Multi-objective optimization of pyrolysis process of Prosopis farcta under non-isothermal conditions

Biochar is a recalcitrant substance that is produced through the pyrolysis process. The location of this study was Ahvaz in the central part of Khuzestan Province, Iran. To produce biochar, the biomass of Prosopis farcta was pyrolyzed at a temperature of 400°C to 800°C using the heating rate of 3 to 7 °C/min. Afterward, the electrical conductivity, cation exchange capacity, pH, specific surface area, and organic carbon of the biochar were recorded by employing standard methods. The pyrolysis factors such as temperature and heating rate were optimized using the Response Surface technique. Based on the results obtained, the temperature of the process was the most effective variable on the biochar characteristics. Besides, the temperature had a more substantial effect on the structure of the biochar than the heating rate. Also, the modeling results indicated that by enhancing the pyrolysis temperature, the electrical conductivity (EC)/pH of the produced biochar was enhanced mainly due to the concentration effect and reduction of acidic functional groups. With the strengthening of the pyrolysis temperature and heating rate, the organic carbon and specific surface area of the biochar were enhanced, while the cation exchange capacity decreased. According to the obtained results, the best model was found to be a quadratic model. In addition, the model for the EC parameter with the P-value of 0.0004 had the lowest effect compared with other studied pyrolysis factors. In general, the conditions of the pyrolysis process had a remarkable impact on the biochar characteristics; therefore, the effectiveness of biochar can be regarded as an organic amendment. To the best of the authors' knowledge, the present work is the first report assessing the effect of heating rate/ temperature on the biochar characteristics produced from Prosopis farcta.