Water Consumption Reduction Strategies in Recycled Paper Production Companies in Iran

Abstract

A close relation exist between Forest products industries and water cycle. Water as a natural resource is assumed to be a necessary and vital element in pulp and paper manufacturing and power generation in the related power plants. The objective of the current study is to determine the main factors affecting the water consumption in recycled paper manufacturing companies using analytical hierarchy process (AHP). Several questionnaires and related tables were forwarded to selected recycled paper manufacturing companies to evaluate the water reduction criteria in different sectors including manufacturing process, final product, raw material, human resources, costs and expenditures, environmental regulations and technical modifications. results were analyzed by Expert Choice 2000 software. The results indicated that 'final product" criterion was ranked first following by manufacturing process, human resources, costs and expenditures, environmental regulations and technical modifications, respectively. Also among alternatives, final product, cooling water network, and water storage tanks were categorized in the first three priorities. The specified priorities would assist the managers and production experts to achieve the optimized water consumption with minimum possible cost.

Keywords

• Analytical Hierarchy Process
• Water Consumption Reduction
• Pulp and

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Paper is a network of fibers and chemicals affecting its properties and quality. Large amount of water and energy in form of steam and electricity other than the raw B R&S\ULJKW‹EHD¶VXQPGOIYF RIU6XVWDLQEOH$JSGF(YP+,&7NK Q,06DOPSVL$WRXHG3UFJIK& QDG&RPXLFW7HKOJV materials are essential for paper manufacturing. Therefore, the most important environmental concerns in pulp and paper industry are the contaminants emission to water and air as well as energy consumption. Moreover, the wastes and residuals resulted by production are increasingly affecting the environmental concerns ( 1 ).

There is a close relation between the forest products industry and water cycle as shown in figure 1. Water is a vital and essential source in pulp, paper and paperboard manufacturing. A major part of water required in the factories is supplied by surface water resources such as rivers and lakes and the remaining is fed by water wells with the depth ranging from very shallow to more than 1000 meters.

In Iran, the water consumption standards in industry has not been determined correctly and no extensive study has been dedicated to clarification of water consumption condition and the water saving potentials in the capital industries ( 2 ).

Similarly, Iranian pulp and paper industry lacks a definite standard for water consumption. Besides, the situation is more severe which is due to the increasing grow in the number of small manufacturing plants of recycled paper products supplying the packaging industry including test liners and corrugating medium as well as a non-existence of supervision in water consumption. On the other hand, in a recent study ( 3 ), the water consumption in pulp and paper industry in Iran has been reported to be above 20 m3/ton (m3 water/ton paper) which is significantly higher than the global standards as summarized in table 1.

Water reduction in papermaking companies have attracted many studies and research projects ( 5- 8 ). By now, different process integration methods including linear models, non-liner models, pinch analysis, genetic algorithms, cleaner production strategies, benchmarking, water re-use and recovery methods and waste water and effluent treatment methods have largely contributed to water reduction in industrial plants. Each of the mentioned methods has definite advantages and drawbacks but generally, implementation of modification or alternation procedures for water reduction in process requires a substantial financial costs and expenditures which is the main obstacle in practical application of the methods ( 9-11 ). The situation in small and medium-size plants with weak management, low technical capacity, limited access to technical data and unstable financial situation is more unsatisfactory. Therefore, priorities determination and proper strategic decision making is of great importance.

One of the qualified tools in the similar situations is Analytical Hierarchy Process (AHP) which has been used in ranking and categorization of many sciences including marketing, architecture, energy resources scheduling as well as social and economical analysis. AHP is the most popular method in Multiple Criteria Decision Making (MCDM) methods which was first introduced by Thomas L. Saaty ( 12 ). When the AHP logic hierarchical structure is formulated, one should first yield the judgment matrices based on pair-wise comparison of all elements in each hierarchy with respect to the higher hierarchy according to certain criteria of comparison within certain scales. The basic idea of AHP is that the factors in a complex system are grouped on different logic levels, forming a chain, or hierarchy, whereby the lowerlevel elements can be compared in pair-wise matrices with respect to the higher level, and so on, so that finally the composite priorities of all levels are achieved ( 13-15 ).

As described in the foregoing paragraphs, the water consumption in Iran is far above the global standards and therefore requires a careful attention. On the other hand, the solutions suggested by some of the available techniques and methods involve high financial expending which is not fully justifiable for industry. The objective of this paper is to apply the Analytic Hierarchy Process (AHP) as a decision making tool for selecting the most prior decision for water reduction in Pulp and Paper manufacturing companies in Iran enabling them to obtain remarkable saving by the most prior approaches.

