Hospido RRC06 47-56

Resources, Conservation and Recycling 47 (2006) 56–72

Environmental assessment of canned tunamanufacture with a life-cycle perspective

A. Hospido a, M.E. Vazquez c, A. Cuevas c,G. Feijoo b, M.T. Moreira b,∗

a Chemical Engineering Department, Institute of Technology, University of Santiagode Compostela, 15782 Santiago de Compostela, Spain

b Chemical Engineering Department, School of Engineering, University of Santiagode Compostela, 15782 Santiago de Compostela, Spain

c R&D Department, Luis Calvo Sanz S.A., 15100 Carballo, Spain

Received 30 November 2004; accepted 24 October 2005Available online 24 January 2006

Abstract

Growing awareness of environmental problems during recent years has led to increased demand forenvironmental information about seafood products. In particular, this report is an attempt to evaluatethe manufacturing process of canned-tuna products. Bearing in mind the lifestyles of people in the 21stcentury, canned products are one of the commonest ways in which seafood products are presented.Spain is the second largest exporter of processed tuna in the world, behind Thailand. The fish andshellfish canning industry is mainly grouped in Galicia where 65% of the total production takesplace.

To this aim, the method used to study the environmental impact of these products is Life CycleAssessment (LCA), which follows a product through its entire life cycle. The system under studyincludes landing at harbour, transport to the factory, processing inside the factory, final productdistribution to markets and use in households. The results show that processing accounted for thegreatest percentage in all the impact categories, except human toxicity potential.

Inside the factory, the production and transportation of tinplate was identified as the most significantcontributor and, consequently, improvement actions were proposed and evaluated, such as an increasein the percentage of the recycled tinplate used and the substitution of tinplate by another packagingmaterial. Both proposals would diminish the adverse environmental effects of this process; however

∗ Corresponding author. Tel.: +34 981 56 31 00x16776; fax: +34 981 54 71 68.E-mail address: [email protected] (M.T. Moreira).

0921-3449/$ – see front matter © 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2005.10.003

A. Hospido et al. / Resources, Conservation and Recycling 47 (2006) 56–72 57

they imply a change in the final appearance of the product to be consumed and, therefore, acceptanceby consumers is a fundamental factor in their success.© 2005 Elsevier B.V. All rights reserved.

Keywords: Canned tuna; Environmental management; Life Cycle Assessment (LCA); Life cycle inventory (LCI);Seafood

1. Introduction

For public health reasons, authorities in many countries promote the health benefitsof seafood and encourage the consumption of more marine products. Such campaigns,together with the recent image problems of the meat and poultry industries in health, animalwelfare and environmental issues, have probably contributed to the increasing demand forseafood products (Ziegler, 2003). In fact, fish is gaining ground as a protein source in thehuman diet. In Spain (year 2002), the consumption of fish was 27 kg per capita as against68 kg of meat per person, the most significant source of protein for humans (Langreo,2003).

Nevertheless, modern lifestyles and news habits of consumption have had a marketinfluence on seafood consumption and tendencies are different with regard to diverse typesof seafood. As can be seen in Fig. 1, canned products have risen continuously since 1990whereas fish, frozen fish, shellfish, molluscs and crustaceans have been somewhat unstablein Spain during the same period of time (Langreo, 2001). Among the species available in themarkets, tuna is the commonest canned seafood product. According to FAO (2004), Spain isthe second largest exporter of processed tuna in the world, behind Thailand. Specifically, thefish and shellfish canning industry is mainly located in Galicia (NW of Spain) where around

Fig. 1. Evolution in consumption of products from fisheries in Spain (1990–2000). Fresh fish in black columns;frozen fish in dark grey columns; shellfish, molluscs and crustaceans in light grey columns; and canned productsin dotted columns.

58 A. Hospido et al. / Resources, Conservation and Recycling 47 (2006) 56–72

65% of the total production takes place. Five large factories are responsible for around 58.6%of the total turnover (Omil et al., 2004), and, one of these facilities in particular was selectedto carry out the present analysis.

The consumers, companies and the authorities responsible for the development ofimproved sustainability have all increased their interest in the environmental performanceof food products (Consoli, 1993). The future systems for food production and consump-tion in particular need to be based on global and ecological points of view, where minimalenvironmental impact and efficient utilisation of natural resources must be important cri-teria in the development of food products and the selection of food systems (Andersson,2000).

