Pyrolysis characteristics of poplar sawdust by pretreatment of anaerobic fermentation

Pyrolysis characteristics of poplar sawdust (PS) pretreated by anaerobic fermentation were investigated by means of thermogravimetric analysis (TGA) and pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) analysis. Results indicated that with an increase of pretreatment time from 0 to 20 days, the contents of cellulose and hemicellulose decreased from 54.05 and 17.96 wt. % to 51.29 and 12.61wt. % and the contents of the extractives and lignin increased from 1.41 and 26.58 wt. % to 7.31and 28.19 wt. %, respectively. The bio-pretreatment enhanced the starting pyrolysis temperature and increased the remains at 700 °C. Distinct weight loss of cellulose between 250-350 °C were observed at the TGA curves of P5, P10 and P20. Activation energy increased from 87.90 to 103.21 kJ mol−1. The bio-oil yield and product distributions also changed. Sugars content firstly increased from 7.64 to 16.73% and then decreased to 13.70%. The content of linear carbonyls initially decreased from 12.40 to 8.64% and then increased to 14.39%. Phenols show similar changing pattern. Its content changed from 24.72 to 22.54 and then 25.03%. The contents of linear acids, linear ketones and furans decreased. The contents of laevoglucose, hydroxyl acetaldehyde and 1, 2-benzenediol in the bio-oil increased from 4.54, 10.78 and 3.07% to 12.30, 13.30 and 5.44%, respectively. This indicated the pyrolysis selectivity of PS was improved. Effects of anaerobic fermentation on wood pyrolysis behaviors were remarkably different not only from straw biomass but from that of white- and brown-rot fungi.