Energy conversion efficiency of pyrolysis of chicken litter and rice husk biomass

Pyrolysis is a well-established method of converting biomass to different types of value-added products, such as high energy density biofuels and chemicals. In this work, chicken-litter waste and rice husk were pyrolyzed at different temperatures with the aim of investigating the thermal behavior and energy recovery potential of the feedstocks. Computer-aided thermal analysis and thermogravimetric analysis were employed to study the pyrolysis properties of each biomass in a temperature-controlled regime. The specific heats of chicken litter and rice husk samples during their pyrolysis and the energy content of their pyrolysis products were investigated to determine the energy required to complete the pyrolysis of each sample and the energy recovery potential of each pyrolytic product. Most of the volatile products were evolved at 350 to 450 °C with CO2, CO, and CH4 being the dominant gas products from both samples throughout the pyrolysis process. At 500 °C and at a heating rate of 10 °C/min, the gas, bio-oil, and biochar yields from chicken litter and rice husk were in the ranges of 18 to 19, 35 to 39, and 42 to 47 wt %, respectively, with a total recoverable energy value of 12.7 MJ/kg from chicken litter and 13.9 MJ/kg from rice husk. The energy consumed to heat the samples to the final pyrolysis temperature of 500 °C was also estimated to be 1.2 and 0.8 MJ per kilogram of chicken litter and rice husk, respectively. With the measured values, the efficiency of the pyrolysis of chicken litter and rice husk samples is estimated to be 84% and 89%, respectively, assuming the heat required to carry out the pyrolysis process is supplied by combustion of the evolved pyrolytic gas products. If the pyrolysis is instead driven by solar thermal energy, the overall efficiency will increase to 92% for the chicken litter and 94% for the rice husk pyrolysis