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Chemical characterization of rice straw-derived biochar for soil amendment

Wu, Weixiang, Yang, Min, Feng, Qibo, McGrouther, Kim, Wang, Hailong, Lu, Haohao, Chen, Yingxu
Biomass and bioenergy 2012 v.47 pp. 268-276
chemical composition, crystallites, rice, cation exchange capacity, greenhouse gas emissions, fertilizers, bioenergy, cations, heat, soil amendments, biochar, carbon sequestration, rice straw, soil fertility, alkalinity, analytical methods, temperature, biomass, pyrolysis, phosphorus
Pyrolysis of rice straw to create biochar for soil amendment appears to be a promising method to address concerns with regard to improving soil fertility, increasing Carbon storage and decreasing Green House Gas emissions. However, the ability of rice straw-derived biochar to affect these factors might vary depending on its characteristics. It is therefore essential to investigate the properties before large-scale application of rice straw-derived biochar. In this study, rice straw-derived biochars produced at different temperatures (300, 400, 500, 600 & 700 °C) and residence time (1, 2, 3 & 5 h) were characterized using a suite of analytical techniques. Results showed that pyrolysis temperature had a greater influence than residence time on the chemical composition and structure of rice straw-derived biochar produced at low heating rate. The rice straw-derived biochars especially produced at 400 °C had high alkalinity and cation exchange capacity, and high levels of available phosphorus and extractable cations. These properties indicate potential application of rice straw-derived biochar as a fertilizer and soil amendment. Fourier transform infrared spectra showed that higher pyrolysis temperatures promote condensation reactions. Rice straw-derived biochars contained turbostratic crystallites at 400 °C, and displayed a high level of aromatization at 500 °C. Increasing charring temperature will increase the aromaticity of biochar, and might include its recalcitrance.