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Paper recycling: a discussion of methodological approaches
Resources, Conservation and Recycling 28 (2000) 55–65 www.elsevier.com/locate/resconrec
Paper recycling: a discussion of methodological approaches Stig Bystro¨m a, Lars Lo¨nnstedt b,* Group Staff Technology, MoDo Company, 891 01 O8 rnsko¨lds6ik, Sweden Department of Forest Economics, Swedish Uni6ersity of Agricultural Sciences, 901 83 Umea˚, Sweden a
b
Received 24 February 1999; received in revised form 11 June 1999; accepted 22 June 1999
Abstract Over the last decades increased use of waste paper as a source of fibre for the pulp and paper production process has meant that the industry has undergone significant changes in material and energy use. However, this means use of technologies that do not generate a significant amount of biomass for energy recovery, and thus requires that more energy is purchased by the industry. If waste paper is incinerated instead of repulped, energy purchases by society can be reduced, which will have a positive effect on CO2 emissions. In this article, we argue that an analysis of these effects requires a systems analytical approach including the different production lines, fibre flows and alternative uses of the fibre rather than a life cycle analysis with allocation methods. In the latter case, one often looks at just one production process and uses allocation methods for in- and outflow from or to other processes. We show that allocation methods sometimes used in life cycle analyses do not give a good approximation. Thus, it is recommended that allocation be avoided by, for example, expanding the system. If allocation cannot be avoided, the allocation should be based on the way in which the inputs and outputs are changed by quantitative changes in the products or functions delivered by the system. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Systems analysis; Life cycle analysis; Allocation methods; Waste paper; Fibre recover; Bioenergy production; CO2 emissions
* Corresponding author. Tel.: +46-90-786-6032; fax: +46-90-786-6073. E-mail addresses: [email protected] (S. Bystro¨m), [email protected] (L. Lo¨nnstedt) 0921-3449/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 9 ) 0 0 0 3 3 - 6
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1. The waste paper cycle Since the 1980s, recycling and reuse have been key issues around the globe. Consumers demand environmental improvements from producers. Producers demand the same of their suppliers. The trends towards increased material and energy efficiencies and increased recycling are similar across various industries. However, pulp and paper production differs in its ability to either use recovered waste paper as a material feedstock or as an energy source for the society [1]. Given this dual-use possibility, it is not a priori clear whether, and how much, recycled fibre should be used as a material source because its use can substitute either virgin wood pulp or purchased energy. For example, when recovered waste paper pulp replaces chemical pulps in paper production, both the energy content of the waste paper and the biomass energy available from chemical pulp residues become unavailable. Although policy changes and consumer attitudes have emphasized recycling, one can argue that waste paper should be used to replace mechanical pulp but not energy producing kraft pulps. This would mean maximized availability of biomass energy and replacement of fossil fuels [2]. Besides as a replacement of virgin fibres in the mechanical pulping process, waste paper can be used for incineration, which would allow for the substitution of renewable resources (wood and biomass energy) for non-renewable energy resources (fossil fuels), whereas waste paper pulping does the opposite. To increase knowledge about the pulping processes, we will use Ruth and Harrington [1] to describe chemical, mechanical and waste paper pulping. The primary material input in paper production is pulp that is derived primarily form wood or waste paper. The fibres from pulpwood and waste paper are processed using technologies with dissimilar material and energy requirements that generate products of different qualities. The main distinction is between chemical and mechanical or thermomechanical (TMP) pulping processes. Of the chemical processes, the kraft process is the most dominant. In the kraft process, wood chips are immersed in a sodium-based liquor and heated under pressure to dissolve the lignin that binds fibres. One advantage of producing pulp with the kraft process is that the lignin-rich liquor can be burned to generate steam and electricity, replacing purchased energy at the pulp and paper mill. One major disadvantage of the kraft process is that the extraction of the lignin and other components of the wood reduces the pulp yield per ton of wood. Current rates of recovery of dry pulp per ton of dry wood inputs in the kraft process is about 50% in Sweden. Kraft pulping currently accounts for more than 70% of Sweden’s, 60% of Western Europe’s, 84% the US’s and 53% of Canada’s pulp production annually and is expected to remain the dominant pulping technology in the foreseeable future [3]. Typical paper and paperboard products based on chemical pulp are office and kraft paper. Mechanical processes, or combinations of chemical and mechanical processes, produce a different quality of pulp with a higher fibre yield than the chemical processes. The most prominent among the mechanical processes is TMP pulping. An advantage of mechanical pulping processes is their high yield of pulp per ton of
