Chemical characterization of char derived from slow pyrolysis of microalgal residue

In this study, the slow pyrolysis (10 degrees C/min) of chlorella-based residue was investigated for the production of biochar in a thermogravimetric system under the different temperatures of 300-700 degrees C and holding times of 0-60 mm. To evaluate their potential for soil amendment, their nutrient properties were obtained by means of elemental analyzer (EA), inductively coupled plasma-optical emission spectrometer (ICP-OES), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). The results showed that the dried microalgal biomass and its resulting biochars contained the high concentrations of N and inorganic elements, including P, Fe, Ca, K, and Mg. The C content of biochar was increased from 56.3% (300 degrees C) to a maximal value of 66.2% (500 degrees C), and then slightly declined to about 65% (700 degrees C). On the other hand, the contents of hydrogen (H) and nitrogen (N) showed a decreasing trend with temperature. Based on the findings, it suggests that the chlorella-based biochar could be used as a high-N (>10%), rich-minerals and porous fertilizer. (C) 2014 Elsevier B.V. All rights reserved.