Effects of plant-biochar interaction on the performance of a landfill cover system: field monitoring and numerical modelling

Abstract

Biochar has been used as a sustainable amendment to moderate the risks of climate change to plant and soil management. A 3-year field monitoring was conducted at Shenzhen Xiaping landfill to evaluate the performance of a three-layer landfill cover using plant and biochar. Coarse-grained completely decomposed granites (CDG) amended with peanut shell biochar at 0%, 5% and 10% (m3/m3) were used for the top layers of three grass plots (10 m×5 m each), respectively. Coarse recycled concrete and fine-grained CDG were used for the middle and bottom layers of all plots. Numerical simulation was conducted to back analyse the monitored results. The results show that the grassed cover with biochar can retain over four times higher negative pore-water pressure than that without biochar. During the monitoring, over 62% of total rainfall was evapotranspirated from biochar amended covers, which was 10% larger than the cover without biochar. With biochar amendments, the infiltration amount was reduced by 13%, but water storage was improved by up to 15%. The measured and computed percolation of the grassed covers with 0%, 5% and 10% biochar meet the recommended criterion by USEPA. It is recommended that 5% biochar content is sufficient to minimise water percolation.