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wood input. In Sweden as in other countries, high-yield mechanical processes recover about 1 ton of dry pulp per ton of dry wood. However, the process significantly damages the fibres by grinding, compressing and/or heating them. As a consequence of damaged fibres, use of mechanical pulp results in paper products with low strength, for example newsprint. Furthermore, mechanical pulping processes do not generate any chemical byproducts for the generation of steam, heat or electricity. Waste paper pulping generally requires less energy per ton of pulp than pulping processes that use virgin fibre and saves the use of virgin fibre inputs. In contrast to chemical pulping of wood from virgin sources, waste paper pulping provides no woodwastes or dissolved chemicals for energy generation. As a consequence, increased waste paper utilization reduces the availability of biomass energy and increases reliance on purchased energy, in many countries fossil fuels. Rather than being pulped, waste paper can be burned in waste-to-energy plants or in coal-fired co-combustion power plants to recover energy for inplant use or sales. If waste paper is burned for energy conversion, however, that part of the recovered fibre resource is irrevocably lost and the ability to substitute for virgin fibre reduced. The disposition of recovered waste paper, whether pulped or burned for energy, involves fundamental trade-offs between the level of purchased, fossilfuel based energy use, virgin consumption and CO2 emissions. Thus, a key issue when trying to answer the question of whether waste paper should be used for fibre recovery or bioenergy production is the impact of energy use when producing pulp, paper and board [compare 1, 2, 4, 5]. In summary, processing waste paper for paper and board production requires energy that is usually derived from fossil fuel, such as oil and coal. Production of virgin fibre-based chemical pulp yields a thermal surplus, which waste paper processing does not. Thus, thermal energy must be supplied to dry the paper web. If waste paper is recovered for energy purposes, the need for fossil fuel would be reduced. This reduction would have a favourable impact on the carbon dioxide balance and the greenhouse effect. Moreover, pulp production based on virgin fibres requires consumption of roundwood, and electricity causes emissions of air-polluting compounds, as does the collection of waste paper. Let us exemplify. Fig. 1 presents two alternatives for producing newsprint. In alternative 1, virgin-based TMP pulp is used. In alternative 2, fibre recycling is used. This means that the waste paper must first be deinked, i.e. pass a deinking process (DIP-process). When the paper production is based on virgin fibres (alternative 1), almost 1 ton of pulp wood is used and 10.5 GJ of electricity [2]. After use of the newspaper and collection, 11.5 GJ of heat (bioenergy production) can be produced. If instead the waste paper is recycled (alternative 2), the use of virgin fibre is 0.14 ton, 5.2 GJ of electricity and 7.1 GJ of heat. Thus, this alternative requires more external energy, produces no energy surplus but saves trees. The corresponding figure for office paper production based on chemical pulp is for alternative 1 (virgin fibres): 2 tons of wood, 5 GJ of electricity and, after collection and energy production, 9 GJ of heat. If instead the office paper is recycled (alternative 2) the need of wood is 0.3 ton, electricity, 4.4 GJ and heat, 8 GJ. No energy surplus will be produced.
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The waste paper cycle has been modelled by [1,2,6]. Bystro¨m and Lo¨nnstedt [2] in their model differ between 12 paper qualities: newsprint, SC paper, LWC, office paper (wood-free), coated paper (wood-free), tissue, white lined chipboard, ‘return fibre chipboard’, wrapping paper, white liner, kraft-liner and fluting. Each product uses its own recipe for how to mix fibres, filler and energy. Fibres could be virgin or recovered. Electric energy could be produced from fossil fuels or from hydroelectric power stations. Furthermore, different types of pulp exist. The two major qualities are chemical and mechanical pulp, respectively. Chemical pulp is classified depending on the type of fibre, i.e. short or long fibres. Still another pulp quality is semichemical. If the pulp mill and paper mill are on the same site, pulp is delivered as flush pulp. However, many paper mills are not integrated with a pulp mill. They have to buy market pulp delivered in sheets. For each pulp quality, the need for pulp wood (short and long fibres) and energy must be specified. At the site of the pulp mill, electricity can be produced from back-pressure power. In Bystro¨m and Lo¨nnstedt’s model [2], pulp and paper are produced in, exported from and/or imported to different countries. In Europe, the Nordic countries (Finland, Norway and Sweden) are sometimes described as the European lumberyard. The products produced can be delivered either to the domestic market and/or to the export markets. After end use, paper is recycled for the production of paper and board, recovered for energy and/or deposited as land-fill. If recycled, the paper is recovered, sorted, baled and transported to paper mills in the country where the consumption took place or exported to countries with waste paper deficits, for example the Nordic countries. If recovered for energy use or transported to a land-fill dump, the waste paper normally follows the waste-handling system. If it is used for energy production, it replaces oil or coal.
