Pyrolysis of plastic species: A review of resources and products

Abstract A long-term and reliable plastic waste management scheme is required to avoid environmental pollution and to overcome the issues of energy crisis simultaneously. Pyrolysis of plastic waste is a thermo-chemical disposal procedure that helps alleviate these issues while recycling valuable commodities such as oil and gas. This article reviewed the current scenario of plastic waste throughout the world, various methods of pyrolysis as well as the products produced from plastic waste pyrolysis. The results showed that the global plastics demands are increasing by 5% every year, causing larger amount of plastic wastes generation. The quantities and characteristics of pyrolysis products were significantly affected by plastic type, pyrolysis method (slow pyrolysis, fast pyrolysis and flash pyrolysis), reactor type, particle size, etc. Liquid oil is the primary product of plastic waste pyrolysis with up to 90 wt%, whereas gases (3 ∼ 90.2 wt%), wax (0.4 ∼ 92 wt%), char (0.5 ∼ 78 wt%) and HCl (0.1 ∼ 58 wt%) are the by-products. The liquid oils produced from plastic waste pyrolysis have similar properties to conventional diesel, i.e., viscosity (up to 2.96 mm2/s), density (0.8 kg/m3), flash point (30.5 °C), cloud point (−18 °C) and energy content (41.58 MJ/kg).