When discussing the environmental impact of food production, it is important to use aholistic approach as the food supply chain is complex and entails several steps that needto be evaluated (Mattsson and Sonesson, 2003). Life Cycle Assessment (LCA) makes theevaluation of the environmental impact of a product through its entire life cycle possible.According to the International Organisation for Standardisation (ISO), LCA is a structuredprocess developed in four stages (ISO, 2000):

• goal and scope definition, in which the intended application as well as the extent of thestudy has to be clearly exposed;

• inventory analysis (LCI), where information about the product system is gathered andrelevant inputs and outputs are quantified;

• impact assessment (LCIA), which converts the flows from the inventory into simplerindicators related to the potential impacts associated;

• interpretation of the results, where the findings of the two previous steps are combinedand evaluated to meet the previously defined goals of the study.

However, these phases are not currently performed in the cited sequence. Carrying out anLCA is an iterative process, in which subsequent reiterations may imply increasing levelsof detail, from a screening LCA to a full LCA, or even, the necessity for changes in the firstphase prompted by the results of the previous phases (UNEP-DTIE, 2003).

In the early 1990s, the first LCA studies of food products were carried out and, sincethen, this environmental tool has been used to address questions about food processingrelating both to the identification of the subsystems that contribute most to their total envi-ronmental impact and to a comparison of products and processes with an identical function(Mattsson and Sonesson, 2003). Seafood products in particular have hardly been stud-ied from an LCA perspective; to the best of our knowledge, the available references arefew and recent. Ziegler et al. (2003) have studied the entire life cycle of frozen cod asan example of seafood emphasising the fishery-specific types of environmental impact.Thrane (2004) has worked on the analysis of a wide range of Danish fish products, suchas flatfish, also from a life cycle perspective. A finding common to both studies is that thefish harvesting stage of the production cycle typically accounts for 70–95% of the totalimpact regardless of the impact category considered. As a consequence of this finding,that stage was studied in detail separately (Hospido and Tyedmers, 2005) and this paperdeals with the post-landing activities, from transport harbour-factory to consumption inhouseholds.

https://www.researchgate.net/publication/222707528_Life_cycle_environmental_impacts_of_Spanish_tuna_fisheries?el=1_x_8&enrichId=rgreq-1a1ef97b-b928-4516-bfb9-838a2ac76d0d&enrichSource=Y292ZXJQYWdlOzIzMzg1Mjc3OTtBUzo5Nzc1MTU2NDAyOTk1M0AxNDAwMzE3MTk3MTAz

https://www.researchgate.net/publication/240606688_Environmentally_Friendly_Food_Processing?el=1_x_8&enrichId=rgreq-1a1ef97b-b928-4516-bfb9-838a2ac76d0d&enrichSource=Y292ZXJQYWdlOzIzMzg1Mjc3OTtBUzo5Nzc1MTU2NDAyOTk1M0AxNDAwMzE3MTk3MTAz

https://www.researchgate.net/publication/240606688_Environmentally_Friendly_Food_Processing?el=1_x_8&enrichId=rgreq-1a1ef97b-b928-4516-bfb9-838a2ac76d0d&enrichSource=Y292ZXJQYWdlOzIzMzg1Mjc3OTtBUzo5Nzc1MTU2NDAyOTk1M0AxNDAwMzE3MTk3MTAz


2. Goal and scope definition

2.1. Objectives

The principal objective of this paper is to evaluate the environmental impact of cannedtuna manufacture as a first approach in the evaluation of the seafood sector from an environ-mental point of view. To achieve this goal, a representative Galician factory that processesmore than 26,000 tonne of raw tuna annually was inventoried and analysed from a gate-to-grave perspective, that is to say, from the gate of the factory to the disposal of the wastesgenerated during the production and the consumption stages.

The identification of the activities with a great environmental impact will make it possibleto establish how to modify the process and to quantify the impact reduction associated tothe proposed strategies. This study is complementary to the analysis of the fishery stage(Hospido and Tyedmers, 2005) and enables us to have a global overview of the environmentalimpact of the canned tuna life cycle.

2.2. Functional unit

The functional unit is defined by the ISO standards as a quantified performance of aproduct system for use as a reference unit in an LCA study (ISO, 2000). Here, the functionalunit (FU) selected is 1 tonne of raw frozen tuna entering the factory.