Fig. 1. Use and production of energy in newsprint production based on virgin fibre and fibre recycling, respectively.
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Fig. 2. Two production lines and their connection.
2. Purpose Many paper products have the option to be based on virgin and recycled fibres, respectively. However, recycled paper can also be incinerated, which would substitute fossil fuels and reduce CO2 emissions and have a positive effect on the greenhouse effect. The system is complex and difficult to analyse. Different methods can be used. The purpose of this paper is to compare a systems analytical approach (SC-approach) with a life cycle analyses approach (LC-approach) where allocation methods are used. The different approaches will be compared through measuring the environmental load when producing the product. We will assume that identical products, for example newsprint, are produced in two different ways. One production line is based on virgin fibres and the other on recycled paper. After use of the virgin-based newsprint, it can be reused in the other process. Thus, the two production lines are linked. In a systems analytical approach, both lines will be included in the same model while the life cycle analysis approach will use allocation methods. Different methods for allocations exist, and we will present two of them.
3. Model The two productions lines, L1 and L2, and their connections are shown in Fig. 2. The products produced are assumed to be identical, but production line L1 uses virgin material while production line L2 uses material recycled from L1. The following notations are used:
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V
The environmental load from the first production step of production line L1, for example forestry and the pulp process R The environmental load when recycling material from production line L1 in production line L2, for example deinking P The environmental load of the second production step of both lines L1 and L2, for example newsprint production W The environmental load for material not recycled but, for example, recovered for energy production X The amount produced (tons) by production line L1 Y The amount produced (tons) by production line L2 C The amount consumed (tons) No inventories are considered, and the following relation exists between consumption and production: C =X + Y
(1)
In general, the systems analytical approach means a simplification of reality. For example, the processes and the transports are simplified and the number of production steps are aggregated. However, if a real structure as that modelled were constructed, the correspondence would be total. As in reality, all measures used are physical. A life cycle analysis usually gives a detailed and accurate description of real subsystems. However, if allocation methods are used for combining the subsystems, a non-physical link is introduced. As a consequence, the answers given when changing the input data do not necessarily correspond to reality.
4. Data Different environmental indexes can be used to calculate the environmental impact of the pulp and paper production, the use of renewable resources and non-renewable resources, and the effects of emissions. Such a method will make it possible to add different quantities. The result presented in the next section will be true regardless of the chosen valuation method or if only one variable is studied, for example energy. For the numerical calculations we have, based on our calculations for newsprint [2], used the following values: V= 8 load units per ton; P= 6 load units per ton; R= 5 load units per ton; W= − 16 load units per ton; C= 1000 tons. The question to be answered is whether the total load will increase or decrease if the production in line L2 increases. When answering this question, we will use both a systems analytical approach and a life cycle analysis approach where allocation methods are used. The purpose of this article is to compare answers given by the two approaches.
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5. Results
5.1. The systems analytical approach When both productions lines are included within the system boundaries, the environmental load can easily be calculated. This is done by adding the loads from production lines L1 and L2, and using the relationship X= C− Y. The environmental load from production line L1 is: X(V + P)+ (X −Y)W.
(2)
The environmental load from production line L2 is: Y(R +P + W).
(3)
After simplification, the total environmental load from both production lines can be expressed as: Y(R − V −W)+C(V +P +W).
(4)
It is obvious that if Y increases by 1 unit, the load for the whole system will increase by (R −V − W) units. If the numerical values given above are used, this means 13 load units.
5.2. The allocation method ‘cut off’ In life cycle analyses, the production lines are sometimes treated separately, and the link between them is handled by allocation methods. The environmental load is measured as units per ton. One such allocation method is ‘cut off’. However, as the name indicates, in this method, the link between the processes is not considered at all, i.e. no allocation is made. In our example, the environmental load from production line L1 is calculated as: V +P +W(X − Y)/X,
(5)
and from production line L2 as: R +P +W.
(6)
According to the ‘cut off’ allocation method the change in environmental load when increasing production from line L2 and decreasing production from line L1 is calculated by subtracting Eq. (6) from Eq. (5). After simplification, the difference can be expressed as: (R −V − W) + W(X + Y)/X.
(7)
In Fig. 3, three different curves are shown. Each of them shows the environmental load (load units/ton) related to the amount of recycled fibres (tons), i.e. L2 production. Calculated from Eq. (4), one graph shows the result when the two production lines are looked at as a system. Calculated from Eq. (5) and Eq. (6), respectively, the two other curves show the result when the two production lines are treated separately.
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Fig. 3. According to the SC and LC approaches, environmental load per ton at different recycling levels.
