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Paper is very useful in most sectors of every economy and it is all made from wood fibre from our forests. Pulp is a soft, wet and shapeless mass of wood fibre which is an intermediate product in paper-making industry. In the making of different forms of pulp and paper, different ways are employed in the industries.

Paper is very useful in most sectors of every economy and it is all made from wood fibre from our forests. Pulp is a soft, wet and shapeless mass of wood fibre which is an intermediate product in paper-making industry. In the making of different forms of pulp and paper, different ways are employed in the industries.

The mechanical pulp is made by grinding of wood logs using grindstones. For a good result, the logs have to be steam treated at high pressure prior to grinding. The use of grindstones is no longer applicable in the modern paper mills. They instead use refiner plates made of metal disks. This separates wood fibres from each other for better paper refining.

There is the thermomechanical method which uses heat and mechanical application of force on wood. The bark is removed from wood logs first and the logs are cut into small chips. These are then pressed by an applied mechanical force to crush them. Heat and water vapor is evolved and this softens lignin which hold the fibres together and so they separate very easily. This is very hard and rigid since lignin is not removed in the process.

The process can also be a chemical reaction. The wood chips and chemicals are combined together in containers known as digesters. The natural glue is broken down leaving the cellulose fibres intact. Heat is applied to speed up the reaction. This is usually not a very rigid product since lignin is removed but its characteristics are changed by mixing it with mechanically refined pulp.

Manufacturers have put into use the four methods simultaneously. This is called chemithermomechanical process. It involves pretreatment of wood logs using sodium hydroxide, sodium carbonate or any other suitable chemical for that matter. The wood is then mechanically ground to separate the wood fibres. Chemical treatment is vital because it makes the whole process easy and fast. The product is generally hard and rigid.

There are also other methods of pulping apart from the four discussed above. They include recycled pulp, organosolv pulping and biological pulping. Recycled one is made from recycling of paper which has already been used. The organosolv process is the use of organic solvents at relatively high temperatures to break the lignin down. Biological pulping is more or less like chemical pulping.

In the production of white paper, bleaching is done. Drying process is done in different ways. The commonly used method is air drying which leaves 10% of moisture. This moisture content prevent binding together of the product which will make dispersion for further processing hard. Flash drying is also applied where the masses are pressed against a nylon mesh to remove up to 50% of moisture content. They are then passed down silos of 15m high with gas ejected hot air. The bales dried using this method are not as compact as those that are air dried.

The whole industrial process is manageable in order to prevent environmental degradation. The cutting of trees for the industries is controlled and also good forest management methods are put into play to ensure that the sources are renewed now and then. Chemical effluents from the industries are treated first to make them nontoxic for the environment.