Life cycle assessment of the waste hierarchy – A Danish case study on waste paper

Waste Management 27 (2007) 1519–1530 www.elsevier.com/locate/wasman

Life cycle assessment of the waste hierarchy – A Danish case study on waste paper Jannick H. Schmidt a

a,¤

, Peter Holm b, Anne Merrild c, Per Christensen

a

Department of Development and Planning, Aalborg University, Fibigerstraede 13, 9220 Aalborg East, Denmark b AAU Innovation, Aalborg University, Niels Jernes Vej 10, 0220 Aalborg East, Denmark c Qaqortop municipality, Qaqortop, Greenland Accepted 18 September 2006 Available online 16 November 2006

Abstract The waste hierarchy is being widely discussed these days, not only by cost-beneWt analysts, but a growing number of life cycle assessments (LCA) have also begun to question it. In this article, we investigate the handling of waste paper in Denmark and compare the present situation with scenarios of more waste being recycled, incinerated or consigned to landWll. The investigations are made in accordance with ISO 14040-43 and based on the newly launched methodology of consequential LCA and following the recent guidelines of the European Centre on Waste and Material Flows. The LCA concerns the Danish consumption of paper in 1999, totalling 1.2 million tons. The results of the investigation indicate that the waste hierarchy is reliable; from an environmental point of view recycling of paper is better than incineration and landWlling. For incineration, the reason for the advantage of landWlling mainly comes from the substitution of fossil fuels, when incinerators provide heat and electricity. For recycling, the advantage is related to the saved wood resources, which can be used for generating energy from wood, i.e., from renewable fuel which does not contribute to global warming. © 2006 Elsevier Ltd. All rights reserved.

1. Introduction Over the last few decades, the waste hierarchy has been the guiding principle in both Danish as well as in European waste management policy. Since its launch, the goal has been to reduce the total quantities of waste and to save energy and resources. Until 1999, the focus was very much on reduction of waste quantities, but since the launch of the oYcial Danish waste-strategy “Waste 21”, focus shifted, implying that the waste hierarchy should not always be followed (Miljø- og Energiministeriet, 1999). Politically, the Danish environmental authorities have followed a strategy very similar to the one used in the European Union (EU), i.e., the waste hierarchy is applicable and it should be followed until proved inappropriate. Thus, the waste hierarchy functions as a guiding principle which can *

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clearly be seen in the goals formulated in oYcial policies. In the “Waste 21” action plan (Miljø- og Energiministeriet, 1999), we Wnd objectives for increased recycling of paper, organic waste from households and a priority for using the Danish system of reusing bottles. In the newly launched action plan “Waste Strategy 2005–2008” (Miljøministeriet, 2003), there is more emphasis on the use of waste indicators and cost-beneWt-analysis. This can be seen as a shift in focus from relying much on the waste hierarchy, i.e., basic guidelines on how to prioritise ways of handling waste in general, to moving more towards speciWc analyses which are based on broader environmental and economic analyses. Denmark also questions the EU policies being formulated in this regard, i.e., it is stated explicitly in the new action plan that it is not reasonable to make general demands on the EU level (Miljøministeriet, 2003). From an economic point of view, several investigations also deal with the waste hierarchy, for instance Brisson (1997). At that time, the conclusion was that it was a good

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idea to prioritise recycling over incineration and then again over landWlling. It was also stressed that the priority of incineration being superior to landWll depends on the type of energy production that is substituted by the heat and electricity produced from the incineration plant. If coal is substituted, then incineration is more favourable. The EUcommission likewise concluded that generally, recycling was the best alternative, while landWlling appeared to be a generally better alternative than incineration (European Commission, 1997). This conclusion, though, generally does not suit the Danish conditions, where a large proportion of the energy from waste is recycled into district heating and electricity production. The Danish “Institute of Environmental Assessment,” founded in 2001 under the leadership of Bjørn Lomborg, claimed in several reports that it was not cost-eVective to recycle a number of waste fractions, which included paper, aluminium cans, steel cans and plastic packaging. Instead the authors argued that these fractions should be kept together with mixed waste fractions from industry and households in order to be incinerated (Petersen and Andersen, 2002; Vigsø and Andersen, 2002). The cost-beneWt analysis was heavily criticised for being based on a too narrow analysis, especially with regards to the number of environmental problems investigated as well as in relation to the limited national delimitations of the study (Christensen and Schmidt, 2003; Wejdling and Carlsbæk, 2003). In the investigations, the national delimitation of the system entails that the environmental impacts, which arise from the production or the substitution of products abroad, are not considered. This is contrary to the state of the art in environmental policy today, where “from cradle to grave” is a fundamental principle. Especially in regards to paper, quite a few LCA investigations have been made, not only in Denmark but also in a host of other countries (Villanueva et al., 2004). The results of these investigations have been quite varied and the conclusions seem to point in somewhat diVerent directions. In a report from the European Topic Centre on Waste and Material Flows, nine investigations were compared and a set of guidelines were proposed in order to make proper delimitations of such studies (Villanueva et al., 2004). Generally, from an environmental point of view, the conclusion is that recycling in most cases is more favourable than incineration and landWlling. However, there are some diVerences, but “they are not found to be due to actual diVerences in the environmental impacts from the paper systems studied, but rather to diVerences in the LCA methodology applied and especially the deWnition of the paper system and its boundaries” (Villanueva et al., 2004). On this background, a common set of criteria is deWned on how to conduct a proper LCA of the waste management system for waste paper. In the following study, we adhere to these criteria and make an LCA of the total Danish waste paper stream, including diVerent scenarios for handling this stream. Following, diVerent strategies are suggested relating to recycling, incineration and landWll in order to experience the overall envi-

