Effects of biochar amendment on geotechnical properties of landfill cover soil (original) (raw)
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Science of The Total Environment, 2020
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Exploring implication of variation in biochar production on geotechnical properties of soil
Biomass Conversion and Biorefinery, 2020
Biochar produced from the pyrolysis of plant based feedstock has been advocated as an alternative soil amendment for landfill cover. Previous literature indicated that the pyrolysis temperature influences the intra-pore distribution and surface functional groups (especially hydroxyl groups), resulting in "love-hate relationship" of the biochar amended soil (BAS) with water. From the purview of geotechnical engineering, the effect of pyrolysis temperature on geotechnical properties are rarely investigated. In total, three biochar rates (0, 5 and 10%) were considered for a set of geotechnical experiments in sand clay mixture soil with biochar produced at 350 ℃ and 550 ℃. Test results show that biochar addition in soil, in general regardless of pyrolysis temperature, increased the optimum moisture content (OMC), plasticity index, soil water retention characteristics (SWRC) and decreased the maximum dry density (MDD), shear strength parameters (cohesion, friction), erosion rates. Whilst comparing the pyrolysis temperature effects on two biochar amended soils, only marginal effects (in terms of magnitude) on SWRC were observed. The most significant decrease of MDD (or increase of OMC) for 5% (w/w) and 10% (w/w) biochar additions occurred at pyrolysis temperatures of 550 ℃ and 350 ℃, respectively. In addition, biochar produced at lower pyrolysis temperature (350 0 C) was more effective in reducing cracks and enhancing shrinkage area ratio. 10% biochar addition with pyrolysis temperature of 350 0 C was the optimum combination in resisting soil erosion. The study provides evidence that the geotechnical properties of biochar amended soils for landfill cover soil applications could be tailor made by controlling the pyrolysis temperature.
International Journal of Damage Mechanics, 2020
Growing awareness of sustainability in the landfill cover system has increased the use of biochar amendment for degraded landfill surface soils. Hydraulic and vegetative benefits of biochar on cover soil have been studied in the past, while ignoring mechanical characteristics, which is important to understand progressive failure of landfill infrastructure. In this study, the mechanical characteristics of four soil–biochar composites were investigated by conducting 81 unconfined compressive strength test. The results based on four in-house produced biochar were used to study the effect of compaction state (density, moisture content) and biochar percentage (5% and 10%) on unconfined compressive strength of soil–biochar. The ductility of soil–biochar was investigated for all the four biochars. Results from this study indicate a contrasting observation of strength gain depending on the type of biochar. The unconfined compressive strength of soil–biochar is potentially influenced by the ...
Journal of Soils and Sediments, 2016
Purpose Biochar has long been proposed for amending agricultural soils to increase soil-water retention capacity and therefore promotes crop growth. Recent studies revealed the potential use of biochar-amended soil in landfill final covers to promote methane oxidation and odor reduction. However, the effects of biochar application ratio, compaction water content (CWC), and degree of compaction (DOC) on soil-water retention characteristics of biochar-amended clay (BAC) at high soil suction (dry condition) are not well understood. The present study aims to overcome this knowledge gap. Materials and methods Soil suction was induced using vapor equilibrium technique by a temperature-and humiditycontrolled chamber, and the water desorption (drying) and adsorption (wetting) water retention curves (WRCs) of compacted pure kaolin clay and peanut shell BAC with different biochar application ratios (0, 5, and 20 %, w/w), DOCs (80, 90, and 100 %), and CWCs (30 and 35 %) were measured. The correlations between these factors and the gravimetric water content were analyzed by three-way ANOVA followed by the Tukey HSD test. The soil microstructure was studied by scanning electronic microscope with energy-dispersive X-ray spectroscopy. Results and discussion Measured WRCs of BAC suggest that the soil-water retention capacity at high suction range (48.49-124.56 MPa) was in general increased, upon biochar application. The BAC compacted with CWC of 35 % at low (80 %) and high (100 %) DOCs for the 5 % BAC were increased by 7.30 and 9.77 %, when compared with clay, while the increases of 20 % BAC were 39.89 and 59.20 %, respectively. This is attributed to the embedded effects of clay particles in biochar pores, which reduce the total pore space of BAC. The soil-water retention capacity of BAC was also increased with CWC and decreased with DOC. The results of three-way ANOVA analysis show that the effects of DOC and biochar ratio on soil gravimetric water content was significant (p < 0.05) only at 48.49 MPa on drying path. For other induced suctions, only effects of CWC were significant (p < 0.05). Conclusions Biochar application increases soil-water retention capacity of the BAC at high soil suction (48.49-124.56 MPa) (dry condition) at both low (80 %) and high DOC (100 %). The soil-water retention capacity of 20 % BAC was much higher than that of 5 % BAC. BAC is a potential alternative landfill final cover soil with a higher soil-water retention capacity to be used in dry areas or regions with a long period of evaporation event.
