From raw materials to packaging: where the environmental impact arises
The second part of our series ‘Packaging Fact Check: Materials, Impact, Recycling’ focuses on the origin and manufacture of the most important packaging materials. Glass, aluminium, paper and plastic are based on different raw materials and manufacturing processes – and their environmental impact factors therefore vary accordingly.
Where environmental impact arises
The environmental impact of a packaging material begins with its raw materials and its manufacture. The processes involved differ significantly – and with them, the respective environmental levers. For glass, a key factor is the melting process; for aluminium, it is the production of the primary metal. Paper, amongst other things, requires energy to dry the fibres, whilst PET and HDPE are produced from specifically manufactured petrochemical building blocks.
Glass: energy-intensive production
Packaging glass consists mainly of quartz sand, soda, lime or dolomite, and recycled glass. The raw materials are mixed, melted at high temperatures and then moulded into bottles or jars. This is precisely where a key environmental lever lies: the melting furnace operates at temperatures of up to 1,600 degrees and requires a great deal of energy. This accounts for a significant proportion of the emissions from production.
The use of recycled glass improves the environmental balance. Glass cullet replaces virgin raw materials and requires less energy to be remelted than the original raw material mix. A higher proportion of high-quality recycled glass can therefore reduce raw material requirements, energy consumption and direct CO₂ emissions. At the same time, weight plays a role: glass packaging is comparatively heavy and thus increases the effort and CO₂ emissions involved in transport.
Aluminium: high initial input
Primary aluminium production begins with the mining of bauxite. This is first processed to produce aluminium oxide, known as alumina. The actual aluminium is then produced through electrolytic reduction and can be further processed into sheets, cans, foils, closures or other packaging formats. The production of the primary metal, in particular, requires large amounts of energy. The environmental impact therefore depends heavily on the source of electricity used for production.
At the same time, aluminium possesses properties that make it attractive for packaging. The material is highly malleable and allows for very thin and lightweight packaging with high barrier properties. In many applications, however, this requires an inner plastic coating.
Renewable fibres with complex processing
Paper and cardboard packaging is produced from virgin wood fibres, recycled paper or a combination of both sources. During the production process, the fibres are pulped and cleaned. In the case of recycled material, additional steps such as the removal of printing inks may be necessary. The highly water-laden fibre pulp is then formed into a web on the paper machine, pressed and dried. The drying process, in particular, requires energy.
The environmental impact also depends on the origin of the virgin fibres, the proportion of recycled fibres and the energy supply. Coatings, dyes and additives also play a role. They can fulfil important barrier functions, but at the same time make subsequent recycling more difficult.
PET and HDPE: purpose-manufactured raw materials
Conventional virgin plastic does, admittedly, originate predominantly from the same crude oil and natural gas value chain as petrol or kerosene. However, PET and HDPE are not worthless waste products from this process, but are specifically manufactured from petrochemical raw materials and basic chemicals. HDPE belongs to the polyethylene family and is produced through the polymerisation of ethylene. This is usually obtained from raw materials such as naphtha, ethane or liquefied petroleum gas. PET is produced from ethylene glycol and terephthalic acid. The starting materials are therefore specifically produced chemical building blocks. In addition to fossil sources, certain plastics can now also be based on renewable raw materials.
PET and HDPE combine high stability with low weight. This means that less packaging material is required and transport costs can be reduced. Nevertheless, the fossil-based origin of conventional virgin material remains a relevant factor.
Different materials, different levers
A look at the manufacturing process shows: Each material has its own strengths and challenges. A single characteristic such as ‘renewable’, ‘natural’ or ‘fossil-based’ is therefore not sufficient to assess its environmental impact. In the case of glass, the energy-intensive melting process plays a central role; for aluminium, it is primary production. In the case of paper, drying and functional coatings, as well as the fibres, influence the environmental balance. Conventional virgin PET and HDPE are predominantly based on fossil raw materials, but their stability and low weight enable highly material-efficient packaging solutions. Another important lever lies in the use of recycled materials. Mechanically recycled PET and HDPE can replace virgin material and thus reduce the demand for new fossil-based raw materials. Appropriate mechanical recycling processes are already widely established for both types of plastic.
This makes it clear that it is not the origin of a material alone that determines its environmental impact. What matters is how resource- and energy-efficiently it is turned into packaging – and whether the material used can subsequently be returned to the cycle.
Click here for Part 1, which has already been published: Why the life cycle matters
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