Excluding site-specific data from the lca inventory: how this affects life cycle impact assessment

LCA Methodology and Case Study Site-Specific Data

Excluding Site-Specific Data from the LCA Inventory: How This Affects Life Cyde Impact Assessment

Stuart Ross 1" and David Evans 2

1 School of Anthropology, Geography and Environmental Studies (SAGES), University of Melbourne, Parkville, Victoria, 3010, Australia 2 Faculty of Architecture, Building and Planning, University of Melbourne, Parkville, Victoria, 3010, Australia

* Corresponding author ([email protected])

Introduction

Ever since the International Standardisation Organization (ISO) agreed to produce a set of standards for Life Cycle Assess- ment (LCA), the technique has been subjected to intense scru- tiny by academia, industry and government. Probably the most controversial aspect of the methodology is the exclusion of site-specific data from the life cycle inventory (LCI). This omission is important because it affects the utility and reliability of conclusions made during impact assessment [1-3].

Although there is general support within the LCA community for the simplified approach to data collection and aggregation described in the inventory phase [4--5], in recent

years there has been much discussion about how these data relate to environmental impacts [6-13]. Indeed, there are an increasing number of environmental practitioners who are questioning the relevance of LCA results for the prediction of actual environmental impacts [14-15]. For example, a study performed by Owens examining toilet paper concluded that many emissions were not related to actual impacts and were difficult to interpret when aggregated [6]. Despite cau- tionary statements in the ISO standards [16-17] and many discussions on this topic in the literature [1-15], the significance of this approach for impact assessment has rarely been tested in practice [18]. This is a concern, because this source of uncertainty has the potential to undermine the credibility of conclusions drawn from LCAs [14].

Thus, it would appear that the implications of not collecting site-specific data for policy development are quite serious. White et al. [7] point out that the practice of calculating global parameters for impact categories by aggregating data across the life cycle assumes a worst-case scenario that could 'misguide improvement measures or policy-making'. Therefore, we conducted a case study to investigate the extent to which it is practical and valuable to collect site-specific data during the inventory phase of an LCA.

To achieve this aim we begin with a brief review of what has already been written by the research community regarding this source of uncertainty. The objective of this review is to show that this limitation, though acknowledged and justi- fied in the literature [19-20], is nevertheless controversial and has the potential to greatly diminish the value of LCA results. Having explored the theoretical basis of the problem, we then examine its practical significance in a case study. Finally, we offer some recommendations on how this problem might be tackled.

1 The Site-Specific Nature of Some Environmental Mechanisms Underlying LCIA Impact Categories

LCA is concerned with the material and energy efficiencies of product systems, and how their emissions may interact with the environment. The category indicator results from the impact assessment are communicated in terms of global mass-loadings on a functional unit basis for substances that have been known to contribute to the formation of undesir- able environmental effects. For example, some of the sys-

Int J LCA 7 (3) 141 - 150 (2002) �9 ecomed publishers, D-86899 Landsberg, Germany and Ft. Worth/TX, USA * Tokyo, Japan �9 Mumbai, India �9 Seoul, Korea

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Site-Specific Data LCA Methodology and Case Study

tem processes will be powered by energy derived from fossil fuel and some of the combustion products will contribute to radiative forcing, otherwise known as the greenhouse effect. All greenhouse gases emitted by product systems any- where in the world are then assumed to contribute to a single global 'effect.' However, this is only true for effects that manifest at a global scale. For all other non-global environmental processes, site-specific information is needed to de- termine whether an emission will make a significant contribution [21-23]. Indeed, Owens [2,11] argues that the current indicators relate to emission burdens or loadings, and that without this additional site-specific data, significant sources of uncertainty are introduced for the impact assessment phase of the LCA and that the magnitude of these uncertainties will vary depending on the environmental impact category.

Therefore, one of the key factors undermining the reliability of LCA results is the lack of site-specific data collected during the inventory phase. In particular, the debate has fo- cused on the exclusion of spatial, temporal, dose-response and threshold data from the life cycle inventory [3,9,10]. Of course, the main reason for omitting such data is to simplify the collection process, the justification being that the additional time and effort required to collect it would render the technique impractical [24]. The present approach is already an expensive and time-consuming exercise without the pros- pect of having to collect even more data.

