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Tetrapaks are almost universal over the whole planet. And, up ‘til now, they have been very difficult to recycle. Each is made of a sandwich, printed plastic on the outside of a layer of white paper and aluminum foil on the inside. The aluminum seems to have a coating too. These three layers are very hard to separate.
I have seen people, on the web, who run these cartons through a shredder, then subject the result to strong agitation in water. This pulps out about 90% of the paper layer, leaving the plastic and Al foil layers. Then spread this out on a form made from a corrugated sheet, dry it and apply heat to semi melt the plastic, thus making a roofing sheet. Nice!
I thought of saving energy by:
1) Putting the shredded and partly pulped cartons into a simple batch biodigester with a source of enough fixed nitrogen, etc. to support digestion of the paper pulp. This is not to produce methane, altho it might make a little. This also takes care of any food residue in the cartons.
2) When the new sheet is dried on the form, remove it and set the plastic using a large fresnel lens to heat it.
I think these roofs would tend to shed some foil over the years but still would be worth while.
Roy 20:02, 8 May 2006 (PDT)
Instead of shredding the tetrapacks and destroying all their desirable properties like watertightness and insulation, why not just flatten the cartons and nail them to a roof like shingles? Fenn 20:31, 11 March 2009 (UTC)
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