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Fertilizer, biomass and CO2 emissions
Frank Brentrup and Tore K. Jenssen, Yara International
2008-03-08, IFA Technical Conference, Sao Paulo/Brazil
Contents of the presentation

The essential role of mineral fertilizer in sustainable agriculture

Climate change – the contribution of agriculture in general and of mineral
fertilizer in particular

High intensity in crop production – problem or solution?

Options to improve the carbon footprint of fertilizers in crop production

Conclusion
Date: 2003-11-18 - Page: 2
The essential role of mineral fertilizer
in sustainable agriculture
Plant nutrients are essential for crop growth


Plant growth depends on the availability of plant nutrients, in addition to
water and climate.
Each plant nutrient has its specific physiological function and it cannot be
replaced by any other nutrient.
Date: 2003-11-18 - Page: 4
Mineral fertilizers bridge the gap between soil
nutrient supply and crop nutrient demand
Supply of crop residues &
organic fertilizer
NPK
Mineralisation
P
S
• some loss of
nutrients to the
environment
Mg
…
Crop residues are decomposed to minerals
Date: 2003-11-18 - Page: 5
• growing demand for
food, feed, fuel
K
N
Org.
substance,
humus
• export of nutrients
with the harvest
Soil
Global trends in population growth, grain yield
and origin of plant nutrients
Date: 2003-11-18 - Page: 9
An increasing world population has to be fed
from a decreasing arable area
Arable area
(in m2 per person)
World population
(in Bio)
3000
8.5
8
2800
7.5
2600
7
2400
6.5
2200
World population increases
up to 8.27 Bio people in 2030.
In the same time the arable
area can only be extended by
about 7%.
Thus, the arable area per
person decreases rapidly.
6
2000
5.5
1998
2015
2030
Source: FAO (2003): World Agriculture: towards 2015/2030. An FAO
Perspective. Ed. Jelle Bruinsma, Earthscan Publications Ltd, London.
Date: 2003-11-18 - Page: 10
Environmental effects of N fertilizer use
Benefits

