European database for cartonboard and carton production, 2023

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where high purity and whiteness is important, it is necessary to remove the printing inks,
glues and other impurities.
After the recovered paper and board has been immersed in water, disintegrated and the
fibres dispersed, heat and/or dispersion agents are used to remove any sticky impurities
from the fibre surfaces. Then flotation techniques, screening and washing, and
sometimes additional bleaching, are used to remove the impurities.
For pulps from both primary fibres and recycled fibres, functional chemicals, fillers and
other pulps can be added to give the final paper the properties required.
Energy
Energy sources depend on the way pulp is made and the location of the mill. Where paper
for recycling is utilised as a fibre source, rejects from the recovered paper (plastics, etc)
may be incinerated with energy recovery on-site. Where pulp is produced from virgin
fibres, bark chips from debarking may be used as an internal energy source. Chemical
pulping also results in a by-product (black liquor) which is used as a significant internal
energy source. Finally, biogas from wastewater treatment may also be used as an internal
fuel source. For virgin cartonboard mills, internal fuels account for more than 50% of the
fuels consumed onsite, whereas for recycled cartonboard mills internal fuels account for
less than 1% of the fuels consumed onsite. Where internal fuel sources are not available
or are not sufficient to meet the full energy needs of the mill, external fuels will also be
consumed, including fossil fuels (mostly natural gas, but also heavy fuel oil, light fuel oil,
diesel oil, liquid petroleum gas, and in some cases coal or peat) and renewable fuels (e.g.,
bark, pitch oil).
Fuels consumed onsite can be used to produce both thermal energy and electricity. Some
mills are able to generate enough electricity to meet all of their needs, and may even be
net exporters of electricity, but most mills also purchased some of the electricity needs.
In this case, electricity may be purchased from the national grid, or specific electricity
product agreements (e.g., for electricity produced from renewables and/or zero carbon
electricity) may be in place.
Water
Water is an essential element for paper and board production. Water acts as a bond
between the fibres and in the production process it is needed for transporting, cleaning,
as a solvent, carrying energy in the form of steam and it is used in cooling process units.
Water is usually taken from a nearby surface source such as a lake or river. >95% of the
water used in the industry is cleaned and reused on site. All water is purified (usually at
a wastewater treatment facility operated by the mill) in accordance with European
regulations and standards before being returned to the environment.
Pulping and the paper machine
The fibre is mixed with water in large hydropulpers until a very fine suspension is
achieved. This is then cleaned to remove any contraries, refined to enhance strength and
then pumped to the cartonboard machine where the cartonboard is manufactured. In the
fibre preparation, before the board making, functional additives are used. The additives
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