Paper & Cardboard Recycling Processes


There is something in the recycling industry which is often referred to as ‘the black door’, and it means the recycling process that happens after the material is taken from the street or from businesses. Behind this ‘black door’, many technologically interesting things happen, with huge machines that rotate and chew and pump and sort and distribute.

National Recycling are here to tell you a little bit about the paper and cardboard recycling processes that go on behind this ‘black door’…

Mixed paper, which is collected with the cardboard, is sorted into quality or by colour. You can often tell if white paper is recycled by its colour. Bleach white often means it is virgin paper, egg shell white on a scale towards grey often indicates how many times it has been recycled. Paper can be recycled about seven times.

The paper is pulped, with magnets and filters pulling out unwanted objects like paperclips and staples. The pulping process means putting the paper in a tank of liquid, which is a mixture of water and solvents. In the pulp format, paper is very squishy and resembles mashed potato! Advanced technology is used to absorb and remove any ink from the paper, then it is cleaned and coloured as required, which involves a type of bleach to whiten the paper.

The pulp moves down a conveyor belt and is pressed to the remove water and large heated rollers bond the paper fibres together. As it passes down this belt and becomes paper once again, it is coiled into large amounts to be sent somewhere else for shaping and sizing.

In this format, it’s possible for the paper to be turned into printing paper, newspaper, toilet or kitchen roll or many other things.

Let’s move on to cardboard.

Cardboard is separated into at least two different types, which are quite easily distinguishable. Consider the type of card that your cereal boxes are made from; it is a single layer of card. Now consider the sort of box a large package might arrive in, this corrugated cardboard involves two layers of card with a layer of wavy card between. These three layers improve strength and allow for pockets of air to make the package weigh less and thus cost less on postage. There is a third type of cardboard called Tetrapack which is still finding its legs in the recycling industry.

The separated cardboard is pulped in a similar way to paper, except soft wood-chips are added to the cardboard pulp to help solidify the old mixture into a new bond. Like with the paper, alien materials are filtered out; with cardboard this is more likely to be tape and glue than paperclips. Inks and dyes are also removed whilst the cardboard is a pulp.

The pulp is pressed, heated and formed into versatile sheets that can go on to be made into new cardboard boxes. Often you will see ‘made with recycled content’ because the cardboard recycling process requires the input of some virgin materials for sufficient strength.