2.3. Description of the system under study

Fig. 2 shows a graph of the process under study. The system starts at the harbour, wherefrozen carcasses are landed and transported to the factory by trucks (named subsystem 1).Inside the factory, the canned tuna manufacture is divided into seven subsystems, six ofwhich are related to the process itself and the seventh comprises the ancillary activities,such as wastewater treatment and tinplate production for packaging:

• Subsystem 2: Reception, thawing and cutting. Frozen tuna is unloaded and stored incold rooms awaiting processing. After quality controls, whole fish are thawed ini-tially by leaving them in a warmer room and thereafter they are submerged in ponds.Then, the fish is cut manually, and, afterwards, the vast majority of the blood isremoved.

• Subsystem 3: Cooking. This is a key step as the quality of the finished product greatlydepends on it. Steam is used to cook the fish which is then sprayed with water to cool itbefore it is cleaned.

• Subsystem 4: Manual cleaning. Skin, viscera, bones and other useless parts are taken outby hand.

• Subsystem 5: Liquid dosage and filling. Cans are filled with cut or flaked fish and differentkinds of sauces such as olive oil, vegetable oil or pickle. Thereafter, they are sealed andwashed.

• Subsystem 6: Sterilisation. The cans are sterilised and cooled in tunnels with steam andwater, respectively. Then, they are dried for final activities.

https://www.researchgate.net/publication/222707528_Life_cycle_environmental_impacts_of_Spanish_tuna_fisheries?el=1_x_8&enrichId=rgreq-1a1ef97b-b928-4516-bfb9-838a2ac76d0d&enrichSource=Y292ZXJQYWdlOzIzMzg1Mjc3OTtBUzo5Nzc1MTU2NDAyOTk1M0AxNDAwMzE3MTk3MTAz

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Fig. 2. System under study: P and T inside circles indicate that production and transportation are included; letters with arrows stand for water (W), wastewater (WW),vapour (V) and cans (C). The dark grey block is the cogeneration plant and the light grey blocks represent the down and upstream stages. Blocks presented in discontinuouslines have been left out of the boundaries.


• Subsystem 7: Quality control and packaging. Different quality control processes takeplace before the final packaging. Apart from cans, cardboard is used as the primarypackaging material as in the case of the triple pack (the most widespread option forcanned tuna). Additional packaging is necessary for product transportation: plastic filmto wrap the packs is often used.

• Subsystem 8: Ancillary activities. Two facilities have been included here: the assemblyshop for cans and easy-open rings as well as the wastewater treatment plant (WTP) whereboth high and low organic load effluents are treated before being released into the river.

Downstream from the canning factory, two more subsystems were considered: subsystem9 (labelled transport to wholesale and retail) considers final product distribution to the marketand subsystem 10 comprises the use of canned tuna at home (household use).

2.4. Data acquisition

The quality of an LCA is only as good as the information upon which it is based. Datamay be collected from the production facilities associated with the processes included inthe system or they may be obtained or calculated from published sources or databases.

During one year, data of all the input and output flows were collected to obtain a detailedinventory for each subsystem. In addition, materials production and transportation data wereobtained from the SimaPro 5.1 database (Goedkoop and Oele, 2003) and scientific papers,such as (Nicoletti et al., 2001). As a summary, Table 1 presents a list of the data takenfrom databases, their main sources, the period of time to which they correspond and theirgeographical origin.

According to Thrane (2004), it was assumed that for pelagic species, such as tuna, thematerial consumption is insignificant at the landing and auction stages. Therefore, only thetransport of frozen carcasses from the harbour to the factory gate was included in subsystem1. The shorter road routes were established (ViaMichelin, 2003) and associated fuel andemissions were estimated from a real world analysis of frozen fish transport systems (Karlsenand Angelfoos, 2000).

With regard to subsystem 9, an internal market study (Cuevas and Vazquez, 2003) madepossible to divide the distribution of the final product into two areas – the Spanish mar-ket (90%) and the European market (10%) – and transportation by road were included(ViaMichelin, 2003). Besides, and according to Thrane (2004), it was assumed that fornon-perishables, such as canned tuna, wholesale and retail phases are irrelevant.

