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To systematically examine the effects of anaerobic digestion (AD) pretreatment on product distribution and kinetics of distillers' grains (DG) and its digestates collected at different AD durations, Py-GC/MS and TG analyses were conducted. Py-GC/MS analysis revealed a reduction in the proportion of oxygenated and nitrogenous compounds in all digestates and increase the share of hydrocarbons: 46.72% (SD-2), 65.53% (SD-4), 43.20% (SD-6) and 50.05% (SD-8) than DG (38.61%). To assess activation energy, Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa models were employed with average values ranging from 159.54 to 170.96 kJ mol−1 for DG, 156.59–165.42 kJ mol−1 for SD-2, 15.67–166.47 kJ mol−1 for SD-4, 153.28-159-45 kJ mol−1 for SD-6, and 156.02–167.37 kJ mol−1 for SD-8, which were lowered than DG. Thermodynamic studies showed positive ΔH and ΔG values, suggesting that the pyrolysis of DG and digestates is non-spontaneous. The negative ΔS values implied that the degree of disorder in products resulting from bond dissociation was lower than initial reactants. These findings provide valuable insight into the potential of AD as a pretreatment method and offer an understanding of the pyrolysis behavior of digestates. This study not only offers practical guidance but also contributes to the theoretical framework for utilizing AD as a pretreatment method for pyrolysis. [Display omitted] [ABSTRACT FROM AUTHOR]