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 1. Introduction 2. Testing Program 3. Methodology 4. Typical Results 5. Conclusions 2015/1/30 2

Introduction CO 2 O 2 Ingression Biochar LFG collection Aerobic & flaring CH 4 +2O 2 CO 2 +2H 2 O Anaerobic Fugitive CH 4 & CO 2 emissions LFG (CH 4 + CO 2 ) Soil cover Methane Oxidation Landfilled waste Bottom liner  Landfills in US are 3 rd largest contributors to anthropogenic CH 4 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 CH 4 oxidation  Bio-based cover systems exhibit higher methane oxidation efficiency compared to conventional soil cover systems Preliminary studies at UIC show that biochars have high potential to adsorb fugitive methane emissions and promote methane oxidation in landfill covers 2015/1/30 3

Introduction (Contd.) Compressive Strength and Shear Strength Critical properties defining the behavior • of 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 Source: International Journal of Geoengineering • Case Histories relating to its overall strength and stability 2015/1/30 4

Study Objectives To evaluate the settlement characteristics of biochars and 1 biochar-amended soils and quantify the constrained modulus To compute the shear strength parameters (cohesion and 2 friction angle) of biochars and biochar-amended soils and to evaluate the stability of cover slopes 2015/1/30 5

Biochars and Soil Tested CE-WP1 BS CK AW CE-WC Soil CE-AWP CE-WP2 6 2015/1/30

Biochars and Soil Tested (Contd.) Biochar Type Feedstock Treatment Treatment Residence Post-treatment Process Temperature Time BS (Biochar Pine Wood Slow pyrolysis 350 - 600 0 C 6 hrs Screened through solutions Inc.) 3mm mesh CK (Char King 90% pine & Fast pyrolysis > 500 0 C < 1 hr Activated with Intl.) 10% fir wood oxygen AW (Aztec Aged wood Pyrolysis – ~ 400 0 C NA Inoculated with Wonder, LLC) chips conventional microbes & kiln screened through 4mm mesh CE-WP1 Wood Pellets Gasification ~ 520 0 C NA N/A CE-WP2 Wood Pellets Gasification ~ 520 0 C NA Not subjected to fine ash filtration CE-AWP Wood Pellets Gasification ~520 0 C NA Fine ash separated CE-WC Wood Chips Gasification ~520 0 C NA N/A DeKalb landfill cover soil, sieved (< 2mm) and homogenized; Obtained from stockpile near active landfill 7 2015/1/30

Compressibility Testing Program To understand compressibility behavior and Study purpose compute the constrained modulus of biochars Testing program (Biochars) Sample Preparation Biochar Seven different wood- types based biochars MC Compression Testing Two levels (dry and 25% WHC) Vertical Sequential loading (0.1 – 100 KPa) Computing Constraint Modulus Total tests = 14 2015/1/30 8

Compressibility Testing Program (Contd.) To understand compressibility behavior and Study purpose compute the constrained modulus of biochar- amended soils Testing program (Biochar-Amended Soils) Biochars Sample Preparation Four selected biochar types BC/S Four levels (0, 2, 5, & 10% d.w.) Compression Testing MC 2 levels (dry and 25% WHC) Vertical Sequential loading (0.1 – 100 Kpa) Computing Constrained Modulus Total tests = 26 2015/1/30 9

Compressibility Testing Methodology Protocol in accordance with ASTM D2435 Air Dried Sample Preparation  Air dried  Sieved Sieved through #10 (< 2mm) Compression Compression Testing Set-up  Apply different vertical Prepare the sample to a loads known density  Record the vertical in cylindrical displacement from the consolidation dial gauge ring 2015/1/30 10

Typical Compressibility Results 9 9 Dry Conditions 25% WHC 8 8 CE-WP2 CE-WP2 7 7 Soil Soil Volumetric Strain, %   10% CE-WP2 10% CE-WP2 6 6  M  5 5 E 4 4 3 3 M = Constrained modulus, Pa 2 2 Δσ = Change in stress, Pa ΔE = Change in strain 1 1 0 0 0 20 40 60 80 100 0 20 40 60 80 100 Normal Stress, KPa Normal Stress, KPa  H   E 7 H Constrained Modulus, MPa Dry 6 25% WHC ΔH = Change in sample height, ft 5 H = Initial sample height, ft 4 3 2 1 0 Soil CE-WP2 10% CE-WP2 2015/1/30 11

