When ‘greener’ packaging has a higher carbon footprint

Packaging materials can have very different carbon footprints depending on weight, production, recycled content, transport and reuse. Life-cycle assessment shows why choosing a ‘greener’ material does not always mean choosing a lower-carbon packaging system.

Switching from plastic packaging to glass, metal or fibre can make a product appear more sustainable, but in some applications the change can increase its carbon footprint.

Packaging weight, manufacturing energy, recycled content, transport, reuse and end-of-life treatment can all influence greenhouse gas emissions. A heavier alternative can generate more emissions than a lightweight plastic package performing the same function.

For packaging manufacturers and brands considering material substitution, the more useful question is not whether one material is ‘greener’ than another, but which packaging system delivers the required function with the lowest life-cycle impact.

Why packaging weight matters for carbon emissions

Packaging generates greenhouse gas emissions at several stages, from extracting and processing raw materials to manufacturing, filling, transport and end-of-life treatment.

Production can account for a large share of packaging emissions. A 2024 analysis of London’s packaging system found that emissions at the packaging factory gate accounted for 76% of packaging-related greenhouse gas emissions, compared with 4% from transport.

Factory-gate emissions included material production, transport to packaging conversion and the conversion process itself.

That makes both material choice and material quantity important.

A lighter package generally requires less material to deliver the same function. Lower weight can also reduce emissions associated with transporting empty packaging and, depending on the product and distribution system, filled packs.

Glass illustrates the trade-off.

Container-glass manufacturing requires high temperatures and is energy intensive. Research into hollow glass containers has identified energy use as a major contributor to environmental impact, while finding that increased use of recycled glass, or cullet, and reduced container weight can improve environmental performance.

Weight can also affect the supply chain after production. A glass bottle can be substantially heavier than a functionally comparable plastic bottle, potentially increasing transport-related emissions.

A systematic review of life-cycle assessment studies comparing plastic packaging with alternative materials found that the weight of glass can significantly affect its environmental performance relative to lightweight plastics. Comparisons between plastics and metals were more dependent on the specific application.

The conclusion is not that glass is inherently worse than plastic. It is that the performance of the packaging system matters more than the environmental reputation of the material.

Why life-cycle assessment changes the comparison

There is no universally lowest-carbon packaging material.

Life-cycle assessment (LCA) examines the environmental impacts associated with a product or system across defined stages of its life. Depending on its scope, this can include raw-material extraction, manufacturing, transport, use, recycling and disposal.

For packaging, comparisons also need to be made on a functional basis — in other words, according to what the package is required to do.

A 500ml bottle should not simply be compared with another package according to the weight or emissions of each material. The assessment needs to consider how much packaging is required to deliver the same quantity of product and whether the alternatives provide equivalent protection and performance.

This helps explain why studies comparing packaging materials do not always reach the same conclusion.

A 2026 systematic review of 51 food-packaging LCA studies found substantial variation in reported environmental impacts. Differences in products, materials, functional units, system boundaries and assumptions made broad material-by-material conclusions difficult.

Geography can change the result too. Transport distances, energy sources, recycling infrastructure, collection rates and waste-management systems vary between markets. A packaging format that performs well in one location may therefore perform differently elsewhere.

Carbon is also only one part of the sustainability calculation. A lower carbon footprint does not automatically mean lower environmental impact overall. A broader LCA can assess other environmental effects alongside greenhouse gas emissions.

When reuse changes the calculation

Reuse can fundamentally alter a packaging system’s carbon footprint.

A returnable glass bottle can have a relatively high initial environmental burden because more material is used to make it. If it is successfully collected, washed and refilled many times, however, that initial impact can be distributed across multiple uses.

A 2026 life-cycle study of beverage packaging in Poland found that returnable glass had significant potential to reduce its carbon footprint where return rates were high. Disposable glass had the highest carbon footprint among the systems modelled, while PET benefited from its low material weight.

The distinction between single-use and reusable packaging is therefore critical.

Asking whether glass is greener than plastic is unlikely to produce a useful universal answer. The more relevant question is which packaging system delivers the required product function with the lowest overall impact.

For reusable packaging, that calculation can include manufacturing, filling, distribution, collection, return transport, washing and refilling. Return rates, transport distances and the number of successful reuse cycles can therefore be as important as the material from which the package is made.