Biomass production

Impacts

Food, Feed, Energy
Eutrophication



Land preservation

Off-site acidification


Carbon fixation

Ammonia volatilisaton
Global warming


Date: 2003-11-18 - Page: 11
Nitrate leaching
Ammonia volatilisation
CO2 emissions
N2O emissions
Climate change – the contribution of
agriculture in general and fertilizers
in particular
Contribution of different sectors to the global
greenhouse gas emissions in 2004
The International Panel on Climate Change (IPCC) is an independent global
network of scientists that provides the most accepted data on global warming.
Buildings & waste treatment
11%
Transport
Industry
19%
13%
14% Agriculture
Energy supply
26%
Source: 4th IPCC Assessment Report (2007)
Date: 2003-11-18 - Page: 13
17% Forestry
The global greenhouse gas emission budget in 2004
Buildings
& waste
Industry
Agriculture (13.5%):
Agricultural GHGs excluding
N2O from soils (mainly CH4)
(8.8%)
Transport
Soil N2O from organic N sources
(3.4%)
Energy supply
Forestry
Soil N2O from mineral N fertilizer
(1.2%) *
Based on IPCC (2007), Bellarby et al. (2008), *own calculation
Date: 2003-11-18 - Page: 14
The global greenhouse gas emission budget in 2004
Production of mineral N fertilizer (0.8%)
Buildings
& waste
Industry
Agriculture (13.5%):
Agricultural GHGs excluding
N2O from soils (mainly CH4)
(8.8%)
Transport
Soil N2O from organic N sources
(3.4%)
Energy supply
Forestry
Soil N2O from mineral N fertilizer
(1.2%) *
Based on IPCC (2007), Bellarby et al. (2008), *own calculation
Date: 2003-11-18 - Page: 15
The global greenhouse gas emission budget in 2004
Production of mineral N fertilizer (0.8%)
Buildings
& waste
Industry
Agriculture (13.5%):
Agricultural GHGs excluding
N2O from soils (mainly CH4)
(8.8%)
Transport
Soil N2O from organic N sources
(3.4%)
Energy supply
Forestry
Soil N2O from mineral N fertilizer
(1.2%) *
Land use change for agriculture (12%)
Total GHG emission related to agriculture: 26% (17-32%)
Date: 2003-11-18 - Page: 16
Based on IPCC (2007), Bellarby et al. (2008), *own calculation
High intensity in crop production
- Problem or solution ?
Yield response to nitrogen application in a
long-term field trial with winter wheat
Grain yield
(t/ha)
10
8
100% intensity
6
50% intensity
4
economic opt .N rate
2
0% intensity
0
0
50
100
150
200
N application rate (kg N/ha)
Long
term -trial:
Date: 2003-11-18
Page: 18Rothamsted, UK
250
300
100% intensity
Date: 2003-11-18 - Page: 19
0% intensity
A life-cycle perspective on fertilizer use
N2
CO2, N2O, …
Production
Natural gas (feedstock)
Fuel
Minerals
Date: 2003-11-18 - Page: 20
CO2, NOx, …
NH3, NO3, N2O, N2 …
Logistic
Application
Fuel
Fuel
Biomass
Uptake
Sunlight
CO2
Land
The carbon footprint of wheat production
increases with the N application rate
Global warming: kg CO2 eq. / ha
3000
2500
2000
1500
1000
500
0
without N
Date: 2003-11-18 - Page: 21
50% of optimum economic optimum
N rate
On the other hand the positive GHG balance
“ex-field” is enhanced by fertilizer use
Global warming: kg CO2 eq. / ha
35000
30000
25000
GHG fixed in biomass
(grain + straw)
20000
15000
10000
5000
GHG emissions
0
without N
Date: 2003-11-18 - Page: 22
50% of optimum
economic
optimum N rate
If the harvested crop is used as food or feed,
the CO2 fixation is only short-term
Global warming: kg CO2 eq. / ha
35000
30000
25000
GHG fixed in biomass
(grain + straw)
20000
15000
10000
5000
GHG emissions
0
without N
50% of optimum
economic
optimum N rate
The CO2 fixation can be regarded as a real CO2 saving, only if the harvested
biomass is used as bio-fuel and, thus, replaces fossil fuels.
Date: 2003-11-18 - Page: 23
To achieve the same yield, reduced production intensity
needs more land and increases GHG emissions
Global warming: kg CO2 eq. / ha
12000
10000
CO2 release due to additional land use
needed to compensate for lower yields
8000
6000
4000
2000
0
without N
Date: 2003-11-18 - Page: 24
50% of optimum
economic
optimum N rate
To achieve the same yield, reduced production intensity
needs more land and increases GHG emissions
Global warming: kg CO2 eq. / ha
How to improve the
carbon footprint ?
3000
2500
2000
1500
1000
500
0
50% of optimum
Date: 2003-11-18 - Page: 25
economic optimum N rate
Options to improve the carbon footprint
of fertilizers in crop production
Contribution of production and transport of farm inputs, and
in-field emissions to the total carbon footprint per ha
Based on a long-term field trial with winter wheat (UK), N source = Ammoniumnitrate
kg CO 2-equivalents / ha
3000
2500
2000
field
trans
prod
1500
1000
500
0
economic optimum N rate
Date: 2003-11-18 - Page: 27
Contribution of the single GHG emissions to the
total carbon footprint per ha
Based on a long-term field trial with winter wheat (UK), N source = Ammoniumnitrate
kg CO 2-equivalents / ha
3000
Hot-spots
2500
2000
N2O
1500
N2O
1000
500
0
economic optimum N rate
Date: 2003-11-18 - Page: 28
N2O_field
CO2_field
CO2_trans
N2O_prod
CO2_prod
Improvements in nitric acid production
Nitric acid plant
Nitrous oxide (N2O)
abatement catalyst
The technology is based on a unique high temperature catalyst
process and pellets of cobalt and cerium oxide. The pellets have
an expected minimum lifetime of three years and no adverse
effect on the production process. The nitrous oxides are broken
down to nitrogen and oxygen and contain no harmful substances.
Date: 2003-11-18 - Page: 29
The carbon footprint of ammoniumnitrate (AN)
and urea at plant gate
8
t CO2-equivalents / t N
7
6
Säule 3
N2O
CO2
4.1
5
4.6
4
with de-N2O
catalyst
3
2
0.7 - 1.3
3.4
2.2
1.7
AN
AN
AN
30 years
old tech.
Avg Europe
2003
1
2.5
0
Urea
Modern technology
CO2 fixation in urea production is not considered as a credit, because the same amount of CO2 that is fixed,
will be released after application in the field (urea hydrolysis)
Source: Jenssen & Kongshaug (2003), Yara data (2007)
Date: 2003-11-18 - Page: 30
Impact of the de-N2O catalyst on the carbon
footprint of crop production
Based on a long-term field trial with winter wheat (UK), N source = Ammoniumnitrate
Carbon footprint (kg CO2-eq. / ha)
3000
2500
2000
1500
1000
without
de-N2O catalyst
with
de-N2O catalyst
N2O_field
CO2_field
CO2_trans
N2O_prod
CO2_prod
500
0
Wheat produced at economic optimum N rate
Date: 2003-11-18 - Page: 31
N2O emissions from nitrogen in the soil