Subsystem 10 starts with shopping: data for transport from retailers to households werebased on internal data from the company (Cuevas and Vazquez, 2003) and, in all cases, aneconomical allocation was performed for this transport (Ekvall and Finnveden, 2001), i.e.the environmental impact was divided between the different products bought on the basisof their economic value.

Life cycle ends at the waste management step and, here, average national recy-cled percentages were handled concerning packaging waste: 63.6% for tinplate cans1

1 http://www.ecoacero.com/cifrasreciclado.php (figure for the year 2004).

http://www.ecoacero.com/cifrasreciclado.php

https://www.researchgate.net/publication/223661433_Allocation_in_ISO_14041-A_critical_review?el=1_x_8&enrichId=rgreq-1a1ef97b-b928-4516-bfb9-838a2ac76d0d&enrichSource=Y292ZXJQYWdlOzIzMzg1Mjc3OTtBUzo5Nzc1MTU2NDAyOTk1M0AxNDAwMzE3MTk3MTAz


Table 1Sources, period of time and geographical origin of data

Element Databasea Period Geographic area

MaterialsLaboratory products ECOINVENTb 1992–2002 EuropeOlive and vegetable oils Scientific Paperc 1998–2000 Europe, ItalySteel stainless IVAM LCA Unspecified UnspecifiedPolypropylene BUWAL 250 1990–1994 Europe, WesternTin plate BUWAL 132 1985–1989 Europe, WesternCardboard BUWAL 132 1985–1989 Europe, WesternPolyethylene BUWAL 250 1990–1994 Europe, Western

EnergyCogeneration unit ECOINVENT 1992–2002 Europe

TransportationFrozen truck Scientific Paperd 1999–2000 Europe, NorwayTruck 28 t BUWAL 250 1990–1994 Europe, WesternDelivery van <3.5 t BUWAL 250 1990–1994 Europe, WesternPassenger car BUWAL 250 1990–1994 Europe, Western

Waste treatmentRecycling of several substances PRE 4 1985–1989 Europe, WesternRecycling of several substances BUWAL 250 1990–1994 Europe, Western

a Consult literature references at SimaPro and www.ecoinvent.ch.b See the special issue of the International Journal LCA for additional information: No. 1, 2005.

http://www.scientificjournals.com/sj/lca/inhalt/Band/10/Ausgabe/1/Jahrgang/2005.c Data presented at Table 1 of Nicoletti et al. (2001): See references section.d Data presented at the Annexe of Karlsen and Angelfoos (2000): see references section.

and 81.7% for cardboard2. The remaining waste was supposed to be disposed of inlandfills.

2.5. Considerations

• Canning processing: Some of the environmental impacts of the process have not beenincluded in full extension, e.g. food sealer, as it has not been possible to gather informationon the environmental costs of their production. However, transportation has been alwaysquantified and considered. On the other hand, viscera, entrails and fats are obtained andwere quantified in the inventory. They can be considered as a raw material for fishmealprocess and, in this sense, it would be a co-product rather than waste. However, due to thelack of available data this production process was left beyond the limits of our study andthose quantities were considered as waste. Finally, the canning factory has a cogenerationplant that requires heavy fuel oil to function (the dark grey block at Fig. 2) and providesboth electricity and thermal energy. In addition, two secondary boilers (running withheavy fuel oil) supply thermal energy when the cogeneration goes off. As a consequence,

2 http://www.aspapel.es/upload/estadisticas.pdf (figure for the year 2003).

http://www.ecoinvent.ch/

http://www.scientificjournals.com/sj/lca/inhalt/band/10/ausgabe/1/jahrgang/2005

http://www.aspapel.es/upload/estadisticas.pdf


no profile of electricity production was considered as all the electricity comes from thecogeneration plant.

• Storage at retail sites: Energy consumption from illumination and air conditioning sys-tems were considered negligible taking into account the small percentage that cannedtuna represents among all the products displayed in stores.

• Consumption in households: Canned tuna is usually used for salads, Russian salads, sand-wiches and filling eggs (Cuevas and Vazquez, 2003). Cooking or frying is not necessaryin any case so energy consumption is not associated to this step. Regarding the disposalof sauces, the common options are to tip them into the sink or use them in salads (Cuevasand Vazquez, 2003). Some load could be attributed to the former alternative; however,due to its smaller contribution to the total organic pollution load per person per year(1.02%), this effect was disregarded in this study.

