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Carbon footprint analysis of mineral fertilizer production in Europe and other world
regions
Frank Brentrup1,*, Antoine Hoxha2, Bjarne Christensen3
1 Yara International ASA, Research Centre Hanninghof, D-48249 Duelmen, Germany
2 Fertilizers Europe, Av. E Van Nieuwenhuyse 6, B 1160 Brussels, Belgium
3 ChemTechnic Consulting, Virumgade 49 A, DK-2830 Virum, Denmark
* Corresponding author: Email: frank.brentrup@yara.com
ABSTRACT
The production and use of mineral fertilizers contributes significantly to the carbon footprint of agricultural crops and crop-
based food products. In arable crops such as winter wheat the share of nitrogen (N) fertilizer-related GHG emissions can be
as high as 80%. The contribution of emissions from the production of mineral fertilizers is often as important as fertilizer-
induced emissions from agricultural soils.
It is therefore important to use appropriate and up-to-date emission data for fertilizer production, which represent the actual
technology and efficiency of manufacturing of specific fertilizer grades. Objective of this study is to provide up-to-date
carbon footprint data for the main fertilizer products produced in selected world regions.
The association of the European fertilizer producers “Fertilizers Europe” has developed a carbon footprint calculator (CFC)
for fertilizer production. This tool has been employed to derive reference values for the main mineral fertilizers produced in
Europe and other relevant fertilizer-producing regions of the world. The European data are reported by all members in a
regular survey to Fertilizers Europe and are representative for the year 2011. Reported data include energy consumption in
ammonia synthesis (Haber-Bosch) and N2O emissions from nitric acid production, as well as expert-validated data for other
sources of CO2 (e.g. energy consumption for urea synthesis and granulation). The non-European figures are based on an
expert evaluation by Integer Research Ltd. of ammonia and nitric acid production in 2011, while for all other emission
sources the European values were used.
The Fertilizers Europe CFC follows general LCA and carbon footprint rules. It covers all main sources of GHG emissions
and has been reviewed by DNV GL to verify its completeness and correct calculations.
This paper explains the methodology applied in the calculation of the carbon footprint values. In addition the results will be
presented per fertilizer product and production region. We suggest that these data should be used in carbon footprint studies
as reference values for fertilizer production in different world regions with the technology baseline 2011.
Keywords: fertilizer production, product carbon footprint, GHG emissions
1. Introduction
Agriculture is responsible for 10 to 12% of the total global greenhouse gas (GHG) emissions
(Smith et al., 2007) and the overall level of GHG emissions from agriculture is expected to grow
further as agricultural production needs to expand in order to keep pace with increasing demand for
food, feed, fiber and bioenergy. The production and use of mineral fertilizers is required to provide
sufficient plant nutrients for sustainable food production. At the same time it also contributes
significantly to the carbon footprint of agricultural crops and crop-based food products. The share of
the global GHG emissions directly related to the production, distribution and use of fertilizers is
estimated at between 2 and 3% (IFA, 2009). In arable crop production such as winter wheat the share
of nitrogen (N) fertilizer-related GHG emissions can be as high as 80% (Brentrup et al., 2004;
Skowroñska & Filipek, 2014). The contribution of emissions released during the production of
mineral fertilizers is in most studies as important as the fertilizer-induced emissions from agricultural
soils.
Information about production of mineral fertilizers used in major global life-cycle assessment
(LCA) databases (e.g. Ecoinvent) is mostly outdated and relates to studies from 1990s (Patyk &
Reinhardt, 1997; Kongshaug, 1998; Davis & Haglund, 2000). Since then production technologies
have improved substantially mainly in terms of nitrous oxide (N2O) emission control during nitric
acid production, which is an intermediate product of nitrate-containing nitrogen fertilizers (EFMA,
2000a; Brentrup & Palliere, 2008). But also energy efficiency in particular in ammonia synthesis has
improved over time (EFMA, 2000b; Jenssen & Kongshaug, 2003; Brentrup & Palliere, 2008).
It is therefore important to use appropriate and up-to-date emission factors for fertilizer production.
The objective of this study is to provide up-to-date carbon footprint data for the main fertilizer
products produced in important fertilizer-producing regions.
2. Methods
The association of the European fertilizer producers “Fertilizers Europe” has developed a carbon
footprint calculator (CFC) for fertilizer production. The CFC is available for free use to anyone on
simple request to Fertilizers Europe (www.fertilizerseurope.com). This tool has been employed to
derive reference values for the main mineral fertilizers produced in Europe and other relevant
fertilizer-producing regions of the world. The European data are based on primary data reported by all
members in a regular survey to Fertilizers Europe. The data are representative for the year 2011.
