Assessment of hydro-mechanical properties of biochar-amended soil sourced from two contrasting feedstock

In geo-environmental applications, the potential of biochar has been explored as a suitable cover material of landfill and vegetated slopes. The inherent nature of biochar affects the geo-environmental properties of the soil-biochar composite like water retention, compressive strength, infiltration, and soil erosion. Performance of a cover depends on biochar’s surface functional groups, which can be either hydrophobic or hydrophilic based on bio-source. The objective of this paper is to investigate the geotechnical properties of biochar-amended soil sourced from two contrasting feedstock, i.e., poultry litter (animal based) and water hyacinth (plant based). The test results show that biochar addition increased the Atterberg limits and reduced the acidity of soil. Biochar addition directly increased the optimum moisture content and decreased the maximum dry density. Both biochar addition decreased the composite compressive strength by 25–50% but increased the ductility of composite. Water hyacinth biochar (WHB) inclusion decreased the erosion rate of soil while it is not the same for poultry litter biochar (PLB). In the case of water retention, only the addition of WHB increases retention and holding capacity of soil. The obtained results have been discussed in context with the conducted microstructural, chemical, and physical tests on both biochar. Through these analyses on biochar of different origin and having contrasting functional groups and intra-pore network, the development of a complex biochar-water network was confirmed.