Enhancing Landfill Covers with Biochar and Vegetation: A Study on Gas Permeability

In the realm of ecological restoration, particularly in landfill cover systems, the amendment of soil with biochar has shown promising results in improving soil properties and reducing gas emissions. A recent study delved into how biochar and plant roots influence CO2 gas permeability in unsaturated soil conditions, highlighting several key findings.

Roots from vegetation, specifically Chrysopogon zizanioides, grown in granite residual soils with a 5% biochar mass ratio, significantly altered soil properties. The presence of roots increased the soil’s gas permeability, hydraulic conductivity, and suction by up to 200%, 600%, and 50%, respectively, compared to bare soil. These changes were primarily due to enhanced preferential flow, increased microporosity, and the negative pressure effects of root growth.

Conversely, the introduction of biochar slightly reduced these metrics—gas permeability and hydraulic conductivity decreased by 21% and 33%, respectively. This reduction can be attributed to biochar’s pore-filling capacity and its ability to enhance capillarity within the soil’s microstructure. Furthermore, biochar’s surface functional groups played a crucial role in promoting CO2 adsorption, highlighting its potential in mitigating greenhouse gas emissions from landfill covers.

The study also developed a model predicting gas permeability based on unsaturated soil properties, revealing a strong dependency on root length density. This insight is vital for designing landfill covers that effectively reduce CO2 emissions while supporting plant growth.

This investigation underscores the complex interplay between vegetation, biochar, and soil properties, offering a nuanced approach to managing environmental impacts of landfills. The findings suggest that while both roots and biochar individually influence soil behavior, their combined effects provide a strategic advantage in ecological landfill management.