(661c) Low Temperature Pyrolysis of Discarded Plastics

Plastics are petroleum based products which contain high value components. Most plastics are non-biodegradable, making their disposal difficult once they are no longer required for their intended purpose without impacting the environment.

With an increasing world population, demand for plastics and plastic products continues to rise, as does the amount of plastic waste. Between 1950 and 2015, an estimated 6300 million tonnes of plastic waste had been generated through various sources. Of this, only around 9% has been recycled and 12% incinerated. The vast majority of waste plastic is either accumulating in landfills or has found its way into the environment. If the current rate of plastic material disposal is carried forward, approximately 12000 Mt of plastic material will end up in landfills. Landfill sites have always been undesirable due to many reasons including, the emission of toxic gases, odour, land use and the unsustainable nature of this disposal method. Domestic and industrial sorting and transport of discarded resources to points where they are supposed to be disposed of are associated with a large carbon footprint. Other processes, such as recycling, have high costs and are labour intensive.

Having a sustainable method in place that is capable of converting the energy content within waste plastic into useful forms of energy would not only be highly advantageous to our environment, but could also be better economically. Low temperature (up to 300ºC) pyrolysis using heat pipe technology offers an attractive solution to converting discarded plastic materials into valuable energy vectors, such as syngas, bio-oils and biochar. Operating pyrolysis reactions at low temperatures ensures lower operating cost of the reactor in-comparison with current conventional, high temperature, pyrolysis reactors. Once the discarded plastic has been converted to other forms of energy (mostly biochar), they can be combusted to transfer the heat produced for use in, for example, process heating.

This paper will discuss the energy and composition of the products formed from pyrolysis of plastic materials, as well as the feasibility of low temperature pyrolysis for their conversion into energy products.