Document Type : Complete scientific research article
Authors
1
Department of Rangeland Management, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Sciences & Natural Resources, Gorgan, Iran
2
Associate Professor, Department of Rangeland Management, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Sciences & Natural Resources, Gorgan, Iran
3
Associated Professor, Islamic Azad University (Ghouchan branch)
4
Associate Professor, Department of Rangeland Management, Faculty of Rangeland and Watershed Management, Gorgan University of Agricultural Sciences & Natural Resources, Gorgan, Iran
Abstract
Background and Objectives: The use of fossil fuels and land use change has caused a catastrophic increase in carbon in the atmosphere, which has led to a decrease in soil quality, global warming, and climate change. The deficiency of organic matter, salinity and alkalinity of the soil are three important limitations of the soils of winter rangelands in Iran. Biochar is a carbon-rich material that is produced during the pyrolysis process from raw materials containing carbon at high temperature and under almost oxygen-free conditions. It is used to improve soil quality, carbon sequestration and remove pollutants from the environment. Biochar can be engineered/designed for specific applications or to achieve specific results. Increasing the percentage of stable carbon and improving the physico-chemical properties of engineered biochars can play an important role in carbon sequestration and improving the properties of winter rangelands soils.
Materials and Methods: After washing and drying, the cotton stalk was cut into pieces of less than 2 cm. Then it was immersed for 4 hours in a solution with a concentration of 20% metal salts of calcium chloride, magnesium chloride and iron chloride, and dried again. Then, in the electric furnace, at various temperatures of 300, 400, 500, 600 and 700 degrees centigrade, within two hours, 20 biochars (control and engineered ) were produced from treated cotton stalks with different metal salts and untreated cotton stalks. Finally, properties of produced biochars including yield percent, organic carbon percentage, stable carbon percentage, acidity and salinity were measured. Statistical analysis was performed in SPSS16 software using one-way analysis of variance and Tukey's test.
Results: The yield of produced biochars (control and engineered) significantly decreased with increasing temperature, so that the highest percentage of their yield was observed at pyrolysis temperatures of 300 °C. The highest percentage of yield (50.20%) was obtained in biochar treated with iron chloride produced at 300°C. The highest organic carbon (50.97%) and stable carbon (99.57%) were obtained in control biochar produced at 500°C and biochar treated with iron chloride produced at 700°C, respectively. The highest increase in the ratio of the weight of stable carbon to the weight of the feed stock was observed in biochar treated with iron chloride produced at 300 °C. The lowest and highest electrical conductivity (1.1 and 7.43 dSm) were obtained in control biochar produced at 300°C and calcium chloride treated biochar produced at 700°C. The highest and lowest acidity (9.83 and 5.60) were observed in control biochar produced at 700°C and iron chloride treated biochar produced at 300°C.
Conclusion: Considering the limitations in the soil of Iran's winter rangelands and the characteristics of control and engineered biochars along with the energy required for their production, Biochar produced from cotton stalks treated with iron chloride salt at 300°C has the highest performance and high stable carbon, the lowest acidity and acceptable electrical conductivity, therefore, it is recommended to use in carbon sequestration and plantation projects in winter rangelands of Iran.
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