Eventually, all tyres become unsafe to use even though the majority of the
material used to make the tyre is still present. Retreading, or the addition of a new
tread to an old tyre, can be performed on heavy vehicle tyres several times over
before these tyres also become unsafe. Therefore, recycling is an integral part to tyre
waste management around the world. The recycling techniques described below are
several of the possible solutions for the recycling of waste tyres in Hong Kong.
2.2.1 Shredded Rubber
Most recycling processes require the tyres to be shredded before further
processing (Clark, Meardon, & Russell, 1993). Shredding allows for much more
efficient transportation of tyre waste, as it can reduce the volume of the tyres by about
75%. Tyre shredding also eliminates many of the problems associated with above
ground storage in stockpiles. The tyre shreds do not allow water to build up and
become breeding grounds for insects, and the volume reduction allows for much more
efficient use of land. Of course the problems with fire hazards still remain.
Tyre shredding equipment is moderately expensive and consumes lots of
power. The tyre as a whole is first shredded to two-inch shreds. These shreds, about
the size of the palm of your hand, are not too useful by themselves other than the
volume reduction as they still contain the metal wires from the tyre (Lundin, personal
communication, November 28, 2006. See Appendix D). These shreds are put through
additional shredding equipment to reduce the size of the shreds to about one inch.
During this last shredding process the metal wires from the tyre are removed by
magnetic means. A rotating magnetic drum draws the metal wires out of the shreds