The Effect of Carbonization Conditions on Characteristics of Corn-Stalk and Rice-Straw Derived Biochar

Abstract. In order to optimize the carbonization conditions and to obtain biochar with good quality, the effect of process parameters including the highest treatment temperature (HTT), heating rate and the retention time at HTT, on the characteristics of corn-stalk and rice-straw derived biochar was studied in this paper. The experiment was designed based on a Taguchi’s L9 orthogonal array with 34 elements. After carbonization, the calorific value of corn stalk derived biochar reached to 27.022MJ/kg, while that of raw corn stalk was 17.652MJ/kg, and that of rice straw derived biochar reached to 27.696MJ/kg, while that of raw rice straw was 17.368MJ/kg. The result of ANOVA analysis by SAS showed that HTT has significant effect on energy yield of corn-stalk derived biochar, with a model F value of 21.42 and P value of 0.0073 (<0.05). Judged by the standard deviation of each level of factors, in order to get the maximum energy yield of biochar, the optimum level combination of these factors was HTT of 350°C, retention time at HTT of 2 hours and heating rate of 15°C /min. However, no significant effects of these factors were found on surface area and absorbability (F value of 0.43, P value of 0.8190) of corn-stalk derived biochar. HTT (F value=13.30, P value=0.0171) and heating rate (F value=10.32, P valued= 0.0263) were found to have significant effect on surface area of rice-straw derived biochar. To get the maximum surface area, the optimum level of these factors was HTT of 500°C, heating rate of 10°C /min and retention time at HTT of 2h. However, these factors were not found having significant effects on energy yield and absorbability (F value of 0.35, P value of 0.8661) of rice straw derived biochar.