Most of the people say its not good to decompose plastic materials by burning, but anyway it has to be decomposed after its use. Is it safe to burn plastics?
If not how can we decompose plastic wastes?
Most of plastic materials when burning in a conventional fire decompose to toxic substances which have bad health effect on many living organisms including humans. Many of the substances are carcinogenic.
The dangerous substances are mainly:
... and a lot of other dangerous substances.
As dax wrote the best solution is to recycle the plastics.
Different solutions are based on various techniques of safe decomposition.
Incineration is controlled burning of various waste at high temperatures with filtering of the produced substances. At high temperatures the dangerous organic compounds are further decomposed to less dangerous substances.
Pyrolysis is a decomposition of organic material at elevated temperatures in absence of oxygen. The products of pyrolysis can be used for example as a fuel.
Certain bacteria can help decomposition of plastics. See for example: In what new ways can bacteria help shrink our landfills? -- Plastic-eating bacteria found in 'ocean desert,' scientist says
You should not burn plastic. Besides the environmental impact, you're wasting resources.
You should recycle plastic - here is how that's done:
Sorting and grouping plastic materials according to resin type is an important first step in the recycling process because contamination can render a batch of material un-reusable. The most frequently recycled resins, including polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polyvinyl chloride (PVC), must be carefully separated from one another in order to enable further processing. Contaminants within each type of plastic must also be removed from the base resin to ensure stock purity.
Plastic materials usually need to be cut into smaller sizes in order to allow further processing and to provide easier packaging, transportation, and distribution of recycled stock.
After the plastic has been cut into smaller pieces, or “flakes,” the stock usually needs to be washed in order to remove lingering dirt or attachments. Paper, glue, sand, and grit are some of the common elements targeted in the washing process, which can be accomplished using water baths, friction washers, or a washing line.
To reduce the potential for stock contamination most recycled plastic undergoes separation treatments, which work to remove any attachments or non-reusable materials that may be present in a batch of flakes.
Pelletizing reclaimed plastic is the final step in most recycling processes. Converting post-consumer plastic into pellets allows for easier distribution and remanufacturing, and ultimately benefits the speed and effectiveness of reintroducing recycled plastic into industrial manufacturing. After sorting, drawing, separating, and drying the reclaimed material, the flake stock is ready to be extruded into pellets. Once the reclaimed plastic has been pelletized, it is ready for distribution and remanufacturing.
You could (possibly) do this yourself, although it seems like a better idea to buy the plastic pellets - if you have something to do with them, that is. Otherwise you can participate in the collection part of the process. Plastic can be sold to collection agencies just like any other material (like aluminum cans, copper wire or junked cars).