As shown in chapter 2, the EIA begins as soon as possible, once the first investigations are finished and the pre-feasibility study starts.
First step (Pre-environmental Impact Assessment)
The first step is to determine the types of processes to be chosen and the different potential sites to be studied. Following the financial and technical thinking throughout, the EIA becomes more precise at each phase, in order to propose the best processes and sites according to local resources and sensitivities.
Once the project is almost defined the EIA analyzes a small range of solutions which compares a few process variations and a few pre-selected sites. Sometimes there is only one site and only one process left.
Second step (detailed Environmental Impact Assessment)
The second step of the EIA begins by scoping and screening the main impacts to be studied. It is important to implement the “scoping” with local authorities and representatives of affected groups to avoid omitting potentially important impact. It is now appropriate to have the terms of reference of the EIA drawn up by a steering committee, in order to pinpoint the exact contents of the EIA and the best way to conduct it.
This part constitutes the first step of the EIA. It leads from the pre-feasibility study to a well defined project that can be shown to authorities and local representatives. This first step towards the project must be the result of a financial, technical and environmental analysis leading to the final project bringing together the best available technologies and the least sensitive sites. The environmental survey during this phase must analyze:
Due to the various negative repercussions of pulp and paper industries on man and the environment, it is not possible to set up such facilities anywhere. To be economically viable, the pre-selected sites must combine:
The pre-selection of the potential sites from an environmental point of view should be focused as shown in check-list 1. Both proposed sites for the plant and for raw material production must be studied.
Check-list 1: Pre-environmental site selection
| QUESTIONS | YES | NO |
| Is the water supply sufficient all year long ? | ||
| Is the water supply of good quality ? | ||
| Are there sufficient raw material resources in this area ? | ||
| Is a sustainable management of these resources possible ? | ||
| Are there resources sensitive to the proposed exploitation scheme ? | ||
| Are there threatened species in this area ? | ||
| Are there sensitive biotopes like rain forest, mangrove, coastal zone, wetland ? | ||
| Is the transport infrastructure sufficiently developed? | ||
| If no, is there negative impact linked with the transportation framework to be built ? | ||
| Is the energy supply assured ? | ||
| If no, will the energy supply have negative impact ? | ||
| Will the plant emissions have negative impact on the environment ? | ||
| Are there affected groups ? | ||
| Will the project destroy important man made patrimony ? | ||
| Does the project imply resettlements ? | ||
| If yes, are there sufficient land resources in the area to allow a correct resettlement ? | ||
| Are there particular risks attached with this area ? | ||
| Is there positive impact of the project in the area ? (to detail) | ||
| Other (to be mentioned) ? |
If the raw material is a by-product of agricultural production, like cereal straw, or of industrial process, such as sawmill residues, it is not necessary to emphasize in the EIA the impact of raw material production because it is linked to agricultural or industrial production.
On the other hand, crops cultivated to supply material to the pulp and paper industry and forestry exploitation are operations that may involve severe negative impact on man and the environment. Thus analysis of these operations must be included in the EIA document.
This analysis has to address all the potential repercussions of the project very precisely, like the destruction of rain forests, the pollution of rivers and subsurface water, the depletion of biodiversity, the cultural and social risks in affected communities.
It is very relevant for integrated forestry and pulpmill projects, where extensive reforestation plans are set up, to study the consequences of both deforestation and reforestation. Risks like biodiversity depletion, fires, and erosion are likely to occur and must be addressed.
Deforestation and reforestation usually necessitate an assessment of the impact on:
the remaining stands:
fire risks have to be considered both in the case of deforestation and reforestation particularly when using sensitive species like pines.
exotic species to be introduced:
the introduction of exotic species does not always work as well as expected. They can either be eliminated by local species or become weeds, spreading all around without any chance of further control.
water resources:
pollution can be generated by fuel leakage and the use of pesticides.
air and climate:
climate changes can affect both micro-climate (generally increasing temperature and wind speed, and diminishing evaporation) and global climate with, for instance, the greenhouse effect caused by deforestation.
soil:
in some cases, fast growing plantations (i.e.: eucalyptus) can gradually both deplete soil fertility and acidify it.
biodiversity:
wildlife often suffers from noise pollution and increased pressure from poaching.
workers safety:
during timber extraction and transportation accidents can occur affecting workers or population.
cultural impact:
cultural practices like burning can have severe repercussions in some forest areas made accessible by new roads.
economic impact:
pulp and paper projects are supposed to result in an improvement of the local economic situation. This positive impact has to balance out all negative aspects, in all potential sites.
At this stage it is most important to cross reference the possible impact of the project with the sensitivity of the site (see check-list 1). Meanwhile it is important to complete a special check-list for forestry management.
