Beverage cartons / Production / From wood fibre to paperboard

From wood fibre to paperboard

Paperboard, the main material used in the beverage carton, is made from wood pulp, derived from trees such as spruce, pine birch and eucalyptus.

Paper mills, make pulp from wood chips. Some of the paperboard is bleached to create a white outer surface for printing. Today, all ACE members use safe bleaching processes (free of elementary chlorine or ‘ECF-free’) and the emissions from the paper mills are strictly controlled.

The pulp is then washed before paperboard production.  On the paperboard machine, wet pulp is combined into multiple layers to make the paperboard. A typical paperboard machine is 200-300 metres long and 5-8 metres wide, and operates at high speeds. Very sophisticated control processes maintain quality. The paperboard surface should be white and smooth to ensure quality printability; other key quality parameters are bending stiffness, thickness, and ability to be cut and folded.

Paperboard gives the carton strength and stability. There are different grades of paperboard, depending on the size of the carton, the distribution system (e.g. chilled or ambient) and the intended shelf-life of the product.

Responsible and traceable sourcing of wood

As virgin paperboard (from wood fibre rather than from recycled paper) is used for beverage cartons (to ensure quality, stiffness, and hygiene), ACE member companies have been working together to commit to source and trace wood from legal and acceptable sources.

Traceability is one of industry’s most important strategic mean to combat illegal logging and to avoid using unacceptable sources of wood. Traceability is independently verified according to ‘chain-of-custody’ standards set by the FSC (Forestry Stewardship Council) and/or the PEFC (Programme for the Endorsement of Forest Certification Schemes).

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• The industry’s voluntary commitment on traceability

Using and producing renewable energy

Paper mills which produce the board for beverage cartons are reducing greenhouse gas emissions by progressively replacing fossil fuels with bio-energy.

More than 80% of the total energy used is from bio-energy these days and some of the mills also distribute excess heat to the nearby communities (district heating), helping further to minimise fossil fuel consumption and CO2 emissions in their neighbourhoods. If this green energy was not generated and sold, it would have to be bought from non-renewable sources.The energy is generated from burning wood residues (bark, small branches, sawdust) and ‘black liquor’ (the hemicellulose- and lignine-containing residue from the pulping process).

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• How member companies save energy and use renewable energy

Water

Paper factories are called ‘mills’ because they were built along waters’ courses where the hydropower was the energy source (mill) and fluvial water was used in various phases of pulping and paper making. Today, most paper mills are still located next to major water sources.

High volumes of water are used in papermaking. At one stage of the paper processing, the dry content of the pulp is only 1%, the rest being water. However, just as the industry recycles carbon in the form of wood fibre in the packaging, the paper mills reuse water many times in a closed loop. And when water is ultimately discharged after purification, it is subject to very strict waste water discharge controls.

The carton conversion stage, however, uses much less water. Water is not used as an input into the ‘converting’ (manufacturing of beverage cartons from paperboard) process, only for cooling and cleaning purposes.