Pyrolysis of post-methanated distillery effluent (PMDE) solid waste: Thermogravimetric degradation, kinetic and thermodynamic study with a circular bioeconomy approach

Post-methanated distillery effluent (PMDE) is a harmful dark brown to black color distillery effluent and is often released in open pond systems after anaerobic digestion by molasses-based distilleries. Due to the high standards imposed by Environmental Protection Acts, various methods of treating effluent were explored. However, pyrolysis showed excellent potential to treat it and recover energy. Hence, the present study explores the viability of producing energy from PMDE solid waste through pyrolysis. The reaction was performed at 900 degrees C with 20 degrees C min(-1) heating rate in a fixed bed reactor, resulting in 36.12 wt% condensable volatiles, 22.6 wt% non-condensable gases, and 41.28 wt% solid biochar. The gas chromatographic (GC) analysis of the non-condensable gas revealed the presence of CO (17.83 vol%), H-2 (8.10 vol%), and CH4 (4.30 vol%) in significant amounts, and C2H4, C2H6, C3H8, and C4H10 in minor quantities. Biochar obtained from the process has a microscopic surface area of 62.13 m(2) g(-1). A kinetic and thermodynamic study was performed using isoconversional methods to understand the reaction mechanism. Kinetic analysis showed the activation energy of PMDE solid waste pyrolysis to vary from 120 kJ mol(-1) to 180 kJ mol(-1) as conversion increases, and thermodynamic parameters (Delta H, Delta S, and Delta G) show the explanation for variation in activation energy. Additionally, the bio-circular economic approach of PMDE solid waste was presented. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study investigates the feasibility of producing energy from PMDE solid waste through pyrolysis. The pyrolysis process results in the formation of condensable volatiles, non-condensable gases, and solid biochar. The non-condensable gas contains CO, H2, and CH4 in significant amounts, as well as other gases in minor quantities. Kinetic and thermodynamic analysis were performed to understand the reaction mechanism, and a bio-circular economic approach for PMDE solid waste was presented.