Optimisation of Temperature and Retention Time for Co-Pyrolysis of Coconut Shell and Low-Density Polyethylene Biochar With Response Surface Methodology (Rsm)

Abstract

Indonesia is facing critical challenges in the effective management of increasing volumes of organic and plastic waste. Coconut shell waste and low-density polyethylene (LDPE) plastic are abundant yet underutilised resources with significant environmental impacts if left unmanaged. This study explores the potential of co-pyrolysis as a sustainable waste valorisation method to convert these waste materials into biochar, a promising alternative solid fuel. The objective of the research is to determine the effect of pyrolysis temperature and retention time on solid yield, identify optimal operating conditions using Response Surface Methodology (RSM) with Central Composite Design (CCD), and the characteristics of the resulting biochar. The experimental results obtained demonstrated that both temperature and retention time exert a significant influence on solid yield. The optimum yield was achieved at a temperature of 150°C and a retention time of 15 minutes, yielding a solid yield of 56.27%. The Quadratic model was found to best represent the relationship between process variables and solid yield (R² = 0.9256). The characterisation of the biochar revealed favourable properties, including a higher heating value (HHV) of 25.93 MJ/kg, a moisture content of below 8%, a low ash content, and an acceptable carbon content. However, the volatile matter and fixed carbon did not fully meet Indonesian biochar standards (SNI 1683:2021), suggesting opportunities for improvement through process refinement.