What is a product carbon footprint?

Explaining the meaning of this term and highlightsing its relevance to companies working within the footwear and leather industries.

by Nicola Pichel-Juan

‘Product carbon footprints’ are becoming increasingly prevalent as a way for organisations to measure and understand the environmental impacts of the items they design, source, manufacture or sell. This article will discuss the concept of product carbon footprints in relation to the footwear industry, considering what they are, how they can be calculated, the challenges involved, and finally what significance they may have for the footwear industry in the future.

Firstly, what is a ‘product carbon footprint’? It is defined by ISO 14067:2018 as ‘the sum of greenhouse gas emissions and greenhouse gas removals in a product system, expressed as CO₂ equivalents and based on a lifecycle assessment using the single impact category of climate change’.

For instance, extracting fossil fuels that are burned to produce electricity, processing fossil fuels to produce plastic materials, and using diesel or petrol to transport goods, are all going to generate greenhouse gas emissions. However, fossil fuels are not the only source of greenhouse emissions. As an example, cattle (due to their digestive process) emit a considerable amount of biogenic methane into the atmosphere. It is generally accepted when calculating a carbon footprint that some of the environmental impact from the methane is carried forward into the leather that is manufactured as a by-product from beef production. The sustainability credentials of leather will be discussed in more detail in the article ‘Is leather sustainable?’, which is to be published in a future issue of SATRA Bulletin magazine.

It is also useful to understand the difference between a product carbon footprint and another term that is often used – ‘Lifecycle Assessment’ (LCA). These differ in that a carbon footprint focuses only on the global warming impact of greenhouse gas emissions, whereas an LCA can also consider other environmental impacts. These may include acidification, water depletion and footprint, land depletion and land use.

Global warming potential comparison of greenhouse gases
Greenhouse gas	Warming potential in CO2e
Carbon dioxide Methane Nitrous oxide Hydrofluorocarbons Perfluorocarbons Sulphur hexafluoride Nitrogen trifluoride	1 25 298 124 to 14,800 7,390 to 12,200 22,800 17,200
1 kg of methane causes 25 times more warming over a 100-year period than 1 kg of carbon dioxide does. The high short-term global warming potential of methane is being tackled by the ‘Global Methane Pledge’ signed at the COP26 summit. This is looking to reduce global methane emissions by 30 per cent by 2023, which, it is believed, could eliminate 0.2°C of warming by 2050. It is worth noting, however, that globally 11 to 12 per cent of methane is estimated to come from landfill sites, so this problem will be a hard one to fix.

LCA process

The process of conducting an LCA comprises of four stages: i) goal and scope definition, ii) data collection and validation (inventory), iii) impact assessment and, finally, iv) interpretation and feedback.

During the initial goal and scope definition stage, the ‘functional unit’ of the study will be determined. For a footwear LCA/carbon footprint, this is likely to be one pair of finished footwear of a given size. The ‘system boundaries’ will also be defined, which means what is included in or excluded from the study. One of the first decisions to make will be whether or not to carry out a ‘cradle-to-gate’ or ‘cradle-to-grave’ study.

There is no ‘correct’ answer as to which approach should be used, provided it is documented. It may be that an organisation decides to exclude the ‘use’ and ‘disposal’ stages, as it has no direct control over them. However, if an item has been produced with a particular end-of-life solution in mind, it may be relevant to include that stage. Additional potential sources of emissions, such as embedded carbon in buildings or machinery and other capital equipment, are sometimes also excluded as the impact per functional unit over their anticipated life of – for instance, a factory building – is likely to be negligible. Once again, this all must be documented and justification provided.

The second stage of data collection and validation (‘inventory’) is often the most time-consuming. It involves gathering as much relevant primary data as possible about the product being studied and then identifying secondary data sources that can be used to calculate the emissions of a particular item or process. Essentially, primary data multiplied by secondary emissions data equals the environmental impact in kg of CO₂e. The data that is required and the likely data sources are discussed in more detail below.