We believe that for some impact categories the additional effort required to collect the relevant site-specific data is small compared to the improvement that can be achieved in the reliability of conclusions. This is because the quantity of additional data needed varies depending upon the impact category being examined. Owens states that using site-ge- neric inventory data for impact categories that manifest at increasingly small spatial and temporal scales becomes increasingly inaccurate [11]. In other words, if we wish to provide reliable input into policy aimed at reducing the risk of ecotoxicological and health effects, then we need to collect a significant amount of site-specific data, including spatial, temporal, dose-response and threshold information [21- 23]. However, for effects that manifest over time because of an accumulation of relatively small quantities of pollutants from multiple diffuse sources, it is more desirable to identify the potential significance of process emissions in terms of their contribution to a cumulative environmental effect rather then quantifying the actual dose emitted from the product system. For global cumulative effects of long duration this is simple, because all emissions linked to these effects will contribute regardless of where and when the emissions take place. However, for non-global cumulative effects, whose significance varies across time and space, we need to collect spatial and temporal information before we can state confidently that some or all of a product system's emissions will contribute in a significant way to these effects. To test this hypothesis, we undertook a case study of a product system whose life cycle processes occurred in a variety of locations and whose emissions contributed to a cumulative environmental effect that varied in severity across time and space.

2 The Case Study: Comparison of Plastic Packaging Systems

The Australian company Email Ltd. produces approximately 350 thousand refrigerators per year in its factory in Orange in inland New South Wales, 300 km by road west of Sydney. These range in size from 140 to 650 litres capacity. For transport to customers these are encased in protective packaging. To reduce damage rates, Email has begun to replace their present corrugated-cardboard packaging system with a plastic-based system. This packaging consists of expanded polystyrene (EPS) top and bottom caps moulded to fit the refrigerator snugly, plus EPS side-pieces, all enclosed in a tight heat-shrunk transparent polyethylene (PE) bag. Although Email is convinced of the performance benefits of the new packaging system, they are concerned that the additional plastic material will generate an unacceptable landfill burden. Though the current EPS/PE packaging is able to protect the refrigerator during transport and handling, the EPS components them- selves usually suffer enough damage to preclude their reuse, and must be discarded to landfill after a single use. To over- come this, it has been proposed that the packaging be made even more resistant to accidental impact damage than the current system by bonding a layer of high-impact polystyrene (HIPS) onto the outside of the polystyrene foam top, bottom and side pieces before shrink-wrapping in polythene. This EPS- HIPS/PE packaging could then be recycled or reused, thereby reducing the flow of material to landfill.

2.1 Impact category: Photochemical smog

Because we are interested in exploring the advantages and disadvantages of including site-specific data, we have lim- ited our impact assessment to an analysis of a single non- global cumulative impact category, the presence of a significant concentration of photochemical oxidant precursors in the atmosphere. As discussed earlier, we believe that collecting spatial and temporal data will allow us to generate more reliable conclusions about our product system's contribution to this impact category. Besides calculating the aggregate emissions for this impact category, spatial and temporal data will enable us to differentiate between emissions of photochemical oxidant precursors across the life cycle that occur within regional air compartments where the concentration of photochemical oxidants in the Australian environment is known to be a significant problem [25-26].

Thus, we collected information about the location and rate of life cycle process emissions in addition to material and energy input and output data. Though the role of the spatial information has already been discussed, we need to explain the significance of the temporal dimension of the data. The timescale for the removal of photochemical oxidants through a variety of processes (advection, diffusion, conversion and deposition) in urban areas typically ranges from one hour to one day [27]. Therefore, we had to make sure that the accumulation of precursors per functional unit (the packaging for a single refrigerator) occurred within the timeframe of formation of high concentrations of oxidants. As Email produces approximately 1000 refrigerators per day, we were able to conclude that all process emissions were relevant on

142 Int J LCA 7 (3) 2002


a functional unit basis because they occurred within a timeframe that was consistent with the formation of photochemical oxidants in the atmosphere.

2.2 Goal and scope of LCA case study

Our task was to compare the fully aggregated and partially aggregated quantities of photochemical oxidant precursors emitted into the atmosphere of various plastic-based packaging systems. We assessed the following four options:

1. A system of moulded expanded polystyrene (EPS) components encased in a polyethylene (PE) heat-shrink wrap (all packaging is sent to landfill after use) and

2. three different approaches that use a system of moulded expanded polystyrene (EPS) components fused to a high impact polystyrene (HIPS) coating sheet and encased in a polyethylene (PE) heat-shrink wrap. These approaches, given below, differed in the origin of material inputs and the eventual fate of the packaging after use. a. As with the EPS/PE packaging, all EPS-HIPS/PE pack-

aging is manufactured from virgin material inputs and discarded to landfill after use (i.e. 0% recycling and 0% reuse)

b. The EPS-HIPS component of the packaging is recycled back into HIPS. EPS and PE are manufactured from virgin material inputs (i.e. 100% recycling of HIPS- EPS, PE is sent to landfill)

c. The EPS-HIPS component of the packaging is reused and only PE is manufactured from virgin materials (i.e. 100% reuse of EPS-HIPS packaging components, PE is sent to landfill).

