Funded by

Developed by

Explore research‎ > ‎

Methodology

Summary

Product carbon footprints of six major Scottish dairy products were developed using the UK dairy industry’s new footprinting guidelines[1]. These analyses relied mainly on secondary data on Scottish farming and dairy processing[2]. Product carbon footprint results were then scaled-up to the national level by integrating with supply chain-level annual production figures for the six products (see Figure 3). Additional estimates were developed on the quantity of soil carbon stocks under management by Scottish dairy farmers (see Appendix 1). Full details can be found in the accompanying methodology report[3].

The footprinting approach in this project had to be capable of robustly highlighting emissions reduction opportunities across a whole supply chain by product group – but still be deliverable within a relatively short time period (six months).

Analysis year

It should be noted that the footprint analysis draws on data from a number of years (2007-2009), with livestock numbers being taken from 2007 (the most recent year for which national greenhouse gas accounts were available for Scotland (AEA Technology 2009)). The 2007 data was chosen as it was felt important to be able to compare supply chain emissions with robust national emissions estimates.

An appropriate level of accuracy

Before undertaking any sort of environmental assessment it is essential to consider the advantages and disadvantages of different quantification approaches, so that results meet with user expectations. Without this initial scoping stage projects run the risk of wasting time on unnecessary detail – or conversely providing results which are too uncertain for the intended application (e.g. making a green marketing claim or tracking improvements over time).

Given the primary objective of this project was to highlight opportunities for reduction – and there was insufficient time to collect primary data from businesses, it was decided that the majority of data should be sourced from secondary sources e.g. industry publications. Only significant data gaps warranting primary data collection from supply chain businesses[4]. It was also considered unreasonable to collect large amounts of new data from farmers and processors when the industry has made good efforts to collect and publish environmental data already. This approach was seen as low risk given the number of recent studies into the environmental impact of milk.

Most importantly, the collection of a representative sample of new primary data from individual companies across all products from grass-to-consumer would not have improved delivery of the ultimate objective of highlighting emissions hotspots. For a discussion of different supply chain footprinting approaches see Appendix 3.

Limitations of this analysis

It is important to be transparent about the limitations of any emissions assessment, so that results can be interpreted and communicated without fear of misinterpretation.

The modelling approach chosen above means that project results should not be used to make an unqualified claim about the ‘average emissions intensity’ of Scottish dairy products. As described above, this would require considerable primary data collection efforts, rather than reliance on secondary data[5]. Similarly, the results of this study could not be used to say that, for instance, Scottish milk is lower/higher emissions than the UK average. Result uncertainty was not quantified as part of this work – and so a claim of better performance would be difficult to substantiate.

Finally, the results of this analysis could not be used for detailed tracking of supply chain emissions changes over time – again due to uncertainties inherent in such a high level assessment. Changes in emissions would be better tracked via different means e.g. individual product and company GHG reporting, national GHG inventories, or an agreed programme of primary data collection by the whole industry (such as being undertaken by DairyCo17).

Key references

The carbon footprinting approach draws heavily on three documents:
  • PAS2050[6];
  • The Guidelines for the Carbon Footprinting of UK Dairy Products[7] (the ‘Dairy Guidelines’); and
  • Greenhouse Gas Emissions from the Dairy Sector - A Life Cycle Assessment (Gerber, et al., 2010).

These carbon footprinting methodologies & studies have already been widely consulted on by a range of stakeholders and the use of their boundaries and assumptions enables a degree of comparability with existing and future footprint studies (see limitations section above). It is important to note that, due to the scope of the analysis, it was not possible to produce an assessment which is fully compliant with PAS2050 or the Carbon Trust Dairy Guidelines – mainly because they set-out specific requirements on primary data collection. This does not devalue the analysis, given its objectives. It is also worth noting that the IDF dairy LCA guidelines[8] had not been published by the time the analysis was undertaken.

Quality assurance

Staff at Best Foot Forward were responsible for analysis and report quality assurance procedures – i.e. a cell-by-cell checking of spreadsheet models, references, assumptions, sources, etc.

The Carbon Trust reviewed overall modelling approach, key assumptions, data sources and accounting methods to ensure consistency with the draft Dairy Guidelines and footprinting best practice. This was through a face-to-face workshop at the start of the project, on-going e-mail/phone discussions and finally through a review of the final methodology paper. The Carbon Trust did not undertake a cell-by-cell check of the spreadsheet models – nor were the results/models certified e.g. to PAS2050 or Carbon Trust Carbon Label (this was not an option for a high-level assessment, as explained above). In all the Carbon Trust provided 7.5 days of support to the project. This amount of time was deemed adequate considering the overall aims of the project.


Summary of method, by life cycle stage

Grass-to-farm gate

The GHG emissions associated with raw milk production on Scottish dairy farms were modelled for three milk yield classes: low, medium & high[9]. Organic milk production was not modelled separately (see Box 1 below). The average intensity of Scottish milk production was then developed from an assumed average milk yield in Scotland of 6,427 litres per dairy cow per year in 2007[10].

No primary data was collected from farms – instead a variety of published data sources were used in the analysis, including the SAC Farm Management Handbook (McBain and Curry 2009) and custom extracts of the Scottish Farm Accounts Survey (2007/8)[11]. Considerable modelling effort was invested in developing Scotland-specific livestock and manure storage emissions factors using IPCC equations (IPCC 2006). Full details can be found in the methodology report.

Processing

Processing activities were modelled using environmental benchmark data from Dairy UK, Climate Change Agreement reports on energy use and other published sources of information on resource use and waste e.g. WRAP packaging benchmarks, published life cycle assessments.

Distribution, use & end-of-life

Downstream emissions were modelled using Carbon Trust footprinting models (which are used by industry to undertake studies). Only the retail route was modelled as it accounts for 95% of consumer sales[12].



[2] Where no Scottish-specific data was available, proxies were used e.g. UK average data

[3] ‘Method white paper on the assessment of greenhouse gas emissions from the Scottish dairy sector’.

[4] For example, cheddar maturation energy consumption.

[5] The Dairy Guidelines also stipulate levels of primary data collection required to be able to make such claims. DairyCo are using these guidelines in a three year project, recently commissioned, to properly benchmark dairy farm emissions. Another good example of a recent dairy emissions study which has taken this approach is the three year Innovation Center for US Dairy life cycle study: http://www.usdairy.com/Sustainability/

[6] PAS2050: Specification for the assessment of the life cycle greenhouse gas emissions of goods and services. BSI (2008)

[9] Low (<6,500 litres per dairy cow per year); medium (6,500-8,500litres); high (>8,500 litres) – these classes were taken from the SAC Farm Management Handbook.

[10] In 2007: 1,272 million litres of milk were produced by 197,900 dairy cows (Sources: June Census and Scottish Agriculture Output, Input and Income Statistics)

[12] DairyCo Insiders Guide 2010: http://dairyco.net/library/