[Terrapreta] plastic "char" TP

[Sean K. Barry]

Hi Kevin,

I do not know what the relative amounts of the listed toxic chemicals and heavy metals are, but below here is an excerpt from a paper I read some of today.  It describes these in more detail.  You could look at the whole paper if you are interested (available at http://mindfully.org/Berkeley/Berkeley-Plastics-Task-Force.htm<http://mindfully.org/Berkeley/Berkeley-Plastics-Task-Force.htm>).  From what I gathered, most of the pollution problems in the plastic products are in the additives (plasticizers, antioxidants, coloring dyes, heat stabilizers, etc.) to basic plastic resins like polyethylene, polypropylene, and etc.  There are even bigger problems with toxin releases to the environment when plastics are manufactured new.
I think recycling plastics would be better than destroying any, so that new ones would not have to be made.


3. OVERALL IMPACT OF PLASTICS ON THE ENVIRONMENT, WITH AN EMPHASIS ON CONTAINERS
Pollution and hazards from manufacturing

The most obvious form of pollution associated with plastic packaging is wasted plastic sent to landfills. Plastics are very stable and therefore stay in the environment a long time after they are discarded, especially if they are shielded from direct sunlight by being buried in landfills. Decomposition rates are further decreased by anti-oxidants that manufacturers commonly add to enhance a container's resistance to attack by acidic contents.

Plastics also put a big chemical burden on the environment. The Oakland Recycling Association commissioned an analysis of the toxic chemical burden that relied heavily on information from EPA data, especially the Toxics Release Inventory.[17] These data were limited because manufacturers within the "miscellaneous plastics sector" did not file reports. Nevertheless, the information available showed that most toxic releases went into the air, and the plastics industry contributed 14% of the national total. Of the top ten manufacturers ranked by total releases, seven made plastic foam products. Significant releases of toxic chemicals included :

  a.. trichloroethane 
  b.. acetone 
  c.. methylene chloride 
  d.. methyl ethyl ketone 
  e.. styrene 
  f.. toluene 
  g.. benzene 
  h.. 1,1,1 trichloroethane 
Other major emissions from plastic production processes include sulfur oxides, nitrous oxides, methanol, ethylene oxide, and volatile organic compounds.[18]

Less visible but very serious is the pollution generated by producing plastic resin. As ethylene is polymerized, the reactive mixture is scrubbed with dilute aqueous caustic solutions[19] that become high-volume pollutants. The refining process uses waste-minimization methods, but point-source air emissions are still high because of inherent difficulties in handling large flows of pressurized gases. Manufacturing PET resin generates more toxic emissions (nickel, ethylbenzene, ethylene oxide, benzene) than manufacturing glass. Producing a 16 oz. PET bottle generates more than 100 times the toxic emissions to air and water than making the same size bottle out of glass.[20]

Producing plastics can be hazardous to workers, too. Serious accidents have included explosions, chemical fires, chemical spills, and clouds of toxic vapor. These kinds of occurrences have caused deaths, injuries, evacuations and major property damage.[21] A review of the US EPA's data base of 10,000 accidents and spills from 1980-87 shows that nearly 1,600 (16%) of industrial accidents were associated with producing plastics or plastic constituents.[22]

Negative health effects - toxic additives, migration into food

In addition to creating safety problems during production, many chemical additives that give plastic products desirable performance properties also have negative environmental and human health effects. These effects include direct toxicity, as in the cases of lead, cadmium, and mercury; or carcinogens, as in the case of diethyl hexylphosphate (DEHP). Problem chemicals are used as plasticizers, antioxidants, colorants, flame retardants, heat stabilizers, and barrier resins. A single resin type might be mixed with many such additives, adding complexity to the chemical composition and possibly generating new classes of incompatible resins within the grossly simplified SPI resin code. An example of internal incompatibility is resin type 2, noted earlier as a recycling problem because the blow-mold resin grades and injection-mold grades must be separated for most primary recycling applications.

People are exposed to these chemicals not only during manufacturing, but also by using plastic packages, because some chemicals diffuse (migrate) from the packaging polymer to the foods they contain. Migration potential exists for traces of monomers, oligomers, additives, stabilizers, plasticizers, lubricants, anti-static nucleating agents, and reaction products of the polymer or its additives. Such substances may be toxic.

Examples of plastics contaminating food have been reported with most polymers, including styrene from polystyrene, plasticizers from PVC, antioxidants from polyethylene, and acetaldehyde from PET.[23] Among the factors controlling migration are the chemical structure of the migrants and the nature of the packaged food.[24] In studies cited in Food Additives and Contaminants,[25] LDPE, HDPE, and polypropylene bottles released measurable levels of BHT, Chimassorb 81, Irganox PS 800, Irganix 1076, and Irganox 1010 into their contents of vegetable oil and ethanol. Evidence was also found that acetaldehyde migrated out of PET and into water.

  > Another important consideration when making charcoal to amend into 
  > soil and form "Terra Preta Nova" soils is that its source is 
  > BIOLOGICAL, hence "biochar".  It's not just because the name has "bio" 
  > in it either!  One of the concepts that we are trying to develop in 
  > this group is to use biochar put into soil as a way to harvest carbon 
  > from the atmosphere and sequester it into the soil.  We are after a 
  > mitigation strategy for the green house gas problem.  To do this, the 
  > biochar feedstock must be "grown" biomass.  That biomass feedstock has 
  > to have been part of a living plant, which took CO2 out of the 
  > atmosphere when it grew, in order for it to have "harvested" any 
  > carbon from the atmosphere.

  I said this before (just above), and I think it is really the best reason for not using plastic as a feedstock for charcoal to put into agricultural soil.

  Jim Mason said this too, "... plastics are already 'fixed carbon' ..." !!!

  Regards,

  SKB


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