Effect of Pyrolysis Temperature on Chemical Properties of Sugarcane Bagasse and Pistachio residues Biochar

Organic wastes from agricultural activities have created short- and long-term problematic consequences for farmers and environment. Sugarcane bagasse and pistachio residues are considered important agricultural residues for which application management is necessary. One of the management approaches is the pyrolysis process and transforming the residues into biochar. This study was conducted to investigate some characteristics of sugarcane bagasse, pistachios residues (dried foliar parts) and their biochars produced at different pyrolysis temperatures (300, 400 and 500 °C). The results showed increasing the pyrolysis temperature significantly reduced the percent of solid phase (i.e. biochar’s efficiency) and increased gas and liquid (leachate) phases (LSD0.05). Moreover, increasing the pyrolysis temperature from 300 to 500 °C significantly increased the biochar’s pH from 8.4 to 10.8. Pyrolysis led to an increment in the total content of nutrients for both residues. In addition, carbon to nitrogen ratio in the biochars was lower than that in the original residues. In general, total contents of nitrogen, phosphorus, potassium and sodium were greater in the pistachio treatments than in the sugarcane bagasse treatments. Since the sugarcane bagasse's biochars have less nutrients and higher carbon than the pistachio’s biochars, careful management is needed for their application in the soil as a fertilizer and amendment. On the other hand, salinity of the pistachio residues and its biochars was greater than that of sugarcane bagasse treatments. Therefore, it is probably necessary to combine application of biochar of pistachio residues with soil leaching, or to use it for cultivation of salt-resistant plants. Pyrolysis increased the total contents of iron, zinc, copper, manganese, nickel, chromium and lead in the biochars of both residues. Based on our results, it seems that the best pyrolysis temperatures for biochar production from pistachio residues and sugarcane bagasse are 300 and 500 °C, respectively.