Reported data include energy consumption in ammonia synthesis (Haber-Bosch) and N2O emissions
from nitric acid production, as well as expert-validated data for other sources of CO2 (e.g. energy
consumption for urea synthesis and granulation of final products). The non-European figures are
based on an expert evaluation by Integer Research Ltd. (2014) of ammonia and nitric acid production
in 2011, while for all other emission sources the European default values were used. The reference
data for Europe and other world regions will be regularly updated and published.
The CFC is a cradle-to-factory-gate calculator based on the principles developed by Kongshaug
(1998). This means that the emission factors of the final products (expressed as kg CO2-equivalent/kg
fertilizer product) are calculated stepwise in building blocks that represent the actual steps in the
production process. The building blocks include importation of raw materials, production of
intermediates and the finishing process combining the materials into a final product (Fig. 1). All
building blocks are characterized by emission factors and energy consumption values. The CFC takes
into account all emissions with global warming potential (GWP), i.e. N2O, CO2 and CH4. Using the
GWP conversion factors (IPCC, 2007) N2O and CH4 emissions are converted to CO2-equivalents
(CO2e). The CFC contains built-in default values for important fertilizer-producing world regions
(EU, Russia, China and US) for the reference year 2011, but the user can also insert own individual
values in order to calculate the carbon footprint of specific own-produced fertilizer products
(Christensen et al., 2014).
Figure 1: The building blocks used in the CFC for fertilizer production. Intermediates contributing to
the majority of emissions are marked yellow (Christensen et al., 2014).
The Fertilizers Europe CFC follows the lines of the general LCA and carbon footprinting rules
(ISO 14040/14067), but is not completely compliant with established standards such as PAS 2050 or
Carbon Trust. The calculation covers all main sources of GHG emissions and has been externally
reviewed by DNV GL to verify its completeness and correct calculations. Tables 1 and 2 summarize
selected key background information used to calculate the default reference carbon footprint values
for the different world regions.
Table 1: Background information on energy, raw materials and transportation used to calculate the
reference carbon footprint values
Energy data
kg CO2e/GJ
Energy source
Region
Supply a
Use b
Natural gas
Europe
10.6
56.1
Natural gas
Russia
13.1
56.1
Natural gas
USA
20.8
56.1
Natural gas
China
12.9
56.1
Liquid petroleum gas (LPG)
Europe
16.3
63.1
Heavy fuel oil
Europe
10.6
77.4
High viscosity residue
Europe
0.0
80.7
Coal (bituminous)
Europe
10.7
94.6
Coal (bituminous)
China
10.5
94.6
Electricity
Europe
34.1
97.8
Electricity
Russia
45.8
121.4
Electricity
USA
47.0
139.7
Electricity
China
54.5
212.2
Electricity (coal-based)
Europe
26.8
238.9
Steam from natural gas (93% efficiency)
Europe
11.4
60.3
Steam from natural gas (93% efficiency)
Russia
14.1
60.3
Steam from natural gas (93% efficiency)
USA
22.3
60.3
Steam from natural gas (93% efficiency)
China
13.9
60.3
Steam from LPG (93% efficiency)
Europe
17.5
67.8
Steam from oil (93% efficiency)
Europe
11.4
83.2
Steam from coal (90% efficiency)
Europe
11.9
105.1
Raw material data c
kg CO2e/t
Type of raw material
Supply
Phosphate rock (sedimentary, 4% CO2)
47.7
Phosphate rock (sedimentary, 6% CO2)
67.7
Phosphate rock (igneous, 2% CO2)
89.7
Phosphate rock (igneous, 4% CO2)
109.7
Potassium chloride (Muriate of potash/MOP)
232.2
Potassium sulphate (Sulphate of potash/SOP)
108.4
Dolomite (ground)
61.9
Limestone (ground)
61.9
Transport data d
kg CO2e/t*km
Means of transport
Deep sea vessel
5
Coastal shipping
16
Barge
31
Rail
22
Truck
62
a Data from GaBi database (PE International, 2013)
b Data for fossil fuels and steam from IPCC (2006), for electricity from IEA (2012)
c Data for raw materials based on Jenssen & Kongshaug (2003), validated by Fertilizers Europe
Technical Committee (personal communication, 2014)
d Data for transport from McKinnon & Piecyk (2011)
Table 2: Reference values for the energy input required for ammonia and nitric acid production and
direct emissions of nitrous oxide (N2O).