ronmental eVects of the changes. Hence, the waste hierarchy is examined in order to see the impact of the diVerent strategies on the environment. We hope that investigations such as these can clarify for what materials, and under which circumstances, the waste hierarchy can be used, i.e., leading to speciWc rules of thumb for speciWc materials. 2. Methodology The waste hierarchy implies that some of the strategies for handling waste are more appropriate than others, from an environmental point of view. In this investigation, an LCA will be undertaken not only regarding a speciWc paper product, but on the entire paper production system, which handles the recycling and the waste disposal. At this level, alternative strategies can be modelled, impacts calculated and comparisons made between the diVerent strategies. Choosing LCA as the method for assessing the environmental impacts is state-of-the-art within this research Weld, because it is the most comprehensive method, being able to handle hundreds of inputs and outputs in the diVerent stages from cradle to grave and, last but not least, it oVers a framework for comparing impacts of diVerent natures. The framework for conducting an LCA is found in the ISO standards, especially 14040-43 (Jerlang et al., 2001) which is followed in this study. By expanding the boundaries of the system analysed, coproduct allocation can be avoided (Weidema, 2000, 2003; Ekvall and Weidema, 2004; Schmidt, 2004). This consequential approach to the problem of allocation has been described in several studies (Thrane, 2004; Schmidt and Weidema, in preparation) and is also proposed by ISO 14040 as state-of-the-art for such studies. Co-product allocation, which is handled by the use of economic or technical criteria, is thus avoided. Worldwide, a host of diVerent methods is available for assessing environmental impacts, including the most prominent methods such as EDIP 97 (Wenzel et al., 1997; Hauschild and Wenzel, 1998), Eco-indicator (Goedkoop and Spriensma, 2001) and CML (Guinée et al., 2002). In these methods, a number of impact categories are considered, normally related to global warming, ozone depletion, eutrophication and up to more than ten other categories of impacts. For each of the impacts a host of emissions can contribute to it, for example for global warming where methane (CH4), dinitrogenous oxide (N2O), and carbon monoxide (CO) together with CO2 contribute to the total impacts in question, here calculated as CO2-equivalents. Going one step further in the assessment in order to compare the size of impacts and their relative importance, procedures for normalizing and weighting of the impacts are also oVered. Comparisons are made at a local, regional or global level depending on the nature of the impacts. In this investigation the calculations are made according to the Danish method EDIP97, which is due to the fact that it was developed to describe Danish and European condi-

J.H. Schmidt et al. / Waste Management 27 (2007) 1519–1530

tions. The method has been implemented into the PC-tool SimaPro. The EDIP-methodology has recently been launched in a revised EDIP2003 version (Hauschild and Potting, 2003). As the new revised method has not been implemented as yet into any PC-tool, the decision was to continue to use the well documented EDIP97 methodology. EDIP97 includes 15 impact categories and a number of resources. The impact categories included in this study are global warming, ozone depletion, eutrophication, acidiWcation and photochemical smog. Besides the impact categories included, EDIP97 also includes human toxicity, eco-toxicity, waste and resource use; however, we have chosen not to include these impact categories. The data used for mapping exchanges from the individual steps in the life cycle are primarily found in the available literature. The calculations are performed by the PC-tool SimaPro 6.0 (PRé, 2004). Many of the data used for this assessment are furthermore found in the BAT-notes on the pulp and paper industry made by the European Commission (2001). Data for the use of energy and materials, as well as transport, are provided by databases already existing in SimaPro, such as BUWAL 250 (1996) and ETH-ESU (1996). The total mass Xow for Danish paper is considered for the year 1999. Data for the Danish production of paper is based on EMAS-reports from the Danish manufacturers of paper and pulp (Dalum, 2000; Hartmann, 2000a,b; SCA, 2000). Data for foreign paper production and export and import are based on national statistics made by the Danish EPA as well as the annual statistics from the Confederation of European Paper Industries (CEPI) (Tønning, 2001; CEPI, 2000). Mass balances for foreign paper manufacturers are produced from data which are obtained from EMAS-reports and from four large manufacturers, producing newspaper, cardboard, coated and non-coated woodfree paper as well as corrugated paper (Hylte Mill, 1999; Skoghall, 2000; Nymölla Mill, 2000; SCA, 2001). The mapping of paper in the stages of waste and recycling are based on the statistics of the Danish EPA (Miljøstyrelsen, 2000; Tønning, 2001). 3. Functional unit and system delimitation In LCA, the functional unit describes the entity analysed. In our case, we have refrained from looking at the beneWts or impacts from an additional kilogram of paper recycled and instead, we have chosen to look at the entire mass Xow of paper through Danish society, i.e., provision and disposal of paper in Danish society in a given year. The functional unit is deWned as “Denmark’s consumption of paper in 1999, totalling 1.2 million tons (1.122 million tons Dry Solids)”. All life cycle stages of paper are included in our investigation; from forestry to Wnal disposal of waste paper. Furthermore, the deWned product system includes diVerent types of paper and diVerent qualities as well, being composed of weighted fractions of the most used types and qualities. Virgin pulp used as input to the Danish market is

