1. Introduction
2. Calculation of a Carbon Footprint
3. Detailed methodology
4. Product results and comparison of regional references

Introduction

Fertilizers Europe has commissioned a tool for estimating the carbon footprint related to the production of selected fertiliser products.

The calculator estimates the emission factor (tonnes CO₂ equivalent [CO₂eq] per tonne product) related to the production of fertilisers. All emissions with GWP (Global Warming Potential) are included. The calculator includes direct and indirect emissions from all materials related to the production of the particular final product delivered in the final product storage at the production site.

The Calculator also includes the estimated emissions related to exploitation and transport of energy from the source to the user.

The online Carbon Footprint Calculator (web-CFC) is freely available through the Fertilizers Europe web-site .

The Calculator provides options for selecting and inserting the basic assumptions related to raw materials, transportation, energy and production specific data.

The tool has been developed to

• calculate and provide reference values for carbon emissions for selected fertilisers based on EU average (ammonia and nitric acid), EU BAT (ammonia and nitric acid) as well as other defined references.
• calculate emission factors required in a LCA (Life Cycle Assessment) calculator for agriculture, such as the CoolFarmTool or other similar tools for calculating the LCA for food products and from agriculture.
• provide regional data (North America, Latin America, Africa, Middle East, CIS, South East Asia, South Asia, Oceania, China) for ammonia and nitric acid for inclusion in the Calculator for reference calculation of emission factors. The goal is to obtain carbon emission averages for the selected fertilisers in the above regions, to be used as reference points for global comparisons. The regional averages can also be used as an input for LCA calculators (such as Cool Farm Tool).

The tool is also intended to be used by fertiliser manufacturers to calculate their own emission factors for internal company reference purposes. Provided that the data are verified by an external auditor (The Carbon Trust has been appointed by Fertilizers Europe as such auditor) fertiliser producers can use the calculator for:

• the purpose of legal reporting and/or sustainability and CSR reports.
• the purpose of communicating with local or national authorities concerning energy and environmental issues.

Calculation of a Carbon Footprint.

The Calculator is divided into four main parts:

1. Defining the fertilisers to be calculated.
2. Energy sources using either built-in average data or own specified data.
3. Components part for specifying imported materials and own produced intermediates.
4. Summary part showing the calculated CO2eq for the selected fertilisers.

A detailed pdf report containing all the details can be generated and down-loaded.

The main structure in the calculations is based on the principles described by Kongshaug, (1998), as shown in Figure 1.

Detailed methodology

The CFC is a cradle-to-factory-gate calculator based on the principles developed by Kongshaug (1998). This implies that the emission factors (kg CO₂-eq./ton fertiliser product) of the final products are calculated stepwise by defining the imported raw materials, production of intermediates and the finishing process combining these materials into the final product

The CFC takes into account that fertiliser factories are not always constructed with facilities to produce all intermediate products. In such cases one or more intermediate products will be defined as imported raw materials.

Although, the CFC contains built-in default values for regional references (EU, Russia, China and US) and EU-BAT (Best Available Technique), the user can insert its own values.

Energy

The three energy sources considered in the CFC are (i) fossil fuel, (ii) electricity and (iii) steam. The emission factor for the different energy sources depends on the carbon factor (kg CO₂/GJ) for energy use and energy supply. The latter refers to emissions associated with the exploration and production of the energy used and its transport from ‘source’ to the user.

Ammonia and nitric acid production have the most significant impact on the carbon foot print and the data for these processes has been included on a regional basis. Fertilizers Europe commissioned Integer Research to estimate the emission factors from ammonia and nitric acid plant in various global regions (North America, Latin America, Africa, Middle East, CIS (Russia Commonwealth), South East Asia, South Asia, Oceania and China).

Fossil fuel.

Fossil fuels can be used both as an energy source and also as the feedstock for making the syngas needed for the ammonia production.

Steam.

Depending on the fuel used for the steam boiler, different carbon factors can be assigned for energy use and energy supply. Next to the fuel, the efficiency by which the steam boiler runs can differ from site to site. Reference values for steam are based on the fuel references assuming 93% fuel efficiency, except for steam boilers powered with coal, for which 90% efficiency is assumed. With the selection of ‘own data’ the user can work with their own efficiency figures.

Steam export from the ammonia, nitric acid and sulphuric acid units may gain emission credits providing the steam is fully used in other production units. As it is a credit it is included as a negative value in the CFC. The credit given for steam export to other production units is the same as for steam use.

