The paper recycling process
The recycling process: collection
The collection of used paper and board is the first step in the recycling process. There are different national and regional collection systems for paper. Papermakers usually buy their raw material for recycling from recovered paper merchants. These merchants may be owned by paper mills and be an integrated part of a mill company, or they may be an independent firm which specialises in particular grades or which perhaps operates in a smaller geographical area.
In Europe, a small but growing amount of waste paper is now being supplied by waste management companies, which are finding it economically advantageous to sort recovered paper for recycling. This is helping to reduce the amount of paper going for landfill.
Until recently, apart from old newspapers and magazines, most recovered paper came from industrial and commercial sources, because it was the easiest, cleanest and most economical to collect. As demand for recovered paper has grown, so additional sources, such as households, need to be tapped.
The collecting system in operation must be cost-effective and efficiently organised so that the necessary volumes and qualities of recovered paper can be obtained and appropriately recycled. The paper mills that depend on recovered paper must have assurance of a regular supply.
Paper for recycling has to be collected separately from other materials. It is important that it is kept separate from other waste as contaminated papers are not acceptable for recycling. If, in some cases, paper is collected together with other recyclable materials, such recovered paper must be specifically marked.
The requirements of the papermaker must also be taken into account: a packaging manufacturer can use mixed grades of recovered paper while a manufacturer of graphic paper can only use certain recovered paper grades.
The recycling process: pulping
Broadly speaking, the final production process for recycling paper is the same as the process used for paper made from virgin fibres but, as the recovered paper fibres have already been used, they also have to be sorted and cleaned. For certain paper (e.g. graphic paper and hygienic products) ink has to be removed from the recovered paper, i.e. the fibres have to be de-inked.
As a first step, recovered paper is sorted and graded then delivered to a paper mill. Having reached the paper mill, it is 'slushed' into pulp and large non-fibrous contaminants are removed (for example staples, plastic, glass etc.). The fibres are progressively cleaned and the resulting pulp is filtered and screened a number of times to make it suitable for papermaking.
The recycling process: de-inking
Before the recovered paper can be used to manufacture certain grades of paper the printing inks have to be removed to increase the whiteness and purity. The recovered paper is first dissolved in water and separated from the non-fibre impurities.
The fibres are then progressively cleaned in order to obtain the pulp and during this stage the ink is removed in a flotation process where air is blown into the solution. The ink adheres to bubbles of air and rises to the surface from where it is separated. After the ink is removed, the fibre may be bleached, usually with hydrogen peroxide.