Recycled vs. Virgin Materials: How They Impact Product Carbon Footprints

In 2022, global primary aluminium production, from mine to cast house, had an average carbon footprint of 15.1 tonnes of CO₂e per tonne. By comparison, processing aluminium scrap into recycled aluminium generated 0.52 tonnes of CO₂e per tonne on a gate-to-gate basis.

The two figures have a numerical ratio of approximately 29:1, but they are not directly comparable because they use different life-cycle boundaries. Comparing the two figures gives an indicative saving of roughly 97%, although the boundaries differ: cradle-to-gate for primary aluminium and gate-to-gate for recycling. However, the recycling figure does not represent the full carbon footprint of recycled aluminium, which varies depending on the life-cycle assessment (LCA) method.

This distinction matters when comparing recycled and virgin materials. This guide explains how material choices affect a product carbon footprint (PCF), examines published data for aluminium, steel and plastics, and explains how to document data sources, system boundaries and calculation assumptions.

A product carbon footprint (PCF) quantifies the greenhouse gas emissions associated with a defined unit of a product across specified life-cycle stages. Results are expressed in carbon dioxide equivalent (CO₂e). ISO 14067:2018 provides requirements and guidance for quantifying product carbon footprints consistently with the life cycle assessment principles in ISO 14040 and ISO 14044. The allocation and cut-off rules applied to a calculation depend on the applicable methodology and system boundaries.

Virgin materials are produced from primary resources. Examples include metals extracted from ores, aluminium produced from bauxite and plastics manufactured from fossil feedstocks. Their carbon footprint can include resource extraction, refining, material processing and the energy used to convert raw resources into usable materials.

Recycled materials are produced from recovered scrap or waste through processes such as collection, sorting, transport and reprocessing. Their carbon footprint depends on the energy and resources required for these processes, as well as the allocation method used to assign emissions between product life cycles.

That distinction matters. Recycled materials do not automatically have zero emissions, because collection, sorting, transport and reprocessing still generate them. Under a cut-off or recycled-content approach, the recycled input generally carries the emissions associated with its recovery and processing, rather than the original virgin material production burden. Other approaches can allocate recycling-related burdens and benefits differently, affecting the calculated result.

Within a PCF, the choice between recycled and virgin inputs directly affects the material acquisition stage and can also influence end-of-life accounting. For products in which metals or plastics account for a substantial share of the bill of materials, this choice can significantly affect the final footprint.

Recycling can reduce greenhouse gas emissions because processing recovered materials generally requires less energy than producing materials from raw resources. However, the size of the reduction varies by material, production method, energy source and life cycle assessment (LCA) methodology. Aluminium, steel and plastics illustrate why these differences matter when calculating a product carbon footprint (PCF).

Producing primary aluminium from bauxite requires energy-intensive extraction, refining and smelting. Recycled aluminium avoids the need to repeat these primary production stages, although collecting, sorting, transporting and reprocessing scrap still generate emissions.

The actual carbon savings depend on the electricity mix, recycling process and system boundaries used in the calculation. Recycling figures based only on scrap processing should not be treated as the complete carbon footprint of recycled aluminium.

For a PCF, document whether the selected emission factor represents primary production, scrap processing or a broader life-cycle boundary. This helps ensure that recycled and virgin aluminium data are interpreted consistently.

Steel’s carbon footprint depends heavily on its production route. Traditional blast furnace-based production uses iron ore and carbon-intensive processes, while electric arc furnaces can use substantial amounts of recovered steel scrap.

However, recycled steel does not have one universal carbon footprint. Electricity sources, scrap quality, furnace efficiency and other production inputs affect the result. A scrap-based electric arc furnace using lower-carbon electricity can have lower production emissions than a conventional blast furnace route.

When calculating a PCF, identify the steel production route and use supplier-specific data where available. If you rely on industry averages, document the dataset, geographical coverage and assumptions.

The carbon benefits of recycled plastics vary by polymer and recycling method. Recycled PET and HDPE, for example, can have different footprints depending on collection systems, sorting requirements, processing technologies and the quality of the recovered material.

Mechanical recycling generally involves collecting, sorting, cleaning and reprocessing plastic waste. These activities consume energy and generate emissions, but they can reduce the need for virgin plastic production. Other recycling technologies have different energy requirements and environmental impacts.

The allocation method used in an LCA also affects the reported result. When comparing virgin and recycled plastics, use data with compatible system boundaries and clearly document the recycling method and assumptions.

