a literature search before showing the world the results. I look forward to seeing what my readers think of the debate between Greenpeace and the chlorophiles.


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