2

Methodology

2-1 Questionnaire and preliminary data collection

Based on the similarity in product and manufacturing process, 20 companies producing packaging paper and paperboard (Test Liner and Corrugating Medium) were selected. The reason for selection of this particular type of manufacturing plants was the increasing number and the lack of technical supervision on their operation. In the first stage of this research, a preliminary questionnaire was designed asking several questions about the manufacturing process, water supply resources of the company, water consumption estimates as well as the main locations of this consumption and major production costs. This data were used in the company selection and design of the hierarchy tree by which 9 companies representative for their capacity, water supply source and major water consumers were selected. Table 2 summarizes the list of selected companies and their response to some of the questions.

2-2 Analytical Hierarchy Process

Utilization of Analytical Hierarchy Process involves four major levels as followings:

a) Modeling and the Hierarchy Tree Development

In this step, the objective and problem of decision making is derived from the decisions ' elements which are related to each other. The elements of decision include decision making criteria and alternatives. The hierarchy process requires the breakdown of a complex decision problem in a logical manner into many small but related sub-problems in the form of level of a hierarchy. The top level indicates the main objective of the decision making process. The second level comprises the main criteria which can be broken into subcriteria in the following levels. The last level presents the decision alternatives. Based on the data collected from the companies, The Training Resource Package published by United Nations Environment Program ( 16 ), Technical Guidelines published by European Community ( 17 ) and the preassumption of the following white water cycle in the paper machines as figure 2 shows, the hierarchical tree developed. The hierarchy tree for determining the water reduction consumption potentials was structured into tree levels as figure 3 shows. The effective factors were divided into manufacturing process, product, raw material, human resources, costs, environmental regulations and technological aspects. Subsequently, the criteria were extended to sub-categories (figure 3) from which the comparison tables are derived.

Developing the questionnaire and pair-wise comparisons

The next step in AHP is data collection. This was done through a systematic series of pair-wised comparisons among the specific criteria and sub-criteria. AHP provides unique features for criteria weight and subjective evaluations by pair wise comparison and the 1-9 ratio scale in Table 3. The pair-wised comparison matrices were completed with the aid of 10 experts from industry and academia. The AHP then converts these comparisons to criteria weights using a matrix algebra-based algorithm while also checking for consistency in the results.

Very strong importance of one over another

Extreme importance of one over another Intermediate values

Determining the normalized weights

Then the local weight W Bi was calculated according to the formula:

W B i $ ' n ) + j $ 1

( 1 n b ij *

, n ' n . ) i $ 1 + j $ 1

( 1 n b ij * ,

After determining the local weights, the global weights of each criteria and subcriteria are calculated. To avoid misdirection analysis affected by interviewees’ incompatible judgments, AHP establishes a consistency indicator as the standard judgment if the values are incompatible. The questionnaires involved in incompatible judgments were normally discussed with their answerers. Only the matrices that passed the consistency test were included in the final analysis.

d)

Aggregating the weights and Expert Choice Software

To prioritize the decision alternatives, the weights of each element were multiplied by the weight of prior element to reach to the final weight. The implementation of this method for each stage would lead to final weight. The Expert Choice Software (http://www.expertchoice.com/) was applied for weight calculations. Expert Choice is a multi-attribute decision support software tool based on the analytic hierarchy process (AHP) methodology. Expert Choice poses a series of pair-wise comparisons of each of the alternatives identified in relation to each of the criteria and objectives. Expert Choice's five Sensitivity Graphs enables taking some of the uncertainty out of the decision making by quickly and easily testing the results using "what if" scenarios. A full range of reports - either printed in hard copy or pasted into other Windows applications - can be customized to individual needs for presenting results or documenting the decision making process through this software. Reports may include the entire decision hierarchy in sideways or tree view, specific segments of the hierarchy, details of the synthesis process, or sensitivity analysis.

3 Results and Discussion

As indicated in table 2, except Kahrizak the other companies are categorized in small-scale and medium-scale papermaking plants (lower than 5000 and between 5000 to 15000 tons annual production, respectively). Highlighted in table 2, despite the considerable water consumption by papermaking plants, only two companies of Namiran and Omid Kaghaz mentioned the cost of water consumption as their major production costs while the other 7 companies did not refer to the costs due to water utilization from water wells and the industrial complex and pretty likely the water consumption reduction is not considered as their challenge. On the other hand, although 6 out of 9 companies in this study stated the existence of water treatment plant in their factory, it should be noted that other than exceptions the only available technology for water treatment in this sort of companies is Dissolved Air Flotation System (DAF) which is responsible for fiber recovery and presents less effects on reducing the pollution of the wastewater to the required environmental standards.