However, it is more interesting to look at the change in the environmental load when production from line L2 increases by 1 ton and production from line L1 decreases by 1 ton. Fig. 4 shows the answers given by the two approaches. Once again, the environmental load per ton is plotted against the amount of recycled fibres. Change in environmental load according to the systems analytical approach is given by Eq. (4) as the coefficient of Y. The answer given when using the ‘cut off’ allocation method is calculated from Eq. (7). It is worth noting that this graph is
Fig. 4. According to the SC and LC approaches, change in environmental load when production from line 2 increases by 1 ton and production from line 1 decreases by 1 ton at different recycling levels.
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non-linear, which is remarkable as the system is linear. As can be seen from Fig. 4, the answers are very different! The difference between the two curves shows the ‘error’ introduced by the ‘cut off’ allocation method.
5.3. The allocation method CIT 50 /50 Another allocation method sometimes used in life cycle analyses is the CIT 50/50 method [7]. This method was developed at Chalmers Industrial Technique (CIT). In this method, the environmental load for production line L1 is reduced and the environmental load for production line L2 is increased by the term (V− W− R). This term is based on a judgement of environmental loads up- and downstream, respectively. The factor used for this correction term has in this method been set to 0.5. This explains the name ‘CIT 50/50’. Using this allocation method, the environmental load per ton for production line L1 is calculated as: V +P + W(X −Y)/X − 0.5(V −W −R)Y/X,
(8)
and for production line L2 as: R +P +W + 0.5(V −W− R).
(9)
As for the ‘cut off’ allocation method, the difference in environmental load between production line L2 and line L1 represents the effect of increasing production in line L2 and decreasing production in line L1. After simplification, the difference can be expressed as: (R − V −W) +(V − R + W)(X + Y)/2X.
(10)
It can be noted that, if the factor used is set to zero instead of 0.5, Eq. (10) will be the same as Eq. (7). As for the ‘cut off’ method, Fig. 5 shows three different curves. Each of them shows the environmental load (load units/ton) related to the amount of recycled fibres (tons), i.e. L2 production. Calculated from Eq. (4), one graph shows the result when the two production lines are looked at as a system. Calculated from Eqs. (8) and (9), respectively, the two other curves show the result when the two production lines are treated separately and the link between them is taking care of by the CIT 50/50 allocation method. However, as above, it is more interesting to look at the change in environmental load when production from line L2 increases by 1 ton and production from line L1 decreases by 1 ton. Fig. 6 shows the answers given by the two approaches. Once again, the environmental load per ton is plotted against the amount of recycled fibres. Change in environmental load according to the systems analytical approach is given by Eq. (4) as the coefficient of Y. The answer given when using the CIT 50/50 allocation method is calculated from Eq. (10). As for the ‘cut off’ allocation method, it is worth noting that this graph is non-linear. The difference between the two curves shows the error introduced by the allocation method. The answers differ by 50 – 100%!
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Fig. 5. According to SC and LC approaches, environmental load per ton at different recycling levels.
6. Comments Not least among Scandinavian industrialists does concern exist that policy-making may lock in inappropriate technologies. The reason is the shift in emphasis in environmental policy from clean-up to avoidance. Environmental policy instruments have been introduced that specify preferred technological directions for an industry, for example take-back requirements and mandatory recycling. These
Fig. 6. According to the SC and LC approaches, change in environmental load when production from line 2 increases by 1 ton and production from line 1 decreases by 1 ton at different recycling levels.
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policy instruments directly affect the mix of materials and the technologies used by an industry. These effects spread throughout the industry and influence market conditions for everyone both up- and downstream in the supplier–client chains, regardless of national borders. Thus, it is of utmost importance that thorough and correct policy analyses are made. The analysis of recycling and reductions in material and energy use and emissions by the pulp and paper industry is complex and difficult. The analyses have often been too narrow. We call for a systems analytical approach. If the purpose is to approximate a technical system, the allocation methods tested above can’t in general be regarded as useful methods. At least in the case of open loop recycling the interaction between the products involved is incorrectly described by the allocation methods. Decisions concerning the use of recycled materials should therefore not be based on such methods.