A data quality assessment should also form part of any study to validate the representative of the data used. This includes considering the technological, geographical and time-related representative of the data. As an example, where secondary emissions data is used, it is important to note how old that dataset is and if the study generating the data took place in a location that is similar to the current study and with equivalent prevailing technologies and production processes. The completeness and precision of the data should also be reviewed to identify any gaps or areas where its quality could be improved.

The impact assessment stage involves calculating the carbon footprint (or other environmental impacts) of the product using all the data collected, in line with the goal and scope defined and drawing conclusions from those results. This may include ‘normalisation’ and ‘weighting’ of the results. Normalisation involves, for instance, a comparison of the impact calculated in the study with the average impact of a global citizen. Weighting can be used to convert scores across multiple different environmental impacts into one overall score if multiple environmental impacts are being considered.

The final stage is ‘interpretation and feedback’. This involves taking a deeper look at the study that has been completed to confirm that any conclusions made can be substantiated, and carrying out checks such as a sensitivity analysis to verify the data and procedures used.

Data

A large amount of data will be required to complete a product carbon footprint. This includes both ‘primary’ (inventory) data and ‘secondary’ (reference) data.

Primary data covers data specific to the product being studied in line with the system boundaries determined. For footwear, this is will include the following:

• sufficient information to accurately identify each material or component – for example, if the lining is a mono-material or a blend and, if it is the latter, from which materials it has been made and in what proportions
• the weights of each material, component, or packaging item
• details of where each material, component or packaging item is produced, how far it must be transported to the footwear production site and how it was transported
• waste/scrap percentages during production
• energy consumption per pair and the energy sources
• the origin and destination ports for shipping finished goods
• locations of the finished goods warehouses
• the mode of transport used to send out finished goods
• the likely end-of-life scenario.

All this information then needs to be converted into an associated carbon footprint, using secondary/reference data. Typical sources for this data include:

• lifecycle inventory databases such as Ecoinvent
• industry bodies
• government publications
• regional and national statistics
• academic studies.

Some of this secondary data will be freely available in the public domain. For instance, The United Kingdom’s Department for Environment, Food & Rural Affairs (DEFRA) publishes carbon emissions factors on an annual basis. This provides impact data for items and activities such as electricity generated in the UK and different modes of commuter and freight transportation. However, to complete a full carbon footprint analysis of a shoe, organisations may have to pay for access to some data sources such as Ecoinvent, or work with an organisation such as SATRA which offers LCA services.

Challenges and considerations

There are several challenges of which any organisation undertaking a carbon footprint study for footwear will need to be aware. These are particularly relating to the availability of appropriate and representative impact data.

The data for some materials (a good example being leather) may be based on a very small number of studies that are potentially not representative of either the wider industry, the prevailing technologies being used, and certainly not the individual material or product being studied. This has led to many tanneries now commissioning their own independent studies to calculate the impacts of the materials they produce.

For other materials that are developed to have a lower impact, including some of the new bio-based alternatives, data may not be available in standard databases and may need to be sourced directly from the manufacturers. Data may not be available for other items from a specific country or region, and global average or aggregate data may have to be used instead. Additional research may also need to be carried out if a material used is a blend of multiple fibre types. This may be necessary in order to understand the ratio of those different fibres, as each one is likely to have a different impact.

Applications

There are many reasons why an organisation may choose to undertake a carbon footprint study on one of its products. It could be simply to gain an understanding of the likely impacts of a product and to identify what the main sources of emissions or ‘hotspots’ are. However, studies are often carried out to compare products or to understand the impact of making a particular change. This could include, for instance, a change in a supplier’s location, a move to a different energy source (often a transition to renewable energy), substitution of a material, a change to the packaging (potentially from plastic to paper), or an alteration to the shipping method.