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composed of 61% chemicals, 10% semi-chemicals and 29% mechanical paper pulps (Holm et al., 2002). The diVerent qualities of paper are divided into: 31% corrugated paper and paper bags, 23% newspaper, 20% coated paper, 15% cardboard and 12% uncoated, wood-free paper. The system analysed includes the following stages: forestry, production of pulp (both virgin and recycled), manufacturing of paper products, transportation of paper and paper waste and Wnally disposal as either incineration or deposit onto landWlls. In a recent “meta-study” of nine LCAs made on alternative ways of handling waste paper, the European Topic Centre on Waste and Material Flows (Villanueva et al., 2004) investigated the relationship between system delimitations and their impacts on the obtained results. The study concluded on the assumptions that were most valid, when conducting LCAs on paper and pulp. In the LCA on the Danish mass Xow of paper, the assumptions are followed as closely as possible. According to Villanueva et al. (2004), one of the most important questions to address when making an LCA of increased rates of recycling is the alternative uses of land/wood, as the recycling of paper implies a reduction in the demand for virgin paper; and consequently it leads to a reduction in the demands for land or wood. The problem of land consumption in the LCA can be included in two diVerent ways. It can either be included as an impact category that mirrors an increase in biodiversity being a function of less intensive forestry, or the system boundaries can be expanded to include alternative uses of wood, such as renewable energy production. The latter is used in this investigation, as currently the measure for biodiversity is not regarded as reliable or even valid (Lindeijer et al., 2002; Mattson et al., 2000). The considerations are addressed in the forestry phase of the life cycle, where each ton of wood, which is saved due to recycling, is assumed to be used for energy production, which substitutes electricity and heat produced at a CHP-plant (as cogeneration of heat and electricity which is today state-of-the-art in Denmark). In Denmark mixed waste from households are incinerated and the energy content of the waste is used for the production of electricity and heat. It is assumed that paper waste that is not collected for recycling is to be found in mixed waste for incineration. The production of energy displaces marginal electricity and heat. When recycling paper to pulp, the handling of waste from this process is also included. Furthermore, it is assumed that it will be incinerated, but without any concomitant production of energy, as the water content of this fraction is fairly high (>50%). Marginal technology for energy production of electricity and heat is used. Marginal electricity from the Danish grid is assumed to be based on gas (Weidema, 2003). Most production of pulp and paper is integrated, i.e., taking place within the same factory. This is also the fact for foreign manufacturers in this case study. Generally, the CHPplants are dimensioned so that they are able to cover the need for heat in the production. The produced electricity is used in the production and eventually, any surplus would

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be sold to the grid in the same way as a deWcit in electricity production is compensated for by buying it from the grid. Generally, capital goods are not included in this investigation, i.e., construction, maintenance and disposal of machinery, buildings and infrastructures. We have chosen not to include the environmental impacts from printing houses and other industrial processes producing paper goods or the impacts from the use of paper, e.g., printing, copying, use of staples and transport from retailers to private consumers. We also do not include emissions related to the fraction of waste paper that is disposed in the wastewater streams of households (»29,000 tons of paper per year). 4. Product system The description of pulp and paper processing in this section is mainly based on the EU Commission’s Reference Document on Best Available Techniques in the Pulp and Paper Industry (European Commission, 2001). In the LCA, the product system is divided into Wve stages: forestry, production of pulp, production of paper, waste treatment (incineration/landWll) and transport. The production of paper takes place in two steps; Wrst, wood is processed into pulp, next, the pulp is processed into paper through pressing and evaporation of the water in the pulp. Almost all paper processing takes place in integrated pulp and paper processing plants. However, in this study, the pulp and paper productions are presented as two distinct stages due to their very diVerent nature. By integrating the two steps, energy will be saved, because there is no need for drying the pulp before transporting it to the paper processing stage. Pulp primarily consists of plant Wbres mixed with water. In producing paper, additives are added; additives mainly consist of chalk and starch and comprise up to 35% of the paper. The most common types of virgin pulp are chemical pulp, mechanical pulp and chemo-mechanical pulp. The three types of virgin pulps are deWned according to whether the wood is cooked, whether the Wbres (cellulose) are separated from the binders in the wood (lignin) by using chemicals, or whether the wood is grinded mechanically. In this study, we do not distinguish between the diVerent types of virgin pulps, but we use a weighted average of the three virgin pulps according to their present contribution to paper use in Denmark. Pulp from recovered paper is manufactured by grinding collected waste paper in water. The pulp is de-inked and other impurities are removed, and it is then ready for paper production. Every time waste paper undergoes the process of recycling, its Wbres are worn down (down cycled). Thus, it is only possible to recycle the Wbres 4–6 times. Even when all waste paper is collected for recovery, it is necessary to add virgin pulp to keep the total stock of paper. In the paper production stage, the wet pulp is put on a wire, which is a long, up to 10 m wide band conveyer. The wire is made of a small meshed sieve/fabric, which holds the Wbres while the water drains oV. Furthermore, at the end of the wire, the water is sucked out of the pulp and it is then