References [1] Ruth M, Harrington T Jr. Wastepaper repulping versus incineration in the US pulp and paper industry: a dynamic systems analysis. Int J Energy Environ Econ 1997;5:151 – 82. [2] Bystro¨m S, Lo¨nnstedt L. Paper recycling: environmental and economic impact. Resource Conserv Recycl 1997;21:109–27. [3] Anon. Statistical Yearbook of Forestry. Official Statistics of Sweden. Jo¨nko¨ping: National Board of Forestry, 1998. [4] Anon. Burn me. New Sci 1997; 22 November: 31 – 4. [5] Leach MA, Bauen A, Lucas NJD. A systems approach to material flow in sustainable cities: a case study of paper. J Environ Plan Manage 40: 705 – 723. [6] Virtannen Y, Nilsson S. Some Environmental Policy Implications of Recycling Paper Products in Western Europe. Laxenburg, Austria: IIASA, 1992. [7] Ekvall T, Tillman A-M. Open-loop recycling: criteria for allocation procedures. Int J Life Cycle Anal 1997;2:155–62.
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Paper recycling: a discussion of methodological approaches Stig Bystro¨m a, Lars Lo¨nnstedt b,* Group Staff Technology, MoDo Company, 891 01 O8 rnsko¨lds6ik, Sweden Department of Forest Economics, Swedish Uni6ersity of Agricultural Sciences, 901 83 Umea˚, Sweden a
b
Received 24 February 1999; received in revised form 11 June 1999; accepted 22 June 1999
Abstract Over the last decades increased use of waste paper as a source of fibre for the pulp and paper production process has meant that the industry has undergone significant changes in material and energy use. However, this means use of technologies that do not generate a significant amount of biomass for energy recovery, and thus requires that more energy is purchased by the industry. If waste paper is incinerated instead of repulped, energy purchases by society can be reduced, which will have a positive effect on CO2 emissions. In this article, we argue that an analysis of these effects requires a systems analytical approach including the different production lines, fibre flows and alternative uses of the fibre rather than a life cycle analysis with allocation methods. In the latter case, one often looks at just one production process and uses allocation methods for in- and outflow from or to other processes. We show that allocation methods sometimes used in life cycle analyses do not give a good approximation. Thus, it is recommended that allocation be avoided by, for example, expanding the system. If allocation cannot be avoided, the allocation should be based on the way in which the inputs and outputs are changed by quantitative changes in the products or functions delivered by the system. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Systems analysis; Life cycle analysis; Allocation methods; Waste paper; Fibre recover; Bioenergy production; CO2 emissions
* Corresponding author. Tel.: +46-90-786-6032; fax: +46-90-786-6073. E-mail addresses: [email protected] (S. Bystro¨m), [email protected] (L. Lo¨nnstedt) 0921-3449/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 9 ) 0 0 0 3 3 - 6
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1. The waste paper cycle Since the 1980s, recycling and reuse have been key issues around the globe. Consumers demand environmental improvements from producers. Producers demand the same of their suppliers. The trends towards increased material and energy efficiencies and increased recycling are similar across various industries. However, pulp and paper production differs in its ability to either use recovered waste paper as a material feedstock or as an energy source for the society [1]. Given this dual-use possibility, it is not a priori clear whether, and how much, recycled fibre should be used as a material source because its use can substitute either virgin wood pulp or purchased energy. For example, when recovered waste paper pulp replaces chemical pulps in paper production, both the energy content of the waste paper and the biomass energy available from chemical pulp residues become unavailable. Although policy changes and consumer attitudes have emphasized recycling, one can argue that waste paper should be used to replace mechanical pulp but not energy producing kraft pulps. This would mean maximized availability of biomass energy and replacement of fossil fuels [2]. Besides as a replacement of virgin fibres in the mechanical pulping process, waste paper can be used for incineration, which would allow for the substitution of renewable resources (wood and biomass energy) for non-renewable energy resources (fossil fuels), whereas waste paper pulping does the opposite. To increase knowledge about the pulping processes, we will use Ruth and Harrington [1] to describe chemical, mechanical and waste paper pulping. The primary material input in paper production is pulp that is derived primarily form wood or waste paper. The fibres from pulpwood and waste paper are processed using technologies with dissimilar material and energy requirements that generate products of different qualities. The main distinction is between chemical and mechanical or thermomechanical (TMP) pulping processes. Of the chemical processes, the kraft process is the most dominant. In the kraft process, wood chips are immersed in a sodium-based liquor and heated under pressure to dissolve the lignin that binds fibres. One advantage of producing pulp with the kraft process is that the lignin-rich liquor can be burned to generate steam and electricity, replacing purchased energy at the pulp and paper mill. One major disadvantage of the kraft process is that the extraction of the lignin and other components of the wood reduces the pulp yield per ton of wood. Current rates of recovery of dry pulp per ton of dry wood inputs in the kraft process is about 50% in Sweden. Kraft pulping currently accounts for more than 70% of Sweden’s, 60% of Western Europe’s, 84% the US’s and 53% of Canada’s pulp production annually and is expected to remain the dominant pulping technology in the foreseeable future [3]. Typical paper and paperboard products based on chemical pulp are office and kraft paper. Mechanical processes, or combinations of chemical and mechanical processes, produce a different quality of pulp with a higher fibre yield than the chemical processes. The most prominent among the mechanical processes is TMP pulping. An advantage of mechanical pulping processes is their high yield of pulp per ton of
