A cladistic approach to grouping the items found at the site was taken. The final product would look similar to the tree of life.
The items would be initially split into either plastic or other material.
Plastics are made of polymers which are large molecules composed of repeating monomers. An example of a monomer is ethylene glycol, HO-CH2-CH2-OH. Polyethylene has a repeating unit based on this ethylene monomer.
Fig. 2. Ethylene glycol
The plastics could be split into seven groups based on their SPI resin identification code. This is the set of symbols (arrows that cycle clockwise to form a rounded triangle and enclosing a number) placed on the plastic to identify the polymer type. The primary purpose of the codes is to allow efficient separation of different polymers for recycling. The number does not indicate how difficult the item is to recycle, or how often the plastic was recycled. It is an arbitrarily-assigned number that categorizes the plastics.
Plastics are challenging to recycle because heating alone is not enough to dissolve them. Due to their high molecular weight of their large polymer chains, plastics must often be of nearly identical composition in order to mix efficiently. When different types of plastics are melted together they tend to phase-separate, like oil and water, and set in these layers. This causes structural weakness in the resulting material.
PET or PETE (polyethylene terephthalate)
Fig. 3. Repeating unit of polyethylene terephthalate
Found in: Soft drink, water and beer bottles; mouthwash bottles; peanut butter containers; salad dressing and vegetable oil containers.
PET plastic is the most common for single-use bottled beverages, because it is inexpensive, lightweight and easy to recycle
Recycled into: Polar fleece, fiber, tote bags, furniture, carpet, paneling, straps, new containers.
HDPE (high density polyethylene)
Found in: Milk jugs, juice bottles; bleach, detergent and household cleaner bottles; shampoo bottles; some trash and shopping bags; motor oil bottles; butter and yogurt tubs; cereal box liners
Recycled into: Laundry detergent bottles, oil bottles, pens, recycling containers, floor tile, drainage pipe, lumber, benches, doghouses, picnic tables, fencing.
V (Vinyl) or PVC
Polyvinyl chloride is produced by polymerization of the vinyl chloride monomer (VCM). About 57% of its mass is chlorine. This makes it very tough and therefore weathers well.
Found in: Window cleaner and detergent bottles, shampoo bottles, cooking oil bottles, clear food packaging, wire jacketing, medical equipment, siding, windows, piping. Recycled into: Decks, paneling, mudflaps, roadway gutters, flooring, cables, speed bumps, mats
LDPE (low density polyethylene)
Found in: Squeezable bottles; bread, frozen food, dry cleaning and shopping bags; tote bags; clothing; furniture; carpet
Recycled into: Trash can liners and cans, compost bins, shipping envelopes, paneling, lumber, landscaping ties, floor tile
PP (polypropylene)
Fig. 5. Repeating unit of polypropylene
HDPE (high density polyethylene)
Found in: Some yogurt containers, syrup bottles, ketchup bottles, caps, straws, medicine bottles
Recycled into: Signal lights, battery cables, brooms, brushes, auto battery cases, ice scrapers, landscape borders, bicycle racks, rakes, bins, pallets.
Polypropylene has a high melting point, and so is often chosen for containers that must accept hot liquid.
PS (polystyrene)
Found in: Disposable plates and cups, meat trays, egg cartons, carry-out containers, aspirin bottles, compact disc cases
Recycled into: Insulation, light switch plates, egg cartons, vents, rulers, foam packing, carry-out containers
Polystyrene can be made into rigid or foam products — in the latter case it is popularly known as the trademark Styrofoam. Evidence suggests polystyrene can leach potential toxins into foods. The material was long on environmentalists’ hit lists for dispersing widely across the landscape, and for being notoriously difficult to recycle.
Miscellaneous
Found in: Three and five gallon water bottles, ‘bullet-proof’ materials, sunglasses, DVDs, iPod and computer cases, signs and displays, certain food containers, nylon
Recycled into: Plastic lumber, custom-made products
A wide variety of plastic resins that don’t fit into the previous categories are lumped into number 7. A few are even made from plants (polyactide) and are compostable.
The other branch could be broken down by biodegradable and non biodegradable:
Biodegradable matter is generally organic matter (carbon based molecules) such as plant and animal matter and other substances originating from living organisms, or artificial materials that are similar enough to plant and animal matter. Therefore microorganisms can metabolically breakdown these molecules for energy and they release nutrients into the environment that can be reused by plants and other organisms. These microorganisms are known as decomposers (saprotrophs). In one gram of soil there can be up to 40 million bacteria cells.
Non-biodegradable group:
Metals: Different kinds of metals are separated by strong magnets. They separate out ferrous metals, such as iron, steel, and tin-plated steel cans (“tin cans”). Non-ferrous metals are ejected by magnetic eddy currents in which a rotating magnetic field induces an electric current around the aluminum cans, which in turn creates a magnetic eddy current inside the cans. This magnetic eddy current is repulsed by a large magnetic field, and the cans are ejected from the rest of the recyclate stream. Each kind of metal is then melted down to be reused.
Glass: a non-crystalline (amorphous) structure and that exhibits a glass transition (from a hard and relatively brittle state into a molten or rubber-like state) when heated towards the liquid state.
The glasses could then be broken into different colors. This is because glass retains its color after recycling.
References:
pictures from: Wikipedia
