Pyrolysis of Tibetan Yak Dung for Producing Biochar Pertinent to Agro-environmental Application
2022
Zhong, Lei | Li, Gaoyuan | Wu, Wenzhu | Sun, Yuru | Chen, Guanyi | Kang, Xiaoming
The study was investigated the influence of pyrolysis conditions on the yield and nutrient properties of yak dung-based biochar and its potential of agro-environmental applications. A series of biochars were made by hydrothermal carbonization (HTC) under the different atmospheres, such as Nitrogen (N₂) and carbon dioxide (CO₂), processing temperatures (200-300 °C) and residence times (1-2 h). The results showed the yield of yak dung-based biochar ranges from 35.33 wt% to 58.29 wt%. The concentration of nitrogen (N), phosphorus (P) and potassium (K) in biochar varied from 28.18 mg·g⁻¹ to 15.54 mg·g⁻¹, 16.23 mg·g⁻¹ to 25.31 mg·g⁻¹ and 0.59 mg·g⁻¹ to 1.02 mg·g⁻¹, respectively. And the contents of micronutrients Zn and Fe varied from 4.6 mg·g⁻¹ to 17.42 mg·g⁻¹, and 15.28 mg·g⁻¹ to 29.22 mg·g⁻¹, respectively. The yield, total carbon (C), N, hydrogen (H) and oxygen (O) content of biochar decreased with increasing processing temperature, while the total P and K content, pH and Brunauer-Emmett-Teller (BET) surface area increased; moreover, the P and K content of biochar produced in N₂ increased more compared with CO₂. The heavy metal contents of copper (Cu), cadmium (Cd), chromium (Cr), platinum (Pb) and arsenic (As) all were lower in yak dung-based biochar compare with other manures or sewage sludge-based biochar. Biochar produced in N₂ had higher nutrient content indicating the potential of application for fertilizer compared with it in CO₂; while the biochar produced in CO₂ with larger surface area characteristic and more abundant functional groups showing higher potential of application for the soil amendments and nutrient control materials. Our study provides some new insights for biochar production according to its application.
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