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wood input. In Sweden as in other countries, high-yield mechanical processes recover about 1 ton of dry pulp per ton of dry wood. However, the process significantly damages the fibres by grinding, compressing and/or heating them. As a consequence of damaged fibres, use of mechanical pulp results in paper products with low strength, for example newsprint. Furthermore, mechanical pulping processes do not generate any chemical byproducts for the generation of steam, heat or electricity. Waste paper pulping generally requires less energy per ton of pulp than pulping processes that use virgin fibre and saves the use of virgin fibre inputs. In contrast to chemical pulping of wood from virgin sources, waste paper pulping provides no woodwastes or dissolved chemicals for energy generation. As a consequence, increased waste paper utilization reduces the availability of biomass energy and increases reliance on purchased energy, in many countries fossil fuels. Rather than being pulped, waste paper can be burned in waste-to-energy plants or in coal-fired co-combustion power plants to recover energy for inplant use or sales. If waste paper is burned for energy conversion, however, that part of the recovered fibre resource is irrevocably lost and the ability to substitute for virgin fibre reduced. The disposition of recovered waste paper, whether pulped or burned for energy, involves fundamental trade-offs between the level of purchased, fossilfuel based energy use, virgin consumption and CO2 emissions. Thus, a key issue when trying to answer the question of whether waste paper should be used for fibre recovery or bioenergy production is the impact of energy use when producing pulp, paper and board [compare 1, 2, 4, 5]. In summary, processing waste paper for paper and board production requires energy that is usually derived from fossil fuel, such as oil and coal. Production of virgin fibre-based chemical pulp yields a thermal surplus, which waste paper processing does not. Thus, thermal energy must be supplied to dry the paper web. If waste paper is recovered for energy purposes, the need for fossil fuel would be reduced. This reduction would have a favourable impact on the carbon dioxide balance and the greenhouse effect. Moreover, pulp production based on virgin fibres requires consumption of roundwood, and electricity causes emissions of air-polluting compounds, as does the collection of waste paper. Let us exemplify. Fig. 1 presents two alternatives for producing newsprint. In alternative 1, virgin-based TMP pulp is used. In alternative 2, fibre recycling is used. This means that the waste paper must first be deinked, i.e. pass a deinking process (DIP-process). When the paper production is based on virgin fibres (alternative 1), almost 1 ton of pulp wood is used and 10.5 GJ of electricity [2]. After use of the newspaper and collection, 11.5 GJ of heat (bioenergy production) can be produced. If instead the waste paper is recycled (alternative 2), the use of virgin fibre is 0.14 ton, 5.2 GJ of electricity and 7.1 GJ of heat. Thus, this alternative requires more external energy, produces no energy surplus but saves trees. The corresponding figure for office paper production based on chemical pulp is for alternative 1 (virgin fibres): 2 tons of wood, 5 GJ of electricity and, after collection and energy production, 9 GJ of heat. If instead the office paper is recycled (alternative 2) the need of wood is 0.3 ton, electricity, 4.4 GJ and heat, 8 GJ. No energy surplus will be produced.
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The waste paper cycle has been modelled by [1,2,6]. Bystro¨m and Lo¨nnstedt [2] in their model differ between 12 paper qualities: newsprint, SC paper, LWC, office paper (wood-free), coated paper (wood-free), tissue, white lined chipboard, ‘return fibre chipboard’, wrapping paper, white liner, kraft-liner and fluting. Each product uses its own recipe for how to mix fibres, filler and energy. Fibres could be virgin or recovered. Electric energy could be produced from fossil fuels or from hydroelectric power stations. Furthermore, different types of pulp exist. The two major qualities are chemical and mechanical pulp, respectively. Chemical pulp is classified depending on the type of fibre, i.e. short or long fibres. Still another pulp quality is semichemical. If the pulp mill and paper mill are on the same site, pulp is delivered as flush pulp. However, many paper mills are not integrated with a pulp mill. They have to buy market pulp delivered in sheets. For each pulp quality, the need for pulp wood (short and long fibres) and energy must be specified. At the site of the pulp mill, electricity can be produced from back-pressure power. In Bystro¨m and Lo¨nnstedt’s model [2], pulp and paper are produced in, exported from and/or imported to different countries. In Europe, the Nordic countries (Finland, Norway and Sweden) are sometimes described as the European lumberyard. The products produced can be delivered either to the domestic market and/or to the export markets. After end use, paper is recycled for the production of paper and board, recovered for energy and/or deposited as land-fill. If recycled, the paper is recovered, sorted, baled and transported to paper mills in the country where the consumption took place or exported to countries with waste paper deficits, for example the Nordic countries. If recovered for energy use or transported to a land-fill dump, the waste paper normally follows the waste-handling system. If it is used for energy production, it replaces oil or coal.
