Characterization of Biochars Produced from Various Biowastes

Abstract

Biochar is a product of thermal degradation of organic materials in the absence of air (pyrolysis). Slowpyrolyzed and biowaste-derived biochars show excellent adsorption properties. Studies on biochars produced from pine nut shells, sawdust, and cow dung have been carried out in Mongolia determining the technical characteristics and applying for improvement of soil quality. However, a thorough characterization of biochars is still in lack. In this study, we produced 10 biochars from animal bones and dungs, and firewoods and compared their characterization properties. Physico-chemical parameters of biochars such as moisture, ash, volatile matters, fixed carbons, pH, redox potential (pE), electrical conductivity (EC), total dissolved solids (TDS), cation exchange capacity (CEC), and base saturation were determined and SEM-EDX, FTIR, XRD, main elements, and trace metals analysis were obtained. Methylene blue and iodine absorption tests were carried out in terms of surface porosity. All biochars showed high electrical conductivity and base saturation indicating that they were rich in cations. The highest values of pH, EC, TDS, and CEC were found in biochar produced from sheep dung. Among bone chars, biochar produced from sheep spine bone showed the highest CEC. High Ca content in bone biochars resulted from the nature of the raw material. Biochars hardly contained trace metals. XRD analysis showed that the firewood biochar had amorphous, whereas the bone biochars and dungs had crystal structures. Biochars produced from animal and forestry biowastes have shown great values of adsorbent characteristics, thus the application of such biochars can simultaneously reduce waste and be an environmentally friendly valuable product.