The functional unit for this comparison was the packaging assembly for a single 500 litre capacity refrigerator.

2.3 System boundaries

Product system emissions of photochemical oxidant precursors can occur at every point of the life cycle of the packaging, right through from the extraction of the original materials and energy resources, the transformation of these into useable manufacturing inputs, the manufacturing process itself, the transport and distribution of intermediate and end products, and the use and final disposal. Thus, we chose to include all stages in the life-cycle from 'cradle to grave' and even made a rough estimate of construction energy for the main transport and processing equipment. Fig. 1 and Fig. 2 are simplified systems diagrams for each packaging life cycle. Coal, natural gas and crude oil from the natural environment are used as raw material and energy inputs for both packaging systems.

The second packaging system may be implemented in three ways: (a) all components are made from virgin materials; (b) EPS-HIPS components are recycled back into HIPS, and EPS and PE are made from virgin materials, or (c) EPS-HIPS components are reused 100% of the time and only PE is made from virgin materials. Fig. 2 shows these three options.

Oil - -

Coal

Gas

r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

Construction systems

=I Energy I ,J Transport r I systems ~ systems

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refinery ~ Styrene ~ plant ~ Ethane Packaging

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System Waste boundary gases

Fig. 1 : Life cycle of the EPS/PE packaging system

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,

Oil

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011 refinery

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I I (b) Virgin EPS and recycled HIPS I HIPS-EPS recycled L Damaged EPS-HIPS I i n t o ~ e r = s

| Pentane I ~(a) Virgin EPS and virgin HIPS

=,n,ne r J Eps-.,ps plant I q resin ~ moulds ~ plant

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System Waste boundary gases

Fig. 2: Life cycle of the three options for the EPS-HIPS/PE packaging system

3 Process Descriptions and Data Sources

In this section we briefly describe the methods used in Aus- tralia to make the three major components of these two packagings: EPS, EPS-HIPS, and PE shrink-wrap. In particular, we detail the assumptions made and the sources of data used for each of these materials.

3.1 Manufacture of EPS, EPS-HIPS and PE

The starting material for EPS packaging is s t y rene m o n o -

mer . This is made by reacting benzene with ethylene after cracking ethane. In Australia, benzene is derived from the benzene/toluene/xylene mixture (BTX) obtained as a by- product in the manufacture of coke from bituminous coal, and ethane is separated from natural gas. EPS resin is formed by adding pentane to the polymerisation process. EPS packaging is then moulded under temperature and pressure from this resin [28].

As with EPS the starting point for virgin high impact polystyrene (HIPS) is the s t y r e n e m o n o m e r whose manufacture is discussed above. Rubber is added during the polymerisation stage to give the HIPS toughness and impact resis- tance. HIPS resin can also be manufactured in a recycling process using discarded EPS-HIPS components and a small amount of dissolved rubber. HIPS sheets are made by first melting the resin, extruding the viscous material through a

sheet die, cooling and then slitting to the desired width. These toughened polystyrene sheets are then fused onto the EPS moulded packaging components to increase their resilience to knocks and provide opportunities for re-use [29].

PE shrink-wrap film is manufactured from polyethylene resin made from low-density polyethylene (LDPE), but can include up to 10% of linear low-density polyethylene (LLDPE). In Australia, LDPE is produced by the high-pressure flee-radical polymerization of ethylene in a stirred-autoclave reactor and LLDPE is produced using gas-phase 'Unipol' polymerization [29]. The PE bags are then shipped in gussetted-tube roll form to Email, who heat-shrink the wrap over the EPS or EPS-HIPS assembly encasing the refrigerator.

3.2 Sources of data

Energy and material requirements for the operation of oil wells, gas wells, oil refineries and gas separation plants were either supplied by Broken Hill Pty Ltd. or taken from the work of Boustead [30]. All of our data on materials requirements and energy flows for the manufacture of EPS and HIPS resin were provided by Polystyrene Australia. However, we took the precaution of comparing our results for the manufacture of resin with those obtained for Europe by Boustead [31]. Though the results for total energy consumption compared well with Boustead's findings, the contributions from

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the various sources of fossil fuel varied considerably. In Aus- tralia, coal is used to derive benzene, whereas in Europe this input is derived from the naphtha fraction of crude oil.