Fig. 1. Use and production of energy in newsprint production based on virgin fibre and fibre recycling, respectively.
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Fig. 2. Two production lines and their connection.
2. Purpose Many paper products have the option to be based on virgin and recycled fibres, respectively. However, recycled paper can also be incinerated, which would substitute fossil fuels and reduce CO2 emissions and have a positive effect on the greenhouse effect. The system is complex and difficult to analyse. Different methods can be used. The purpose of this paper is to compare a systems analytical approach (SC-approach) with a life cycle analyses approach (LC-approach) where allocation methods are used. The different approaches will be compared through measuring the environmental load when producing the product. We will assume that identical products, for example newsprint, are produced in two different ways. One production line is based on virgin fibres and the other on recycled paper. After use of the virgin-based newsprint, it can be reused in the other process. Thus, the two production lines are linked. In a systems analytical approach, both lines will be included in the same model while the life cycle analysis approach will use allocation methods. Different methods for allocations exist, and we will present two of them.
3. Model The two productions lines, L1 and L2, and their connections are shown in Fig. 2. The products produced are assumed to be identical, but production line L1 uses virgin material while production line L2 uses material recycled from L1. The following notations are used:
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V
The environmental load from the first production step of production line L1, for example forestry and the pulp process R The environmental load when recycling material from production line L1 in production line L2, for example deinking P The environmental load of the second production step of both lines L1 and L2, for example newsprint production W The environmental load for material not recycled but, for example, recovered for energy production X The amount produced (tons) by production line L1 Y The amount produced (tons) by production line L2 C The amount consumed (tons) No inventories are considered, and the following relation exists between consumption and production: C =X + Y
(1)
In general, the systems analytical approach means a simplification of reality. For example, the processes and the transports are simplified and the number of production steps are aggregated. However, if a real structure as that modelled were constructed, the correspondence would be total. As in reality, all measures used are physical. A life cycle analysis usually gives a detailed and accurate description of real subsystems. However, if allocation methods are used for combining the subsystems, a non-physical link is introduced. As a consequence, the answers given when changing the input data do not necessarily correspond to reality.
4. Data Different environmental indexes can be used to calculate the environmental impact of the pulp and paper production, the use of renewable resources and non-renewable resources, and the effects of emissions. Such a method will make it possible to add different quantities. The result presented in the next section will be true regardless of the chosen valuation method or if only one variable is studied, for example energy. For the numerical calculations we have, based on our calculations for newsprint [2], used the following values: V= 8 load units per ton; P= 6 load units per ton; R= 5 load units per ton; W= − 16 load units per ton; C= 1000 tons. The question to be answered is whether the total load will increase or decrease if the production in line L2 increases. When answering this question, we will use both a systems analytical approach and a life cycle analysis approach where allocation methods are used. The purpose of this article is to compare answers given by the two approaches.
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5. Results
5.1. The systems analytical approach When both productions lines are included within the system boundaries, the environmental load can easily be calculated. This is done by adding the loads from production lines L1 and L2, and using the relationship X= C− Y. The environmental load from production line L1 is: X(V + P)+ (X −Y)W.
(2)
The environmental load from production line L2 is: Y(R +P + W).
(3)
After simplification, the total environmental load from both production lines can be expressed as: Y(R − V −W)+C(V +P +W).
(4)
It is obvious that if Y increases by 1 unit, the load for the whole system will increase by (R −V − W) units. If the numerical values given above are used, this means 13 load units.
5.2. The allocation method ‘cut off’ In life cycle analyses, the production lines are sometimes treated separately, and the link between them is handled by allocation methods. The environmental load is measured as units per ton. One such allocation method is ‘cut off’. However, as the name indicates, in this method, the link between the processes is not considered at all, i.e. no allocation is made. In our example, the environmental load from production line L1 is calculated as: V +P +W(X − Y)/X,
(5)
and from production line L2 as: R +P +W.
(6)
According to the ‘cut off’ allocation method the change in environmental load when increasing production from line L2 and decreasing production from line L1 is calculated by subtracting Eq. (6) from Eq. (5). After simplification, the difference can be expressed as: (R −V − W) + W(X + Y)/X.
