Plastic waste as an alternative source of fuel through thermochemical conversion process- A review

With the progression of science and technology, the fabrication of plastic products has heightened day by day, and the extensive usage of these products has brought convenience to the whole world. Though these products have proved to be a favorable addition to our daily lives, they have also generated acute environmental concern globally since most waste plastics are landfilled due to poor maintenance and disposal, even though they are completely recyclable and reusable. These plastic wastes can become sustainable feedstock and promising alternatives to non-renewable fossil fuels and can become third-generation biofuels using thermal conversion technologies like hydrothermal liquefaction (HTL) and pyrolysis. This paper explored the technology along with the detected plastic type that would be best for the production of maximum bio-oil yield from plastic waste. The ultimate composition component value range of crude oil obtained from the elemental analysis data comprised C (63.6–90.5%), H (6.9–9%), O (0.9–17%), and HHV (29.44–42.61 MJ/kg). This review article also explored the reaction parameters, which include the type of reactor, thermal conversion technology used, temperature, pressure, the addition of solvent, and retention time. In a pressurized batch reactor at a temperature of about 425°C, polystyrene produces the highest yield percentage of about 97% through pyrolysis. However, due to the high abundancy, easy availability, and favorable thermal properties of plastic, as this review article suggests, one of the best courses of action to produce biofuel can be the proper utilization of unmanaged plastic waste as raw feedstocks through a suitable conversion process, which will prove a double-edged solution to minimize plastic waste along with getting valuable crude products.