Energy requirements for the manufacture of EPS components were those we calculated in a previous study [32]. Our data for resin manufactured using the recycling process was supplied by National Polystyrene Systems. HIPS sheets are manufactured by Flight Plastics in Wellington, New Zealand. They provided the necessary data for the extrusion process and transportation of the product back to Australia. The final fusing together of EPS and HIPS is done by National Polystyrene Systems in Orange. Any waste from this process or returned packaging that cannot be reused is fed into a recycling plant that produces HIPS resin. Data for these processes were supplied by National Polystyrene Systems. Material and energy data for the PE film manufacturing process were supplied by Orica Australia and AEP Visqueen.

Transport energy for road tankers and trucks was calculated from data provided by Polystyrene Australia and Email. For shipping and pipelines we used data from life cycle assessments undertaken in Switzerland and Sweden [33-34]. Because the Swiss and Swedish data are quite old, we performed a sensitivity analysis at the conclusion of the study. This analysis indicated that errors in these data would not have a significant effect on the results.

Construction energy was estimated from the indicative costs of equipment provided by Emait, Santos, Orica Australia and AEP Visqueen for the various process steps, and the energy intensity for that type of equipment in megajoule (MJ) per dollar. This method is rather crude, but is adequate from a sensitivity analysis viewpoint, and we feel it is certainly better to make a reasonable estimate of this energy than to entirely ignore it, as is the custom in most life cycle assessments [35].

4 Life Cycle Inventory

In this section, we present the results of the Life Cycle In- ventory [36].

4.1 Energy delivery systems and virgin material inputs

Table 1 reports the results of our preliminary calculations for inputs of energy and feedstock. In this table direct energy input refers to the coal, oil or gas in the ground; process energy refers to other forms of energy required to oper- ate the harvesting and converting processes; transport energy refers to the energy required to bring the harvested material to the conversion plant; and construction energy refers to the energy required to build the harvesting, conversion and transport equipment, spread out over its lifetime.

4.2 Recycling subsystem

One of the packaging options includes a recycling subsystem as part of the life cycle. National Polystyrene Systems pro- pose to use recycling technology that will allow damaged EPS-HIPS components collected after use to be recycled back into HIPS resin. Fig. 3, which is one possible option for the product system described in Fig. 2 (see option b), shows that the material flows involved in 100% recycling of EPS- HIPS components exhibit characteristics of both open- and closed- looped systems [38--42]. An important life cycle ben- efit of this approach is the production of excess HIPS roll that is available for use by other product systems. This oc- curs because the quantity of HIPS roll produced from recycling damaged EPS-HIPS packaging is more than is required for the manufacture of an equivalent quantity of new EPS- HIPS components. In the next part of the analysis, we have credited this excess to the recycled packaging system by calculating the quantity of primary energy and photochemical

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S i t e - S p e c i f i c D a t a L C A M e t h o d o l o g y a n d C a s e S t u d y

Fig. 3: 100% recycling of EPS-HIPS components: material flows in kg for 1 kg of EPS-HIPS/PE packaging for a 500 Iitre refrigerator

oxidant precursors avoided for HIPS roll made from virgin inputs per kg and then deducting this from the burden calculated for the manufacture of EPS-HIPS components [38].

4.3 Packaging materials

In this section, we calculate energy and then photochemical oxidant precursors for the manufacture, use and disposal of various combinations of packaging materials used to make up the components involved in the refrigerator packagings under examination. These materials are EPS mouldings from virgin materials; HIPS sheets from virgin and recycled ma-

terial; EPS-HIPS mouldings from virgin and recycled materials; and PE film from virgin materials.

4.3.1 Energy flows

Table 2 is a summary table showing the energy flows for the production of I kg of each of the packaging components, en- tries in this table represent the amounts of primary energy required to produce the energy in its useable form. For example, the transport energy is used in the form of diesel distillate, but the entry here is for the crude oil and other types of primary energy required to produce this distillate (see Table 1).

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As can be seen from Table 2, the energy required to manufacture 1 kg of EPS-HIPS mouldings using a recycling strategy is much less than the energy required to manufacture it from virgin inputs of EPS and HIPS. This is because recycling of EPS-HIPS components back into HIPS resin allows the packaging manufacturer to avoid processing steps for HIPS rolls made from virgin materials that are more energy- intensive than the transport and recycling processes.

