Friday, May 30, 2008

Burning Plastics

A lot of homo sapiens evolved to like fires. In countries with cold nights, fires kept people warm. Under open skies, fires frightened away wolves, tigers, or other predators. Inside dark caves and rooms, fires lit up the walls and created little worlds that could be seen with their eyes.

So to many people, burning wood seems natural. Indeed, a forest fire in any part of the world wastes more energy and carbon dioxide than a thousand (and usually millions and billions) home wood fires.

In a world overflowing with plastic waste from every angle, it is tempting to burn the plastics as well, is it not? What could be more self-sufficient? Especially if you can make heat or electricity from it, should it not be good for the planet?

So today's prize weblink is given to the simplest:
Separate plastics – separate plastic waste from other waste. Do not burn any plastics in your yard or house.
Avoid plastics – Avoid plastics, in particular do not purchase goods packed in PVC packaging, which generates dioxins when burned.
Reduce waste – Buy products that can be reused or refilled (glass and metal containers)
To which I add: Buy less, Use less, Waste less.

But if you have been puzzled by all the recycling codes on all the bits of plastic packaging of things beautifully manufactured in China and elsewhere, enlighten yourself with the Resin Identification Code.

Look out for Number 3
Vinyl and PVC
Are BAD x 3

Further websites of interest, all Googled, I confess:

A 2002 study from the US Environmental Protection Agency (USEPA) states that "backyard barrel burning" is the largest source of dioxin and furan emissions in the US, and a 2003 Environment Canada report indicates that this practice is the largest remaining single source of environmentally occurring dioxins in Canada. The burn barrels of less than 40 households can release the same combined amount of dioxins as a modern incinerator designed for servicing up to 120,000.

Some types of plastic contain elements besides the standard carbon,hydrogen, and oxygen. Nylons contain nitrogen, and polyvinyl chloride contains, of course, chlorine. These constituents also find their way into the combustion products. Probably the particular component you have heard about most is TCDD, which is an abbreviation for the chemical name tetrachloro-dibenzo-dioxin. This compound contains four chlorine atoms, and is inevatibly formed when polyvinyl chloride plastics are burned. (Complete combustion of PVC would yield only water, carbon dioxide, and hydrogen chloride; in practice, some incomplete combustion products such as TCDD are
always formed, if at low levels.) TCDD is also formed when wood burns, because wood also contains small amounts of chlorine. Because of the much higher proportion of chlorine in PVC, however, it is the material leading to the highest levels of TCDD.
The toxicity of TCDD to animals is well-established. It is often considered to be the man-made compound most toxic to animals. Its toxicity to humans,however, is not as well-established. The only absolutely confirmed human health effect from exposure to TCDD is a skin rash called chloracne. Other health effects are suspected. It is considered a carcinogen on the basis of animal studies.

TCDD is also an unwanted by-product of the manufacture of the herbicides 2,4-D and 2,4,5-T. A manufacturing accident at a plant manufacturing these chemicals occurred near Sevesto, Italy in 1976 released an estimated 1-10 lb of TCDD into the surrounding countryside, killing many farm animals and causing chloracne. Since 2,4-D and 2,4,5-T were components of the defoliant "Agent Orange" used in Vietnam, many U.S. servicemen (and of course Vietnamese) were exposed to elevated levels of TCDD. TCDD is thus suspected as the cause of the symptoms attributed to "Agent Orange" exposure.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

Some of the most dangerous chemicals created and released during burning some types of plastic are dioxins.... Dioxins, which are byproducts formed when chlorine-containing products are burned, tend to adhere to the waxy surface of leaves and then enter the food chain. Even if certain types of plastic (such as polyethylene or polypropylene) do not contain chlorine, other materials attached to or burned with the plastic may be a chlorine source.

Other chemicals released while burning plastics include benzo(a)pyrene (BAP) and other polyaromatic hydrocarbons (PAHs), which have both been shown to cause cancer. If film or containers are contaminated with pesticides or other harmful substances, those will also be released into the air. If plastics are burned with other materials, additional toxic chemicals may be created from the interaction of the different substances.

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