Check-list 2: Raw material production
| QUESTION | YES | NO |
| Does the project include a forestry management plan ? | ||
| If yes, is there negative impact on the remaining stands ? | ||
| Are there threatened endemic species in this area ? | ||
| Are exotic species supposed to be introduced ? | ||
| If yes, are there references on comparable introductions ? | ||
| Do these references indicate that such introductions have produced negative impact ? | ||
| Are those species sensitive to fire ? | ||
| Is the soil of this area sensible to erosion ? | ||
| Is this area a water catchment ? | ||
| Are there areas of cultural or religious interest for the local population ? | ||
| Are there medicinal plants in this area ? | ||
| Are those species threatened by the proposed exploitation/reforestation ? | ||
| Does this forest produce significant food supply to the local population ? | ||
| Is the project supposed to be profitable to local communities ? | ||
| Have these communities been involved in the project conception ? | ||
| Other (to detail) |
It is important to note here that the EIA is implemented before project construction. This implies that data will not be available on site. The EIA team must at this stage include a process specialist to predict the various emissions and performances of the proposed processes and procedures.
Generally, the choice between the main types of industrial processes tends to be made according to the paper quality to be produced rather than on environmental or financial considerations. Nevertheless once a main type of process is chosen (i.e., mechanical or chemical), many technologies are available to improve the performance of the process or to limit environmental issues. The role of the expert in charge of EIA, with the help of the process specialist(s), is more to input environmental considerations in the project definition than to propose technologies which are generally very sophisticated and hard to master for an environmental generalist.
Environmental issues are too complicated and interconnected to be solved one at a time. The limits of the “end of pipe” approach, commonly used during decades, are well-known and it is now necessary to use systematic approaches in order to introduce a more global conception of the environment and to address the source of the problems directly.
For the person conducting an EIA, this logical framework means that the sooner causes for concern are well understood, the better environmental issues are resolved. It is thus very important to put a strong emphasis on assessment before project implementation. This will prove not only more environmentally friendly but also more cost effective.
It is very important to note that technology is always evolving and, in the EIA team, it is the process specialist's role to propose the best available solution to any problem related to environmental considerations and human well-being. This chapter is mainly constructed to allow EIA authors to classify the project in comparison with international standards. The different tables given below provide simple data to help the EIA author.
Figure 8 : Simplified diagram of a typical pulp and paper process
Source: Environment Canada
The pulp and paper industry has made great progress in recent years. For example, a modern paper mill uses about 85% less water than it did 3 decades ago, reductions in Total Suspended Solids (TSS) and in five-days Biological Oxygen Demand (BOD5) have also been considerable. Table 1 shows process evolution and performances.
Table 1: Integrated kraft mill wastewater, TSS waste load and BOD5 waste load
| Technology | Waste water discharge (gal/ton) | TSS waste load (lb./ton) | BOD5 waste load (lb./ton) | |||
| Bleached | Unbleached | Bleached | Unbleached | Bleached | Unbleached | |
| 1964 Older | 110 000 | 90 000 | 200 | 170 | 200 | 160 |
| 1964 current | 45 000 | 27 000 | 170 | 130 | 120 | 90 |
| 1964 new | 25 000 | 16 000 | 90 | 80 | 90 | 80 |
| 1990 design | 16 000 | 8 000 | 50 | 45 | 60 | 50 |
| % reduction 64/90 | 85% | 91% | 75% | 73% | 70% | 69% |
Source: K Ferguson
It is also important to remember that 70% of the pollution in a pulp and paper mill is caused in the pulp mill (due to pulping and associated operations like screening, washing, thickening and bleaching) and that the remaining 30% happens in the paper mill.
Table 2 shows the evolution of TSS, BOD5, COD and OM (oxidizable matter) from 1970 to 1987 in pulp mills and paper mills. These data show the decreasing pollution over a 17 years' period at 3 or 7 years' intervals, depending on the observed parameter.
| Parameter | Pulp mill (non mechanical) | Paper mill | ||||
| 1970 | 1984 | 1987 | 1970 | 1984 | 1987 | |
| TSS | 42.1 | 14.7 | 11.1 | 29.7 | 5.4 | 4.3 |
| BOD5 | - | 16.3 | 13.2 | - | 3.7 | 3.3 |
| COD | - | 88.1 | 70.3 | - | 9.2 | 8.5 |
| OM | 227.2 | 40.2 | 33.2 | 16.0 | 5.5 | 5.0 |
Source: French Ministry of Environment. Enquête COPACEL
The water discharge pollution levels (before treatment) of different pulping processes are naturally variable. The Oxydizable Material (kg/t of pulp) can be a good indicator of this pollution. See Table 3.
Table 3: Oxydizable matter in water effluents of various processes.
| Process | Oxydizable material (kg/t of pulp) |
| Mechanical | 10 |
| Unbleached Kraft | 15 |
| Thermo-mechanical | 30 |
| Bleached Kraft | 50 |
| Chemi-thermo-mechanical | 50 |
| Semi chemical | 90 |
| Bisulphite | 110 |
Source: Centre Technique de l'Industrie des Papiers
Large quantities of raw material are necessary to ensure the supply of the facility. These stocks can either be stored in the plant yard or close to the production site until entering the process.
In-plant stocks can be hazardous due to odours, polluted water leakage, fire or breakdown, depending on the type of raw material used. Outside the plant, stocks can have similar effects and also be the focus of infestation, principally by parasites like insects.
All these potential issues have to be addressed by EIA authors and mitigating measures have to be proposed if necessary.
