SMALL-SCALE PAPERMAKING
Introduction
Paper making is a good example of how small industry can be developed to make use of local resources and cater for local markets while keeping capital investment down. This is especially so in countries like India where machinery and equipment is produced in-country. When considering papermaking, there are many factors to take into account in deciding on the scale, the type of product, the raw materials, the investment and the required skill levels. In addition, there are equally as many non-technical considerations such as environmental issues, marketing and competition, consumer expectations and economics. Together, all these issues will help you decide on the viability of the operation.
Figure 1: Range of handmade paper, Bangladesh. Zul / Practical Action.
Before starting a papermaking enterprise, it is necessary to examine what is currently available on the market and to consider whether it is possible to offer a product which will compete for quality and price. The papers available may be an imported product from the high technology industry. Unfortunately, such imports have conditioned the reactions of the consumers who now believe that writing paper must be ultra white and of a certain texture etc. In practice, it is very difficult for the average person to distinguish quit e large differences in the whiteness of papers except by direct comparison. Nevertheless, the larger buyers of paper often specify a certain 'brightness' number, without really understanding what it means. This alone can preclude a local product from the market place as it is frequently not possible to achieve quite such high standards in a small operation. It is therefore essential to consider consumer preferences at a very early stage. The price of the local product may need to be considerably lower to compensate for a (perceived) lower quality. The market size should also be considered and the proposed output of the operation along with the availability of adequate raw material on a regular basis. Together, these effectively dictate the technology to be employed and this in turn determines the cost of the venture. Having decided on a size for the operation, the next problem faced is that of finding suitable equipment. There is no difficulty for lager operations making 1000 tonnes of paper per day or more but for the 5 tonne per day plant it is more difficult to find equipment. There are producers of smaller paper production machinery and associated equipment in India. Hand papermaking less equipment. It has enjoyed a major revival over the years, using new and innovative approaches it can produce unique textures and qualities. In addition, the versatility of paper in its wet form has led artists to experiment with paper -making as an art medium, creating two- and three-dimensional images of textural richness and diversity.
It will be obvious from the above that the whole subject of papermaking is far more complex
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Small-scale papermaking
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than it would first appear. For the best chances of success, a lot of careful study is needed for starting. Since the subject is so complex and the options are many, no sizable commercial venture should be embarked upon without expert guidance from a specialist consultant experienced in small-scale operations.
Services
When considering purchasing or renting premises for setting up a pa per-making facility, care should be taken to ensure that there are adequate services provided at the premises, or that these services can be easily accessed. One of the main points to consider is the availability of an adequate water supply. The commercial processing of raw material through to finished paper can consume as much as 50 tonnes of water for each tonne of paper produced. If this quantity of water is not available, there is little point in pursuing the project further. Although efficiencies in water consumption are improving, there will always be a need for relatively large quantities of water during the paper making process. The next consideration is adequate power at the site. Papermaking is also an energy intensive industry, especially when the process is mechanised. This energy can come from a variety of sources such as electricity, wood, oil, gas or coal. This energy is used to provide much of the heat energy required. Crop residues, such as bagasse or rice husks can also be used as fuel. An electrical supply is required in most circumstances to power motors, pumps, lighting, etc. This can be supplied from the mains where the mains is accessible, from a diesel generator set, or from a renewable energy source (such as hydro-power or wind power). Steam raising for the drying process can be carried out using a variety of technologies; oil -fired boiler, steam engine, combined heat and power plants. Careful costing of the available options can bring considerable savings. The energy demand for processing of reclaimed paper is much less that for virgin wood. In order to understand what might or might not be possible in papermaking it is first necessary to have knowledge of the technicalities of the process. The basic process of making paper involves two stages: the breaking up of raw material (which contains cellulose* fibre) in water to form a pulp (i.e. a suspension of fibres*), and the formation of sheet paper by spreading this suspension on a porous surface, and drying, often under pressure. This Technical Brief only covers small-scale papermaking technologies for application in developing countries. For this purpose we will define scale in papermaking as shown in Table 1 below. Category Output (tonnes of paper per day – t.p.d.) Large scale More than 100 t.p.d. Medium scale Between 30 and 100 t.p.d. Small scale Less than 30 t.p.d., including hand-made paper Table 1: Definition of scale in papermaking
Source: Small-scale papermaking, ITDG Publishing.
