Characterization of selected biochars to determine their suitability as a soil amendment from a climate change mitigation perspective

Biochar is pyrolyzed organic matter produced from various feedstock using different production processes is largely used as a soil amendment to sequester carbon. However biochar is a multipurpose material and the application depends on its physicochemical properties, which are governed by the pyrolysis conditions and the feedstock type. Biochar's physical and chemical characteristics may significantly alter key soil physical properties and are, therefore, important to consider prior to its application to soil. Furthermore, these will determine the suitability of each biochar for a given application, as well as define its behaviour, transport and fate in the environment. Presently available analytical methods for biochar characterization provide useful information regarding the chemical and physical properties of the prepared char. From a carbon sequestration perspective the gained carbon stability of biochars in terms of various carbon functional groups in comparison with the original feedstock is an important feature. In the present study characterization of six different biochars derived from different feed stocks like cow dung, coconut husk, coconut shell, rice husk, rubber seed shell, Eichhornia plant were done. Considering the parameters like potential of hydrogen ion concentration (pH), cation exchange capacity (CEC), bulk density, ash content, nutrient status in terms of nitrogen (N), phosphorus (P) and potassium (K), elemental analysis, scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) spectrum, biochar derived from Eichhornia plant and coconut shell were more suitable for soil application from a climate change mitigation perspective. Thus characterization studies reveal the biochar properties which in turn determine the suitability of a particular biochar as a better soil amendment to increase soil fertility and also carbon sequestration.