Comparative study of microwave and conventional hydrothermal treatment of chicken carcasses: Bio-oil yields and properties

Abstract

This study was conducted to explore the effects of microwave and conventional hydrothermal (MH and CH) treatment on the conversion of chicken carcasses into bio-oil. The differences between MH and CH treatment in terms of bio-oil yields and properties under different reaction temperatures (120–240 °C) were investigated. The bio-oil yield under CH treatment was higher at low temperatures (120–160 °C), whereas that under MH treatment was higher at high temperatures (200–240 °C). The maximum bio-oil yield of 59.41% was obtained by MH treatment at 240 °C. The higher heating values of all bio-oils (34.98–37.22 MJ·kg−1) were significantly higher than that of chicken feedstock (26.46 MJ·kg−1). The bio-oil contained a complex mixture of components that were mainly fatty acids. The bio-oil obtained by MH treatment at 240 °C showed the best flammability and comprehensive combustion performance. The gaseous products in the entire combustion process of bio-oil were mainly CO2 and (C–H)-containing volatiles; additionally, compounds containing H2O, CO, SO2, HCN, CO, and C–O were detected. Compared to bio-oil obtained by CH treatment, that obtained by MH treatment showed a higher calorific value, lower relative content of nitrogen, better flammability, and improved comprehensive combustion performance under the same hydrothermal reaction conditions.