Product Carbon Footprint for Railway Components: A Practical Guide

A practical introduction to Product Carbon Footprint for railway components, covering system boundaries, materials, manufacturing, supply-chain data and the standards and methodologies relevant to the rail sector.

What is a Product Carbon Footprint for a railway component?

A Product Carbon Footprint (PCF) quantifies the greenhouse gas emissions associated with a product over a defined part or all of its life cycle. The result is normally expressed in kilograms of carbon dioxide equivalent (kg CO₂e) for a clearly defined unit of product.

In the railway sector, the product does not need to be an entire train. A PCF can be calculated for a subsystem, an assembly or an individual component — for example a bogie component, braking device, door system, electrical assembly, cable, connector, interior component or rail fastening product.

This distinction is important. Railway vehicles and infrastructure are assembled through complex, multi-tier supply chains. The carbon footprint of the final system therefore depends on carbon data originating much further upstream, often at component and material level.

A useful PCF is also more than a single CO₂e value. It should identify what was calculated, which life-cycle stages were included, which data were used and which methodological choices were made.

Why is PCF becoming relevant for railway suppliers?

Rail is widely recognised as an important part of lower-carbon mobility. But low emissions during transport do not mean that manufacturing trains, railway systems and their components is carbon-free.

Steel, aluminium, copper, polymers, electronics, manufacturing energy and complex international supply chains all contribute to the embodied carbon of railway products.

As manufacturers extend their decarbonisation strategies beyond their own operations, attention increasingly moves upstream. Suppliers may therefore be asked to provide product-level carbon information that can be incorporated into a larger subsystem, vehicle or project assessment.

A PCF can also serve purposes beyond customer reporting. It can identify carbon-intensive materials and manufacturing processes, support comparisons between alternative designs or suppliers and provide a quantitative basis for product decarbonisation.

The railway industry already has considerable experience with Life Cycle Assessment (LCA) and Environmental Product Declarations (EPDs). Product Carbon Footprint, however, introduces a somewhat different question: how can reliable, comparable product-level carbon information be calculated and passed through the railway supply chain?

That question is becoming increasingly relevant as other mobility sectors move towards more standardised exchange of product carbon data.

PCF, LCA and EPD are related but they are not the same

The three concepts are sometimes used as if they were interchangeable. They are not.

A Product Carbon Footprint focuses specifically on greenhouse gas emissions and their contribution to climate change. Its result is expressed as CO₂ equivalent.

A Life Cycle Assessment can evaluate a much broader range of environmental impacts throughout a product's life cycle. Climate change is normally only one of the impact categories considered.

An Environmental Product Declaration communicates quantified environmental information based on an LCA performed according to defined Product Category Rules. It normally contains several environmental indicators and follows the requirements of an EPD programme, including independent verification.

An EPD can therefore be an excellent source of information for carbon-footprint work, but an EPD and a PCF should not automatically be considered equivalent deliverables.

This distinction becomes particularly important when a railway supplier receives a simple request from a customer: Please provide the carbon footprint of this component.

Before starting the calculation, it is necessary to establish what the customer actually expects.

Which standards are relevant?

The methodological foundation comes from the established international standards for Life Cycle Assessment and product carbon footprinting.

ISO 14040 and ISO 14044 establish the principles, framework, requirements and guidelines for Life Cycle Assessment.

For Product Carbon Footprint specifically, ISO 14067 provides the principal international framework for quantifying and reporting the carbon footprint of products in accordance with life-cycle principles.

The railway sector also has more specific methodological resources.

One important example for rolling stock is PCR 2009:05 – Rolling stock and parts thereof, developed within the International EPD System. It provides Product Category Rules for conducting LCA and preparing EPDs for rolling stock and related products and has been used for environmental declarations covering railway vehicles and their parts.

However, an important distinction should be maintained.

PCR 2009:05 is a Product Category Rule for LCA and EPD work. It should not simply be described as the railway PCF standard.

For a component-level carbon footprint, ISO 14067 can provide the general PCF framework, while relevant railway-specific PCRs and sector methodologies can provide valuable guidance when defining technically appropriate boundaries, assumptions and modelling choices.

This distinction is particularly relevant today because methodologies specifically intended for harmonised PCF calculation and digital exchange across railway supply chains are still developing.

Start with the product not with the emission factors

A common temptation is to start a PCF by looking for emission factors. That is usually too early.

The first questions should be much simpler:

What exactly is the product? Why is its PCF being calculated? And who will use the result?

A railway cable assembly, for example, should be defined by its actual configuration, material composition, mass and manufacturing route. Calculating a generic footprint for railway cables would provide very different information from calculating the footprint of the specific cable assembly supplied to an OEM.

The same applies to braking equipment, connectors, seats, doors, electronic equipment or bogie components.

The purpose also matters. A PCF requested by an OEM for integration into a vehicle-level footprint may require a different boundary from a study comparing two alternative component designs.

Defining the product and the purpose first prevents many methodological problems later.

Where should the calculation stop?

The system boundary is one of the most important decisions in any PCF.