Raw materials.

Raw materials such as phosphate rock, potash, sulphur and inerts are mined, processed and transported to the plant site. Emissions are therefore defined by these practices.

Mining and processing.

Mining of raw materials is relatively energy intensive and thus causes emissions (similar to emission related to energy supply). Additionally, in the case of phosphate rock (PR) processing into fertilisers CO₂ is released during the manufacturing process. The amount of CO₂ released depends on the origin of the PR – whether sedimentary or igneous – and on the carbonate content of the rock. For sedimentary rock the mining operation is estimated to consume 0.1 GJ/ton PR while for the mining of igneous rock 0.9 GJ/ton PR is used.

Assuming that heavy fuel is used with an energy use carbon factor of 77.4 kg CO₂/GJ, this converts to 7.7 and 69.7 kg CO₂/ton PR respectively. The carbon factor for energy supply has not been considered in the calculations as local circumstances are unknown. By default the CFC uses a P₂O₅ content of 32%, back calculations are needed when inserting own values.

Potash is either imported as potassium chloride (MOP) or as potassium sulphate (SOP). The energy related to mining and processing is estimated to be 3 and 1.4 GJ/ton for MOP and SOP respectively. When assuming heavy fuel oil is used this results in 232.2 and 108.4 kg CO₂/ton for MOP and SOP respectively.

The mining and processing of inerts is also energy consuming, estimated at 0.8 GJ/ton inert, which converts to 61.9 kg CO₂/ton inert (assuming heavy fuel). CO₂ contained in limestone (CaCO₃) and dolomite can potentially be released when applied in agriculture, depending on the soil pH and other factors. In the CFC results the CO₂ included in the final product and potentially released when used in agriculture is calculated separately.

Transport.

The CO₂ emissions related to transport depend on the mean of transport and the distance over which transport is required. Although the user can use emission factors available from their suppliers, average emission factors related to transport were calculated.

Next to emissions related to transport, other emissions from raw materials should be considered in the total carbon footprint. Specific plant data for the production of intermediate products is therefore included.

Intermediate products and plant specific data.

If intermediate products such as for example ammonia, nitric acid, etc. are imported to the plant site, the same emissions factors for transport apply as described for raw materials. The emission factor of the product is however not calculated but should be estimated based on data available from the supplier.

For each intermediate product which is produced on site (and thus not imported) plant-specific information on energy consumption of the fuel, electricity and steam can be provided. For ammonia (NH₃) and nitric acid (HNO₃) a wide set of reference values are available.

For ammonia the user can define the CH₄ emissions (kg CH₄/ton NH₃) which are converted automatically to CO₂-equivalents. For nitric acid production the release of N₂O (kg N₂O/ton HNO₃) and CH₄ (kg CH4/ton HNO₃) are taken into account for the calculation of the CFC. Default abatement using deNOx or NSCR (non-specific catalytic reduction) is provided as an option.

For nitric acid plants default conversion efficiency is 95% (or 284 kg NH₃/ton HNO₃) but specific efficiency factors can also be used.

Product results and comparison of regional references.

After setting all parameters for the fertiliser production, the total carbon footprint (ton CO₂-eq./ton product) is calculated for the selected fertiliser.

For key fertiliser products such as AN, CAN, urea and UAN more details on the emissions are provided, i.e. the CO₂ emissions related to the raw materials (excluding natural gas as feedstock), CO₂ emissions related to energy supply (including natural gas as feedstock), GHG released during production and the CO₂ captured in the product and potentially released in the field is reported in the case of urea and UAN. A comparison with regional reference values for these products is also available. In Figure 2 an example of output is shown for AN.

The regional emission data and regional energy supply data have been used to calculate the carbon footprint of the following four nitrogen fertilisers: ammonium nitrate, calcium ammonium nitrate, urea and the liquid fertiliser UAN-30.

References

Kongshaug. (1998). Energy consumption and greenhouse gas emissions in fertilizer production. IFA Technical Conference, Marrakech, Morocco

Links to related IFS Proceedings

639, (2008), GHG Emissions and Energy Efficiency in European Nitrogen Fertiliser Production and Use, F Brentrup, C Pallière

751, (2014), Assessing the Carbon Footprint of Fertilisers, at Production and Full LCA, B Christensen, F Bentrup, L Six, A Hoxha, C Pallière

805, (2019), The Carbon Footprint of Fertiliser Production: Regional Reference Values, A Hoxha, B Christensen