How recycled content affects packaging emissions

Virgin versus recycled material is another variable that can substantially alter packaging’s carbon footprint.

Using recovered material can reduce demand for virgin resources and, in many cases, lower the energy and emissions associated with manufacturing. The benefit varies according to the material, production technology and recycling system.

For glass, greater use of cullet can reduce the environmental impact of production. Research into glass containers has also identified lightweighting and increased recycled content as routes to improved environmental performance.

Recycled content can alter the carbon performance of plastics and metals too, although the scale of the benefit differs between polymers, metals and manufacturing processes.

For companies comparing packaging options, the relevant question is therefore not simply whether a material is recyclable. It is how much recycled content can realistically be incorporated, how that material is produced and what happens to the package after use.

A virgin plastic bottle compared with a container made from highly recycled aluminium represents a different carbon comparison from one involving recycled plastic and primary aluminium.

The material name alone reveals relatively little about those differences.

Why product protection matters

Packaging cannot be assessed in isolation from the product it protects.

Reducing packaging weight or switching materials may lower the footprint of the package itself, but that benefit can be undermined if the change increases breakage, spoilage or other product losses.

This is particularly relevant to food and other products where the environmental burden of producing the contents can outweigh that of the packaging.

The lowest-impact package is therefore not necessarily the package using the least material. It is one that uses material efficiently while providing the protection required throughout manufacturing, distribution, retail and use.

Product protection and shelf life consequently need to form part of any functional comparison between packaging alternatives.

Why lightweighting remains a powerful carbon strategy

Material substitution attracts considerable attention, but reducing material use can be just as important to packaging decarbonisation.

Lightweighting can reduce packaging’s carbon footprint while retaining the material and performance characteristics required by the application.

Lightweighting has long been applied to plastic bottles and films, glass containers, metal cans and other formats. Research into glass packaging, for example, has found that reducing container weight can lower environmental impacts.

The principle extends beyond glass. Reducing the amount of material required for a package can lower demand for raw materials while decreasing the weight moving through the supply chain.

Lightweighting and material substitution are not mutually exclusive. A redesigned package could combine lower weight with increased recycled content, improved recyclability or a different material.

What matters is the combined life-cycle result rather than any single design characteristic.

How to compare the carbon footprint of packaging

For packaging companies considering a change, a credible comparison should begin with the function the package needs to perform.

An assessment should consider:

• the quantity of material required to deliver the same packaging function;
• the proportion of virgin and recycled material;
• manufacturing energy requirements;
• package weight and transport distances;
• whether the package is single-use or reusable;
• realistic return rates and the number of reuse cycles;
• collection and return distances for reusable formats;
• local recycling and waste-management systems;
• the potential for product loss, spoilage or breakage;
• equivalent product protection and shelf-life performance; and
• the system boundaries, functional unit and assumptions used in the life-cycle assessment.

Changing any of these variables can alter the result.

This is why claims that one packaging material is inherently lower-carbon than another should be treated cautiously. The same material can perform very differently depending on how much is used, how it is manufactured, how far it travels, whether it is reused and what happens to it after use.

Lower-impact packaging, not simply different packaging

Pressure to tackle plastic pollution has encouraged brands and packaging companies to explore alternatives to conventional plastics. Material substitution can deliver important environmental benefits where it reduces unnecessary material, supports effective reuse or improves recovery.

But perceptions of sustainability do not necessarily correspond with life-cycle carbon performance.

Research into consumer perceptions of beverage packaging has found that people can regard glass as more environmentally sustainable than plastic even where life-cycle analysis shows single-use glass performing worse across the environmental impact categories examined.

That does not make plastic universally preferable. Nor does any other material have an inherent claim to the lowest carbon footprint. Performance depends on the package, its application and the system in which it operates.

For companies pursuing decarbonisation, the objective should therefore be a lower-carbon packaging system, not simply a different material. Sometimes that will mean material substitution. In other cases, it may mean increased recycled content, an effective reuse system, better collection and recycling, a redesigned pack or simply less material.

The central lesson is straightforward: ‘greener’ packaging is not necessarily lower-carbon packaging.

The most credible packaging decisions start with the function a package must perform and assess the complete system required to deliver it.

As companies seek to reduce packaging waste and greenhouse gas emissions, life-cycle evidence offers a more reliable guide than the environmental reputation of any material alone.