pressed and dried. At this stage, the paper may also be sized, coated and calendared at the end of the drying process. Finally, the paper is rolled and cut, and it is then ready for distribution to paper manufacturers, e.g., manufacturers of newspaper, toilet paper, packaging etc. In the disposal stage, a minor part of the waste paper, primarily toilet tissue, is disposed into the wastewater system. The remaining part is disposed either by incineration or by collection for recovery. The fraction not being recycled or discharged as wastewater is disposed as mixed municipal house waste. This fraction is incinerated, as only inert materials are allowed to be deposited into landWlls in Denmark (Statutory order no. 619, 2000). When incinerated, electricity and heat are recovered from the paper, and the residue (slag and ash) is assumed to be deposited in landWlls. The quality of the collected paper varies. In the paper industry, e.g., printing houses, a fairly large amount of paper is cut-oVs; this type of waste is very clean and compared to waste paper collected from domestic households it is of good quality. In Denmark, the municipalities are responsible for handling the waste from households and industries. As waste paper from paper industries is rather valuable, this is often sold directly to the dealers of recycling paper, but in the end it is sold to manufacturers who recycle the pulp. 4.1. Mass Xow of paper in Denmark The description of the mass Xow of paper in Denmark refers to the situation in 1999. As in diVerent stages of the life cycle, the content of water in the paper may vary from a few percent to almost 100%; it is presented as 100% dry solids (DS). The virgin papers used in Denmark are supplied by foreign forestry and pulp and paper producers. The production primarily takes place in Sweden, Germany and Finland. In Denmark there are four pulp and paper factories that all produce recycled paper. The factories use 46% of the collected waste paper in Denmark, and they export 69% of their products. In Denmark, 89,000 tons of the 323,000 tons of recovered pulp are used, while the remaining part is used for exported paper. The foreign production of virgin paper in Germany, Sweden and Finland uses 708,000 tons (100% DS) of wood, while recovered pulp amounts to 399,000 tons (100% DS). A great number of industries manufacture paper into paper products. While 92% of the paper used in Denmark comes from foreign paper production, 73% of the manufactured paper products used in Denmark is produced in the country. During the manufacturing of paper products, the mass Xow of paper increases by 2.2%. The increase consists of printing ink, colouring agents and materials used for sizing and coating. Waste paper is disposed either as separated waste paper from households or industries or as mixed municipal waste for incineration. The waste system receives three kinds of waste paper from industry, i.e., high quality

J.H. Schmidt et al. / Waste Management 27 (2007) 1519–1530 Table 1 Mass Xow of paper related to Xows into and out from the waste system in Denmark in 1999 Paper Xow in Danish waste management system Paper collected for recycling from industry Paper collected for recycling from households Paper collected with the mixed fraction from households and industry Paper for recycling in Denmark Paper exported for recycling Paper for incineration Balance

Inputs to the Danish waste system

Outputs from the Danish waste system

523 131 621

378 276 621 1275

1275

Amounts are given in 1000 tons 100% dry solids.

cut oV paper from the printing industry, separated waste paper for recycling from other industries and rejects from the production of recycled pulps. The latter is sent to incineration, while the two other fractions are recycled. Collected waste paper from households accounts for 131,000 tons (100% DS) that are recycled, while 621,000 tons (100% DS) of waste paper are collected as mixed combustible municipal waste and consequently incinerated. Fig. 1 summarizes the mass Xow of paper related to Danish consumption in 1999. From Fig. 1, it can be derived that in 1999, the consumption of paper in Denmark was 1121 thousand tons (100% dry solids). Table 1, showing the inputs and outputs to the Danish waste management system, also shows the total input of 1275 thousand tons. The reason for this is that the waste management system presented in Table 2 receives waste paper for recycling from paper product manufacturers in Denmark. These manufacturers produce paper products for the Danish as well as the export markets, whereas Fig. 1 only relates to Danish consumption. The total amount of waste paper for recycling collected in Denmark from paper manufacturers and households is 654,000 tons per year (cf. Table 1). 5. Scenarios The life cycle assessment is used to compare diVerent scenarios, where diVerent changes to the present Danish waste system are assumed. The scenarios are made in order to allow for an analysis of the consequences when following or not following the measures which are deWned by the waste hierarchy. In one scenario, we have chosen to increase the fraction of paper recycled, following EU and Danish oYcial policies as laid down in the Danish plan for handling waste, Waste 21 (Miljø- og Energiministeriet, 1999). In the second scenario, the fraction of paper incinerated is increased in order to analyse the consequences of the

