Engineering Properties of Waste-Wood Derived Biochars and - - PowerPoint PPT Presentation

Engineering Properties of Waste-Wood Derived Biochars and Biochar-amended Soils

Bala Yamini Sadasivam and Krishna R. Reddy University of Illinois at Chicago

Illinois Biochar Group Fall Meeting Peoria, November 14, 2014

Outline

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• 1. Introduction
• 2. Testing Program
• 3. Methodology
• 4. Typical Results
• 5. Conclusions

Introduction

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Preliminary studies at UIC show that biochars have high potential to adsorb fugitive methane emissions and promote methane oxidation in landfill covers

Bottom liner Landfilled waste Soil cover LFG collection & flaring Fugitive CH4 & CO2 emissions

Methane Oxidation

Aerobic Anaerobic O2 Ingression

CH4 +2O2 +2H2O CO2 LFG (CH4 + CO2) CO2

Biochar  Landfills in US are 3rd largest contributors to anthropogenic CH4 missions  If gas collection systems are less efficient, fugitive emissions occur which can be addressed by landfill cover systems  Soil & bio-based covers function based on biological CH4 oxidation  Bio-based cover systems exhibit higher methane oxidation efficiency compared to conventional soil cover systems

Introduction (Contd.)

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• Critical properties defining the behavior
• f materials under compressibility and

shearing loads

• Compressibility relates to the

settlement properties of landfill cover during and after placement of cover systems

• Shear strength parameters are used to

compute the stability of landfill cover slopes

• Used to evaluate the cover properties

relating to its overall strength and stability

Compressive Strength and Shear Strength

Source: International Journal of Geoengineering Case Histories

Study Objectives

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To evaluate the settlement characteristics of biochars and biochar-amended soils and quantify the constrained modulus 1 To compute the shear strength parameters (cohesion and friction angle) of biochars and biochar-amended soils and to evaluate the stability of cover slopes 2

Biochars and Soil Tested

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BS CK AW CE-WP1 CE-WP2 CE-AWP CE-WC Soil

Biochars and Soil Tested (Contd.)

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Biochar Type Feedstock Treatment Process Treatment Temperature Residence Time Post-treatment BS (Biochar solutions Inc.) Pine Wood Slow pyrolysis 350 - 6000C 6 hrs Screened through 3mm mesh CK (Char King Intl.) 90% pine & 10% fir wood Fast pyrolysis > 5000C < 1 hr Activated with

• xygen

AW (Aztec Wonder, LLC) Aged wood chips Pyrolysis – conventional kiln ~ 4000C NA Inoculated with microbes & screened through 4mm mesh CE-WP1 Wood Pellets Gasification ~ 5200C NA N/A CE-WP2 Wood Pellets Gasification ~ 5200C NA Not subjected to fine ash filtration CE-AWP Wood Pellets Gasification ~5200C NA Fine ash separated CE-WC Wood Chips Gasification ~5200C NA N/A

DeKalb landfill cover soil, sieved (< 2mm) and homogenized; Obtained from stockpile near active landfill

Compressibility Testing Program

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To understand compressibility behavior and compute the constrained modulus of biochars

Study purpose

Sample Preparation Compression Testing Computing Constraint Modulus

Seven different wood- based biochars Two levels (dry and 25% WHC) Sequential (0.1 – 100 KPa) Biochar types

MC Vertical loading

Testing program (Biochars)

Total tests = 14

Compressibility Testing Program (Contd.)

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To understand compressibility behavior and compute the constrained modulus of biochar- amended soils

Study purpose

Sample Preparation Compression Testing Computing Constrained Modulus

Testing program (Biochar-Amended Soils)

Total tests = 26

Four selected biochar types Four levels (0, 2, 5, & 10% d.w.) 2 levels (dry and 25% WHC) Sequential (0.1 – 100 Kpa) BC/S

MC Vertical loading

Biochars

Compressibility Testing Methodology

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Sample Preparation Compression Set-up Compression Testing  Air dried  Sieved through #10 (< 2mm) Prepare the sample to a known density in cylindrical consolidation ring Protocol in accordance with ASTM D2435 Air Dried Sieved

 Apply different vertical loads  Record the vertical displacement from the dial gauge

Typical Compressibility Results

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E M    

M = Constrained modulus, Pa Δσ = Change in stress, Pa ΔE = Change in strain

H H E   

ΔH = Change in sample height, ft H = Initial sample height, ft

Dry Conditions Normal Stress, KPa 20 40 60 80 100 Volumetric Strain, % 1 2 3 4 5 6 7 8 9 CE-WP2 Soil 10% CE-WP2 25% WHC Normal Stress, KPa 20 40 60 80 100 1 2 3 4 5 6 7 8 9 CE-WP2 Soil 10% CE-WP2

Soil CE-WP2 10% CE-WP2 Constrained Modulus, MPa 1 2 3 4 5 6 7 Dry 25% WHC

Application to Landfill Cover

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Soil CE-WP2 10% CE-WP2 Settlement, inches 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Dry 25% WHC

Methane Oxidation/Biocover Layer LFG from MSW Gas Distribution Layer

M H H     

Settlement of cover material

3’

σn= 40 KPa

Material M (Mpa) Dry M (Mpa) 25% WHC Soil 6.61 2.42 CE-WP2 3.16 1.36 10% CE-WP2 2.91 2.88

Shear Strength Testing Program

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To compute the shear strength parameters for biochars and determine the stability of landfill cover slopes

Study purpose

Sample Preparation Direct Shear Testing Computing Cohesion and Friction Angle

Seven different wood- based biochars Dry conditions Three levels (0.25, 0.5 and 1 tsf) Biochar types

MC Normal Stress

Testing program (Biochars)

Total tests = 21

Shear Strength Testing Program (Contd.)