• Transportation: On the one hand, the capacity of trucks was chosen bearing in mind thatit was the most similar option among those available from the database (BUWAL250,1996). On the other hand, transportation distances were estimated by means of roadguides (ViaMichelin, 2003). If transport turns out to be an important contribution to theglobal environmental impact, a sensitivity analysis would be necessary.

3. Life cycle inventory

As was mentioned, subsystem 1 only relates to the transportation of tuna from the harbourto the factory gate. The average distance of 37 km is covered by trucks (frozen cargo) witha capacity of 26 tonne (Karlsen and Angelfoos, 2000).

The inventory at the canning factory was mainly based on site-specific data for theyear 2003 and represents average data from a typical day of production. A summary foreach subsystem located in the canned factory is presented in Tables 2–8, where the termtechnosphere refers to those process or products related to the use of technology.

In the case of computing transportation at subsystem 9, extra weight for packaging (triplepack) was included as it corresponds to a significant percentage of the total mass (28%3).As was mentioned, two different areas of distribution were identified (the Spanish and theEuropean markets) and in both cases the distances, 650 and 2500 km, respectively, wereassumed to be covered by 28-tonne trucks (BUWAL250, 1996). As far as subsystem 10 isconcerned, Table 9 displays the inventory data obtained. According to an internal report ofthe company (Cuevas and Vazquez, 2003), canned tuna is bought in the following shoppingareas: 30% at superstores (where an average distance of 10 km, roundtrip, covered by carwas supposed), 54% at stores (where an on foot route was assumed) and 16% at grocerystores (where also an on foot route was considered).

As far as we know, inventory data related to seafood products have only been presentedby Ziegler (2002) where data for production, resource use and emissions from the industrialprocess were provided by a Norwegian company. However, direct comparison between

3 The 3-pack final presentation weights 334.4 g, where 240.0 g correspond to canned tuna (71.77%), 81.6 g tocans (24.40%) and the remaining 12.8 g to cardboard (3.83%).


Table 2Inventory data for subsystem 2 (Reception, thawing and cutting)

Inputs from the ThecnosphereMaterials

1. Raw frozen tuna (tonne) 12. Iron shelfa (g) 5693. Laboratory products (selected)

Sodium hydroxide (98%) (mg) 417Boric acid (99.8%) (mg) 258Ether (99%) (ml) 1.25Nitric acid (65%) (ml) 0.83Hydrochloric acid (37%) (ml) 0.83Mercury (mg) 0.33

4. WaterFor thawing (m3) 0.83For cutting (m3) 1.67

Thermal Energy1. Thawing (MJ) 111

Electricity1. Reception and Thawing (kWh) 0.672. Cutting (kWh) 23.62

Transport1. Laboratory Products (kg km) 1.072. Entrails and residual fish (t km) 3.08

Outputs to the ThecnosphereProducts

1. Tuna to subs. 3 (tonne) 0.92Waste to treatment

1. Wastewater to subs. 8 (m3) 2.502. Entrails and residual fish (tonne) 0.08

a A typical shelf is made of iron (185 kg) and can store between 250 and 400 frozen carcasses. However, theylast for years and can be reused indefinitely. As a consequence, this input was not considered a real input as theamount allocated to each tonne of tuna would be insignificant.

Table 3Inventory data for subsystem 3 (Cooking)


1. Tuna from subsystem 2 (tonne) 0.922. Water

For cooking (m3) 0.33For washing and cooling (m3) 0.92

Thermal Energy1. Cooking (MJ) 1385

Electricity1. Cooking and Washing and cooling (kWh) 24.19



1. Wastewater to subs. 8 (m3) 1.25


Table 4Inventory data for subsystem 4 (manual cleaning)


1. Tuna for subsystem 3 (tonne) 0.722. Cleaning instruments (Ua) 1.67

Electricity1. Manual cleaning (kWh) 9.69

Transport1. Cleaning instruments (kg km) 0.162. Dark meatb and entrails (t km) 10.05


1. Tuna to subsystem 5 (tonne) 0.46Waste to treatment

1. Entrails (tonne) 0.172. Dark meat (tonne) 0.09

a U stands for Units.b Also called sangacho.

