An entropy-based TOPSIS approach for selecting best suitable rice husk for potential energy applications: pyrolysis kinetics and characterization of rice husk and rice husk ash

Sustainable utilization of biomass as a renewable energy resource is the most pressing issue today, owing to the high cost and continued depletion of limited fossil fuels. Rice husk (RH) is an abundantly available agricultural waste biomass that can be used for energy production. However, energy production depends on several fuel characteristics, such as composition of RH which is highly influenced by the location and cultivation conditions of paddy. Hence, an entropy-based TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) multi-criteria decision-making method (MCDM) was employed to rank and select suitable RH variety amongst four varieties of paddy, namely Badsha-bhog, Lal-swarna, IR-36, and Shankar. A total of fifteen attributes were considered, including physical, chemical, proximate, ultimate, kinetic parameters. Additionally, structural, functional, and morphological properties of RH and their ash (RHA) were also analysed. Higher heating value (HHV) determined from proximate and ultimate analyses varied between 15.43 − 16.64 MJ/kg and 14.31 − 15.59 MJ/kg, respectively. Thermogravimetry analysis showed active pyrolysis zone for different RHs between 185 and 390 °C with activation energy and order of reaction between 96.43 and 99.37 kJmol⁻¹ and 2.36 to 3.05, respectively. Silica volume percentage was calculated from the X-ray diffraction (XRD) analysis of RHA and ranged between 60.12 and 64.33%. The TOPSIS analysis demonstrated that RH of Lal-swarna variety ranked top with the highest relative closeness value of 0.81, followed by Shankar (0.79), IR-36 (0.65), and Badsha-bhog (0.64). This study hopes to enhance the direct application of RH as energy feedstock by optimizing the paddy variety selection.