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To compute the shear strength parameters for biochar-amended soils and determine the stability

• f landfill cover slopes

Study purpose

Sample Preparation Direct Shear Testing Computing Cohesion and Friction Angle

Testing program (Biochar-Amended Soils)

Total tests = 24

Seven wood-based biochar types 0 & 10% Biochar added to soil (w/w) 15% MC (d.w.) Three levels (0.25, 0.5 and 1 tsf) BC/S

MC Normal Stress

Biochars

Shear Strength Testing Methodology

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Sample Preparation Shear Box Set-up Direct Shear Testing  Air dried  Sieved through #10 (< 2mm) Prepare the sample to a known density in the shear box Protocol in accordance with ASTM D3080 Air Dried Sieved

 Apply different normal stresses  Apply horizontal loading at constant displacement rate for each normal stress  Record horizontal displacement

Typical Shear Strength Testing Results

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Failure envelope is plotted from direct shear test data Slope of the failure envelope corresponds to frictional angle, φ’ (degrees) Intercept of the failure envelope corresponds to the Cohesion, c’ (KPa)

Material Φ (deg) C (KPa) Soil (dry) 49.8 1.2

Soil - Dry Conditions Horizontal Deformation, in 0.00 0.05 0.10 0.15 0.20 0.25 Shear Stress, KPa 20 40 60 80 100 120 140

Normal Stress = 24 KPa Normal Stress = 48 KPa Normal Stress = 96 KPa

Soil - Dry Conditions Normal Stress, kPa 20 40 60 80 100 Shear Stress, kPa 20 40 60 80 100 120 140

Typical Shear Strength Testing Results (Contd.)

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Addition of biochar to soil increased the shear strength parameters of soil Soil exhibited the least value of cohesive strength Biochar under dry conditions had the highest cohesive strength

Normal Stress, KPa 20 40 60 80 100 Shear Stress, KPa 20 40 60 80 100 120 140 Soil (15% MC) Dry CE-WP2 S+10% CE-WP2 (15% MC) Dry Soil

Soil (dry) Soil (15% MC) CE-WP2 (Dry) 10% CE-WP2 (15% MC) Cohesion (kPa)

10 20 30 40 50 60 10 20 30 40 50 60 Cohesion Friction Angle

Friction Angle (Degrees)

Cover Slope Stability Analysis

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H c B A FS    ' tan ' tan  

  

2

1 HCos H A

w w

 

  tan 1

2

Cos B 

Φ’ and c’ = Shear parameters β = Cover slope angle γ and γw= unit weight of cover material and water H = Height of cover soil Hw = Height of water table

Cover Slope Stability Analysis

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2:1 Slope Hw/H 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Factor of Safety 1 2 3 4 5 6 7 Soil 10%WP2 2.5:1 Slope Hw/H 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Factor of Safety 1 2 3 4 5 6 7 Soil 10%WP2 3:1 Slope Hw/H 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Factor of Safety 1 2 3 4 5 6 7 Soil 10%WP2

Addition of biochar to soil increased safety factor for cover slope stability

Conclusions

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Compressibility and shear strength of cover soils can be improved by the addition of wood-based biochars tested in this study 1 Adding biochar to cover soil increased the cover slope stability by at least two times for typical slope angles 2 Certain biochar types can be implemented in engineered systems such as landfill covers or engineered barriers without compromising on the overall strength and stability of the system 3

List of Publications

1. Sadasivam, B.Y., and Reddy, K.R. (2014). “Landfill methane oxidation in soil and bio-based cover systems.” Reviews in Environmental Science and Bio/Technologies, 13(1), 79-107 (DOI: 10.1007/s11157-013-9325-z). 2. Yargicoglu, E., Sadasivam, B.Y., Reddy, K.R. and Spokas, K. (2014). “Physical and chemical characterization of waste wood derived biochars.” Waste Management (In Print). 3. Reddy, K.R., Yargicoglu, E.N., Yue, D., and Yaghoubi, P. (2014). “Enhanced microbial methane

• xidation in landfill cover soil amended with biochar.” Journal of Geotechnical and

Geoenvironmental Engineering, ASCE, 140(9), 04014047 (DOI:10.1061/(ASCE)GT.1943- 5606.0001148). 4. Sadasivam, B-Y., and Reddy, K.R. (2013). “Study of methane adsorption by biochar in landfill cover.” Proc., 106th Annual Conference & Exhibition, Air & Waste Management Association, Chicago, IL, USA. 5. Sadasivam, B.Y., and Reddy, K.R. (2014). “Quantifying the effects of moisture content on methane adsorption capacity of biochars.” Geotechnical Special Publication 241- Geoenvironmental Engineering, Proc. of the Geo-Shanghai 2014, Editors: Reddy, K.R. and Feng, S., American Society of Civil Engineers, Reston, VA, 191-200. 6. Sadasivam, B.Y., and Reddy, K.R. (2014). “Sustainability assessment of Subtitle D cover versus biocover for methane oxidation at municipal solid waste landfills.” Geotechnical Special Publication 234, Proc. of the Geo-Congress 2014, Editors: Abu-Farsakh, M., Yu, X., and Hoyos, L.R., American Society of Civil Engineers, Reston, VA. 7. Sadasivam, B.Y., and Reddy, K.R. (2015). “Influence of physico-chemical properties of different biochars on landfill methane adsorption.” IFCEE2015, San Antonio, TX, March 17-21, 2015 (Accepted).

Illinois Sustainability Technology Center (ISTC) Illinois Biochar Group Chip Energy, Inc.

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