4.3.2 Photochemical smog

Photochemical smog is a serious problem in many cities and even regions around the world. Photochemical oxidant pollution is made up of primarily ozone but includes other species such as nitrogen dioxide (NO2), hydrogen peroxide (H202) and peroxyacyl nitrates (PAN). Oxidants are almost exclu- sively secondary pollutants formed by reactions of primary pollutants in the presence of sunlight. The primary pollutants, often referred to as precursors, are non-methane volatile or- ganic compounds (NMVOCs) and nitrogen oxides (NO,,). The main anthropogenic sources of these pollutants are incom- plete combustion of carbonaceous material [27].

The packaging systems have several life cycle processes that are sources of photochemical oxidant precursors. They include the generation of electricity in power stations, the combustion of fuel used in transporting materials between processes in the life cycle and the combustion of gas in boilers used to produce steam. Many different figures for the generation of NO x and NMVOCs from these sources are given in the literature. We used the figures prepared by the Aus- tralian Greenhouse Office [43-44]. From this information, we calculated the aggregate quantities of each precursor for each packaging system.

Calculating partially aggregated contributions to photochemical oxidant formation is more complicated because we need to identify those emissions occurring in areas where the build up of oxidants and their precursors in the local

atmosphere is known to exceed policy targets. In this study, Sydney and Melbourne are the only cities in Australia where the concentration of ozone exceeds the no-effect threshold defined in the air emission regulations [45--47]. We have therefore identified the processes occurring within these locations and then calculated their combined contribution per kilogram of each material used in the packagings. Thus, the photochemical oxidant precursors emitted during the generation of electricity will be excluded because the power stations are remote from these cities [48]. Also, any package manufacturing steps occurring in Orange can be excluded. However, some oxidant precursors from the use of transportation energy must be apportioned, and the synthesis of plastic resins is also included because these happen in Sydney and Melbourne.

For both packagings there are emissions of NO x and NMVOCs in Sydney and Melbourne from the high temperature combustion of diesel distillate in transport vehicles. In Melbourne there are also contributions from the consumption of gas during the manufacture of EPS and HIPS resin from virgin materials, and likewise in Sydney for the moulding of EPS used in the original EPS/PE package and the production of PE resin.

The pentane emitted during the expansion of polystyrene to EPS is itself a volatile hydrocarbon, and will contribute di- rectly as an oxidant precursor. The amount of pentane emitted is 0.05 kg per kg of EPS. However, the pentane emission only contributes to Sydney's air pollution levels for the EPS/ PE packaging. For the EPS-HIPS/PE packaging, the libera- tion of pentane during the expansion of EPS resin now oc- curs in Orange.

Table 3 presents the approximate quantities of NO x and NMVOCs that are released in aggregate across the packaging life cycle and in partially aggregated format for the Sydney, Melbourne and rural atmospheres as the result of the manufacture, use and disposal of the various packaging materials.

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4.4 Packaging weights

The inventory calculations were made on the basis of the production, use and disposal of 1 kg of various types of packaging material. We now have to re-express our results on the basis of the task performed by the packaging system, that is to bring refrigerators to customers. Table 4 gives a breakdown of the weights and component materials of the two packaging systems for the 500 litre capacity refrigerator.

Table 4 shows that the overall weight of the HIPS modified packaging is about 20% less than the original packaging. This is because the increased strength of HIPS allows less EPS to be used while still increasing the durability of the packaging. Rather than present the aggregated LCI values for each system in this section, we have integrated the relevant data into our discussion on impacts in the next section.

5 Life Cycle Impact Assessment

In this section we will use the results from the life cycle inventory to calculate the impact category indicator results for the emission of photochemical oxidant precursors for each packaging system [17].

5.1 Photochemical oxidant precursors

Using the inventory data in Table 3 and the component weights in Table 4, we can calculate the aggregate emissions of photochemical oxidant precursors for each packaging system. Along with aggregate values, we have also identified and separated the emissions that occur in the Sydney and Melbourne atmospheres because they are the only loca-

tions in Australia that experience high concentrations of ozone. Table 5 lists these burdens for each packaging and Fig. 4 & Fig. 5 displays this data graphically.