While some pulp mills are supplied with pre-treated material like chips or saw dust, raw material most commonly needs to be transformed before entering the pulping process. This preparation, for instance in the case of wood, begins with debarking (bark is removed mechanically or in debarking drums) followed by chipping. Later chips are screened to obtain a product of uniform suitable size and to remove contraries such as stones and metal.
These operations can be different for other raw materials, nevertheless they often generate noise and dust, and they sometimes need a substantial water supply and thus produce big quantities of wastewater. Table 4 compares various debarking processes. For non-wood raw materials, problems are quite different. A screening is first necessary to eliminate undesired materials like seeds, leaves and dirt, which can represent up to 3% of the incoming material. Dry cleaning is usually effected in straw mills, where dust emissions have to be controlled. Wastewater discharge from wet cleaning involves solving far more complex problems than for wood preparation.
Table 4: Comparison of debarking processes
| Parameter | Units | Wet drum | Dry drum | Hydraulic jet | Mech ring | Paprifer chip dbk |
| Effluent flow | m3/t | 3–20 | 0–5 | 5–15 | 0–2 | 0 |
| Suspended Solids(1) | kg/t | 15–50 | 0–10 (2) | 10–30 | 0–3 | 0 |
| BOD (1) | kg/t | 5–10 | 0–3 (2) | 1–4 | 0–1 | 0 |
| Toxicity | LC50 | <10% | (5) | <10% | (5) | 0 |
| Energy consumption (3) | k Wh/t | 20 | 21 | 21 | 3 | 60 |
| Dryness of bark (4) | % OD | 40–55 | 50–55 | 40–55 | 50–55 | 40–55 |
| Reported operating costs (3) | $/t | 2.15 | 2.15 | 1.15 | 0.60 | - |
| Residual bark softwood summer | % wt | 0.5–1 | 0.5–1 | 0.1–0.4 | 0.2–0.5 | 2 |
| Residual bark hardwood summer | % wt | 0.5–1 | 1–2 | - | - | 5 |
| Residual bark softwood winter | % wt | 0.5–1 | 1–2 | - | 0.5 | 2 |
| Residual bark hardwood winter | % wt | 0.5–1 | 1–4 | - | - | 5 |
Source: Environment Canada
Notes:
(1) Effluent data exclude BOD and SS from other sources in the plant
(2) Upper limits are due to use of flume to handle logs
(3) 1977 data from Environment Canada
(4) Lower limit reflecting difficulty of maintaining high efficiency in bark presses
(5) No data available: toxicity is probably low.
These data are typical for full scale installations, assuming that barker is suitable for the local wood supply.
Pulping can be carried out through various processes, which use mechanical, chemical or both mechanical and chemical ways to transform raw material into fibres. The pulp yield (defined as the weight of oven-dry wood fibres produced from unit weight of oven-dry wood) of these processes is very different as shown in Table 5. Mechanical pulping reduces the wood to macerated cellulosic fibres which are generally damaged and still carry non-cellulosic wood components. Due to this particularity, the yield of mechanical pulping is very high. Conversely, chemical pulping dissolves all non-cellulosic wood components in liquors; thus yields are lower than in mechanical pulping. Semi-chemical pulping process has intermediate yields.
| Pulping process | Yield |
| Unbleached Kraft | 50–55% |
| Bleached Kraft | 43–48% |
| Dissolving sulphite | 33–40% |
| Low yield sulphite | 46–55% |
| Medium yield sulphite | 55–65% |
| High yield sulphite | 65–80% |
| Chemi-thermo-mechanical pulp | 80–90% |
| Thermo-mechanical pulp | 91–95% |
| Stone groundwood | 94–96% |
Source: Environment Canada
Pulping in the above table covers the complete operation from raw material preparation to bleaching, and thus includes cleaning, washing and thickening operations.
Various mechanical pulping processes are in use and they generally present comparable results.
Stone Groundwood Pulping (SGW)
This is the oldest mechanical process where logs are forced into contact with a rotating grindstone in the presence of water. Groundwood pulp contains slivers of wood which have to be removed by coarse screening. If, as is commonly the case, rejects from coarse screening are not shredded and recovered into a refiner system, this can cause severe operating problems downstream and excessive discharge of suspended solids.
Refiner Mechanical Pulping (RMP)
This process requires two phases to transform chips into pulp. The first step reduces the chips to a coarse fibre and in the second, fibres are obtained. The advantage of this method is to allow usage of chips and sawdust but the paper quality obtained is not as good as for other process.
Thermo-Mechanical Pulping (TMP)
Thermo-mechanical pulping is an improvement of refiner pulping process (RMP) but three steps are necessary to transform chips into pulp. First, chips are softened by pre-steaming (3 minutes at 120°C). Second, they are defibered under pressure (150–210 kPa). The last step is the same as in refiner pulping. The main advantage of TMP is to produce good quality pulp. The main problem is that it requires 30 to 50% more energy than the stone groundwood method to reach the same level of freeness.
Mechanical processes produce effluents, gaseous emissions and solid wastes. In TMP, the cleaner reject stream can represent 1% of pulp production (mostly composed by fibres, dirt and sand). Without a recycling system, the chip washer rejects about 5 kg/t of pulp produced. On the other hand, there is an extremely high consumption of whitewater (from 20 to 100 m3/t pulp produced) and this flow can carry, depending on the type of process, from 50 to 150 mg of fibre per litre.