For a component manufacturer supplying another industrial company, a cradle-to-gate footprint may often be the most useful starting point.

Such a calculation can include raw-material production, purchased components, upstream transport, manufacturing processes, energy consumption, production losses, packaging and other relevant activities until the finished component leaves the manufacturer's gate.

The result represents the embodied carbon delivered downstream with the product.

But this is not the only possible boundary.

A broader assessment can include distribution, installation, use, maintenance, replacement and end-of-life. For some railway products, those stages can significantly change the environmental picture.

This is particularly important because railway assets frequently remain in operation for decades.

A component that reduces vehicle mass may influence traction-energy consumption over a long service life. A highly durable component may avoid replacements. Conversely, a component requiring frequent maintenance or replacement can create additional life-cycle emissions.

Therefore, cradle-to-gate and cradle-to-grave PCFs answer different questions.

The correct boundary should be determined by the intended use of the result, not chosen automatically.

The quality of the PCF starts with the data

Once the product and boundary have been established, the calculation becomes a data exercise.

For most manufactured railway components, the Bill of Materials is one of the most important starting points. Steel, aluminium, copper, polymers, electronics and other materials can represent a substantial share of the cradle-to-gate footprint.

The calculation then needs to consider the processes that transform those materials into the finished component.

Relevant information may include electricity and fuels consumed during manufacturing, purchased components, machining or forming processes, welding, heat treatment, coatings and other surface treatments, manufacturing scrap and waste, packaging and upstream transportation.

Where possible, actual data from the manufacturing facility should be used for processes controlled by the manufacturer.

Secondary life-cycle datasets and emission factors will still normally be required for activities outside its direct control — particularly raw-material production, electricity supply, transportation and waste treatment.

Supplier-specific PCF or EPD information can improve representativeness, but it should not be accepted simply because it contains a precise-looking number. Its product definition, system boundary, reference period and methodological basis must be compatible with the footprint being calculated.

The calculation itself is usually the easy part

At its simplest, a carbon calculation links an activity with an appropriate emission factor.

Electricity consumption is associated with the carbon intensity of the electricity used. Material quantities are linked to appropriate life-cycle datasets. Transport activity is linked to the relevant transport mode and distance. Fuels, waste treatment and other processes are treated in the same manner.

The individual contributions are converted into CO₂ equivalent and aggregated within the defined system boundary.

The arithmetic is rarely the difficult part.

The difficult part is deciding which data are representative, which processes belong inside the boundary, how shared processes should be allocated and whether information received from different suppliers is methodologically compatible.

Those decisions can have a much greater effect on the credibility of the final PCF than the calculation itself.

A simplified railway component example

Consider a manufactured railway component containing aluminium and steel.

Its cradle-to-gate footprint includes the production of those materials, their transport to the manufacturing site, energy and processes used during production, manufacturing losses, packaging and relevant waste treatment.

Suppose these contributions result in approximately 14.2 kg CO₂e from materials, 1.1 kg CO₂e from inbound transport, 2.8 kg CO₂e from manufacturing, and 0.6 kg CO₂e from packaging and waste treatment.

The resulting cradle-to-gate Product Carbon Footprint would be:

18.7 kg CO₂e per component

The example is deliberately simple. In a real calculation, the result would need to be supported by the product specification, system boundary, reference period, data sources, datasets, allocation rules and other relevant methodological assumptions.

Without that context, 18.7 kg CO₂e is just a number.

With it, the value can become usable carbon data for the next company in the railway supply chain.

Where railway component PCFs become difficult

Materials are often the first challenge.

Metals are particularly important in railway products, and carbon footprints can differ significantly depending on production technology, recycled content, electricity supply and the methodological treatment of recycling.

Simply knowing that a material contains a certain percentage of recycled content is not enough. The calculation must also understand how the selected dataset treats primary and secondary material and how recycling is accounted for.

Manufacturing scrap creates a similar issue. The amount of material purchased is not necessarily the amount contained in the finished product. Cutting, machining, forming and other processes can generate substantial scrap, particularly for metal components.

Another challenge is allocation.

A factory rarely manufactures only one product. Electricity, heating, compressed air, production equipment and auxiliary processes may serve many products simultaneously. Their emissions therefore need to be assigned using a technically justified relationship — for example production quantity, mass, machine time, actual energy consumption or another relevant physical parameter.

There is no universal allocation rule appropriate for every manufacturing situation.

The important point is that the selected approach should reflect the process as realistically as possible and should be documented.

The use stage makes railway products particularly interesting

The long service life of railway assets creates a methodological issue that is less visible in many short-lived products.

For a conventional cradle-to-gate supplier PCF, the footprint ends when the component leaves the factory.

From the perspective of the complete railway system, however, the story may only be beginning.

Component mass can influence vehicle energy consumption. Efficiency can affect operational electricity demand. Reliability and durability can influence replacement frequency. Maintenance may require materials, energy and transportation over many years.

This does not mean that every railway component PCF should automatically include decades of operation.

It means that the purpose of the study must determine whether the use stage belongs in the calculation.

