1. Life Cycle Analysis purpose and methodology
2. Life Cycle Analysis applied to crop production and fertilisers
3. Energy Balance – First Application of the LCA Approach
4. Extension of the Analysis Towards Environmental Impacts – ‘Real’ LCA
5. LCA Indicators relevant to fertilisers
6. LCA and ‘Carbon Footprint’

Life Cycle Analysis purpose and methodology

As explained in the Introduction to ISO 14040, the increased awareness of the importance of environmental protection, and the possible impacts associated with products, both manufactured and consumed, has increased interest in the development of methods to better understand and address these impacts. One of the techniques being developed for this purpose is life cycle assessment (LCA).

LCA can assist in:

• identifying opportunities to improve the environmental performance of products at various points in their life cycle,
• informing decision-makers in industry, government or non-government organizations (e.g. for the purpose of strategic planning, priority setting, product or process design or redesign),
• the selection of relevant indicators of environmental performance, including measurement techniques, and
• marketing (e.g. implementing an ecolabelling scheme, making an environmental claim, or producing an environmental product declaration).

For practitioners of LCA, ISO 14044 details the requirements for conducting an LCA.

LCA addresses the environmental aspects and potential environmental impacts (e.g. use of resources and the environmental consequences of releases) throughout a product’s life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal (i.e. cradle-to-grave).

There are four phases in an LCA study:

1. the goal and scope definition phase,
2. the inventory analysis phase,
3. the impact assessment phase, and
4. the interpretation phase.

The scope, including the system boundary and level of detail, of an LCA depends on the subject and the intended use of the study. The depth and the breadth of LCA can differ considerably depending on the goal of a particular LCA.

The life cycle inventory analysis phase (LCI phase) is the second phase of LCA. It is an inventory of input/output data with regard to the system being studied. It involves collection of the data necessary to meet the goals of the defined study

The life cycle impact assessment phase (LCIA) is the third phase of the LCA. The purpose of LCIA is to provide additional information to help assess a product system’s LCI results so as to better understand their environmental significance.

Life cycle interpretation is the final phase of the LCA procedure, in which the results of an LCI or an LCIA, or both, are summarised and discussed as a basis for conclusions, recommendations and decision-making in accordance with the goal and scope definition.

Life Cycle Analysis applied to crop production and fertilisers

The ‘environmental footprint’ of crop production in general and of mineral fertiliser use in particular includes a wide range of different impacts, such as nitrate leaching, ammonia volatilisation and greenhouse gas emissions, or energy consumption, which itself may contribute to different environmental effects e.g. eutrophication, acidification, and global warming.  (The similar impacts from the use of organic manures are not addressed in this resource).

The life-cycle assessment (LCA) methodology is particularly suitable for the examination and analysis of the ‘environmental footprint’, since LCA is an inventory and evaluation of all environmental impacts (emissions and resource consumption) along the ‘life-cycle’ of a product from ‘cradle to grave’. For fertiliser this means the inclusion of raw material extraction, through production to application (Figure 2).

Today, LCA is a standard methodology for comprehensive environmental analyses because all single impacts are included and evaluated, the entire production system is considered and aggregated, and conclusive indicators can finally be calculated. LCA is mainly used to compare different alternatives (products or services) and to determine their environmental ‘hot-spots’.

In order to evaluate the environmental impact of crop production properly, it is necessary to have appropriate indicators in place. If there are choices between alternatives in crop production such as different farming concepts (organic, integrated, conventional), different production intensities (intensive, reduced) or options in the use of farming inputs (fertilisers, plant protection products, application techniques), indicators are particularly needed for the evaluation of the environmental impact of the alternatives on a scientific basis. Specific LCA adaptations have been developed in order to consider the particular environmental impacts of agriculture. Skowroñska, and Filipek (2014) provide a detailed review of the application of the LCA to fertilisers.

Energy Balance – First Application of the LCA Approach.

The LCA approach can be used in different ways. Its first application was on energy balances, where the energy consumption and energy production is evaluated. The energy balance of crop production is generally very positive, because agricultural crops fix several times more solar energy in their biomass than is consumed during their cultivation in terms of fertiliser, fuel etc.

Figure 3 shows the systems boundaries in an energy balance calculation for cereal production. It follows the life-cycle approach by including the extraction of raw materials (e.g. minerals, fossil fuels), the production and transportation of farming inputs (fertiliser, pesticides, machinery, seeds) up to the on-farm activities.

Production of nitrogenous fertilisers such as ammonium nitrate and urea is a main driver of energy use in crop production and represents about half of the total consumption of energy in an intensive arable crop production system. However, the fertiliser-related energy consumption is several times offset by the additional energy production due to the use of the mineral fertiliser. Depending on the crop, the total energy production per hectare exceeds the energy consumption by up to 15 times (Figure 4).