Typically, a hand-made paper producer will manufacture only a few tonnes of paper per year often for a highly specialised market. Mechanised plants, on the other hand, only become economically viable when dealing with an output above several tonnes per day. In India, where paper making machinery is manufactured indigenously, and hence costs are kept lower, mechanised paper making on a small scale is very common. These mills provide higher levels of employment, not only in the mill, but amongst associated industries, such as waste paper collection and machinery manufacture. Smaller mills are more flexible in their acceptance of raw materials.
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The product range is also more flexible in small paper making plants, with the ability to cater for a variety of demands, but, sometimes, with a slightly lower quality than that of the larger plants. Types, characteristics and physical properties of paper Paper comes in an enormous variety of shapes, sizes, qualities, grades, colours and finishes. Some of the typical characteristics used to determine p aper quality are given here. The types of tests that will be carried out on a batch of new paper depend upon the use for the paper. Weight in grams per square metre (referred to as gsm or grammage) Thickness or calliper (measured in microns) Density or bulk (a function of the previous two qualities) Tensile strength Burst Folding Brightness / shade Porosity Smoothness / gloss Oil-resistance Moisture absorption Moisture content Optical properties (adjustable using mineral fillers)
The quality of paper is often controlled by the National Standards organisation in the country concerned. It is always worth consulting these Standards well in advance if contemplating setting up a paper manufacturing facility.
Delivery of raw materials
For economic production of paper there must be a secure supply of suitable raw material at a reasonable price. Fortunately, there are many fibres which are well suited to paper making. In tropical developing countries, where wood is often in short supply there are a number of other sources of fibre, often by-products of the agriculture or textile industries. It is important to ensure that there is sufficient storage capacity for the raw material. This is particularly important where seasonally available raw materials, such as straw or bagasse*, are used and a large supply will have to be stored for later use. Raw material The raw material for all papers is cellulose fibre which comes from a wide range of natural materials. The large scale producers rely almost entirely on fibre from timber although, especially in India, other materials such as bamboo, straws and grasses are also used. The cellulose fibre can also be extracted from such things as waste cotton rags, banana pseudostem, bagasse, - in fact almost anything which has grown naturally. However, the quality of fibres varies a great deal depending on the natural material from which it is collected. The quality, usually assessed according to the length of the individual fibres, is extremely important to the qualit y of the paper which can be made. A high proportion of long fibres is essential for reasonable paper quality, regardless of scale or method of production. Below are some examples. Raw Material Straw (e.g. from wheat, barley or rice) Bagasse* Maize stalks Source Between 5 and 10% of all straw which is produced is burned. From sugar cane after the sugar has been extracted. Remaining after maize harvest. Suitability Short fibred (1.5mm), it is often mixed with other pulp to provide a suitable pulp stock for a variety of uses. Slightly longer fibre than straw. Suitable for high quality writing and printing paper. The high moisture content and need for collection make maize stalks suitable only for
Figure 2: Mulberry branches used for paper making, Bangladesh. Photo: Zul /
Practical Action.
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Bamboo Cotton Rags (from cotton material) Flax Hemp and sisal Jute Water Hyacinth Jute and Water Hyacinth Mulberry Bark Jute and Hemp
Grown for use. Cuttings, lint and fluff from cotton mills. Collected A residue from the manufacture of linen. From old ropes and tow from ropemaking factories. From old sacks and hessian. Weed
very small-scale production. Properties similar to straw. Fibre length of 2.7mm, suitable for all types of paper making without addition of other fibre. Supply is often limited. Cotton is a high value fabric and is therefore only used for specialist papers. Has a fibre length of 25 32mm. Often require sorting and bleaching. Common writing paper. Long fibres make this material suitable for high quality paper. 6mm fibre length, processing similar to that of cotton. Jute does not bleach well and is therefore used for its strength rather than for high quality grades Paper not having adequate strength Unique textured paper Excellent, silky, transparent papers of different kinds A reasonable good quality paper.