SATRA has conducted studies to i) compare the impacts of the same product using either virgin polyester or recycled polyester as a raw material input, ii) compare the impacts of the same product if the production supply chain was moved closer to the market, and iii) compare new tanning systems with traditional chrome tanning systems.

What is the impact of a pair of shoes?

From data and studies considered by SATRA, the impact for a ‘typical’ pair of synthetic upper running shoes shipped by sea from Asia to Europe or the United States is likely to be in the region of 15 kg to 18 kg per pair. This is equivalent to charging a smartphone around 2,000 times. Much of the footwear being made is now being developed specifically to have a lower impact, and the sports shoe industry in particular has been competing to bring a zero-carbon shoe to market.

The first company to make a claim to a zero-carbon shoe is All Birds, which unveiled its ‘M0.0NSHOT’ shoe in June 2023. This is said to have been achieved through the selection of lower impact bio-based materials, lower impact transportation and the fact that the merino wool used in the shoe’s upper is sourced from a farm that sequesters more carbon than it emits. However, at the time of writing this article, the shoe had not yet been released for sale.

What about off-setting?

In recent years, it has been common to see claims from companies that certain products – or, indeed, the entire organisation – is carbon neutral, based on ‘offsetting’ any associated emissions. Offsetting is the purchasing of carbon credits based on emissions reduction activities unrelated to the product or organisation. For example, a company may pay for trees to be planted in a part of the world that is completely separate from both its own operation and its supply chain.

There has been considerable controversy about carbon off-set schemes and whether they really deliver the environmental benefits that they claim to. SATRA always recommends that an organisation prioritises carbon reduction activities first, before considering off-setting and then to thoroughly research the integrity of any off-setting scheme.

Nevertheless, it is possible that off-setting may not be an option for much longer. The European Union (EU) in its ‘Directive on Empowering Consumers for the Green Transition’ (ECGT) will not allow carbon neutral claims that are based on offsetting emissions outside of the product’s value chain. The concept of ‘in-setting’ is therefore becoming an increasingly popular approach to reducing emissions. This takes place within the value chain and could include activities such as reforestation, generation of renewable energy and regenerative agriculture. The EU has also agreed to establish the world’s first registry to certify carbon dioxide removals.

Benefits from carbon footprint studies

There are clear benefits for a company which decides to carry out a carbon footprint study. The most obvious one is that if an organisation does not understand the impacts of its products, it cannot reduce them. Legislative and consumer pressures to do this are only going to increase, particularly as the impacts associated with the production of footwear is likely to account for a significant proportion of Scope 3 emissions for many organisations within the footwear value chain.

Having a verified carbon footprint can also support an organisation in communicating the sustainability credentials of its products against a backdrop of legislation intended to crack down on ‘greenwashing’ (which has been defined as ‘the use of advertising and public messaging to try to appear to be more environmentally sustainable and green than is really the case’). The previously-mentioned ECGT Directive will prohibit unverified environmental claims.

Finally, there can be a definitive competitive advantage for companies that are able to provide this information to their customers and consumers further down the supply chain, as well as demonstrate that they are taking their environmental responsibilities seriously.

The future?

It certainly appears that product carbon footprints and lifecycle assessments are here to stay. However, a consistent methodology is needed that can be used throughout the industry to ensure that all studies are carried in the same way. This will require use of the same system boundaries and the same impact data sets, to allow consumers to confidently compare different products and be able to select lower-impact goods.

Once again, the European Union is leading the way on this and is working on ‘Product Environmental Footprint Category Rules for Apparel and Footwear’ that provide this consistent methodology and framework. These are expected to be published in the final quarter of 2024. It is also interesting to note that the PEFCR considers the ‘life’ (durability) of a product, so that the environmental impacts can be allocated over the item’s lifetime. This is something that must surely be considered as a key part of any product carbon footprint.

Publishing Data

This article was originally published on page 14 of the June 2024 issue of SATRA Bulletin.

Other articles from this issue »

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