10-15 P02 Water retention -Abraham et al SEAGS E-J 2019-03.pdf (original) (raw)
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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.
Science of The Total Environment, 2020
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Gas permeability of biochar-amended clay: potential alternative landfill final cover material
Environmental Science and Pollution Research, 2015
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 soilgas 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.
Journal of Rock Mechanics and Geotechnical Engineering, 2021
Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties (e.g. suction and water retention) of soil. However, variations in densities alter the properties of the soil–biochar mix. Such density variations are observed in agriculture (loosely compacted) and engineering (densely compacted) applications. The influence of biochar amendment on gas permeability of soil has been barely investigated, especially for soil with different densities. The major objective of this study is to investigate the water retention capacity, and gas permeability of biochar-amended soil (BAS) with different biochar contents under varying degree of compaction (DOC) conditions. In-house produced novel biochar was mixed with the soil at different amendment rates (i.e. biochar contents of 0%, 5% and 10%). All BAS samples were compacted at three DOCs (65%, 80% and 95%) in polyvinyl chloride (PVC) tubes. Each soil column was subjected to drying–wetting cycles, during which soil suction, water content, and gas permeability were measured. A simplified theoretical framework for estimating the void ratio of BAS was proposed. The experimental results reveal that the addition of biochar significantly decreased gas permeability kg as compared with that of bare soil (BS). However, the addition of 5% biochar is found to be optimum in decreasing kg with an increase of DOC (i.e. kg,65% > kg,80% > kg,95%) at a relatively low suction range (< 200 kPa) because both biochar and compaction treatment reduce the connected pores.
Soil Science Society of America Journal, 2019
Biochar has been suggested as soil amendment for improving soil structure and associated functions for agricultural production. We investigated the impact of rice straw biochar application on soil water retention (SWR), air movement through soil, and soil pore characteristics of a tropical sandy clay loam field. A field experiment was conducted at the University of Ghana's Forest and Horticultural Crops Research Centre, Kade, Ghana, which comprised three treatments: soil without biochar (B0), and soil amended with 15 and 30 Mg ha-1 of biochar (B15 and B30, respectively). Three years after biochar application, we sampled intact 100 cm 3 soil cores and measured SWR, air permeability (k a) and gas diffusivity (D p /D 0), and quantified pore characteristics: tortuosity (t), effective pore diameter (d B) and the number of air-filled pores in a given soil cross-section (n B) at selected matric potentials. At all matric potentials (-10 to-15000 hPa), B30 considerably reduced SWR compared to B0, whereas the B15 had similar SWR as B0. Biochar did not significantly affect the plant available water (PAW). The B30 significantly increased k a at-30 hPa relative to B15. At a given air-filled porosity, the B30 tended to have larger D p /D 0 values compared to B0. Despite these improvements in soil air transport, the effect of the biochar treatment was marginal on soil t, d B and n B. We suggest that, probably higher biochar application rates and longer time are needed to significantly improve PAW and soil pore structure characteristics, which control air and gas transport through the soil.
Effects of biochar amendment on geotechnical properties of landfill cover soil
Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA, 2015
Biochar is a carbon-rich product obtained when plant-based biomass is heated in a closed container with little or no available oxygen. Biochar-amended soil has the potential to serve as a landfill cover material that can oxidise methane emissions for two reasons: biochar amendment can increase the methane retention time and also enhance the biological activity that can promote the methanotrophic oxidation of methane. Hydraulic conductivity, compressibility and shear strength are the most important geotechnical properties that are required for the design of effective and stable landfill cover systems, but no studies have been reported on these properties for biochar-amended landfill cover soils. This article presents physicochemical and geotechnical properties of a biochar, a landfill cover soil and biochar-amended soils. Specifically, the effects of amending 5%, 10% and 20% biochar (of different particle sizes as produced, size-20 and size-40) to soil on its physicochemical properti...