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critique raised concerning the waste hierarchy, when following it too blindly. In a third scenario, the environmental impact of disposing paper in landWlls instead of incinerating it has been assessed. For each scenario, a mass Xow is presented, where changes on system level are described. In 1999, it was estimated that only 32% of the paper from households was collected for recycling, compared to 63% from industries and public and private institutions (Miljø- og Energiministeriet, 1999). The mass Xow analysis of paper showed that in 1999, 51% of all paper and cardboard waste was recycled in Denmark. 5.1. Scenario 1: increased recycling When increasing the recycling, waste paper and cardboard are moved from the mixed fraction which is incinerated, to the fraction of paper and cardboard which is recycled. Half of the paper collected in 1999 was used by Danish paper manufacturers and the rest was exported. The additional amount of paper collected in this scenario is to be exported to foreign paper manufacturers, as it does not seem realistic for Danish paper manufacturers to increase their production levels. To assess the impacts of increased recycling, we assume that the foreign paper manufacturers, who produce for the Danish market, will substitute virgin paper and pulp with the increased amount of recycled pulp. Consequentially, the paper production in Denmark is not changed as an eVect of increased collection of recyclable paper and cardboard, but due to the fact that imported paper contains a larger fraction of recycled paper. The objectives for paper and cardboard in the Danish waste plan, “Waste 21” (Miljø- og Energiministeriet, 1999), was, by 2004, to recycle 60% of the paper and cardboard waste from households and 75% of the waste from industries and public and private institutions. The fundamental characteristics of this scenario compared with the situation in 1999 are shown in Table 2. 5.2. Scenario 2: increased incineration When increasing the amount of incinerated paper, we move all waste paper and cardboard from the separately collected fraction for recycling to the mixed fraction for incineration. We assume that the four Danish paper manufacturers have not been closed down, but instead they import pulp to keep up their present production of paper and cardboard. To assess the consequences of this scenario, the imported pulps for these manufacturers are virgin pulps. Besides, a consequence of this scenario is that waste paper for recycling that has been exported is currently being incinerated in Denmark; then the foreign manufacturers also have to substitute this amount of paper with virgin paper pulps. Danish waste paper for recycling will be substituted with virgin paper pulp as the domestic paper manufacturers have 378,000 tons of recycled paper less for their production and the foreign

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Energy input: burning of diesel

Material input: fertilizer, pesticides System boundary in LCA

Forestry

Forest Avoided burning of wood as biofuel 991,000 ton = 18.1 PJ Burning of natural gas 18.1 PJ Waste paper: 520,000 ton Pulp recycled

Pulp virgin

Wood: 991,000 ton Energy and materials Pulping

Pulp - virgin: 708,000 ton

Losses: 283,000 ton

Energy and materials Pulping

Pulp - recycled: 456,000 ton

Losses: 64,000 ton

Paper production

Pulp: 1,163,000 ton Energy and materials

Waste paper that ends in products used abroad: 210,000 ton

Additives: 159,000 ton Paper production Paper: 1,323,000 ton

Manufactoring of paper products

Functional unit

Waste paper to recycling: 229,000 ton Printing ink: 28,000 ton

To incineration: 621,000 ton

Waste paper to recycling: 501,000 ton To landfill: 0 ton

Incineration Avoided heat and electricity

Landfill

Incineration

DK consumption

Paper products: 1,122,000 ton

Landfill

Fig. 1. Illustration of paper Xow in product system in 1999 situation related to Danish consumption of paper. System boundaries and functional units are also speciWed. Grey boxes represent stages in the product life cycle and white boxes represent unit processes for which emission data are inventoried. Dotted white boxes represent avoided processes. All numbers given are in 100% dry solids (DS).

producers 276,000 tons (100% DS) less for their production. The fundamental characteristics of this scenario compared with the situation in 1999 are also shown in Table 2.

5.3. Scenario 3: increased use of landWll When increasing the amount of waste disposed in landWlls, the waste paper currently being incinerated instead is

J.H. Schmidt et al. / Waste Management 27 (2007) 1519–1530

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Table 2 The disposal of waste paper in 1999 and the consequences of the three diVerent scenarios on recycling (scenario 1), incineration (scenario 2) and landWll (scenario 3) Paper Xow in waste management system

1999 Situation

Collected paper for recycling from enterprises, etc. Collected paper for recycling from households Paper-waste in mixed waste for incineration Paper waste for landWll Total

Scenario 1

Scenario 2

Scenario 3

523,060 131,345 620,675 0

653,825 262,690 358,565 0

0 0 1,275,080 0

523,060 131,345 0 620,675

1,275,080

1,275,080

1,275,080

1,275,080

Table 3 Energy consumption related to 1 ton of paper (93% DS) Energy

Virgin pulp

Recovered pulp

Paper

Heat Electricity

8682 MJ 4639 MJ

182 MJ 982 MJ

5982 MJ 2473 MJ

The total energy consumption related to 1 ton of paper is found by adding the numbers for either recovered or virgin pulp with the numbers for paper production.