(7)
In Fig. 3, three different curves are shown. Each of them shows the environmental load (load units/ton) related to the amount of recycled fibres (tons), i.e. L2 production. Calculated from Eq. (4), one graph shows the result when the two production lines are looked at as a system. Calculated from Eq. (5) and Eq. (6), respectively, the two other curves show the result when the two production lines are treated separately.
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Fig. 3. According to the SC and LC approaches, environmental load per ton at different recycling levels.
However, it is more interesting to look at the change in the environmental load when production from line L2 increases by 1 ton and production from line L1 decreases by 1 ton. Fig. 4 shows the answers given by the two approaches. Once again, the environmental load per ton is plotted against the amount of recycled fibres. Change in environmental load according to the systems analytical approach is given by Eq. (4) as the coefficient of Y. The answer given when using the ‘cut off’ allocation method is calculated from Eq. (7). It is worth noting that this graph is
Fig. 4. According to the SC and LC approaches, change in environmental load when production from line 2 increases by 1 ton and production from line 1 decreases by 1 ton at different recycling levels.
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non-linear, which is remarkable as the system is linear. As can be seen from Fig. 4, the answers are very different! The difference between the two curves shows the ‘error’ introduced by the ‘cut off’ allocation method.
5.3. The allocation method CIT 50 /50 Another allocation method sometimes used in life cycle analyses is the CIT 50/50 method [7]. This method was developed at Chalmers Industrial Technique (CIT). In this method, the environmental load for production line L1 is reduced and the environmental load for production line L2 is increased by the term (V− W− R). This term is based on a judgement of environmental loads up- and downstream, respectively. The factor used for this correction term has in this method been set to 0.5. This explains the name ‘CIT 50/50’. Using this allocation method, the environmental load per ton for production line L1 is calculated as: V +P + W(X −Y)/X − 0.5(V −W −R)Y/X,
(8)
and for production line L2 as: R +P +W + 0.5(V −W− R).
(9)
As for the ‘cut off’ allocation method, the difference in environmental load between production line L2 and line L1 represents the effect of increasing production in line L2 and decreasing production in line L1. After simplification, the difference can be expressed as: (R − V −W) +(V − R + W)(X + Y)/2X.
(10)
It can be noted that, if the factor used is set to zero instead of 0.5, Eq. (10) will be the same as Eq. (7). As for the ‘cut off’ method, Fig. 5 shows three different curves. Each of them shows the environmental load (load units/ton) related to the amount of recycled fibres (tons), i.e. L2 production. Calculated from Eq. (4), one graph shows the result when the two production lines are looked at as a system. Calculated from Eqs. (8) and (9), respectively, the two other curves show the result when the two production lines are treated separately and the link between them is taking care of by the CIT 50/50 allocation method. However, as above, it is more interesting to look at the change in environmental load when production from line L2 increases by 1 ton and production from line L1 decreases by 1 ton. Fig. 6 shows the answers given by the two approaches. Once again, the environmental load per ton is plotted against the amount of recycled fibres. Change in environmental load according to the systems analytical approach is given by Eq. (4) as the coefficient of Y. The answer given when using the CIT 50/50 allocation method is calculated from Eq. (10). As for the ‘cut off’ allocation method, it is worth noting that this graph is non-linear. The difference between the two curves shows the error introduced by the allocation method. The answers differ by 50 – 100%!
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Fig. 5. According to SC and LC approaches, environmental load per ton at different recycling levels.
6. Comments Not least among Scandinavian industrialists does concern exist that policy-making may lock in inappropriate technologies. The reason is the shift in emphasis in environmental policy from clean-up to avoidance. Environmental policy instruments have been introduced that specify preferred technological directions for an industry, for example take-back requirements and mandatory recycling. These
Fig. 6. According to the SC and LC approaches, change in environmental load when production from line 2 increases by 1 ton and production from line 1 decreases by 1 ton at different recycling levels.
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policy instruments directly affect the mix of materials and the technologies used by an industry. These effects spread throughout the industry and influence market conditions for everyone both up- and downstream in the supplier–client chains, regardless of national borders. Thus, it is of utmost importance that thorough and correct policy analyses are made. The analysis of recycling and reductions in material and energy use and emissions by the pulp and paper industry is complex and difficult. The analyses have often been too narrow. We call for a systems analytical approach. If the purpose is to approximate a technical system, the allocation methods tested above can’t in general be regarded as useful methods. At least in the case of open loop recycling the interaction between the products involved is incorrectly described by the allocation methods. Decisions concerning the use of recycled materials should therefore not be based on such methods.
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