About Paper making
Making paper depends on the simple fact that wet cellulose fibres bind together as they dry under pressure. Paper recycling simply reverses this process, making old fibres wet and agitating them so that they can be separated and recycled.
The basic papermaking process has not changed for the last 2000 years. Fibres soaked in water are drained on a fine wire screen and dried under pressure and heat.
However, a modern paper or board mill has streamlined the procedure and converts cellulose pulp in a continuous process which uses a multiplicity of rollers through which the web of steadily more stable paper is drawn on. The huge machine on which this takes place could be more than 300 metres long, have the height of a two storey building and run with a speed of 75 mph (120 km/h).
By far the most important source of cellulose is woodpulp, derived mainly from softwoods such as spruce and pine. But hardwoods like poplar or eucalyptus are also used. Trees are grown as a crop in many parts of the world, Scandinavia, America and Canada among the most renowned. Overall, more trees are planted than are cut down for paper making.
Paper manufacture also utilises trimmings from trees grown for structural timber. The claim that “recycling saves trees” is primarily emotional, relying on a mental picture of ancient forests and stately old specimens rather than the more accurate view of a tree crop from farmed softwood or hardwood.
The parallel concept, that recycling paper saves the threatened rain forests of the world, is also false, for this type of timber is not used to make paper. Campaigns aimed at saving rain forests can be better supported by avoiding the purchase of furniture and other household articles made from tropical hardwoods.
In the past, many other fibrous vegetable materials have been used to make paper, and to a limited extent this is still the case. These include certain grasses, stems and leaves like straw, esparto, sisal and bagasse (sugar cane fibre), as well as rags made from natural fibres such as cotton.
Woodpulp is made by reducing timber to small chips which are then treated chemically or by mechanical grinding to produce fibre. To make a high-strength paper, most of the lignin and other impurities have to be removed. This type of pulp, which is produced chemically, is often - confusingly - referred to as “woodfree”. Mechanical pulping, which is wholly satisfactory for less critical forms of paper - like newsprint - does not remove such a high proportion of the impurities and the product is often referred to as “woody”.
Worldwide, more than 163 million tonnes of new pulp is produced each year - more than 95% of it from wood. Over 95 million tonnes of recycled fibres are added to that in making nearly 260 million tonnes of new paper and board per year.
Typically around 30 million tonnes of paper products are contaminated or destroyed in use, and cannot be recovered. About 39% of the total is currently recycled, leaving another 120 million tonnes that could in theory be brought into the recycling chain.
In making the best use of resources, still greater consumer awareness could lead to demand for paper products that are appropriate to their purpose and are not of higher quality than is really necessary. Toilet tissue, for example, can contain lower grade recycled fibre and the market for this type of product is growing. In influencing paper and board making, as in other manufacturing industries, the impact of public demand can be very powerful.
Recycling does not only cut import bills. It can reduce water use by nearly 60% and energy consumption by 40%. Air pollution can be decreased by more than 70% and water pollution by almost 40%.
Progress in technology has enabled paper and board makers to make greater use of reclaimed paper, particularly with the increased ability to remove contaminants - such as staples and paper clips, glues and inks. De-inking techniques have made it possible to use old newspapers on a considerable scale to make fresh newsprint. A sequence of washing, cleaning and filtration also removes the very short fibres that would serve to weaken the new product. De-inked recycled fibre now accounts for up to 100% of the raw material used in the production of newsprint.
Unlike metals or glass, paper cannot be continuously recycled, because the fibres will gradually break down in the repeated pulping process. It will always be necessary to introduce virgin fibre somewhere into the overall production cycle. Rather than pursuing a goal of 100% recycled products, the greatest scope and overall environmental benefit may be in introducing the highest practicable proportion of recovered material in a wide range of papers, commensurate with end use performance demands.
Although technology can solve many problems of contamination of recyclable paper, the way in which paper and board products are designed can present new obstacles.
If paper is to be recycled it must be pulpable, and if it is laminated to plastic, for example, that cannot readily happen. Synthetic glues that are commonly used in binding books and magazines can create grave difficulties by causing a sticky residue in the paper-making plant. Some modern inks are actually formulated to resist dispersion in water.
Designing new products for easier recycling at the end of their first life can maximise recycling opportunities.
Last no least, used paper which cannot be recycled into new paper or made into alternative products still represents a valuable substitute fuel.