Application to Landfill Cover σ n = 40 KPa    H   H M 3’ Methane Oxidation/Biocover Layer Settlement of cover material Gas Distribution Layer 1.2 LFG from MSW Dry 1.0 25% WHC Settlement, inches 0.8 M (Mpa) M (Mpa) Material Dry 25% WHC 0.6 0.4 6.61 2.42 Soil 0.2 3.16 1.36 CE-WP2 0.0 Soil CE-WP2 10% CE-WP2 2.91 2.88 10% CE-WP2 2015/1/30 12

Shear Strength Testing Program To compute the shear strength parameters for Study purpose biochars and determine the stability of landfill cover slopes Testing program (Biochars) Sample Preparation Biochar Seven different wood- types based biochars MC Direct Shear Testing Dry conditions Normal Three levels (0.25, Stress 0.5 and 1 tsf) Computing Cohesion and Friction Angle Total tests = 21 2015/1/30 13

Shear Strength Testing Program (Contd.) To compute the shear strength parameters for Study purpose biochar-amended soils and determine the stability of landfill cover slopes Testing program (Biochar-Amended Soils) Biochars Sample Preparation Seven wood-based biochar types BC/S 0 & 10% Biochar added to soil (w/w) Direct Shear Testing MC 15% MC (d.w.) Normal Three levels (0.25, Computing Cohesion and Stress 0.5 and 1 tsf) Friction Angle Total tests = 24 2015/1/30 14

Shear Strength Testing Methodology Protocol in accordance with ASTM D3080 Air Dried Sample Preparation  Air dried Sieved  Sieved through #10 (< 2mm) Direct Shear Testing Shear Box Set-up  Apply different normal stresses Prepare the  Apply horizontal loading at sample to a constant displacement rate known density in the shear box for each normal stress  Record horizontal displacement 2015/1/30 15

Typical Shear Strength Testing Results Normal Stress = 24 KPa Failure envelope is plotted Normal Stress = 48 KPa 140 Soil - Dry Conditions Normal Stress = 96 KPa 120 from direct shear test data Shear Stress, KPa 100 80 Slope of the failure 60 envelope corresponds to 40 frictional angle, φ’ 20 0 (degrees) 0.00 0.05 0.10 0.15 0.20 0.25 Horizontal Deformation, in Intercept of the failure 140 envelope corresponds to Soil - Dry Conditions the Cohesion, c’ ( KPa) 120 Shear Stress, kPa 100 80 Material Φ (deg) C (KPa) 60 40 49.8 1.2 Soil (dry) 20 20 40 60 80 100 2015/1/30 16 Normal Stress, kPa

Typical Shear Strength Testing Results (Contd.) 140 Soil (15% MC) 120 Dry CE-WP2 S+10% CE-WP2 (15% MC) 100 Dry Soil Shear Stress, KPa Soil exhibited the least 80 value of cohesive strength 60 40 20 Biochar under dry 0 conditions had the highest 20 40 60 80 100 cohesive strength Normal Stress, KPa 60 60 Friction Angle (Degrees) Cohesion Addition of biochar to soil 50 50 Friction Angle Cohesion (kPa) increased the shear 40 40 strength parameters of soil 30 30 20 20 10 10 0 0 Soil (dry) Soil (15% MC) CE-WP2 (Dry) 10% CE-WP2 (15% MC) 2015/1/30 17

Cover Slope Stability Analysis  tan ' ' c   FS A B   tan H Φ’ and c’ = Shear parameters β = Cover slope angle  γ and γ w = unit weight of cover material and H   w w 1 A water   2 HCos H = Height of cover soil H w = Height of water table 1 B   tan  2 Cos 2015/1/30 18

Cover Slope Stability Analysis 7 2.5:1 Slope 7 2:1 Slope Soil Soil 6 6 10%WP2 10%WP2 Factor of Safety Factor of Safety 5 5 4 4 3 3 2 2 1 1 0 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Hw/H Hw/H 3:1 Slope 7 Soil 6 10%WP2 Addition of biochar to Factor of Safety 5 soil increased safety 4 factor for cover slope 3 stability 2 1 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Hw/H 2015/1/30 19

Conclusions Compressibility and shear strength of cover soils can be 1 improved by the addition of wood-based biochars tested in this study Adding biochar to cover soil increased the cover slope 2 stability by at least two times for typical slope angles Certain biochar types can be implemented in engineered systems such as landfill covers or engineered barriers 3 without compromising on the overall strength and stability of the system 2015/1/30 20