Suspended solids can be discharged accidentally. Common values vary from 7 to 50 kg/t pulp. BOD loads levels and toxicity decrease as the yield increases. (see Table 6).
Gaseous emissions are mainly composed of steam. The amount of solid wastes produced at all stages of the process can be from 15 to 30 kg/t.
| Process Parameter | Stone groundwood pulping (SGW) | Refiner mechanical pulping (RMP) | Thermo-mechanical pulping (TMP) |
| Dissolved organic substances (%) | 1–2 | 2 | 2–5 |
| BOD (kg/t) | 10–22 | 12–25 | 10–30 |
| COD (kg/t) | 22–50 | 23–55 | 22–60 |
| Suspended solids (kg/t) | 10–50 | 10–50 | 10–50 |
Source: UNEP
For these methods, pulps can be processed like TMP with the addition of a chemical pre-treatment, commonly with sodium sulphite or by a quick cooking followed by a mechanical treatment. Semi-chemical pulping was first developed in order to use a larger range of hardwood species. The yields of such methods vary from 60 to 80%.
Principal methods are:
Chemi-Thermo-Mechanical Pulping (CTMP). Generally the process involves the use of sodium sulphite. The pulp quality is better but effluents contain heavy loads of organic material.
Neutral Sulphite Semichemical Pulping (NSSP). The main environmental outcome of this method is the treatment of the spent cooking liquor which contains organic acids.
Kraft Semichemical pulping (KSC). Semichemical pulping is always used in an integrated mill. Main typical effluents are lost fibres from the press (0.1 kg/t pulp) and 15% dissolved solids with a BOD of approximately 40 kg/t. Gaseous emissions are mainly SO2.
Contrary to the processes described above, chemical pulping mainly uses chemical energy to separate fibres from raw material. Generally, more than 90% of the lignin is removed from the wood, resulting in lower pulping yields (from 40 to 55%). There are two principal pulping processes : acid (sulphite) or alkaline (kraft).
Kraft Pulping (KP). This group of processes is one of the most developed world-wide. Chemical agents used to dissolve lignin and separate fibres are Na2S and NaOH (known as white liquor). Nowadays most pulping installations use continuous digesters. Diffusion washing allows the extraction of most of the chemicals used after cooking. The spent cooking liquors (black liquor) are regenerated while energy is recovered from the organic residue to produce steam. Nevertheless, soda losses occur with the sodium sulphate remaining with the pulp leaving this process (expressed as kg Na2SO4/ODt), these liquors will react further with the chlorine of bleaching operations and produce chlorinated lignin. Pulp at this stage also contains organic materials which can represent up to 25 kg BOD/t pulp. Some components of these materials can be toxic like resin acids and large organic molecules. Gaseous emissions from the digester can contain up to 6 kg turpentine/t pulp and reduced sulphur (TRS) which gives off unpleasant odours. Failure in the knot recovery system can produce solid wastes which cannot be burnt because of their sodium impregnation. Large quantities of water are also necessary for washing, and this must be precisely assessed in the EIA.
High Yield Sulphite Pulping (HYSP). Derived from basic sulphite pulping, this variation involves less steam pollution. It associates chips cooking and the use of a refiner like in mechanical processes. The raw acid is SO2 dissolved in water, generally mixed with combined SO2. The liquor pH varies from 2 to 5. Delignification is made by sulphonation and hydrolysis which lead to lignosulphonates production. By-products of typical sulphite cook are shown in Table 7 and characteristics of ultra high yield sulphite spruce processes in Table 8.
Table 7: By-products of a typical sulphite cook
| Compound | Origin | Quantity (kg/t pulp) |
| Methanol | Methoxyl groups of the glucoronoxylan | 7–10 |
| Acetic acid | Acetyl groups of the xylan | 30–90 |
| Formic acid | Bisulphite oxidation of formaldehyde | 0.5–1 |
| Formaldehyde | Hydroxymethyl groups of lignin | 2–6 |
| Methyl Glyoxal | Degradation of hexoses | 5–6 |
| Furfural | Dehydration of pentoses | 5–6 |
| Sugarsulphonic and aldolic acids | Bisulphite substitution and oxidation of sugars | 150–200 |
| Sugars | Hemicellulose and cellulose | 200–400 |
| Cyneme | Bisulphite oxidation of terpenes | 0.3–1 |
| Lignosulphates | Lignin | 600–800 |
Source: S.A.Rydholm
Table 8: Characteristics of ultra high yield sulphite spruce pulps for various processes
| Process Parameter | Consolidated Bathurst system | CIP process (SCMP) | Price Abitibi process | Opco process | Typical TMP process |
| Na2SO3, on wood (%) | 6 | 4–7 | 4 | 7–12 | 0 |
| pH | 4.5 | 9.5 | 5 | 4.5–9.5 | 7 |
| Reaction temperature(°C) | 147 | 150 | 100 | 135–170 | 135 |
| Reaction time (h) | 4 | 0.5 | 0.5 | 0.5 | 0.05 |
| Yield on wood | 80–85 | 88 | 94 | 90 | 95 |
| Refiner energy(MWh/t) | 0.6 | 1.8 | 2.2 | 1.8 | 2.7 |
| Freeness (CSF) | 600 | 300 | 100 | 187 | 125 |
| Effluent BOD5 (Kg/t) | 100 | 80 | 20 | 50 | 20 |
Source : Environment Canada
Processes for transforming these raw materials are generally similar to those used to deal with wood. Table 9 shows the main constituents of some non-wood fibrous raw material compared to wood. Some specificities of non-wood material sometimes involve adaptations of the standard processes, especially for handling and initial preparation.
