TG-FTIR and Py-GC/MS analyses of pyrolysis behaviors and products of cattle manure in CO2 and N2 atmospheres: Kinetic, thermodynamic, and machine-learning models

The increased amounts of manure have become an issue of environmental management due to the rapid growth of livestock industry. This study quantified the pyrolytic performance and gaseous products of cattle manure using (derivative) thermogravimetric ((D)TG), Fourier transform infrared spectrometry (FTIR) and pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) analyses. The pyrolysis process of cattle manure was determined to occur in three stages, with the main reaction in the range of 161-600 degrees C. The N-2 atmosphere was found to be more favorable for the release of volatiles according to a higher comprehensive pyrolysis index in the range of 30 - 600 degrees C. The lower activation energies were shown to be required in the CO2 than N-2 atmosphere. Random forests algorithm outperformed multiple linear regression, gradient boosting machine, and artificial neural networks for the prediction of mass loss due to the cattle manure pyrolysis. The main gaseous products were CO2, phenol (23.23%), and furans (12.98%). The theoretical and practical guidance for the energy and resource utilization of cattle manure was provided by this study.