Pyrolysis study on cattle manure: From conventional analytical method to online study of pyrolysis photoionization time-of-flight mass spectrometry

Cattle manure is a kind of abundant agriculture waste but potential renewable resource to be converted into fuel by pyrolysis. The pyrolysis behavior of cattle manure was analyzed by three methods in this work: thermogravimetric analyzer (TG), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis photoionization time-of-flight mass spectrometry (Py-PI-TOFMS). The pyrolysis process of cattle manure included four stages, dehydration stage, lignocellulose decomposition stage, lignin and protein decomposition stage, char and mineral matter decomposition stage. The products were mainly classified into six groups: ketones, aldehydes, phenolic compounds, acids, hydrocarbons and N-containing compounds. Based on the time-evolved profiles and temperature-programmed profiles, the characteristics of these major products were analyzed and discussed. Maillard reaction has great effects on the pyrolysis process of cattle manure because cellulose can easily react with protein to produce abundant Amadori products and then generate cyclopentanes and furanmethanol. In addition, some Amadori products and amino acids can also be cyclized to generate N-heterocycle compounds like pyrroles and pyrazines. The decomposition of lignin basic units with more methoxy groups require higher reaction temperature, and the removal of hydroxy and methoxy group on phenols mainly occurred at around 350 degrees C. Furthermore, primary decomposition pathways of cattle manure were also proposed and discussed.