*4.1. Oil from Waste Tyres*

The oil extracted from waste tyres via a thermochemical conversion process varies depending on the conversion process and the operating conditions. The colour of pyrolysis tyre oil (TPO) is generally black, and it has a distinct odour. Table 2 summarises the physicochemical properties of oil produced from waste tyre pyrolysis reported in the recent literature and compares the value to conventional diesel and biodiesel. For automobile engine application, one of the important quality parameters is the higher heating value (HHV) of the oil. The HHV of TPO is reported in the range of 38–42 MJ/kg, which is less than conventional diesel but is, however, higher than biodiesel. The Cetane index of PTO was found to be 28.6, which is much lower than both diesel (53.2) and biodiesel (58.6). Furthermore, TPO has a much higher density, kinematic viscosity, and aromatic content than both diesel and biodiesel. As a result of these findings, TPO may not be suitable for direct use as a fuel in commercial automobile engines; however, blending TPO with diesel and biodiesel can be utilised.


**Table 2.** Physicochemical properties of tyre oil, WCBD and diesel.