Table 9 : Concentrations of important chemical constituents in various fibre sources
| Component Material | Cellulose (%) | Pentosan (%) | Lignin (%) | Ash (%) | Silica (%) |
| Softwoods | 40–45 | 7–14 | 20–35 | 0.3 | 0.006 |
| Hardwoods | 40–45 | 19–26 | 20–25 | 0.4–0.8 | |
| Cotton Linters | 80–85 | 3 | 1–1.5 | ||
| Flax | 70–80 | 0.7–1.3 | |||
| Hemp | 65–75 | 1.0 | |||
| Jute | 60–65 | 0.7 | |||
| Rice straw | 25–35 | 25 | 12 | 14–18 | 6–8 |
| Cereal straw | 35–50 | 25–30 | 15–20 | 6–8 | 2.5 |
| Bamboo | 35–55 | 16–30 | 22–30 | 1–5 | |
| Esparto | 50 | 27–32 | 17–19 | 3 | |
| Bagasse | 30–40 | 25–32 | 18–20 | 2 | 1.5–2 |
Source: World Bank
The most commonly used non-wood materials are cereal straw, rice straw, bamboo and bagasse. Two processes, soda and sulphate are widely developed. They produce paper of similar qualities. Non-wood pulp is considerably more difficult to wash than wood pulp, thus washing requires 25 to 30% more water than for wood. Chemical losses are more important than those of wood mills (2 to 5 times more) as BOD discharges and solids suspended in liquors are less important.
Recycled paper is becoming a major source of raw material world-wide. If, considered from a civic point of view, it seems to be an excellent occasion to preserve natural fibre stocks, it is not so evident from an environmental point of view. The preparation of recycled paper requires particular treatments which can produce polluted water and highly toxic solid wastes, difficult to eliminate.
The main problem to solve, when starting pulping operations, is to remove contaminants such as wires, staples, plastic and strings. Once the raw material is purified, de-inking is usually necessary. Two ways of achieving this are available at base: flotation de-inking and washing de-inking.
The main advantages of a flotation system are: high yield (85 to 95%), lower water consumption than in washing de-inking, simple implementation of a closed water circuit, since the process inorganic fillers are not removed. On the contrary, washing de-inking has lower yield, larger water consumption and generates larger volumes of contaminated effluent, since process inorganic fillers are removed. Due to its advantages the flotation system has become predominant. Table 10 shows the main characteristics of water consumption and pollutant loads for both processes.
| Parameter | Water consumption (m3/t) | BOD7 (Kg/t) | COD (Kg/t) | TDS (Kg/t) | ||
| Process | Total amount | Dissolved amount | Total amount | Dissolved amount | ||
| Mechanical treatment | 1 | 15 | 15 | 40 | 40 | NA |
| De-inking by flotation | 10 | 40 | 25 | 140 | 55 | 100 |
| De-inking by washing | 90 | 50 | 30 | 190 | 65 | 130 |
Source: UNEP
Table 11: shows the typical newsprint pulp and effluent characteristics of the main processes described in this brochure.
Table 11 : Typical newsprint pulp and effluent characteristics
Process Parameter | SGW | PGW | RMP | TMP | CTMP | HYS | SBK |
| Freeness (ml CSF) | 100 | 100 | 100 | 100 | 350 | 500 | 500 |
| Shive contents (%) | 1.6 | 1.4 | 1.2 | 0.4 | 0.3 | 0.3 | |
| Bauer McNett + 30 (%) | 15 | 23 | 25 | 37 | 40 | - | 86 |
| Bauer McNett 30–200 (%) | 55 | 55 | 52 | 39 | 35 | - | 12 |
| Bauer McNett -200 (%) | 30 | 22 | 23 | 24 | 25 | - | 645 |
| Breaking length | 3000 | 3600 | 3600 | 3900 | 5000 | 6000 | 10000 |
| Tear index (mN.M2/g) | 3.5 | 4.2 | 6.5 | 8 | - | - | 10.6 |
| Sulphur dioxide | 0 | 0 | 0 | 0 | 2.5 | 5 | |
| Specific energy (Gj/t) | 5 | 5 | 7 | 7 | 5 | 2.7 | |
| Yield (%) | 96 | 96 | 95 | 93 | 88 | 80 | 50 |
| BOD Kg/t | 7–15 | 10–15 | 10–25 | 10–35 | 70 | 130 | 250 |
Source: Environment Canada
Pulp products coming from mechanical or chemical pulping processes are from brown to beige depending on the raw material and process used. At this stage, pulp can be manufactured to go into the fabrication of products such as newsprint, boxes, packaging, etc. To produce white paper, bleaching is necessary. This operation combines removal and alteration of dark products included into the pulp. The bleaching operations sequence widely depends on the type of pulp to be bleached and the end product to be produced.
