Engineering properties of waste wood-derived biochars and biochar-amended soils

The application of biochars or biochar-amended soils in engineered systems (e.g. landfill biocover and in-ground filtration system) is contingent upon specific properties such as compressibility and shear strength that define their structural stability during and after construction under expected loading conditions. In this study, seven different types of waste wood-derived biochars were tested for their compressibility and shear strength properties. In addition, selected biochar-amended soils were tested. Compressibility testing was performed using one-dimensional compression testing apparatus, and shear strength testing was performed using direct shear testing apparatus. Biochars and biochar-amended soils were tested under dry and moist conditions. The results of compression testing were used to calculate constrained modulus and that of shear strength testing were used to calculate shear strength parameters (cohesion and angle of internal friction). The constrained modulus and shear strength parameters were correlated with the physicochemical properties of biochars or biochar-amended soils to develop relationships that can aid in the selection of suitable biochars or biochar-amended soils for engineering applications. Overall, this study provided critical engineering properties needed for the analysis and design of engineered systems using biochars or biochar-amended soils.