These materials demonstrate why recycled content alone does not determine a product’s carbon footprint. For a meaningful comparison, use emission factors that match the material grade, production route, geography, data year and applicable methodology. Record the source and assumptions so the calculation can be reviewed and reproduced.

Two analysts can assess the same material and reach different carbon footprint results. This happens because the calculation method, system boundaries and data sources influence how emissions are assigned and reported.

ISO 14044, which provides the life cycle assessment framework that ISO 14067 builds upon, sets out a hierarchy for handling allocation. Analysts should first seek to avoid allocation, for example by subdividing processes or expanding the system where appropriate. If allocation cannot be avoided, they should use physical relationships where possible, followed by other relationships, such as economic value, when justified.

Recycling creates a particular challenge because a material can pass through several product life cycles.

The cut-off approach, also known as the recycled content approach, is widely used because it is relatively straightforward. Under this approach, the original virgin material production burdens generally remain with the first product life cycle, while the product using recycled material carries the burdens associated with its recovery and processing, according to the chosen system boundary.

Other allocation approaches distribute recycling-related burdens or benefits differently. Some assign part of the original material production burden to recycled material, while others account for the benefits associated with recycling at the end of a product's life. These choices can change the apparent difference between recycled and virgin materials.

Research on recycled fibres and plastics demonstrates that allocation methods can produce substantially different results. Therefore, when comparing published carbon footprints, check which allocation method each study applies rather than assuming the results are directly comparable.

Product carbon footprint methodologies are not automatically interchangeable. Different frameworks can use different rules for allocating emissions, accounting for recycled content and modelling end-of-life processes.

For example, the Product Environmental Footprint (PEF) method uses a Circular Footprint Formula to account for material recycling and related life-cycle impacts. Other PCF frameworks apply their own requirements for secondary materials and recycling.

Industry-specific frameworks, such as the Catena-X PCF Rulebook, provide additional calculation and data-exchange rules for their intended supply chains. If a customer specifies a particular framework, use its applicable requirements rather than combining methods from different frameworks without justification.

When comparing results, record the methodology and version used, along with any recycling allocation rules that affect the calculation.

System boundaries determine which processes are included in a carbon footprint. For example, a primary aluminium dataset measured from raw material extraction to the factory gate cannot be directly compared with a recycling dataset that covers only scrap processing. The figures may each be valid within their stated boundaries, but they do not represent equivalent life-cycle stages.

Data sources also affect the result. Plant-specific data reflects the processes and operating conditions of a particular facility during a defined period. Generic database values typically represent an industry, region or technology average. Both can be useful, but they answer different questions.

For a defensible product carbon footprint, check that recycled and virgin material datasets use compatible system boundaries, appropriate geographical and temporal coverage, and consistent units. Document the source, methodology and assumptions so that another analyst can understand and reproduce the calculation.

Recycled content does not always guarantee a lower product carbon footprint (PCF). The outcome depends on recycling technology, energy sources, material quality and life cycle assessment (LCA) methodology.

Recycling technology matters. Argonne National Laboratory’s circular-economy analysis of PET found that chemical recycling and upcycling can reduce virgin material use and solid waste without reducing the life-cycle greenhouse gas impacts of the current supply chain. Mechanical recycling and chemical recycling can have different emissions depending on processing requirements and energy sources.

Material quality matters. Some applications require specific material properties that recovered scrap cannot consistently meet. For example, certain aluminium alloys require primary aluminium to meet composition and performance requirements. Effective sorting can improve scrap quality and increase its suitability for reuse.

Energy sources matter. Recycling processes powered by carbon-intensive electricity can have higher emissions than those using lower-carbon power. Steel production also demonstrates how the production route and electricity supply affect the final footprint.

For an accurate PCF, assess the actual recycled content, processing method, energy source and system boundaries. Recycled content can reduce emissions, but the result should be supported by appropriate data rather than assumed.

Use this process to make your product carbon footprint (PCF) comparison consistent and traceable.

Comparing recycled and virgin materials can reveal important opportunities to reduce a product carbon footprint. However, the size of the benefit depends on the material, production route, energy source, system boundary and allocation method.

For sustainability, procurement and product teams, the priority is to treat recycled content as a documented input rather than an automatic emissions reduction. Define the boundary, follow the applicable methodology, use reliable data and test key assumptions. This makes the resulting PCF more transparent, traceable and easier to review.