The result of bleaching is commonly measured on a brightness scale. The two major reflectance photometers in use are the General Electric Brightness Meter (GE) and the Elrepho Photoelectric Reflectance Photometer. There are some discrepancies in value between these two systems but they are generally very limited.
The main objective in mechanical pulping is to bleach the pulp without letting lignin become soluble. Hydrosulphites are the agents most frequently used, but zinc hydrosulphites are considered more and more unacceptable. Peroxides can also be used but are more expensive. Table 12 shows bleaching processes for mechanical pulp and their efficiency. The yield from mechanical pulp bleaching can be over 99%, usually between 95 and 99%. Dissolved substances are mainly organic and increase BOD in the mill effluents.
Table 12 : Bleaching processes for mechanical pulps
| Bleaching process | Usual method of application | Brightness increase (GE Units) |
| Reducing | ||
| Sodium bisulphite | Applied at grinders or to chips before refining | 1–4 |
| Sodium hydrosulphite | Added to pulp before entering tower or storage chest | 3–6 |
| Zinc hydrosulphite | Not environmentally acceptable | |
| Sodium borohydride | Not used commercially | |
| SO2 Borol | Added in sequence to pulp before storage chest | 10 |
| Oxidizing | ||
| Calcium hypochlorite | Limited to hardwoods, added ahead of storage chest | 10–12 |
| Sodium hypochlorite | ||
| Hydrogen peroxide | Usually in tower process, sometime on wet machine | 10–14 |
| Sodium peroxide | Not used commercially | 10 |
| Peracetic acid | ||
| Combined | ||
| Peroxide-hydrosulphite | Tower process | 12–18 |
Source: Environment Canada
While chemical pulping is first of all a delignification process, chemical pulp bleaching is often the continuation of this operation. Chemical pulping is mainly achieved by kraft and sulphite processes. Bleaching kraft pulp is much harder than bleaching sulphite pulp because of the initial colour of the pulp; the brightness of kraft pulp is about 20 while that of sulphite pulp is almost 60.
Bleaching is mostly conducted with a succession of chlorination, alkaline extraction and oxidation. One cycle is usually sufficient to raise the brightness of sulphite pulps to 90. For kraft pulps 2 or 3 cycles are still necessary.
Effluents from bleaching operations are the main source of colouring agents and often very toxic substances, chlorinated organic compounds can represent 3 to 8 kg/t pulp, in some cases dioxin can be discharged (this is discussed in the next chapter). Table 13 shows the sources of bleach plant effluent colours.
Raw material Stage | Softwood (kg/t pulp) | Hardwood (kg/t pulp) |
| Chlorination | 50 | 26 |
| Caustic extraction | 226 | 78 |
| Chlorine dioxide | 11 | 6 |
| 2nd Caustic extraction | 6 | 4 |
| 2nd Chlorine dioxide | 1 | 1 |
Source: Environment Canada
Some variations in the conventional process have been developed to try to reduce bleach plant effluents toxicity.
Displacement bleaching. This method does not change the effluent characteristics radically, it mainly allows a reduction of effluent volume and thus facilitates its management.
Oxygen bleaching. This method replaces the first chlorination and caustic extraction by oxygenation in an alkaline medium. The main advantage of this is to concentrate in the oxygen filtrate BOD, toxicity and colour which can be recycled in a chemical recovery system to allow the incineration of organic compounds. Reduction in BOD, COD and colour can reach 40 to 60%.
Alkali-oxygen extraction. The addition of a little oxygen at the caustic extraction stage makes it possible to reduce the input of chlorine and thus simplifies downstream effluent treatments.
Table 14 shows the characteristics of chemicals used in bleaching.
Table 14 : Chemicals used in bleaching
| Element | Form | Function | Advantages | Disadvantages |
| Oxidants | ||||
| Chlorine | Gas | Oxidize and chlorinate lignin | Effective, economical delignification and good particle bleaching | Can cause loss of pulp strength if used improperly |
| Oxygen | Gas used with NaOH solution | Oxidize and solubilize lignin | Low chemical cost, provides chlorine-free effluents for recovery | Used in large amounts requires expensive equipment, can cause loss of pulp strength |
| Hypochlorite | Ca(OCl) or NaOCl solution 40g/l | Oxidize, brighten and solubilize lignin | Easy to make and use, good particle bleaching | Can cause loss of pulp strength if used improperly expensive |
| Chlorine dioxide | 7 to 10g/l ClO2 solution in water | 1 Oxidize, brighten and solubilize lignin 1 (In small amounts with Cl2) protect against degradation of pulp | Achieves high brightness without pulp degradation, good particle bleaching | Expensive, must be made on site |
| Hydrogen peroxide | 2 to 5% solution | Oxidize and brighten lignin in chemical acid high yield pulp | Easy to use, low capital cost | Expensive, poor particle bleaching |
| Ozone | Gas | Oxidize, brighten and solubilize lignin | Effective, provides chloride free effluents for recovery | Expensive, degrades pulp, poor particle bleaching |
| Reductants | ||||
| Hydrosulphite | Solution | Reduce and brighten lignin in high yield pulps | Easy to use, low capital cost | Decomposes readily limited brightness gain |
| Alkali | 5 to 10 NaOH solution | Hydrolyze chlorolignin and solubilize lignin | Effective and economical | Darkens pulps |
Source: D W Reeve
Dioxin and furans are toxic chemicals that contain chlorine and are trace elements found after the bleaching stage. Dioxin found in paper and in effluents belongs to several groups: tetrachlorodibenzo-p-dioxin (TCDD), octachlorodibenzo-p-dioxin (OCDD), and tetrachlorodibenzo-furan (TCDF). Dioxin is produced in the pulp mill during the bleaching operation. At this stage the quantity of chlorine entering the process is directly linked with the dioxin production. Consequently solutions to reduce dioxin production are to try and replace chlorine by chlorine dioxide in the bleach plant and by oxygen for delignification.