Table 5 shows that the aggregate photochemical emissions from the EPS/PE packaging are about 25% more for NO x and twice as much for NMVOCs on a functional unit basis than for non-recycled and recycled EPS-HIPS/PE packaging. This is mostly due to the 20% reduction in weight achieved with the new packaging. However, the real improvement comes when we move to a system of 100% reuse of the EPS-HIPS components. NO x emissions are less than a quarter of the original packaging system and emissions of NMVOCs are almost zero. This is because the energy-intensive steps involved in the manufacture of EPS- HIPS mouldings are no longer required. Thus, from the perspective of reducing photochemical oxidant precursors, the EPS-HIPS/PE packaging is superior in all cases to the current EPS/PE packaging.

The reduction in photochemical oxidant precursors of the new packaging is even more significant when we examine emissions in Sydney and Melbourne . By changing packagings, we achieve a reduction in NO x emissions of 90% in Sydney and 40% in Melbourne and even greater reduc- tions in NMVOCs. As for our analysis of the aggregate emissions, we can credit this improvement in part to the reduction in overall weight of the new packaging. However, the application of spatial information in our analysis has uncovered additional important factors. These are the relo- cation of the energy intensive EPS moulding processing-step away from Sydney to Orange and the substitution of some EPS with HIPS, which is a less energy-intensive material to produce (see Table 2).

Table 5 also shows that if we were only considering a choice between EPS-HIPS/PE made from virgin materials and EPS- HIPS/PE made from a combination of virgin materials and recycled HIPS, there would seem to be little justification, based on aggregate photochemical emissions, for going to the extra trouble and expense of implementing the recycling subsystem. Indeed, Polystyrene Australia informed us that the recycling option is only financially viable if a significant proportion of the EPS-HIPS components can be reused rather then recycled.

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However, the story changes when we analyse the effect on emissions in areas where the concentration of photochemical oxidants is a significant problem. Table 5 shows that, for the production of EPS-HIPS/PE packaging, NO x emissions fall by 75% and NMVOC emissions fall by 20% in Melbourne because the main recycling process for HIPS oc- curs in Orange whereas the main processing steps for the manufacture of virgin HIPS occur in Melbourne. Again, this cannot be appreciated in the aggregated values and demon- strates the important contribution that spatial information can make to life cycle assessment.

6 Conclusions

Several important observations can now be made.

�9 This case study is important because it shows that the aggregation of photochemical oxidant precursor emissions into a single global parameter is an unreliable indicator of environmental burden and that for non-global environmental impact categories, the inclusion of site- specific data in the life-cycle inventory enhances the utility and reliability of conclusions drawn from LCA re- suits. It achieved this by demonstrating that the real significance of each packaging's contribution to photochemical oxidant precursors in the atmosphere could only be properly understood after the appropriate spatial and temporal factors were taken into account. With this additional information we were able to separate out those emissions from the packaging's life-cycle that contributed to places where significant concentrations of photochemical oxidants were common. In Australia, only Melbourne and Sydney have recurring photochemical smog incidents [45-47] and so only emissions in these locations are actually important.

�9 The case study illustrates how policy developers could draw very different conclusions from impact category data that was aggregated into a single global parameter and data that was aggregated based on spatial factors. By collecting the appropriate site-specific data, we were able to get a better understanding of the potential environmental impacts of each packaging system.

�9 This study has also indicated that for non-global environmental impact categories, significant improvements can be achieved by simply changing the geographical location of certain process steps, and that this strategy should be considered as a legitimate way of reducing the burden of a product system.

The aim of our study was to investigate the extent to which it was practical and valuable to collect site-specific data during the inventory phase of an LCA. We found that the collection of spatial and temporal data about the emissions from our product systems was a straightforward task that could be done easily whilst gathering input and output data for materials and energy. Our case study also showed that the addition of spatial and temporal information describing product system emissions together with an assessment of the significance of cumulative environmental effects in the area can greatly enhance the insights and value of LCA results.

If assessors wish to produce reliable conclusions regarding the contributions of a product system to non-global cumulative impact categories, spatial and temporal information should be collected in addition to the existing inventory requirements. Without this additional level of analysis, which is not part of the current ISO methodology, the significant reduction in emissions of photochemical oxidant precursors in locations where they are a problem would not have been apparent. Indeed, the use of aggregate data alone to describe the contribution of a product system to non-global environmental impact categories could mislead policy development and limit the opportunity for environmental improvement.

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Received: December 28th, 2001 Accepted: April 20th, 2002

OnlineFirst: April 29th, 2002

150 Int J LCA 7 (3) 2002

Excluding site-specific data from the lca inventory: how this affects life cycle impact assessment

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