title: Gas permeability of biochar-amended clay: potential alternative landfill final cover material.
abstract: Compacted biochar-amended clay (BAC) has been proposed as an alternative landfill final cover material in this study. Biochar has long been proposed to promote crop growth, mitigate odor emission, and promote methane oxidation in field soils. However, previous studies showed that soil-gas permeability was increased upon biochar application, which will promote landfill gas emission. The objective of the present study is to investigate the possibility of using compacted BAC as an alternative material in landfill final cover by evaluating its gas permeability. BAC samples were prepared by mixing 425-μm-sieved peanut shell biochar with kaolin clay in different ratios (0, 5, 10, and 15 %, w/w) and compacting at different degrees of compactions (DOC) (80, 85, and 90 %) with an optimum water content of 35 %. The gas permeability of the BACs was measured by flexible wall gas permeameter and the microstructure of the BACs was analyzed by SEM with energy-dispersive x-ray spectroscopy (EDX). The results show that the effects of biochar content on BAC gas permeability is highly dependent on the DOC. At high DOC (90 %), the gas permeability of BAC decreases with increasing biochar content due to the combined effect of the clay aggregation and the inhibition of biochar in the gas flow. However, at low DOC (80 %), biochar incorporation has no effects on gas permeability because it no longer acts as a filling material to the retard gas flow. The results from the present study imply that compacted BAC can be used as an alternative final cover material with decreased gas permeability when compared with clay.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Room 3556, Clear Water Bay, Kowloon, Hong Kong SAR, China.
authors.forename: James Tsz Fung
authors.initials: JT
authors.lastname: Wong
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Room 3556, Clear Water Bay, Kowloon, Hong Kong SAR, China.
authors.forename: Zhongkui
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Room 3556, Clear Water Bay, Kowloon, Hong Kong SAR, China. cecwwng@ust.hk.
authors.forename: Charles Wang Wai
authors.initials: CW
authors.lastname: Ng
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Room 3556, Clear Water Bay, Kowloon, Hong Kong SAR, China. minghwong@ied.edu.hk.|Consortium on Health, Environment, Education and Research (CHEER), The Hong Kong Institute of Education, Tai Po, Hong Kong SAR, China. minghwong@ied.edu.hk.|Department of Science and Environmental Studies, The Hong Kong Institute of Education, Office B3-2/F-33, Tai Po, Hong Kong SAR, China. minghwong@ied.edu.hk.
authors.forename: Ming Hung
authors.initials: MH
authors.lastname: Wong
mesh_terms: D010367:Arachis / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D007616:Kaolin / Q000737:chemistry*; D010539:Permeability; D012987:Soil / Q000737:chemistry; D064091:Waste Disposal Facilities
chemical_list: D012987:Soil; C540010:biochar; D002606:Charcoal; D007616:Kaolin
keywords: Biochar; Biochar-amended clay; Compacted soil cover; Gas permeability; Landfill final cover