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Methane Adsorption by Different Biochars
Illinois Biochar Group Meeting
Yamini Sadasivam & Krishna R. Reddy University of Illinois at Chicago
04/05/2013
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Presentation Outline
Methane oxidation in landfill cover systems Biochar as a landfill cover material Ongoing research at UIC Batch adsorption testing
Types of biochars used Physical-chemical properties Testing protocol Results Major conclusions
Future goals & objectives
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Methane oxidation in landfill covers
Methane oxidation
CH4+2O2→CO2
+2H2O
Aerobic
Anaerobic
Landfill gas
CH4+CO2
O2
LFG emissions are among the major sources of greenhouse gases to the atmosphere
Traditionally soil covers were used to achieve microbial methane oxidation by methanotrophs Major issues with cracking of soil surfaces Inefficient performance in the absence of LFG extraction systems
Biocover materials with organic amendments were used to increase methane oxidation efficiency Major issues with material’s self-degradation Formation of EPS causing pores to clog & hindering the transport of gases Cannot contribute to methane adsorption
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Biochar – A Potential Landfill Cover Material
Methane oxidizing material
CH4 and CO2
Oxygen Exhaust gases
Porous material
Biocover
GDL
MSW
Biochar can be amended to landfill cover soils to enhance CH4 adsorption and oxidation
Biochar can be used
Biochar is advantageous over current compost biocovers
Enhanced CH4 adsorption
Greater porosity and specific surface area (limits pore clogging due to EPS formation)
Favors growth and CH4 oxidation activity of methanotrophs which can conveniently exist within the highly porous biochar
Enhanced gas transport through the pores Sustainable and cheap option to mitigate LFG
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Ongoing Biochar Research Goals
To quantify the physical, chemical and geotechnical characteristics of biochars and biochar-amended soils.
To determine the adsorption and enhanced gas transport properties of biochars and biochar-amended landfill cover soils for CH4 and oxygen.
To characterize the main factors that affect CH4 oxidation.
To investigate adsorption and oxidation of CH4 under various conditions such as biochar composition and size, soil composition, CH4 source strength, CH4 concentration, moisture content, and temperature.
To model the mechanisms of CH4 oxidation within biochars and biochar-amended landfill cover systems and determine kinetic parameters defining these mechanisms.
To conduct a full-scale field demonstration. To prepare guidance manual to design biochar and biochar-amended
landfill cover soil systems for landfill applications.
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Batch Adsorption Testing – Biochars used
1. BS : Biochar Solutions Inc.2. CK : Char King International3. AW : Aztec Wonder, LLC4. CE – WP1 : Wood pellets w/ash5. CE – WP2 : Wood pellets w/o
ash6. CE – AWP : Aged wood pellets7. GAC : granular activated
carbon
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Batch Adsorption Testing – Biochars used
Biochar Source
Feedstock Treatment Process
Treatment Temperature
Residence Time
Post-treatment
Biochar Solutions Inc.
Pine Wood Slow pyrolysis 350 - 6000C 6 hrs Screened through 3mm
mesh
Char-King International
90% pine & 10% fur wood
Fast pyrolysis > 5000C < 1 hr Activated with oxygen
Aztec Wonder, LLC
Aged oak & hickory wood
biochar
Pyrolysis – Missouri type concrete kiln
~ 5000C ---Mixed
w/innocula & sieved (1/4”)
Chip Energy Inc. Wood Pellets Gasification 5200C --- N/A
Wood Pellets --- --- --- Not subjected to fine ash filtration
Wood Pellets --- --- --- Fine ash separated
Feedstock & Production Processes:
In addition to biochars, GAC was obtained from Fisher Scientific and tested for its methane adsorption capacity
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Biochar type
pHMoisture Content (% d.w.)
Organic Content
(%)
Average Particle
Size (mm)
Specific Gravity
Water Holding Capacity (% total mass)
BS 8.5 0 29.2 0.7 1.1 54.66
CK 9.0 5.6 31.3 0.2 1.5 63.94
AW 8.2 49.2 76 0.9 1.2 49.96
CE-WP1 6.4 3.2 96.9 1.1 0.8 58.73
CE-WP2 6.9 3.7 96.8 3.2 0.6 32.91
CE-AWP 7.2 4.3 82.3 5.8 0.8 44.52
GAC 9.0 21.3 89 2.9 1.6 49.06
Batch Adsorption Testing – Material characteristics
pH of biochars range from 6 – 9; pH values for biochars from Chip Energy are around neutral
MC of sterilized biochars range from 0 – 6% d.w. except for AW & GAC
BS, CK AW & GAC have SG > 1; CE biochars have SG < 1
WHC refers to the amount of moisture the biochars can absorb; WHC of finer grained biochars are higher than coarse grained
biochars
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Batch Adsorption Testing – Material characteristics
Grain Size Distribution
Particle size (mm)
.01.1110100
Per
cent
pas
sing
0
10
20
30
40
50
60
70
80
90
100BSCKAWCE-WP1CE-WP2CE-AWPGAC
D50 of biochars range between 0.2 mm and 7
mm
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Batch Adsorption Testing – Protocol
Step 1:
Sterilization of biochars - 1210C (15 psi);30 min/cycle for 2 consecutive days
Step 2:
Evacuation of vials – 5 mm glass serum bottles crimped w/ butyl septa & aluminum caps
Biochar
Glass bottle
Rubber stopper
Syringe
Step 3:
5g material used; controls (no biochar); gas samples
stored in 5 ml vials & analyzed within 4 hr using HP 6890 GC w/ FID and GS
Carbon plot column
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Batch Adsorption Testing -Results
Adsorption Capacity of Biochars
Biochar Type
BS CK AW CE-WP1 CE-WP2 CE-AWP GAC
Qe,
mol
/Kg
0
1000
2000
3000
4000
10% CH4 v/v 8% CH4 v/v 5% CH4 v/v 2% CH4 v/v
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Effect of Moisture on Adsorption
Moisture Content (% WHC)
0 20 40 60 80 100 120
Qe,
mL/
Kg
900
1000
1100
1200
1300
1400
Moisture Content vs Qe, mL/Kg
Batch Adsorption Testing -Results
CE-WP2 tested at 10%
headspace CH4 (v/v)
MC was varied at 4 levels (25, 50, 75 & 100%
WHC)
WHC of Biochar ≈ 50% (d.w.)
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Batch Adsorption Testing -Results
Adsorption curves at different temperatures
Time, min
0 20 40 60 80 100 120 140
Qe,
mL/
Kg
0
200
400
600
800
1000
1200
1400
1600
Qe vs time, 24 oC
Qe vs time 35 oC
Qe vs time 41 oC
CE-WP2 tested at 10%
headspace CH4 (v/v)
Positive heat of adsorption; Qe decreases w/ increasing T
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Major Conclusions
Methane adsorption capacities of biochars are strongly dependent upon their physical-chemical characteristics
Generally, methane adsorption capacity of fresh biochars increases with decreasing particle size
Presence of moisture negatively affects the methane adsorption capacity of biochars
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Methane adsorption capacity decreases with increasing temperature
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Activated – pine & fur wood biochar showed the highest methane adsorption capacity (Qe ≈ 3500 mL/Kg)
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Future Goals and Objectives
Characterize more biochar types in the lab for their physical-chemical and geotechnical properties
Test the effects of biochar properties, MC, temperature & biochar amendment ratio on CH4 adsorption & oxidation capacity
Develop an effective design based on modeling the laboratory results and determine optimum biocover size for field implementation
Test the biochar in the field and monitor its performance for LFG mitigation
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16 Thank you!