Table 2: Raw materials commonly used for paper production Recycling waste paper Using waste paper is the easiest way into papermaking as all the difficult first stages have been done. There is no need for chemical digestion, bleaching and complex screening operations. The waste may only require repulping before being reformed as 'new' paper. Compared with producing a tonne of paper from virgin wood pulp, the production of one tonne of paper from discarded paper may use half as much energy and water. The clay originally added to the paper to make it glossy will help to separate the ink from the paper during recycling. There are limitations to recycling that need to be considered. Paper can be recycled only 5 to 8 times before the fibres become too short and weak to be reused. It is therefore essential to use as high a grade of waste as possible as the starting point. From both pulp quality and ink points of view, computer waste is a very useful raw material for the recycler. Old newspapers are commonly used to make tissue and cardboard, while magazines are often recycled into newsprint. Figure 3: Water Hyacinth used for paper making, Bangladesh. Photo:
Zul / Practical Action.
Waste paper will carry some form of printing which, if not Practical Action. removed, will cause the product to be discoloured. The process of removing the print, called de-inking, is often, not worthwhile for the small-scale operator, involving as it does, even more, expensive equipment. It is a better policy to concentrate on unprinted materials if these can be obtained. Alternatively, paper with as little print as possible should be selected. When t he final product is used for packaging it is sometimes acceptable to mask the discolouration due to ink by tinting the pulp to produce a coloured paper. One of the major parts of recycling is the collection, sorting, baling, and transportation of waste pap er. 4
Figure 4: Jute used for paper making, Bangladesh. Photo: Zul /
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The next step is re-pulping. Industrial production involves disintegrating the bails in a hydro pulper, where they are reduced to individual fibres. Chemicals are added so that ink particles, coatings and additives, and extremely small contaminants such as fillers start to separate from the paper. Depending on the required level of improvement, the pulp is sent through several stages, where heat, chemicals, and mechanical action may be used to further improve the pulp. Finally, the pulp mixture enters a flotation device, where calcium soap and other chemicals are added. Air bubbles in the mixture float the remaining ink and contaminants to the surface as a scum, where it is skimmed away. The pulp is sent to the stock preparation area, where it is treated and loaded into the flowbox* of a paper machine. From this point, the pulp is treated just the same as if it had been freshly made from any other raw material rather than recycled.
Papermaking
The process of making paper is based on wet cellulose fibres binding together in a random fashion when dried under restraint. The process of paper usually involves the initial separation of the cellulose fibres to form a wet pulp, some form of treatment, such as beating and refining, while in the pulped state, to enhance the quality of the final product, then forming of the sheet paper by hand moulding or by paper making machine, and drying. Some Figure 5: Women stripping mulberry and cutting jute further processing is often carried out for pulp, Bangladesh. Photo: Zul /Practical Action. before or during drying to acquire the desired finish. The process is similar, whatever the raw material (or mixture of raw materials), and at whatever scale of paper production, but the complexity of the technology involved will vary considerably. Small scale preparation of materials In a small scale operation the raw materials, such as rags, are sorted manually to remove buttons, plastic, synthetic fibres and other foreign materials. Then given shaken vigorous to remove the dust and dirt. The rags are sorted and chopped into small uniform sized pieces. Straw preparation requires the straw to be cleaned to remove dust and then cut into short lengths. Bagasse will have been reduced to a suitable size at the sugar mill, but the pith will need to be removed. Wood will be chipped to an appropriate size. Specialised equipment is required for this kind of preparation. The material will then usually be transported to the pulping area on a conveyor belt or by hand. Mulberry bark is prepared by cutting the branches into lengths measuring 6 to 8 inches. The bark is removed from the stem with a knife and the outer green / grey skin is removed from the bark. The bark is then beaten with a wooden hammer by placing it on a wooden block to obtain fibres. 5 Figure 6: Zohrabanu & Amina boiling mulberry branches for pulp. Bangladesh.
Photo: Zul / Practical Action.
Figure 7: Mulberry pulp. Bangladesh.
Photo: Zul / Practical Action.
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