When municipal garbage goes into a "mass burn" incinerator, one of the
products that goes out the smokestack (or is trapped by a filter and
ends up in an ash landfill) is the family of chemicals called dioxins.
No one disputes that dioxins are produced by mass burn incineration,
but scientists disagree on where the dioxins come from.
Just a few years ago, many scientists were saying that the dioxins was
produced by low-temperature combustion (less than, say, 1400 degrees
Fahrenheit). They advocated that incinerators should be designed to
burn hotter to "burn up" the dioxins or perhaps not ever create the
dioxins at all. Others scientists were saying that dioxins was produced
by the burning of pvc plastic and if we would just keep the pvc out of
the waste stream, all would be well.
Dr. Barry Commoner had a different idea. He thought that dioxins was
being created inside the smokestack itself, after the smoke left the
combustion chamber of the incinerator. If he was right, running the
firebox hotter wouldn't prevent the formation of dioxins. He did some
experiments, wrote up his results, and then began advocating his ideas.
He's a persuasive speaker and a tough opponent in a debate. His
effective arguments angered his opponents and they began to call him a
charlatan and a "pseudo-scientist."
Recently, new research has confirmed Dr. Commoner's original ideas. In
the JOURNAL OF CHROMATOGRAPHY, Vol. 389 (1987), pgs. 127-137 and in
SCIENCE Vol. 237 (August 14, 1987), pgs. 754-756, Canadian scientists
report that they have found a major mechanism for creating dioxins in
waste combustion: the fly ash (the particles that make up the smoke in
the smokestack) acts as a catalyst (a chemical promoter) and causes the
formation of dioxins. They reported experiments in which they created
dioxins with chlorine-containing wastes but they also reported creation
of dioxins from non-chlorinated compounds. SCIENCE NEWS (Aug. 22, 1987,
pgs. 118-119) quoted one of these researchers saying, "We found that
[fly ash] is indeed a very strong catalyst which causes dioxins to form
from almost anything." They are now hard at work trying to manipulate
the composition of garbage to minimize the production of certain types
of fly ash catalysts, especially those containing metals. Pigments in
printing inks, for example, contain metals that may produce fly ash
that produces dioxins. They think that getting the metal out of garbage
might substantially reduce dioxin production.
Still other recent research throws additional light on the "dioxin from
mass burn" problem. Experiments at an incinerator in Pittsfield,
Massachusetts were aimed at discovering relationships between
combustion conditions, garbage constitu-ents, and dioxin production.
The report, RESULTS OF THE COMBUSTION AND EMISSIONS RESEARCH PROJECT AT
THE VICON INCINERATOR FACILITY IN PITTSFIELD, MASSACHUSETTS appeared in
June, 1987. Some of its more interesting conclusions were:
** There is no evidence that the amount of PVC plastic in the garbage
affects the amount of dioxin produced (pg. 10-4);
** Wet garbage produces more dioxins than drier garbage (pg. 10-4);
** There is no consistent relationship between the amount of dioxin in
the raw garbage and the amount of dioxin in the smoke stack gases (pg.
** There is a relationship between the amount of carbon monoxide in the
smokestack gas and the amount of dioxin (pgs. 10-1, 10-5); "However,"
the report says, "one must be cautioned that the specific relationships
between operating tempera-ture, carbon monoxide levels, and levels of
[dioxins] found during this study cannot necessarily be generalized to
other incinerators, particularly of a different design."
** The location of measuring devices in the incinerator affects how
much dioxin is found (pg. 10-1).
What can we conclude from all this? Authors of the Pittsfield study say
future research should focus on the effects of facility design and
operation (especially carbon monoxide levels, operating temperature,
and air pollution control systems) on the production of dioxins,
instead of focusing on characteristics of the garbage.
On the other hand, the Canadian researchers believe that manipulating
the contents of the garbage is the key to discouraging dioxin
From the citizen's perspective, faced with a machine that will be in
operation for 20 to 30 years, during which time the chemical contents
of American garbage are likely to change dramatically (if the last 20
or 30 years are any indication), trying to manipulate the contents of
the garbage seems complicated, untrustworthy and doomed to fail. No
government authority will ever be able to control the contents of the
stream of garbage entering a mass burn incinerator.
On the other hand, trying to find and maintain the exact operating
conditions that minimize dioxin formation (a narrow range of
temperatures, for example, and 100 ppm of carbon monoxide in the stack)
seems equally hopeless. Garbage incinerators are not going to be run
under laboratory conditions by chemists. They're going to be run by
garbage companies who have demonstrated time and time again that
they'll cut any corner necessary to make a buck. The garbage industry,
including the incineration industry, is dominated by organized crime or
by people who competed with organized crime and won out. These are not
the kind of people to whom you want to entrust an enormous, complex and
dangerous machine, the careful operation of which will dramatically
affect public health and safety.
In any case, knowing what minimizes dioxin production under controlled
conditions cannot ease the public's fear that mass burn will pollute
the air. The fly ash researchers writing in Science noted that "more
than 600 organic compounds" have been identified on incinerator fly
ash. That's 600 more than the public wants to breathe or dump into the
local landfill. Dioxin is simply No. 601 on the public's list of
unwanted pollutants from mass burn.
The Pittsfield study is NYSERDA Report 87-16, available from Department
of Communications, NY State Energy R&D Authority, Two Rockefeller
Plaza, Albany, NY 12223; phone (518) 465-6251.
Descriptor terms: msw; incineration; waste disposal technologies;
dioxin; barry commoner; fly ash; heavy metals; pittsfield, ma; ma;