deposited in landWlls. However, this scenario is highly unlikely, as it would imply that the entire mixed fraction of waste has to be deposited, contrary to national Danish policies and EU policy within this Weld. Furthermore, today, 33 waste incineration plants are established in Denmark. However, the scenario is used to shed some light on the diVerences between incineration and the use of landWlls. Only the disposal stage has been changed in this scenario meaning that the recycling continues, as it was in 1999. Only the environmental impacts related to paper waste are considered. The fundamental characteristics of this scenario compared with the situation in 1999 are shown in Table 2. 6. Life cycle inventory In this section, the data collection on emissions from the processes throughout the life cycle of paper is described. 6.1. Forestry The inventory of the forestry stage is based on Swedish data based on Miljøstyrelsen (1996). The inventory includes 75 MJ diesel burned in forest machinery per kilogram wood (45% DS), limestone, pesticides and nitrous fertilisers. According to the guidelines for scoping the LCA of recycling of paper, utilisation of wood should be accounted for either by contribution to land use (biodiversity) impact category or by perceiving wood as a fully utilised resource; i.e., increased consumption of wood will then cause decrease in other applications of wood, e.g., wood for energy purposes. Here, the latter was applied. Hence, consumption of 1 kg of wood for pulp production results in 1 kg less wood available as biomass for energy purposes. The ‘missing’ energy supply will be met by increased use of marginal sources of energy, which are identiWed as natural gas. Thus, consumption of 1 kg of wood saves emissions equivalent to the burning of 8.2 MJ wood (the caloriWc value for wood is 18.3 MJ/kg 100% DS) and causes the emissions equivalent to the burn-

ing of 8.2 MJ natural gas. The applied inventory data for forestry machines is based on the burning of diesel in the BUWAL database (BUWAL, 1996). Inventories for burning of wood and natural gases are also based on the BUWAL database and the ETH-ESU database, respectively. 6.2. Pulp and paper Heat in the pulp and paper industry is produced in combined heat and power plants with eYciencies at 85% (60% heat and 25% electricity) based on the European Commission (2001). The surplus or remaining demand for electricity is met by exchanges with the grid. Fuel composition in production of virgin pulp and paper is met by 69% wood residuals, 20% natural gas, 8% oil and 3% coal (StoraEnso, 1999), while fuel consumption in production of recovered pulp is met by natural gas. Energy and material inputs, as well as emissions related to pulp and paper production, are based on the European Commission (2001). For production of virgin pulp, a weighted average of 61% chemical, 10% semi-chemical and 29% mechanical pulp, which represents the average consumption in Denmark, has been applied. Correspondingly an average of 23% new paper, 12% non-coated paper, 20% coated paper, 31% corrugated paper and 15% cardboard has been applied for paper production. The energy consumption is summarised in Table 3. It appears that the total energy requirements for the production of 1 ton of virgin paper are 21.8 GJ; while the corresponding energy requirements for the production of 1 ton of paper from recovered pulps are 9.6 GJ. The inventory includes all signiWcant ancillary materials and Wllers such as sodium hydroxide, sulphuric acid, bleaching agents, starch, chalk, and kaolin. For most of the material inputs, inventories from the ETH-ESU database in SimaPro have been applied (ETH-ESU, 1996). Also emissions of N, P, chlorine as well as heavy metals are included.

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Table 4 Characterised results for the 1999 situation Life cycle stage

Global warming, in million ton CO2-eq

Ozone depletion, in kg CFC11-eq

AcidiWcation, in 1000 ton SO2-eq

Eutrophication, in 1000 ton NO3-eq

Photochemical smog, in ton ethane-eq

Forestry Pulp and paper production Transport Incineration

1.75 1.14 0.22 ¡0.85

43 189 177 ¡4

0.2 7.7 2.9 ¡0.7

¡1.5 12.5 5.0 ¡1.3

¡319 413 38 ¡13

2.27

404

10.1

14.7

119

Total

6.3. Incineration Emissions and material inputs related to incineration of paper are based on an inventory in BUWAL (1996). The BUWAL inventory includes Xue gas treatment with acid and alkaline treatment and catalytic removal of NOx. However, since the BUWAL database represents Swiss waste incineration in cases where no heat and electricity is recovered from the process, avoided heat and electricity representing Danish technology have been applied to the inventory. According to Energistyrelsen (1995), Danish waste incineration plants have total energy eYciency at 85%, distributed on 24% electricity and 61% heat. According to Bennedsen (1993), dry paper send to incineration has an average caloriWc value of 12.6 MJ/kg (92% DS). 6.4. LandWll Emissions and material inputs to landWll are based on an inventory in BUWAL (1996). This inventory includes wastewater treatment, sludge treatment and sludge incineration and energy recovery from biogas. The electricity included in inventory has been adjusted in order to reXect marginal electricity (i.e., based on natural gas) instead of average Swiss electricity. 6.5. Transport Transport includes transportation of the paper by lorry through its life cycle. Transportation of ancillaries and Wllers has not been taken into account. Transport distances are based on a weighted average of distances to central areas of the countries who supply paper to Denmark. The applied inventory for transportation is based on the BUWAL database (BUWAL, 1996). 7. Life cycle impact assessment In this section the results of the LCA are presented and discussed. 7.1. Reference scenario First, the results from the basis scenario in 1999 are shown as both characterised results cf. Table 4, as well as normalised results, i.e., calculated as person equivalents

