Outline of Presentation
Urea for CO2 Fertilization
Importance of CO2 and
Fertilizers
Job Fugice, Upendra Singh and Deborah Hellums
Nutrient Dynamics Program
International Fertilizer Development Center (IFDC)
Muscle Shoals, Alabama
Carbon Footprint of
Fertilizers
Improved Efficiency
CO2-Enrichment Effect
on Crops and Soils
Quantifying CO2
Emission from Urea
Concluding Remarks
Agricultural Greenhouse Gas (GHG)
Emissions
Importance of Carbon





Carbon is an essential element and the main
building block for all life forms on earth.
Carbon dioxide (CO2) in the atmosphere at 398
ppm (~0.04%) is source for photosynthesis.
Enrichment of CO2 concentration increases
photosynthesis in most plants.
Aquatic plants enjoy higher CO2 concentration
(0.15%) for photosynthesis.
CO2 is also responsible for 82% of GHGs.



Overall agricultural GHG emissions will continue
to rise for the foreseeable future as agricultural
production expands to keep pace with growing
food, feed, fiber and bioenergy demand.
Increasing agricultural efficiency is critical to keep
emissions as low as possible and to reduce the
level of emissions per unit of agricultural output.
Efficient and responsible production, distribution
and use of fertilizers are central to achieving
these goals.
Manufacturer
Carbon Footprint of Fertilizers
Greatest Impact on Nutrient and
Emission Efficiency
Warehouse







Fertilizers account for 1/3 of N2O emissions from
agricultural soils.
Expect to increase further with increasing fertilizer use.
Combined fertilizer use, manufacture, distribution ~ 2.5% of
global GHG emissions or 10% of agricultural GHG
emissions.
Fertilizer Use = 1.5% of global GHG emissions.
Urea hydrolysis alone = 0.2% of Global GHG Emission.
Low Soil Fertility: reduces yield and increases GHG
emission.
48% people are currently fed as a result of
manufactured N fertilizer use (Erisman et al., 2008).
Ocean Transport
A Healthy Crop
Port Discharge
Trucks to Warehouse
Farmer Application
Inland Transportation
Training of Farmers
Agro-Dealer Shop
1
Total Emission: Urea and Ammonium
Nitrate Production and Consumption
Carbon Footprint for Urea and
Ammonium Nitrate Production
Total CO2-Equivalent Emission-BAT1 and BMP2
Total CO2-Equivalent Emission (Average Today)
UREA
CO2 Emission Urea Production
Total CO2-eq Emission NH3
Production
Total Urea Production Emission
kg CO2-eq /kg Urea
0.32
AMMONIUM NITRATE (AN)
kg CO2-eq /kg AN
kg CO2-eq /kg N
0.69
1.38
2.95
1.70
CO2 (N2O) Emission Nitric Acid
Total CO2-eq Emission NH3
Production
Solidification
Total AN Production Emission
CO2-eq Emission Production
N2O Emission Nitric Acid
Production
Total Production Emission
CO2 Emission Application
N2O Emission Application
Total Application Emission2
Total Emission
3.64
kg CO2-eq /kg N
1.84
5.27
0.85
2.44
0.03
2.73
0.10
7.81
AMMONIUM
NITRATE
UREA
kg CO2-eq /kg N
1.30
0.00
kg CO2-eq /kg N
2.40
1.40
1.30 (3.64)
2.30
6.70
9.00
10.30
3.80 (7.81)
0.80
4.80
5.60
8.80
1. BAT is best available technology (cleansing, etc).
2. BMP for all management with surface broadcast N application under upland
conditions.
Adapted from IFA (2009), Bellarby et al (2008), and Yara (2012).
Improve N Efficiency and Reduce
Emission
Improve Efficiency – Practice
NH3
N2O
NO

Ammonia
UREASE
INHIBITOR
WORKS HERE
Urea

NH3

Ammonium

NITRIFICATION
INHIBITOR
WORKS HERE
CONTROLRELEASE
WORKS HERE
N2
NO3-
NH4+
DEEP
PLACEMENT
WORKS HERE

Nitrate

Leaching

Knifed into the soil
Dribbled (banded) on the soil surface
Banded at planting
Side-dressed or top-dressed during the growing
season
Fertigation
Foliar spray
Deep placement (urea, NPK briquettes)
Runoff
Urea Hydrolysis and CO2 Emission
2NH3 + CO2 + H2O
Globally about 140 million tons of urea is
consumed in agriculture annually resulting in
>100 million tons (Tg) of CO2 emission as a
byproduct of urea hydrolysis
Reducing CO2 Emission and Increasing CO2
Trapping

