a field study of biochar amended soils: water retention and nutrient
TRANSCRIPT
A Field Study of Biochar Amended Soils: Water Retention and Nutrient Removal from Stormwater Runoff
Funded through the Chesapeake Bay Stewardship Fund by a National Fish and Wildlife Foundation grant
Joseph D. Brown, Sr., P.E.University of Delaware, Department of Civil and Environmental Engineering
Outline
• Background• Research Hypotheses• Experimental Methods• Preliminary Results• Future Research
What is Biochar?
• Produced from the pyrolysis of wood or waste biomass
• Important properties– High surface area– High porosity– Significant cation exchange capacity– High adsorption capacity– Stable carbon structure
Biochar’s Potential Benefits:
• Decreased overall stormwater runoff rates & volumes
• Reduced soil erosion and sedimentation
• Reduced nutrient & metal loading• Improved groundwater recharge• Reduced flooding
Background Research• Biochar Impact on Soil Hydraulic
Properties:
• Impact on Nutrient Removal
0.0 0.1 0.2 0.3 0.4 0.5
-70
-60
-50
-40
-30
-20
-10
0 Ctrl-wet Exp-wet Ctrl-dry Exp-dry
Volumetric water content (m3/m3)
Dep
th (c
m)
0
10
20
30
40
50
60
70
Cap
illar
y pr
essu
re h
ead
(cm
H2O
)
• Ksat Increased 4X
• Water Retention Increased 30%
• 43% NO3 Reduction
• 6.1% increase in NO3 in control cell without biochar
Jing Tian, Jing Jin, Paul T. Imhoff, Pei C. Chiu, Daniel K. Cha, MingxinGuo, Julia A. Maresca
Research Hypotheses:Roadside Filter Strips:• Biochar increases
– water retention – unsaturated hydraulic conductivity – hydraulic residence time of
pollutants in soilsRoadside Swales:• Biochar increases
– water retention – hydraulic residence time
Project Site: Rt 896 & Bethel Church RoadMiddletown, De
Experimental Methods - Filter Strips
Test Equipment:• Soil Moisture sensors• Water potential &
temperature sensors• Automated water samplers• Ultrasonic flow sensors• Rain gauge
Experimental Methods - Filter Strips
Experimental Methods – Roadside Filter Strips
Control Strip 4% Biochar Strip
Experimental Methods - SwaleTest Equipment:• Soil Moisture sensors• Rhizon Pore Water Samplers• Rain gauge
Experimental Methods - Swales
Experimental Methods - Parameters:Soil Data:• Volumetric Water Content• Soil Water Potential• Soil pH and Temperature• Electrical Conductivity• Soil Compaction• Unsaturated Hydraulic Conductivity• Nitrogen Compounds in Pore WaterSurface Water Data:• Stormwater Runoff Rate and Volume• Influent and Effluent N Loading
(Total N, NH3, NO3, NO2, TOC, etc.)• Total Suspended Solids
Results – Runoff Profile (Typical Rain Event)
0
200
400
600
800
1000
1200
6/24/2016 12:36 6/24/2016 13:04 6/24/2016 13:33 6/24/2016 14:02
Wat
er F
low
Rat
e, (m
l/s)
Date
Storm Event 27: Area Flow Rates
Sampler 1
Sampler 2
Sampler 3
Roadway Runoff
Control
Biochar
Rainfall, (in/hr)
Results – Cumulative Runoff (Typical Rain Event)
Stormwater Runoff Summary
0
500
1000
1500
2000
2500
3000
3500
4000
4500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 35 36
Pea
k R
unof
f Rat
e, (m
l/s)
Storm Event
Peak Runoff Rate Summary
Runoff Rate (ml/s)
Control Rate (ml/s)
Biochar Rate (ml/s)
Stormwater Runoff Summary
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 35 36
Cum
ulat
ive
Run
off V
olum
e, (l
)
Storm Event
Runoff Volume Summary
Runoff Volume (l)
Control Volume (l)
Biochar Volume (l)
Stormwater Runoff SummaryResults for 34 Rain Events
• Average Peak Stormwater Runoff Rate Reduction:
43% (Std Dev: 28%)
• Average Cumulative Stormwater Runoff Volume Reduction:
68% (Std Dev: 24%)
Results – Soil Moisture Content
• 0-15cm Depth: 83% Increase
• 15-30cm Depth: 50% Increase
Results – Infiltration
0
1
2
3
4
5
6
biochar control undisturbed
log
Ksa
t(cm
/day
)
Filter Strip
• Tillage: 50% Reduction
• Biochar: 732% Increase
42.6 cm/day
21.4 cm/day
354.4 cm/day
Results – Compaction
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80
Dep
th, (
cm)
Cone Stress, (kg/cm2)
Compaction Testing Summary
Biochar 12/08/15
Control 12/08/15
Biochar 7/31/16
Control 7/31/16
Existing 11/15/2015
Results – NO3 –N Concentration(Typical Rain Event)
• 23% NO3 Reduction
Results – NO2 –N Concentration(Typical Rain Event)
• 21% NO2 Reduction
Results – TN (Typical Rain Event)
0
1
2
3
4
5
6
6/24/2016 12:28 6/24/2016 12:57 6/24/2016 13:26 6/24/2016 13:55
NH
4-N
, (m
g/L)
Time
TN: Storm 27
Roadway
Control
Biochar
• 26% TN Reduction(First 80% of Storm)
• 15% TN Increase(Overall)
Results – Grass Growth
Control Strip (4/25/2016) 4% Biochar Strip (4/25/2016)
Results – Dissecting Microscopic Imagery
Existing Soil Existing Soil with 4% Biochar
Results – Soil Temperature
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
2/10/2016 12:00 3/26/2016 12:00 5/10/2016 12:00 6/24/2016 12:00 8/8/2016 12:00
Tem
pera
ture
, (oC
)
Date
NFWF Soil Temperature
Control
Biochar
Future Work
• Construct swales – Summer 2016• Monitor and test throughout 2016• Author recommendations for regulatory credit applications for
use of Biochar• Model the hydrodynamics of stormwater flow and infiltration
using Richards equation and results from lab and field experiments
Acknowledgements:
• Advisor: Dr. Paul Imhoff• Consultants: Chuck Hegberg, Larry Trout• Funded By: National Fish and Wildlife Foundation thru the
Chesapeake Bay Stewardship Fund• Fellow Researchers: Sriya Panta, Seyyed Ali Akbar Nakhli,
Susan Yi, Tian Wenling, Jing Jin, Fang Tan• In Cooperation with: DelDOT