Recycling by product massive number of types of plastic, they each carry a resin identification code, and must be sorted before they can be recycled. This can be costly; while metals can be sorted using electromagnets, no such 'easy sorting' capability exists for plastics. In addition to this, while labels do not need to be removed from bottles for recycling, lids are often made from a different kind of non-recyclable plastic. To help in identifying the materials in various plastic items, resin identification code numbers 1-6 have been assigned to six common kinds of recyclable plastic resins, with the number 7 indicating any
Polystyrene and many aromatic hydrocarbon solvents. Because of its resilience and inertness, it is used for fabricating many objects of commerce. It is attacked by many organic solvents, which dissolve the polymer. Foamed polystyrene is used for packaging chemicals. Like all organic compounds, polystyrene burns to give carbon dioxide and water vapor. Polystyrene, being an aromatic hydrocarbon, typically combusts incompletely as indicated by the sooty flame. Polystyrene is generally non-biodegradable. There are a couple of exceptions: To quote: Methanogenic consortia have been shown to degrade styrene as sole carbon source (Grbić-Galić et al. 1990). In this case styrene degraded to a