If an OEM requires embedded carbon data from its suppliers for aggregation into a vehicle-level assessment, a well-defined cradle-to-gate PCF may be exactly what is needed.

If the objective is to compare two component designs whose weight, efficiency or durability affects railway operation, excluding the use stage could lead to the wrong conclusion.

This is one reason why applying generic PCF approaches to railway products requires care.

A PCF should never be communicated as just one number

Imagine receiving the following information from a supplier:

PCF = 18.7 kg CO₂e/component

Is that enough?

Not really.

Was the calculation cradle-to-gate or cradle-to-grave? Which component configuration was assessed? Which year does the manufacturing data represent? Was supplier-specific aluminium data used or a generic dataset? Which electricity mix was applied? How was manufacturing scrap treated? Was inbound transport included?

Without these answers, comparing that PCF with another supplier's value may be misleading.

A technically useful PCF should therefore accompany the result with enough methodological information to make the number understandable and reproducible.

The product and reference unit, system boundary, data period, included and excluded processes, important data sources, emission factors or databases, electricity modelling, transport assumptions, allocation approach, recycling and scrap treatment, GWP method and significant limitations should all be transparent.

The objective is not to produce a hundred-page report for every component.

It is to ensure that the number being exchanged means the same thing to the sender and the receiver.

What should a railway supplier prepare?

A supplier preparing its first PCF does not necessarily need sophisticated carbon-management software before starting.

It needs good product and manufacturing information.

A clearly defined product specification and Bill of Materials are the foundation. Material quantities should be linked to actual product mass, purchased components should be identifiable, and manufacturing energy should be related as closely as practical to the product or relevant production process.

Information about scrap, waste, packaging and logistics should also be available. Where suppliers already provide EPDs or product-specific carbon information, those documents should be collected together with information about their methodological basis.

In practice, one of the most valuable preparatory exercises is simply to determine which information already exists inside the company, who owns it and which important data are missing.

PCF calculation frequently reveals data-management issues before it reveals carbon issues.

From carbon calculation to product improvement

The most valuable PCF is not necessarily the one with the most decimal places.

It is the one that helps explain where the emissions come from.

For one railway component, aluminium or steel production may dominate the result. For another, electronic components may be responsible for most of the footprint. In another case, manufacturing electricity, heat treatment or a particular surface process may become significant.

Once those hotspots are visible, useful questions can be asked.

Could the quantity of a carbon-intensive material be reduced? Could supplier-specific lower-carbon material be sourced? Could manufacturing scrap be reduced? Could renewable or lower-carbon electricity change the production footprint? Could a design modification reduce both material consumption and operational energy?

At that point, Product Carbon Footprint stops being merely another customer reporting requirement.

It becomes a tool for engineering, procurement and supply-chain decision-making.

The direction of travel for railway PCF

The railway industry already has established LCA methodologies and substantial experience with environmental declarations. What is now becoming increasingly important is the ability to calculate and exchange reliable product-level carbon information throughout complex supply chains.

Automotive initiatives such as Catena-X demonstrate how this can evolve beyond isolated carbon-footprint reports towards structured, interoperable exchange of PCF data between suppliers and customers.

Rail does not need to copy the automotive model blindly. Railway products have different lifetimes, operating conditions and life-cycle characteristics.

But the underlying challenge is similar: a carbon value becomes much more useful when companies throughout the supply chain understand how it was calculated and what it represents.

For railway suppliers, developing that capability now can therefore provide value beyond responding to today's individual customer request.

Conclusion

Product Carbon Footprint is becoming an increasingly useful tool for understanding the embodied carbon of railway components and for transferring carbon information through the supply chain.

ISO 14067 provides the general methodological framework for product carbon footprinting, while railway-specific LCA and EPD methodologies can provide important sector context.

But the credibility of a railway PCF ultimately depends on something more fundamental than the final calculation.

The product must be clearly defined. The system boundary must match the purpose. Data should be as representative as reasonably possible. Allocation, recycling, scrap and supplier information should be handled transparently.

Only then does the final value in kg CO₂e per component become meaningful carbon information rather than simply another number in a spreadsheet.

References

ISO 14040:2006 — Environmental management — Life cycle assessment — Principles and framework. International Organization for Standardization.

ISO 14044:2006 — Environmental management — Life cycle assessment — Requirements and guidelines. International Organization for Standardization.

ISO 14067:2018 — Greenhouse gases — Carbon footprint of products — Requirements and guidelines for quantification. International Organization for Standardization.

The International EPD System. PCR 2009:05, Version 4.0.2 — Rolling stock and parts thereof. Product Category Rules for the environmental performance assessment of rolling stock and related EPDs. The current registered version is valid until 6 July 2027.

Weise, S., Holsten, J., Blömeke, S. & Herrmann, C. (2026). Harmonizing product carbon footprint methodologies for a digital platform: Comparative analysis and recommendations for guideline development in the railway industry. Procedia CIRP, 140, 365–370. DOI: 10.1016/j.procir.2026.05.062.