The importance of mineral ingredients in biochar production, properties and applications

Biochar is a carbonaceous material that is rich in both carbon and mineral ingredients. Previous research has recognized that properties and various applications of biochar are often correlated with its carbon fraction. However, recent research advancement has validated that mineral ingredients of biochar also strongly influence the properties and eventually the application of biochar in various fields. Nevertheless, an in-depth review on this aspect is lacking. To fill this knowledge gap, the present review explores the importance of mineral ingredients in production, properties and applications of biochar. The impact of pyrolytic settings and the nature of feedstock on the mineral composition of biochar were discussed. The previous investigations identified that the mineral composition of biochar was impacted by the feedstock type and pyrolysis parameters. The mineral ingredients of biochar also in turn strongly impact the properties of biochar, such as pH, electric conductivity, specific surface area, structure and morphology of biochar. During biosorption of various contaminants such as metals, nutrients and organic constituents, the role of mineral ingredients was found to be indispensable. The presence of minerals also facilitates biochar to be employed in various other applications, including soil amendment, a precursor for supercapacitor, photoactive component and fuel cell.