EFFECT OF BIOCHAR ON WATER RETENTION IN SOIL, A COMPARISON BETWEEN TWO FORMS: POWDER AND PELLET
Biochar, thanks to its porosity, can have a positive effect in water retention on sandy soils. In this work pellet from Arundo Donax L. was produced at the Biomass Research Centre of the University of Perugia (Italy), then it was used to produce biochar in a pyrolytic stove in the laboratories of the Institute of Biometeorology in Florence (Italy). This biochar was analyzed and characterized at the laboratory of MAC (Minoprio Analisi e Certificazioni) and Richard Pressure Plates were produced to test its action on water retention. Two forms of biochar were tested: pelletized biochar and biochar in powder. While the effect on soil water retention of biochar in powder has already been tested, the effect of pelletized biochar has not. The retention efficiency of biochar pellet was higher than that of the powder. In fact at field capacity an increase in water retention of 20% was measured with biochar in pellet, while the increase was about 4% with biochar in powder. This can bring important advantages to the crops cultivated with biochar as soil amendment, in terms of their water footprint.
Scientific reports, 2021
Recent studies on water retention behaviour of biochar amended soil rarely considers the effect of pyrolysis temperature and also feedstock type into account. It is well known that pyrolysis temperature and feedstock type influences the physical and chemical properties of biochar due to stagewise decomposition of structure and chemical bonds. Further, soil density, which is in a loose state (in agricultural applications) and dense (in geo-environmental engineering applications) can also influence water retention behaviour of biochar amended soils. The major objective of this study is to investigate the water retention properties of soil amended with three different biochars in both loose and dense state. The biochars, i.e. water hyacinth biochar (WHB), chicken manure biochar (CMB) and wood biochar (WB) were produced in-house at different pyrolysis temperature. After then, biochars at 5% and 10% (w/w%) were amended to the soil. Water retention behaviour (soil suction and gravimetric water content) was studied under drying and wetting cycle simulated by varying relative humidity (RH, 50–90%). Results show that 10% WHB produced at 300 °C were found to possess highest water retention. CMB is found to possess higher water retention than WB for 10% amendment ratio. In general, the addition of three biochars (at both 300 °C and 600 °C) at 10% (w/w) significantly improved the water retention at all suction ranges in both loose and dense compaction state as compared to that of the bare soil. The adsorption (wetting) and desorption (drying) capacity of biochar amended soils is constant at corresponding RH.
Impact of biochar on water retention of two agricultural soils – A multi-scale analysis
Geoderma, 2019
The ability of soil to retain water under drought and other extreme hydrological events is critical to the sustainability of food production systems and preserving soil ecosystem services. We investigated the impact of biochar on water retention properties in California agricultural soils in a series of column, lab incubation, and field studies. Results from studies based on similar variables (soil, biochar) were used to demonstrate the impact of biochar on soil-water relations at different scales. The influences of biochar type (softwood, 600-700°C, low surface area; walnut shell, 900°C, high surface area), application rate (0, 0.5, 1% wt.), and particle diameter (0-0.25, 0.25-0.5, 0.5-1, 1-2 mm) were investigated. Only the higher surface area biochar increased the field capacity of a sandy soil. Neither biochar, altered the field capacity of the higher clay content soil. The walnut shell biochar with 1-2 mm particle diameter was more effective at increasing field capacity in sandy soils compare to smaller biochar size fractions. Neither biochar affected the wilting point in either soil. Neutron imaging was used to explore potential mechanisms involved in water retention by observing the spatial and temporal distribution of water in and surrounding biochar particles (~2 mm diameter). After wetting, water retained in the internal pores of biochar was continuously released to surrounding space (~2.2 mm sphere) during a 7-day air drying at room temperature, suggesting that soil water retention is improved via the biochar's intraparticle structure. In the field trial, (6 yr., corn-tomato rotation), neither walnut shell biochar amendment (10 t/ ha, equivalent to 0.5% wt. in lab scale experiments) nor agricultural management practices (organic, conventional) altered the water retention capacity of a silty clay loam soil. These data suggest that biochars with a high pore volume can temporarily increase the field capacity and plant available water in a coarse-textured soil, until biochar internal pores are filled by clay and soil organic matter. Our results suggest that biochar can have a limited impact on soil water retention when biochar pore volume is low, or soil texture is fine. High dosage (≥10 t/ha) of high pore volume biochar with bulky particle size (≥1 mm) can improve water retention of coarse-textured soil with limited capacity of water storage and may improve soil's resilience during hydrological extremes.