Batch pyrolysis of cotton stalks for evaluation of biochar energy potential

Institute of Chemical and Energy Engineering, Department of Material Sciences and Process Engineering, University of Natural Resources and Life Sciences, Vienna, Muthgasse 107, 1190 Vienna, Austria

^* Corresponding author: rafat.alafif@boku.ac.at

Abstract

The thermal cracking of cotton stalks (CS) via pyrolysis was performed using a laboratory scale batch pyrolysis reactor. The effects of the final pyrolysis temperature varying from 300 to 800°C on the pyrolysis products distribution has been investigated. The maximum biochar yield of 46.5% was obtained at 400°C. As the pyrolysis process temperature increased, the solid char product yield decreased. The lowest biochar yield of 28% was obtained at 800°C. The largest higher heating value (HHV, 25.845 MJ kg^-1) was obtained at 600°C. All biochar samples produced between 500 and 700°C had an energy densification ratio of 1.41, indicating a higher mass-energy density than the initial feedstock. A larger share of syngas and bio-oil were produced at higher temperatures, as estimated. Preferential selection of a char based on the energy yield would lead to a selection of the 400°C product, while selection based on the energy densification ratio would be for a product obtained between 500 to 700°C.