In Hong Kong, plastic waste is one of the main components in municipal solid waste. It constitutes 15 to 20% by weight and around one third by volume in the waste stream. Current trends show that the amount of plastic waste will continue to increase in the near future. This makes the problem of handling the waste increasingly difficult. At present, landfill and incineration are the most common methods for disposing of such waste globally. However, both methods are becoming less attractive because of their high operating costs and associated environmental problems. As a result of this,people have begun to examine alternative methods which involve recycling, rather than disposal....[ Read more ]

In Hong Kong, plastic waste is one of the main components in municipal solid waste. It constitutes 15 to 20% by weight and around one third by volume in the waste stream. Current trends show that the amount of plastic waste will continue to increase in the near future. This makes the problem of handling the waste increasingly difficult. At present, landfill and incineration are the most common methods for disposing of such waste globally. However, both methods are becoming less attractive because of their high operating costs and associated environmental problems. As a result of this,people have begun to examine alternative methods which involve recycling, rather than disposal.

In this project, pyrolysis was used to examine the potential for tertiary recycling. Four plastics were studied - polypropylene (PP), polystyrene (PS), low-density polyethylene (LDPE) and high-density polyethylene (HDPE) - individually as well as in two defined mixtures. The effects of the reaction conditions on the product distribution were investigated in some detail. Results for the effect of temperature, the presence of a zeolite catalyst and the composition of the purge gas will be presented and discussed in terms of degradation rate, product yields and distributions. Consistency with published mechanisms for the degradation of individual plastics will be examined and the implications of mixture interactions will also be considered.