A Pyrolysis-Based Strategy for Harnessing Renewable Energy via Waste to Energy Conversion under Normal and Catalytic Pyrolysis Process Conditions

Abstract

The process of converting plastic waste into alternative energy through pyrolysis has currently gained attention as an innovative strategy that presents an alternative renewable approach for plastic waste management. This study investigated the recovery of the energy embedded in plastic waste through normal and catalytic pyrolysis processes. Product yields from polymeric materials such as polypropylene, low-density polyethylene and high-density polyethylene were compared under both process conditions. Waste plastic was collected locally from multiple dumpsites across Nairobi, sorted into different categories according to their resin codes, cleaned, sun dried and shredded to 2mm sizes. 700g of each shredded plastics type were fed into the reactor and heated with varying of temperature between 220˚C and 420˚C. Incondensable pyrolytic gases were collected in gas bags for analysis while the condensable volatile gases were cooled in a shell and tube condenser and stored in clean plastic container for further chemical analysis at the chemistry lab in JKUAT .The chemical properties of liquid fuels was analyzed using Fourier Transform Infrared Spectrometry and the Gas chromatograph with a mass spectroscopic detector.  The most favorable process conditions were achieved within 220°C to 420°C, with a controlled heating rate of 10°C per minute. Under these conditions, the oil yields were 53.72% for polypropylene (PP), 62.10% for low-density polyethylene (LDPE), and 64.14% for high-density polyethylene (HDPE). There was a statistically significant difference in gas yields due to Fe2O3 and Al2O3 catalysts during pyrolysis, increasing yields from 18% to 61% and 47% respectively with a p-value of <0.001. In conclusion, these findings affirm the potential of catalytic pyrolysis as a promising approach for sustainable energy recovery and plastic waste management.