(PE). Negative numbers represent an environmental improvement compared to the 1999 situation; positive numbers represent deterioration. In order to identify which of the impact categories in Table 4 are most signiWcant, the characterised results are normalised, see Fig. 2. As can be seen from Fig. 2, the most signiWcant impacts from handling paper in the 1999 situation is global warming, acidiWcation and eutrophication. Thus, no further attention will be given to ozone depletion and photochemical smog. It appears from Fig. 1 that forestry is a very signiWcant life cycle stage regarding global warming. This seems counter logic, as forestry is normally regarded as a stage requiring low resource input and causing low levels of emissions. This is the case when only analysing the inputs and outputs to the forest stage. However, as mentioned in part 6, alternative use of wood is taken into account. Therefore, when using wood, the marginal processes aVected are the marginal sources of energy, i.e., natural gas. This system expansion is responsible for more than 99% of the contribution to global warming from the forestry stage. The second highest contributing stage regarding global warming is the production of pulp and paper. Incineration contributes to negative values, i.e., impacts are avoided due to the production of heat and electricity at the incineration plant. This causes avoided production of heat and electricity produced from fossil fuels (natural gas). More than 90% of the contribution to global warming comes from CO2, primarily derived from the provision of heat and electricity in the diVerent phases of the life cycle. AcidiWcation mainly originates from the phases of pulp and paper production and transportation. For pulp and paper production it primarily stems from SO2 from the CHP-plants, while NOx is the primary contributor from transportation. Eutrophication comes primarily from NOx from energy production, as well as from transportation and from N and P emissions in wastewater from pulp and paper production. 7.2. Scenarios The results from the three scenarios compared to the impacts of the 1999 situation are presented as normalised results in Fig. 3. The bars representing scenario 1 in Fig. 3 show the eVect of moving paper from incineration to recycling. Scenario 2

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Fig. 2. The environmental impacts in the 1999 situation, shown as normalised results for selected impact categories: global warming, ozone depletion, acidiWcation, eutrophication and photochemical smog. Net contributions are given above each chart.

Fig. 3. The impacts from the proposed scenarios for handling the paper waste stream compared to the basis scenario, the 1999 situation. The numbers reXect the normalised results calculated as person equivalents (PE).

shows the eVects of terminating the collection scheme for paper in Denmark, moving paper from recycling to incineration causing a signiWcant increase in demands for virgin pulp. Scenario 3 shows the eVect of closing down incineration plants in Denmark and disposing waste onto landWlls instead but at the same time maintaining the same level of recycling as in 1999. It can be seen from the Wgure that the results conWrm the validity of the waste hierarchy, when it comes to global warming and acidiWcation. For eutrophication and photochemical smog, an increase in incineration

(scenario 2) is better than increased recycling, while the diVerences regarding ozone depletion seems insigniWcant. The main reason for increased recycling being the best alternative compared to incineration regarding global warming and acidiWcation is that the ‘indirect’ eVects of using wood have been taken into account. As described in relation to Fig. 1, alternative use of wood/land is taken into account, assuming that consumption of wood will aVect alternative applications of wood, i.e., for energy purposes thus increasing use of natural gas.

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When it comes to eutrophication, incineration is better than increased recycling. The reason for this is that increased recycling means less incinerated paper, less produced energy, and consequently, we will see an increase in Danish district heating which is based mainly on fossil fuels and technologies with relatively large NOx emissions. When recycling increases, the processes most signiWcantly aVected are forestry and production of recovered pulps and virgin pulps. As there is no production of virgin pulp in Denmark and as Danish forestry only exports insigniWcant amounts of wood for pulp, the environmental beneWts of increased recycling take place outside Denmark. Conversely, increased recycling means less incineration and following less avoided energy production in Denmark. Hence, the environmental ‘costs’ of increased recycling will take place in Denmark. Depositing waste paper in landWlls is the worst alternative for all impact categories. For example, the bars in Fig. 3, which represent scenario 3, are all positive, meaning that there are undesirable environmental impacts related to the landWlls compared to incineration. The reason why the landWlls are the worst alternative is that there is no energy savings in this scenario; i.e., the use of fossil fuels are not substituted by paper waste used for energy production in incineration or wood saved for energy purposes. In general, landWlls can be concluded to be less preferable than incineration. When it comes to ranking of increased recycling compared to increased incineration, increased recycling turns out to be preferable for global warming and acidiWcation while increased incineration seems to be preferable in relation to eutrophication and photochemical smog. Of course, the question is then, whether global warming and acidiWcation are more important than eutrophication and photochemical smog. Fig. 3, presenting the normalised impacts, i.e., calculated as total PE, gives an indication of the beneWts being signiWcantly larger in the recycling scenario than in the incineration scenario. Taking the weighting factors of EDIP into consideration does not change this at all. Global warming has Wrst priority when it comes to Danish as well as European environmental policy. On this basis, it seems reasonable to conclude that recycling is preferable compared with incineration and that landWlling is the worst scenario. 7.3. Uncertainties The following discusses the most signiWcant uncertainties. One signiWcant hot spot is the forestry stage caused by the system expansion, where alternative use of wood is taken into account. Since the system expansions related to the consumptions of wood are often left out from LCAs on waste management systems for paper, a sensitivity analysis has been conducted. Should alternative use of wood or any impacts on biodiversity not be included (i.e., what most LCAs on recycling of paper do (Villanueva et al., 2004)), this study will still prove that increased recycling is preferable to increased incineration for global warming. However,