Extension of the Analysis Towards Environmental Impacts – ‘Real’ LCA.

A complete LCA study aims at including all relevant environmental impacts occurring during the life-cycle of a product. For crop production systems the relevant impacts are eutrophication, off-site acidification, global warming, toxicity, and resource consumption (land, water, minerals, fossil fuels). Figures 5 and 6 show the system boundaries considered in an LCA of wheat grain production, the data inventory derived from this system (Figure 5), and the impact assessment step that is performed in order to get to a limited number of conclusive indicators (Figure 6). IFS Proceedings 728 gives examples of wheat production at different nitrogen application rates and with different nitrogen fertiliser types.

LCA Indicators relevant to fertilisers

Researchers (Gaidajis and Kakanis, 2021) who have analysed the impact of fertilisers have used a methodology that incorporates the ReCiPe 2008 indicators. This provides the ability to assess systems and processes by using both midpoint (targeting the environmental mechanisms) and endpoint (targeting the impact) indicators. The overall objective of the ReCiPe method implementation is to translate the list of LCI results into a number of indicator scores, expressing the relative severity on an environmental impact category. These indicators are determined at two levels: 18 midpoint indicators and 3 endpoint indicators. These indicators are:

Mid-Point Indicators

1. Climate change
2. Ozone depletion
3. Terrestrial acidification
4. Freshwater eutrophication
5. Marine eutrophication
6. Human toxicity
7. Photochemical oxidant
8. Particulate matter formation
9. Terrestrial ecotoxicity
10. Freshwater ecotoxicity
11. Marine ecotoxicity
12. Ionising radiation
13. Agricultural land occupation
14. Urban land occupation
15. Natural land transformation
16. Water depletion
17. Mineral resource depletion
18. Fossil resource depletion

Endpoint Indicators

1. Damage to human health
2. Damage to ecosystem diversity
3. Damage to resource availability

However in practice the major impacts are found to related to climate change, fossil fuel depletion, freshwater eutrophication and ecotoxicity. The former two are those that production processes can have most impact upon.

LCA and ‘Carbon Footprint’

Accordingly the LCA approach is often applied in order to determine the so-called ‘carbon footprint’ of products or production systems. Carbon footprint studies of crop production are particularly critical, because it is not only the energy-related CO₂ emissions that are relevant, but in addition there are other specific issues to be considered. These are for instance (1) direct and indirect nitrous oxide (N₂O) emissions, (2) potential land-use change impacts (e.g. CO₂ from deforestation), (3) varying greenhouse gas emissions from different fertilisers and fertiliser production technologies, and finally, the CO₂ fixation in crops, which is only accountable if fossil fuels are replaced by bio-energy sources. Within the production phase of the fertiliser supply chain, the focus in on improving energy efficiency.

References

Gaidajis, G., & Kakanis I., 2021 “Life Cycle Assessment of Nitrate and Compound Fertilizers Production—A Case Study” Sustainability 13(1), 148;

ISO (2000). Environmental management – Life cycle assessment – Life cycle impact assessment, International Standard ISO 14042:2000. International Organization for Standardization (ISO), Geneva, Switzerland.

ISO (2006). ISO 14040:2006. Environmental management — Life cycle assessment — Principles and framework. International Organization for Standardization (ISO) Geneva, Switzerland

Skowroñska, M. and Filipek, T. (2014). Life cycle assessment of fertilizers: a review, Int. Agrophys, 28, 101-110

Links to related IFS Proceedings

375, (1995), Life Cycle Assessment for Food Production Systems, S Cowell, R Clift

438, (1999), Life Cycle Approach to Nutrient and Energy Efficiency in European Agriculture, J Küsters

477, (2001), Life Cycle Analysis: An Expanded Perspective, A C Janetos, A Wagener

687, (2011), LCA to Assess the Environmental Impact of Different Fertilisers and Agricultural Systems, F Bentrup, J Lammel

728, (2103), Comparison of the Environmental Impact of Three Forms of Nitrogen Fertiliser, S Marquis, T Genter, A Buet, A Berthoud

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

External information sources

LCIA: the ReCiPe model

Hasler, K., Bröring, S., Omta, S.W.F., Olfs, H-W. (2015). Life cycle assessment (LCA) of different fertilizer product types, European Journal of Agronomy, 69, pp41-51.

Chojnacka, K., Kowalski, Z., Kulczycka, J., Dmytryk, A., Górecki, H, Ligas, B. and Gramza, M. (2019). Carbon footprint of fertilizer technologies, Journal of Environmental Management, 231 pp962-967

Interpretation of LCA results: A Worked Example on a CO₂ to Fertilizer Process, University of Michigan

Building an LCA Inventory: A Worked Example on a CO₂ to Fertilizer Process, University of Michigan