Technologies available today seem to bring satisfactory solutions to deal with that problem. The EIA authors must take care of that particular point.
As reported in this chapter, about 70% of the pollution originates in the pulp mill and the balance, 30%, in the paper mill; nevertheless pollution can still occur at this stage and must be addressed in the EIA.
Papermaking is generally divided into four main operations: stock preparation, sheet formation, drying and finishing. These operations involve the use of large amounts of water, chemicals, additives and fillers depending on the type of paper to be produced.
Water is the main concern at this stage, since pulp enters the stock preparation plant at a consistency varying from 3 to 12%, while paper at the end of the process will have 10 percent moisture content. For each ton of paper produced, 7 to 30 tons of water have to be discharged. Table 15 shows water consumption and pollution for a range of paper qualities.
Table 15 : Water consumption and discharges of suspended solids and BOD7 in modern paper mills
| Parameter Type of paper | Water consumption (m3/t) | Suspended solids (kg/t) | BOD (kg/t) |
| Newsprint | 20–30 | 8–20 | 2–4 |
| Magazine paper | 20–30 | 10–20 | 2–4 |
| Wood free printing paper | 10–20 | 12–25 | 3–6 |
| Kraft paper | 10–20 | 8–15 | 1–3 |
| Folding boxboard | 20–30 | 2–8 | 2–5 |
| Food board | 20–40 | 2–8 | 2–5 |
| Corrugating medium | 10–20 | 10–25 | 1–3 |
Source: UNEP
The toxicity of some additives also has to be addressed, particularly heavy metals like mercury. Conversely, there are no environmentally significant gaseous emissions since steam is non toxic but very visible.
Paper manufacturing is energy intensive. Three quarter ton of oil equivalent (toe) are necessary to product one ton of paper in developed countries and from one to two toe (sometimes more) in developing countries, and only 50% of this energy can be self-generated by incineration of in-plant organic wastes. Energy is a major cost factor for this type of production. In some cases energy cost can exceed that of raw material. Vast improvements, brought about by increasing energy costs, have been achieved in the past decades. Table 16 shows some data on this progression.
| Process | Before Energy-Efficiency Improvement | After Energy-Efficiency Improvement | ||||||||||
| BK Pulp | Linerboard | Newsprint | BK Pulp | Linerboard | Newsprint | |||||||
| Heat | Power | Heat | Power | Heat | Power | Heat | Power | Heat | Power | Heat | Power | |
| Wood preparation | 0.1 | 65 | 0.1 | 55 | 0.1 | 45 | 0.1 | 60 | 0.1 | 50 | 0.1 | 45 |
| Pulping and washing | 3.5 | 120 | 3.0 | 210 | - | 1710 | 2.8 | 115 | 2.4 | 200 | - | 1625 |
| Bleaching | 5.0 | 190 | - | - | - | - | 2.2 | 150 | - | - | - | - |
| Pulp drying | 3.6 | 160 | - | - | - | - | 2.5 | 150 | - | - | - | - |
| Chemical recovery | 5.5 | 75 | 4.2 | 65 | - | - | 4.1 | 70 | 3.3 | 60 | - | - |
| Stock preparation | - | - | - | 240 | - | 100 | - | - | - | 230 | - | 95 |
| Paper machines | - | - | 6.5 | 190 | 5.8 | 250 | - | - | 4.6 | 180 | 4.1 | 240 |
| Miscellaneous | 1.1 | 130 | 1.2 | 140 | 1.0 | 100 | 0.8 | 125 | 0.9 | 135 | 0.8 | 95 |
| TOTAL | 18.5 | 740 | 15.2 | 900 | 6.9 | 2205 | 12.5 | 700 | 11.3 | 855 | 5.0 | 2100 |
Source: World Bank
It is generally agreed that small plants have a higher energy consumption than large ones, and that a plant working under capacity results in an over-consumption of energy.