3-1 Water Consumption Reduction Criteria Results

As shown in figure 4, the "Product" category is the most prominent water reduction criteria with a normalized global weight of 0.250 followed by manufacturing process, raw material, human resources, costs, environmental regulations and technological aspects, respectively. In the Product category, the "Type" of the product gained more global weight than the "Quality" of the product. As table 2 indicates, the companies in this research manufacture three products of Topliner, Corrugating Medium and Testliner ordered from lower quality to higher quality. To produce the higher quality products, more complex manufacturing process and unit operations and application of new chemicals are indispensible and essential. The increase in the number of wastepaper processing stages and chemical preparation requires more water consumption implying the result signified by figure 4. Also, the raw material in all of these companies is mixed wastepaper. Despite, the higher quality of Old Corrugated Container (OCC) due to source sorting practices for this material compared to other types of wastepaper, OCC contains several process contaminants including Pressure Sensitive Adhesives (PSAs), low molecule weight extractable polymeric materials like styrene butadiene rubber (SBR), Copolymers, Polyvinyl Acetate (PVAc), Polyvinyl Alcohol (PVOH) and etc. ( 18-19 ) which pollute the process water and limit its re-use. As a rule of thumb, the amount of contaminants in raw material directly affects the fresh water utilization in recycled paper companies. The technical knowledge of human resources and training would indirectly influence the reduction of water consumption in the factories. The knowledge of fiber line potential to decrease water consumption and identification of major water consumers in the process and optimization of manufacturing process through training of personnel and operators can significantly affect the water consumption.

The environmental regulations and technological aspects were ranked in the lowest weighting levels. This result is expected because no water consumption standard has been defined yet for papermaking companies in Iran. On the other hand, since no wastewater and effluent discharge legislation or permit has been issued for recycled paper companies, the environmental regulations do not seem to be an effective factor in water consumption reduction in Iranian papermaking companies.

As figure 5 shows, in the manufacturing process criteria, the process design subcriteria is regarded as more prominent than paper machine and in process design subcriteria, the tanks and vessels of water storage are weighted more.

The judgment of the experts about Human Resources criteria implies the priority of Technical Knowledge than Training as figure 7 shows.

Figure 10 indicates that the Modern Technologies in Water Treatment subcriterion is more prominent than Water Cycle Modifications sub-criterion in Technological Aspects criteria.

Decision alternatives in the prioritization of 30 criteria effective on Consumption Reduction Potentials have been summarized in figure 11.

Water

According to figure 11 and as indicated before, the Type of Product directly affects the water consumption. Considering this priority, the selection of final product and setting the process variables in a way to optimize the production of the selected product would significantly influence the water consumption. The other major alternatives affecting the water consumption included cooling and sealing water network in the factories.

Other research projects have confirmed the importance of water cycle network in the manufacturing plants ( 20-21 ) in which the recovery of the water used in cooling and sealing of pumps, vacuum pumps and other equipment has been emphasized. Also, they have reported that in the case of water loops separation and use of white water from each section in the previous section, the suspended and organic solid content would reduce 2 to 4 times.

The significance of storage tanks and vessels and leaks control in water cycle network have been emphasized elsewhere ( 17, 22 ) in which storage capacity of process water tanks and broke pulp should be adjusted in a way to contain the maximum water discharge in the accidental shut downs preventing the overflows and leaks.

Despite that wire nozzles, press machine nozzles and steam loss in the dryers were placed in the lower levels of decision alternatives in the present research, others (2324) have stated the remarkable loss of water in the mentioned sections and some practical approaches have been outlined.

Acknowledgment The authors would like to thank the assistance and collaboration of the companies taking part in information and data providing in form of the questionnaire and comparison tables. It is hoped that the results of this research can lead to a significant improvement in the manufacturing productivity.

Conclusion

Recycled paper production companies in Iran consume water far beyond the global standards and therefore require a careful attention. On the other hand, the solutions suggested by some of the available techniques and methods involve high financial expending which is not fully justifiable for the industry. The present project applied the Analytic Hierarchy Process (AHP) as a decision making tool for selecting the most prior decision for water reduction in Pulp and Paper manufacturing companies in Iran to enable them to obtain remarkable saving by the most prior approaches. The results indicated that 'final product" criterion was ranked first following by manufacturing process, human resources, costs and expenditures, environmental regulations and technical modifications, respectively. Also among alternatives, final product, cooling water network, and water storage tanks were categorized in the first three priorities. Regarding the results in the present paper, it is stated that reaching to optimized water consumption in the factories requires significant modifications as well as cooperation and partnership of the manufacturing personnel and management of the company. Considering the high costs and expenditures related to some alternations and modifications in the manufacturing process, the specified priorities in this paper can considerably help the decision makers in the companies to have more intended and prioritized decisions in water consumption reduction with minimum possible costs.

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