Product
Region
Energy input
Direct
emissions
Feedstock & fuel
Electricity a
Steam a
N2O
Type
GJ/t product
GJ/t product
GJ/t product
kg/t product
Ammonia
Europe
Natural gas
34.7
0.79
-1.37
0
Ammonia
Russia
Natural gas
40.5
0
0
0
Ammonia
USA
Natural gas
35.7
0
0
0
Ammonia
China
Natural gas
42.2
0
0
0
Ammonia
China
Coal
54.0
0
0
0
Nitric acid
Europe
-
0
0.3
-1.75
0.87
Nitric acid
Russia
-
0
0.3
-1.75
7.40
Nitric acid
USA
-
0
0.3
-1.75
6.00
Nitric acid
China
-
0
0.3
-1.75
5.70
a Assumptions by Integer Research Ltd (2014):
For non-European ammonia no steam generation and zero electricity consumption were assumed.
For non-European nitric acid the steam and electricity data from Europe were assumed.
3. Results & discussion
Table 3 shows the carbon footprint (CFP) values for the main mineral fertilizer products. The new
European reference values are also included in the on-farm GHG calculation tool “Cool Farm Tool”
and the regional values will be added soon (www.coolfarmtool.org).
Table 3: Reference carbon footprint (CFP) values for main mineral fertilizer products from different
regions (reference year 2011)
Fertilizer product
Nutrient content
CFP at plant gate (kg CO2e/kg product)
Europe
Russia c
USA c
China c
Ammonium nitrate
AN
33.5% N
1.18
2.85
2.52
3.47
Calcium ammonium nitrate
CAN
27% N
1.00
2.35
2.08
2.86
Ammonium nitrosulphate
ANS
26% N, 14% S
0.82
1.58
1.44
2.22
Calcium nitrate a
CN
15.5% N
0.67
2.03
1.76
2.20
Ammonium sulphate
AS
21% N, 24% S
0.57
0.71
0.69
1.36
Di-ammonium phosphate
DAP
18% N, 46% P2O5
0.64
0.81
0.73
1.33
Urea b
Urea
46% N
0.89
1.18
1.18
2.51
Urea ammonium nitrate b
UAN
30% N
0.81
1.65
1.50
2.37
NPK 15-15-15
NPK
15% N, 15% P2O5,
15% K2O
0.73
1.40
1.27
1.73
Triple superphosphate
TSP
48% P2O5
0.18
0.25
0.19
0.26
Muriate of potash
MOP
60% K2O
0.23
0.23
0.23
0.23
a CN is assumed to be produced as co-product from NPK production via nitro-phosphate route
(EFMA, 2000c)
b Urea and UAN contain CO2, which will be released shortly upon application to soil (0.73 kg
CO2/kg urea and 0.25 kg CO2/kg UAN). This amount is not included in the plant gate CFP.
c For Russia, USA and China specific values were used for energy supply, energy consumption for
ammonia production and N2O emissions from nitric acid production. All other values are equal to
Europe. Specific assumption for China: 80% of ammonia production is based on hard coal;
remainder on natural gas (IFA, 2009).
Figure 2 documents the improvements in fertilizer production which are particularly obvious when
comparing the CFP of nitrate-containing products produced in Europe as shown for the example of
calcium ammonium nitrate (CAN), which contains 50% nitrogen as nitrate. Values such as that from
Ecoinvent (2002) represent European production technology of the 1990ties or earlier (Patyk &
Reinhardt, 1997; Kongshaug, 1998). At that time nitric acid, which is the precursor of nitrate-N in
mineral fertilizer, was produced without any abatement technology for N2O emissions occurring at
significant rates during the nitric acid production process (see also Table 2). The first Fertilizers
Europe reference value for CAN represents production technology in 2006 (Brentrup & Palliere,
2008) and shows already some improvement due to partly installation of N2O abatement catalysts in
European nitric acid plants. Today, practically all European nitric acid plants are equipped with this
technology, which led to an average reduction of N2O emissions by 80-90% as compared to the pre-
abatement time.
Figure 2: Development of carbon footprint values for Calcium ammonium nitrate (CAN) production
in Europe from the 1990s until 2011
In order to compare the production carbon footprint of different fertilizer products the values need
to be related to the same functional unit, which is in the case of nitrogen fertilizers one kg of N.
Figure 3 compares three different products (AN, Urea, UAN) that contain only N as a plant nutrient
and are therefore directly comparable without any allocation that would be required for multi-nutrient
products. The graph shows that European production of all three products results in the lowest CFP
among the production regions compared. The European values for AN, Urea and UAN are very close
to each other at around 3.5 kg CO2e/kg N. The CO2 released during the hydrolysis of urea after
application to soil is included in this comparison because it is in principle only a delayed emission of
CO2 that has been previously used in the factory to produce urea from ammonia. The same amount of
CO2 needed to synthesize urea will be emitted after application in the field. This is also valid for the
urea part in UAN (50% urea, 50% ammonium nitrate).
