A comparison of CO2, N2, and Ar to maximize plant nutrient retention in biochar
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Nutrient-rich biochar improves soil significantly; however, the nutrients nitrogen (N), phosphorous (P), and potassium (K) can be easily lost during the pyrolysis of straw feedstock. To resolve this problem, the mechanism for retaining the biochar nutrient elements in the solid, liquid, and gas products of pyrolysis under different atmospheric conditions and at different temperatures was studied systematically so that the best method for the preparation of the biochar could be determined. The observations are as follows: (1) the CO2 atmosphere was more favourable than the N2 atmosphere for biochar preparation; (2) at 400 °C, the carbon in the biochar was mainly in the form of conjugated aromatic carbon; (3) when the temperature increased from 300 to 600 °C, the nitrogen content in the biochar decreased from 88.42 to 39.02%; (4) most of the phosphorus and potassium were mainly retained in the biochar; (5) the lower pyrolysis temperature (400 °C) under a CO2 atmosphere is the best biochar preparation conditions for promoting lettuce growth.
KeywordsAgricultural waste Rice straw Biochar Nutrient distribution
This study was supported by the National Natural Science Foundation of China (No. 41571283) and National Key Research and Development Program of China (2016YFD0800702).
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