Nitrous oxide is released during nitrification of ammonium (NH4+) to nitrate
(NO3-) and during the denitrification of nitrate to nitrogen gas (N2).
Reduction controlled by
NO3 and C availability and
O2 deficiency
Oxidation controlled by
NH4 and O2 availability
N2O
N2O
NH4+
NO2-
NO3-
NO2-
N2
Ammonium
Nitrite
Nitrate
Nitrite
Gas
Nitrification
Date: 2003-11-18 - Page: 32
Denitrification
Average N2O emissions are lower from Nitrates
than from urea and ammonium fertilizers

Up to now, N2O emissions from N fertilizers are estimated independently from the
N form (default IPCC factor, red bar in the graph below).

But a new analysis of about 900 in-field measurements from 139 experiments
shows differences in N2O emissions from different N fertilizers.
N2O-N emission (% of applied N)
1.2
1
0.8
0.6
0.4
0.2
0
default
IPCC
factor
Date: 2003-11-18 - Page: 33
Urea
UAN
AS
Source: Bouwman et al. (2002)
AN
CAN
Impact of soil and climate on the carbon
footprint of crop production
6000
kg CO 2-equivalents / ha
4.67% of total N input as N2O_field *
5000
4000
N2O_field
CO2_field
CO2_trans
N2O_prod
CO2_prod
2.05%
3000
1.28%
0.84%
2000
1000
Other important factors:
- Soil organic carbon
- Soil pH
0
Drainage:
Texture:
Climate:
Date: 2003-11-18 - Page: 34
good
loam
temp
poor
loam
temp
poor
clay
temp
poor
clay
trop
* Calculated according to Bouwman model (Bouwman et al., 2002), uncertainty range –40% to +70%
Options to reduce in-field N2O emission

Any means that improve nitrogen use efficiency, in particular

Adjust N application rate to actual crop N demand ( soil and plant analysis)

Synchronize N application with crop N uptake ( split application, “just-in-time”
fertilization)

Apply nitrate-based N sources on well aerated and non-waterlogged soils

Maintain a good soil structure (no compaction, good drainage)
Date: 2003-11-18 - Page: 35
Carbon footprint of different crop production
systems
kg CO2 eq. / t cereal unit
400
350
300
250
200
150
100
50
0
Low-input
(organic)*
High-input*
* Küstermann & Hülsbergen, 2007
Date: 2003-11-18 - Page: 36
Broadbalk, Nopt,
AN_avg2003
Broadbalk, Nopt,
AN_BAT2007
Conclusions

Mineral N fertilizers are essential to sustain optimum yields that are needed
to satisfy the increasing need for food, feed and bio-energy.

The agricultural contribution to climate change is substantial, with land use
change (deforestation), cattle farming (methane), and N2O emissions from
organic and mineral nitrogen inputs being the major sources.

To produce agricultural crops on the existing agricultural area at optimum
intensity supports the preservation of natural ecosystems with high carbon
sequestration potential.

Improved fertilizer production technology (energy, N2O) and best
agricultural management practices allow a significant reduction in the
carbon footprint of crop production.
Date: 2003-11-18 - Page: 37