Check-list 3 : Impacts of industrial process during pre-EIA phase
| QUESTION | YES | NO |
| Are the standards proposed by the investor in compliance with new mills performances ? | ||
| Is the estimated water consumption in compliance with new mills performances ? | ||
| Is the water from raw material preparation recycled ? | ||
| Are the wastes from raw material preparation valorized ? | ||
| Does the future plant include in plant processes to lower noxious emissions ? | ||
| Does the future plant include out plant processes to lower noxious emissions ? | ||
| Will the wastewater emissions be in compliance with national standards ? | ||
| Will the wastewater emissions be in compliance with international standards ? | ||
| Will the gaseous emissions be in compliance with national standards ? | ||
| Will the gaseous emissions be in compliance with international standards ? | ||
| Is the composition of solid wastes characterized ? | ||
| Are the treatments of those wastes studied in the project ? | ||
| Does the future plant include chemical recovery ? | ||
| If yes, are the performances of this process in compliance with standard data ? | ||
| Does the bleaching phase include non chlorine processes ? | ||
| Does the bleaching phase produce dioxins or furans ? | ||
| Are the energy performances in compliance with new mills performances ? | ||
| Is there a training programme for plant personnel in the project ? | ||
| Is a monitoring programme included in the project conception ? | ||
| Are there particular risks attached with the proposed technologies ? | ||
| If yes, is there a detailed study of those risks ? | ||
| Is it proposed to establish the base of an Emergency Response Plan in the EIA ? | ||
| Are the risks involved by the plant cross referenced with site sensitivity ? | ||
| Others (to detail) |
In most cases, transport of raw materials, general supplies and final products causes an increase in traffic around the facilities. Transportation may have repercussions, hence the need to consider the five key activities concerned: planning transport development, siting transport facilities, the construction of transport infrastructure, maintenance and operation of transport infrastructure and the use of transport infrastructure and vehicle maintenance.
Planning transport development
If the creation of the pulp mill involves important changes in traffic conditions, the EIA must study the transportation alternatives both for the siting of transport facilities and for the modes of transportation. It is important to compare at this stage the different possibilities of transportation (road, rail or shipping) and to choose the least expensive in terms of investment, maintenance, environment and security. A matrix analysis can be relevant in evaluating each possibility.
Siting transport facilities
Roads, railways and harbours are infrastructures which generally need their own EIA. The pulp mill EIA must nevertheless study this problem and propose a global solution for the plant services which truly respects the environment. Any change in the road capacity also has to be seriously addressed, mainly for affected communities.
Construction of transport infrastructures
The construction of infrastructures can result in negative consequences like deforestation, destruction of ecosystems, foreclosure of other land uses, drainage modifications, erosion, landslides, deterioration of landscape and cultural sites, and interference with the movements of local residents. These impacts can appear not only on the construction site itself but also at quarries, borrow pits, material storage sites, and petroleum product storage areas serving the construction project. Certain periods of the year, in connection with climate (rainy season, frost…), are inappropriate for several working activities, in particular earth moving and piling. The construction of infrastructures can lead to employment opportunities for local communities and thus have a positive impact.
Maintenance and operation of transport infrastructures
Infrastructures must be maintained in good repair to ensure the safety of users. When possible, all equipment for collecting accidental spills of oil products, acid or alkaline products, has to be installed in sensitive areas.
Use of transport infrastructures and vehicle maintenance
The installation must have dimensions allowing for heavy traffic. Trucks must be maintained in good repair to avoid leakage of oil products, excessive noise, poor fuel efficiency, road accidents…
Check-list 4 : Impacts of transportation
| QUESTION | YES | NO |
| Does the project involve important changes in transport network ? | ||
| Does the project involve important changes in traffic conditions ? | ||
| Have the alternatives : road/rail/shipping been studied in the project ? | ||
| Have the alternative routes been studied precisely in the project ? | ||
| Is there public financing involved in infrastructure construction ? | ||
| Is there investor financing involved in infrastructure maintenance ? | ||
| Is there a training plan for drivers included in the project ? | ||
| Is there a precise study on fuel storage, risks, transports, etc. ? | ||
| Are there significant communities affected by transportation issues ? | ||
| Are there special facilities proposed to protect communities from transports issues ? | ||
| Are there special facilities proposed to protect the environment from transports issues ? | ||
| Others (to detail) |
Once the different sites are pre-selected and a comparative analysis effected, and once the best technologies available have been selected to remedy possible environmental problems, the project is well defined and can be presented to the authorities and the affected populations.
The definition of the project represents extensive studies and work. This aspect must be valorized at this stage of the EIA to explain as precisely as possible the reasons which have led to advocate the project as it stands. Matrix explanation of why each site, resource, process, infrastructure, have been chosen over others can help to justify the project.
Depending on the authorities' requirements, the owners' choice or other considerations, the EIA plan can vary from case to case. Some EIAs study the different alternatives right to the end of the assessment and leave the final decision to the authorities, some others, as presented before, define the best project in the best site and then propose to study more precisely its environmental and social impacts. There are no standard best solutions, each case must be treated as a particular case where the best solution has to be defined by the steering committee.
Chapter 3.2 showed that great advances in raw material, energy and water supply have been accomplished during the past decades. New technologies and processes have also led to a decrease in pollutant emissions and thus to an improvement in environmental protection. The role of the EIA author is to assist the investor's team in order to define together what is possible while setting up a viable project which does not have uncontrolled negative impact on the environment and communities.