Application: incorporation, sub-surface (band), deeppoint placement

Reduce urea hydrolysis rate with urease inhibitors

Reduce rate of urea release (control-release)

Hypothesis: Slowed/controlled release of CO2
from urea and/or trapped in soil will have greater
impact on crop growth and GHG mitigation
9000
Evidence
CO2-Enrichment: Growth Chamber
8000
-1
(NH4)2CO3
Rice Grain Yield (kg ha )
urease, 2H2O
CO2 Enrichment Effect on Yield
7000

6000

5000
4000
3000
Growth chambers
Free-air CO2
enrichment (FACE)
experiments with >
18 sites worldwide.
Exp 1
Exp 2
2000
200
400
600
CO2 Concentration (ppm)
800
1000
Baker et al.
2
Split
Application
Deep Placement:
Long-Term Effect of Urea Deep
Placement on Soil Health
Increased N Uptake,
Reduced N Loss, Higher
Productivity.
In Grain
23%
Unaccounted
35%
In Straw
9%
CO2 fertilization?
Y = 640+1.04 x; R2 = 0.92;
N = 3124
-1
In Soil
33%
Rice Grain Yield with UDP (kg ha )
12000
Unaccounted
4%
Deep Placed
Urea Briquette
In Soil
31%
In Grain
42%
10000
6000
4000
Boro
Aman
1:1 Line
2000
2000
4000
6000
8000
10000
12000
Rice Grain Yield with Prilled Urea (kg ha-1)
IRRI-IFDC, 1993
IFDC, 2012
In Straw
23%
Urea Deep
Placement
Urea
Broadcast
Incorporation
8000
Long-Term Effect – C Sequestration
CO2 Emission: Urea Hydrolysis Rate
Organic Matter Content (%)
Changes in Urea-N Content on Greenville Soil
12
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5

UDP
Soil Depth (cm)
-20
1% increase in OM
for 10 cm soil
depth
= 10 t ha-1 OM
-30
-40
Urea-N Content (mg N/cup)
10
Urea
-10
8

Slope = -0.75
6

Slope = -1.56
4
2
Urea
Agrotain

Modified by urease
inhibitor
Soil Types
Duration also
influenced by urearelease
Importance of duration
0
-50
0
2
4
6
8
Time (Days)
-60
-70
Comparison of Organic Matter Content with UDP and Urea
Soil
Product
Greenville
Urea
Agrotain
Urea
Agrotain
Brownfield
Quantifying CO2 Emission from Urea
Hydrolysis
Sample
Agrotain
SuperU
Phosphoric
Acid Scrubber

NaOH Traps
0.056
0.027
0.084
0.050
14.3
7.8
24.9
14.3
Days of
Hydrolysis
7.00
12.87
4.01
6.98
CO2 Emission from Urea Application
Product
Urea
NaOH
Scrubbers
Urea Hydrolysis Rate
(mmol/day)
(% applied/day)
Amount
Applied
(g)
77.83
77.66
77.17
77.5
78.33
78.17
CO2
Incubation Release
(Hrs)
(mmol)
37
19.461
61
25.595
39
12.226
67
19.103
41
13.762
69
23.382
CO2 Release
CO2 (% Rate
Applied) (mmol/hr)
25.0
33.0
0.445
15.8
24.7
0.287
17.6
29.9
0.339
Modified by: urease inhibitor (above)
- soil types and urea-release rate (not presented)
BaCl2 is added to 10 mL aliquot from NaOH trap and titrated with HCl
3
Concluding Remarks
1. Fertilizer use will continue to increase to meet the
increasing demand for food, feed, fiber, and fuel.
2. Urea is most widely used N fertilizer and most
economical N source
3. It’s carbon footprint during manufacturing is much
lower than Ammonium Nitrate.
4. Improved urea management – enhanced efficiency
fertilizers and 4R – would not only increase
productivity and N use efficiency but improve CO2
capture including enrichment effect on crops.
5. On-going studies: quantify CO2 fertilization effect
on crop growth using C-labelled urea under
different management.
Acknowledgement
Julie Howe, Auburn University
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