The Making of a Recycled Box for Cornflakes
Report from a day in the lab
Paper Raw Material in a Recycling Factory.
Recycled boxes contain unwanted substances. But how do these
substances get into the box and how are recycled boxes made?
Cardboard boxes made of recycled paper – a sensible
For environmental and cost-saving reasons over 70% of paper is recycled
today, from which, for example, cardboard boxes are made. In fact, 90 %
of cardboard boxes (for all purposes) are produced with the addition of
recycled paper . Many boxes used for food packaging are also made of
recycled paper, including those for Cornflakes.
Recycled boxes, however, also contain unwanted substances such as
newspaper ink or glue, which enter the recycling cycle and end up in
paper. Food packaging material made of recycled paper was analyzed on
a broad scale by CVUA Stuttgart in a joint project with her partners in
Dresden and Zurich (see article “Recycled Paper – Appropriate for Food
A cardboard box is cheap and has excellent properties. It is stable, it can
be stacked, it protects food from mechanical harm, and sees to it that the
Cornflakes keep their crunchy form. Much information can be provided on
the box, such as the contents, nutritional value, manufacturer, shelf life,
ADDRESS Schaflandstraße 3/2 70736 Fellbach E-MAIL Poststelle@cvuas.bwl.de
PHONE +49 711 3426 - 1234 INTERNET www.cvua-stuttgart.de
+49 711 3426 - 1727 (Diagnostics)
FAX +49 711 588176 +49 711 3426-1729 (Diagnostics)
Seite 2 von 5
The Production of Recycled Boxes for Food Packaging
Scrap paper is collected in the household. But also offices and especially
printing companies generate a lot of waste paper that is no longer needed
and is then purchased by recycling factories. At the factory the paper runs
over a conveyor belt and lands in large pulp kettles. There it is mixed with
water and made into pulp. The pulp is then pressed through a sieve to
separate out larger particles such as plastics.
Raw material separation
Grinding Deinking Air
Smoothing Drying Coating
Process of recycling scrap paper for food cartons.
The smaller contaminants such as paper clips or sand are separated out
by means of large centrifuges (centrifugal separation). The removal of
printing ink is sometimes achieved via deinking (flotation). For this
purpose air is blown into the paper mash from below. The printing ink
gathers together into a ball agglomerate encased in fine air bubbles and
Seite 3 von 5
rises to the surface. From there the deinking sludge is removed. In some
cases the paper mash will also be chemically bleached, thus making the
material significantly lighter in color.
Construction of a recycled box for food packaging.
How is a paper box made from the scrap paper pulp?
A Cornflakes box made of recycled paper consists not only of one layer,
but up to 8 different layers. Different qualities of basic raw material are
used for each layer. The whitest paper is used for the outer layer, which
will be later printed; the inner layers are born down with more pressure
and are therefore darker in color. When you tear a box open, you often
see grey recycling material in the inner layers; boxes made from virgin
material alone are yellowish or white (see Info Box).
In order to make the carton more stable, groundwood pulp is added. The
various layers are fed on top of each other into the carton machine,
where they are pressed and dried. Next, the carton is white-coated with
calcium carbonate and latex (coating), in order to seal off the pores and
to prepare the outer layer for printing. The up to 8 meter wide carton is
then rolled out on large drums (roller) or cut into meter lengths. Then the
carton is printed and varnished, folded together, and glued into the form of
a box. Finally, the cornflakes are packaged inside a plastic bag and put
into the box, which is then glued shut. I find the cornflakes on the
supermarket shelf and take them home with me.
Seite 4 von 5
Recycled or Virgin Fiber Carton?
If you tear open the side of a box you can often see the grey recycling material
inside the carton; in contrast, virgin fiber boxes are yellowish or white inside.
virgin fiber board
recycled fiber board
Recycled cartons: a possible, but not the only, source of
contamination for food
Advent calendar made from paperboard, with chocolate filling.
The question of where food contaminants come from is not always easy to
answer. Food packaging made from recycled paper can be a possible
source (see article “Recycled Paper – Appropriate for Food Packaging?”).
Nevertheless, other paths of contamination must also be taken into
account as seen in, for example, the problem with mineral oil in chocolate
advent calendars. Investigations made at the end of 2012 revealed that 23
of the 24 analyzed advent calendar cartons where mineral oil was
detected were actually made from virgin fiber cardboard . Thus, in
addition to analyzing recycled boxes, other sources of contamination must
also be examined, including paper processing aids, printing inks, plastic
inner trays, outer packaging, or the food itself, which could have been
contaminated due to the raw material used or during the production
Seite 5 von 5
process. Until the real source is found and the problem remedied it is often
a game of detective work. CVUA Stuttgart investigates food and its
packaging, thereby supporting the scientific work of elucidation and
elimination of contaminant sources.
Who wants to know more:
Recycled Paper – Appropriate for Food Packaging?
 Papier Kompass 2012, Verband Deutscher Papierfabriken (vdp)
 „Mineralöl in Schokolade aus Adventskalendern - Recyclingkarton
kann nicht die Ursache sein“, S. Schabel, TU Darmstadt,
Dr. Antje Harling.
Vorfreude auf Heiligabend – Nikolaus war schon, Tom Kleiner, Pixelio.de,
Dr. Antje Harling.