The differences between the production regions are more obvious for nitrate-containing products
than for urea. However, the differences are not only related to the existence and efficiency of N2O
abatement in nitric acid, but also strongly influenced by the source of fossil fuels used for the
production of ammonia. China’s ammonia production is still dominantly based on coal (IFA, 2009;
Zhang, 2013) and this is the reason for the high CFP values for all three N fertilizers. N2O emissions
from nitric acid production in China is even lower than in the US and Russia (Table 2), but this does
not compensate for the higher CO2 emissions from coal-based ammonia production. The reason for
lower N2O emissions in China is the Clean Development Mechanism (CDM) under the Kyoto
Protocol of the United Nations (IPCC, 2007), which supports certain emission reduction projects in
particular in countries not included in the Annex I of the Kyoto Protocol (e.g. transition and
developing countries). Russia and USA show low CFP of urea indicating high energy efficiency, but
higher values for AN and UAN due to missing or very limited installation of N2O abatement in nitric
acid production.
Figure 3: Carbon footprint of ammonium nitrate (AN), urea, and urea ammonium nitrate solution
(UAN) expressed per kg of N and produced in different regions.
Fertilizer production is an important contributor of GHG emissions to the carbon footprint of
agricultural products. When evaluating the CFP of fertilizers it is even more important to consider the
complete life-cycle emissions in order to account for all additional sources of GHG emissions beyond
the production step. This is mainly relevant for nitrogen fertilizers because their use in agriculture can
lead to N2O emissions via different pathways. In addition, the use of most N fertilizers acidifies the
soil, which is usually compensated by application of lime releasing CO2 after conversion in soil.
Figure 4 summarizes the GHG emissions from production and application of different N fertilizers.
The emissions from the use of the fertilizers were estimated using current default values for the
different pathways:
(1) IPCC Tier1 emission factor for direct N2O emissions,
(2) EMEP/EEA Tier 2 emission factors for NH3 emissions (EEA, 2013) plus IPCC (2006) for
indirect N2O via NH3,
(3) IPCC (2006) for indirect N2O via NO3,
(4) KTBL (2005) figures for lime demand together with IPCC (2006) for CO2 from lime.
The resulting values are only rough estimates since for instance potential differences between the
N products in their agronomic efficiency are not taken into account. This means that for example high
losses as ammonia could lead to an additional need for N application in order to substitute for the lost
nitrogen, which would then increase the CFP of this product. There is also evidence that different N
forms behave differently in terms of direct N2O emissions from soil. Applied to well drained soils
without anaerobic conditions, the emission rates are often clearly lower than the default IPCC factor
of 1% N2O-N per unit N applied and the emissions usually decline with an increasing share of nitrate
in the product. Poorly drained soils and high precipitation can lead to anaerobic conditions. This
together with high organic soil carbon availability triggers N2O emissions by denitrification. Under
those conditions urea and ammonium based N fertilizers often show lower emissions than nitrate-
containing products. However, using standard default emission factors for all pathways the overall
CFP of urea is 8% higher than that of AN (see Fig. 4).
Figure 4: Carbon footprint of N fertilizer production and use based on default emission factors (for
references see text).
4. Conclusions
The paper explains the methodology applied in the calculation of the carbon footprint values. The
results show carbon footprint values per fertilizer product and production region (Europe, Russia,
USA, and China). We suggest that these data should be used in carbon footprint studies as reference
values for fertilizer production with the technology baseline 2011. The data clearly show the
improvements made in Europe in particular in terms of N2O emission reduction in nitric acid
production, which is an intermediate in the production of all nitrate-containing N fertilizer products.
The differences between the production regions are mainly due to two aspects, (1) absence or
presence of N2O emission control and (2) energy source (coal or gas) and efficiency in ammonia
production.
For a valid conclusion about the carbon footprint of fertilizers it is necessary to include the use of
the fertilizers into the analysis in order to have a complete picture along their life-cycle. Emissions
from N fertilizer use on field can be even higher than of their production, in particular when improved
production technology as in Europe is employed. Emissions from N fertilizer use are highly variable
depending on soil and climate conditions and need to be assessed with care. The use of standard
default emission factors suggests slightly higher life-cycle GHG emissions from urea as compared to
ammonium nitrate.
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