Abstract
Biochar, as an environment-friendly soil amendment, has been extensively proposed in landfill cover, primarily for promoting soil
hydraulic properties, such as hydraulic conductivity and soil water retention. However, the impact of biochar derived from various
feedstocks on soil-biochar mix properties, particularly gas permeability under unsaturated conditions, remains under-explored. This
study evaluates how different types of biochar influence gas permeability and soil water retention. Five biochars pyrolyzed using different biomass waste, such as apple wood, reed straw, walnut, corn cob and corn straw, were each mixed with sandy soil in a 5% mass
ratio. Gas permeability and hydrological response (water content, matric suction) were measured during wet-dry cycles. Results indicated that biochar amendments generally enhanced water retention compared to bare soil. Apple wood biochar, in particular, significantly improved both water content (reaching 90% of the control's maximum moisture content) and suction (peaking at 2755kPa),
outperforming reed straw, walnut, corn cob and corn straw biochars. This enhancement stems from apple wood biochar's hydrophilic
functional groups (e.g., –OH), which improve soil hydrophilicity and water-biochar interactions. Its large specific surface area and
tightly arranged micropores further enhance suction. Gas permeability rose with increasing suction, with reed straw and apple wood
biochars increasing gas permeability by 196% due to their larger average pore sizes and the formation of more meso-macro pore
structures in the sandy soil. Conversely, walnut and corn cob biochars reduced soil permeability, suggesting their suitability for highpressure applications. These findings guide the use of biochar-amended soil in landfill covers to mitigate gas emissions.
hydraulic properties, such as hydraulic conductivity and soil water retention. However, the impact of biochar derived from various
feedstocks on soil-biochar mix properties, particularly gas permeability under unsaturated conditions, remains under-explored. This
study evaluates how different types of biochar influence gas permeability and soil water retention. Five biochars pyrolyzed using different biomass waste, such as apple wood, reed straw, walnut, corn cob and corn straw, were each mixed with sandy soil in a 5% mass
ratio. Gas permeability and hydrological response (water content, matric suction) were measured during wet-dry cycles. Results indicated that biochar amendments generally enhanced water retention compared to bare soil. Apple wood biochar, in particular, significantly improved both water content (reaching 90% of the control's maximum moisture content) and suction (peaking at 2755kPa),
outperforming reed straw, walnut, corn cob and corn straw biochars. This enhancement stems from apple wood biochar's hydrophilic
functional groups (e.g., –OH), which improve soil hydrophilicity and water-biochar interactions. Its large specific surface area and
tightly arranged micropores further enhance suction. Gas permeability rose with increasing suction, with reed straw and apple wood
biochars increasing gas permeability by 196% due to their larger average pore sizes and the formation of more meso-macro pore
structures in the sandy soil. Conversely, walnut and corn cob biochars reduced soil permeability, suggesting their suitability for highpressure applications. These findings guide the use of biochar-amended soil in landfill covers to mitigate gas emissions.
| Original language | English |
|---|---|
| Journal | Soil Use and Management |
| Volume | 41 |
| Issue number | 2 |
| Publication status | Published - Mar 2025 |