Effects of Pyrolysis Temperature and Holding Time on Physicochemical Properties of Swine-Manure-Derived Biochar
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Biochars were slowly pyrolyzed from dried swine manure waste by slow pyrolysis at different temperatures (300–750 °C) and heating times (0–120 min). The influence of pyrolysis temperature and heating time on the physicochemical properties of the biochars were studied. It was found that the ash content, pH, mineral nutrients, total heavy metals (except Zn), and pore properties of all swine-manure-derived biochars increased with increasing temperature and time. The yield and N, O, and H contents decreased with increasing temperature and time. The manure-derived biochar was rich in soil macronutrients and micronutrients, such as N, P, K, Ca, Mg, Na, Fe, Mn, Cu, and Zn. Excessive pyrolysis temperature (i.e., 750 °C) significantly increased the electrical conductivities of the biochars, i.e., the amount of soluble salts, and was also associated with the risk of volatilization of heavy metals (e.g., Zn) with low melting point. Linear correlation analyses showed that there were significant correlations between physical and chemical characteristics of the biochars, and the P values of correlation coefficients were often < 0.001. The principal component analysis implied that the properties of the swine-manure-derived biochars were mainly affected by ash content. Furthermore, the chemical and pore properties were also consistent with the observations of the XRD and FTIR. The swine-manure-derived biochar at 450 °C after 60 min could be used as an excellent medium to soil environment because of relatively low soluble salts and heavy metals, abundant mesoporous pores, surface functional groups, and nutrients.
KeywordsBiochar Pyrolysis Swine manure Physicochemical properties
This work was financially supported by the National Natural Science Foundation of China (No. 21507042), and the Guangdong Provincial Natural Science Foundation (Nos. 2016A030307010 and 2018A030307014).
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