Geotechnical Characterization of Biochar-Based Biocover
International Journal of Innovation and Research Technology, 2020
Landfills are one of the major sources of methane (CH4) emission which is a very potent greenhouse gas. The use of a natural process for microbial CH4 oxidation through biocovers provides a source reduction of CH4 emission. Previous studies have mostly focused on biochemical properties, and limited research has been conducted with regards to the geotechnical characterization of biochar based biocovers. This paper presents the results of a comprehensive laboratory investigation on laterite, Igbokoda sand and their mixtures with biochar at 2%, 4%, 8%, 10% and 20% to determine the compaction properties of biochar based biocovers. From the result, it was shown that the laterite has medium plasticity while the Igbokoda sand is non-plastic. Also, Addition of biochar to landfill cover soil increased the particle sizes, and consequently the porosity of the soil is increased which can promote the air flow through the landfill cover. Thus, greater O2 diffusion within the landfill cover will r...
Journal of environmental management, 2017
Alternate landfill covers designed to enhance microbial methane (CH4) oxidation and reduce the negative impacts of landfill gas emissions on global climate have recently been proposed and investigated. In this study, the use of biochar as a soil amendment is examined in order to assess the feasibility and effectiveness for enhanced CH4 removal in landfill covers when incorporated under high compaction conditions and relatively low soil moisture. Four different cover configurations were tested in large soil columns for ∼510 days and potential CH4 oxidation rates were determined following long-term incubation in small batch assays. Cover designs tested include: a thin biochar layer at 15-18 cm; 2% mixed soil-biochar layer at 20-40 cm; 2% mixed soil-uncharred wood pellets at 20-40 cm; and soil obtained from intermediate cover at an active landfill site. The placement of a thin biochar layer in the cover significantly impacted moisture distribution and infiltration, which in turn affect...
Effects of biochar on the ecological performance of a subtropical landfill
Science of The Total Environment, 2018
• Effects of biochar on ecological restoration of disturbed lands are not clear. • Biochar was added on landfill to study the ecological performance. • Biodiversities (plant, bacteria and fungi) and ecological functions were studied. • Biochar enhanced biodiversities (especially plant) and nutrient-cycling functions. • Biochar amendment is a considerable approach for ecological restoration.
Enhancement of the methane removal efficiency via aeration for biochar-amended landfill soil cover
Environmental Pollution, 2020
Methane (CH 4) mitigation of biocovers or biofilters for landfills is influenced by the bed material and oxygen availability. The improvement of active aeration for the CH 4 oxidation efficiency of biocharamended landfill soil cover was investigated over a period of 101 days. There were column 1 as the control group, column 2 with biochar amending the soil cover, and column 3 with daily active aeration besides the same biochar amendment. All groups were inoculated with enriched methane oxidation bacteria (MOB). The average CH 4 removal efficiency was up to 78.6%, 85.2% and 90.6% for column 1, 2, and 3, respectively. The depth profiles of CH 4 oxidation efficiencies over the whole period also showed that the stimulation of CH 4 oxidation by biochar amendment was apparent in the top 35 cm but became very faint after two months. This probably was due to the rapid depletion of nitrogen nutrition caused by enhanced methanotrophic activities. While through aeration, CH 4 oxidation efficiency was further improved for column 3 than column 2. This enhancement also lasted for the whole period with a reduced decline of CH 4 oxidation. Finally, the major MOB Methylocystis, commonly found in the three columns, were most abundant in the top 35 cm for column 3. A more balanced ratio of MOB and more homogeneous microbial community structures across different soil depths were also the results of active aeration.