the result for acidiWcation shifts in favour to incineration when not including alternative use of wood/land. The LCA has been conducted applying marginally aVected processes, i.e., mainly marginal energy sources rather than averages. The applied marginal technology for electricity is natural gas. However, according to Weidema (2003), it is debatable whether the marginal technology is natural gas or coal. Should coal be applied as the aVected technology, the total contribution to global warming increases by 28%, ozone depletion by 3%, acidiWcation by 77%, eutrophication by 19% and photochemical smog by 43%. Although the conclusions of this study are conWrmed, it appears that the result is sensitive to changes in identiWcation of the marginal technology for energy. This calls for cautiousness when deciding on the system delimitations and the types of technologies assumed used in these studies. Some uncertainties are related to determination of inventory data for the paper industry regarding general representative energy consumption, energy eYciencies for CHPs and emission levels. Uncertainties are also attached to determination of caloriWc values for waste paper and energy eYciency at waste incineration plants. However, the results seem quite clear, regarding global warming. Even when the energy consumption in production of virgin pulp equals zero, increased recycling is preferable to incineration. Energy consumption in production of recovered pulp can be increased 4.5 times before incineration becomes preferable to recycling, and energy production at waste incineration has to be increased by 60% before incineration turns out to be preferable to recycling. As it appears, the results do not seem to be sensitive; not even signiWcant uncertainties in inventory data and in the deWnition of system boundaries can change these conclusions. 8. Conclusion The LCA on diVerent ways of handling the paper Xow in Denmark clearly shows that the waste hierarchy is an appropriate principle for guiding the handling of waste in society, at least for paper waste. With some reservations, it can be concluded that recycling is better than incineration, which again seems better than depositing in landWlls. The investigation of the diVerent environmental impacts clearly shows that the beneWts very often are to be found abroad; in this case regarding the eVects on forestry in other countries and the alternative uses of the wood that is no longer needed for production of virgin pulp and paper. Although we conclude that the waste hierarchy is a sound principle regarding the handling of waste paper, it does not necessarily apply for other types of waste. In similar studies, it shows that the principle does not work for inert materials such as glass, because incineration is a far worse alternative than landWlls (Holm et al., 2002). For other types of organic materials, it appears that some types of recycling, such as composting or even making biogas, are often worse than incineration (Kromann et al., 2004; Jansen and Christensen, 2003).

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The type of investigations comparing diVerent waste handling strategies is necessary in order to validate or reject the waste hierarchy as a principle. It could be argued that the principle should be rejected altogether and substituted with speciWc assessments both based on LCA and also economically validated by using cost-beneWt or cost-eVectiveness methods. Ideally, such investigations could demonstrate the whereabouts and the size of environmental beneWts. The combination of economic methods such as cost-beneWt analysis or cost-eVectiveness could give a clearer indication of the most cost-eVective use of allocated resources to waste management. At times, the debate among environmental researchers and economists was intense, especially in Denmark, where the Institute of Environmental Assessment has produced several reports questioning the validity of the waste hierarchy. One of the major problems seems to be that system delimitations are not comparable in the two diVerent methodologies. Environmental scientists increasingly seem to emphasise that the entire life cycle is the study focus. Contrary to this, economists preferably take the national economy as their starting point (Dengsøe, 2005), producing awkward conclusions such as recycling not being beneWcial, because they neglect the beneWts from substituting the use of wood in Swedish forestry (Petersen and Andersen, 2002). The use of LCA in speciWc types of investigations is important in order to validate the actual environmental pros and cons of waste handling strategies. This does not necessarily mean that we have to keep the waste hierarchy as a guiding principle for decision making. Such analyses could delimit the fractions and the circumstances under which the waste hierarchy is appropriate. If in doubt, speciWc investigations should be undertaken. However, we should not forget that the principle reXects fundamental insights, which are gained from decades of environmental policy making, i.e., leaving behind strategies as dilution and clean-up strategies on behalf of more preventative strategies. The waste hierarchy principle has some pedagogical advantages such as when citizens use it to make decisions on whether to throw away empty beer cans into the countryside, into the rubbish bin or to collect them into a separate box for recycling. Should speciWc investigations be requested for each and every diVerent waste fraction, producing diVerent results, confusion will probably arise which would make the whole exercise even more insurmountable than it is today. References Bennedsen, J., 1993. Konsekvenser for forbrænding ved frasortering af organisk aVald (Consequences for incineration when source separating organic waste). Enviroplan A/S for Miljøstyrelsen, Arbejdsrapport fra Miljøstyrelsen, nr. 59, Miljøstyrelsen, Copenhagen. Brisson, I.E., 1997. Assessing the Waste Hierarchy – a social Cost-beneWt analysis of Municipal Solid Waste Management in the European Union, AKF Forlaget, Copenhagen, Denmark. (accessed 14.03.2001). BUWAL 250, 1996. Ökoinventare für Verpackungen, Schriftenreihe Umwelt 250, Bern, Switzerland.

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