Table 5Inventory data for subsystem 5 (liquid dosage and filling)


1. TunaFrom subs. 4 (tonne) 0.46From other factories (tonne) 0.20

2. Cans from subs. 8 (U) 120833. Tops from subs. 8 (U) 120834. Plastic bags (U) 1255. Liquid (sauces)

Olive oil (l) 107.5Vegetable oil (l) 346.7Pickle (l) 53.3

6. Water for can washing (m3) 0.5Electricity

1. Liquid dosage and filling (kWh) 47.19Transport

1. Tuna from other factories (t km) 14.692. Plastic bags (t km) 6.253. Liquid (sauces) (t km) 0.474. Entrails (t km) 0.25



1. Entrails (kg) 6.422. Wastewater to subs. 8 (m3) 0.5


Table 6Inventory data for subsystem 6 (sterilisation)


1. Tuna from subsystem 5 (tonne) 0.662. Coagulants (ml) 5.333. Flocculants (ml) 8.254. Water from subs. 6a (m3) 2.5

Electricity1. Sterilisation and recycling water system (kWh) 45.61

Thermal Energy1. Cans sterilisation (MJ) 12452. Bags sterilisation (MJ) 6923. Thawing room (MJ) 146

Transport1. Coagulants (kg km) 3.102. Flocculants (kg km) 4.783. Fats (kg km) 4.88



1. Fats (kg) 0.122. Wastewater to subs. 66 (m3) 2.5

a This stream is reused by means of a recycling water system included in this subsystem, so water here circulatesin a closed-circuit.

Table 7Inventory data for subsystem 7 (quality control and packaging)


1. Tuna from subsystem 5 (tonne) 0.662. Cardboard boxes (kg) 92.013. Film (kg) 5.424. Pallets (U) 2.08

Electricity1. Packaging (kWh) 33.332. Storage (kWh) 0.17

Transport1. Cardboard (t km) 10.932. Film (t km) 0.013. Pallets (t km) 5.274. Cardboard and film to recycling (t km) 0.09



1. Cardboard to recycling (kg) 1.922. Film to recycling (kg) 1.14


Table 8Inventory data for subsystem 8 (Ancillary Activities)

INPUTS from the ThecnosphereMaterials

1. Lubrication oil (ml) 502. Tinplate (kg) 3503. Food sealer (ml) 6334. Copper thread (kg) 3.885. Flocculants at WTP (kg) 0.016. Water for general cleaning (m3) 1.42

Electricity1. Packaging assembly shop (kWh) 58.732. WTP (kWh) 5.56

Transport1. Lubrication oil (kg km) 1.202. Tinplate (t km) 415.453. Food sealer (kg km) 0.554. Copper thread (t km) 4.375. Flocculants (kg km) 4.636. Residual tinplate (t km) 0.717. Residual food sealer (kg km) 8.238. Oil used and fats (t km) 1.33

OutputsTo the ThecnosphereWaste to treatment

1. Wastewater to subs. 8 (m3) 1.422. Residual tinplate (kg) 503. Residual food sealer (ml) 63.334. Used oil and fats (ml) 47.50

To the EnvironmentEmissions to water

1. Treated wastewater (m3) 5.67CODa (g/m3) 130N-NO3

− (g/m3) 0.5Emissions to soil

1. Sludge (kg) 1.74Emissions to air

1. Biogas (m3) 3.60a COD stands for Chemical Organic Demand.

those and these data is not possible as they are rather different case studies (frozen codversus canned tuna).

4. Life cycle impact assessment

The purpose of the third phase of the LCA is to analyse the inventory results to understandtheir environmental significance better by classifying the inputs and outputs of the inventoryphase in specific categories and modelling the inputs and outputs of each category into anaggregate indicator (ISO, 2000).


Table 9Inventory data for subsystem 10 (Household Use)


1. Tuna from subs. 7 (tonne) 0.662. Plastic bags (kg) 2.51

Transport1. Shopping (km) 0.09

Outputs to the ThecnosphereWaste to treatment

1. Tinplate cans (kg) 346.472. Cardboard (kg) 54.353. Plastic bags (kg) 2.51

In accordance with the default list of impact categories elaborated by Guinee et al.(2001), some categories were chosen among the so-called “baseline impact categories”:eutrophication, stratospheric ozone depletion, climate change (also called global warming),acidification, photo-oxidant formation and abiotic resources depletion.

First, emissions and resources are sorted into different categories according to theirpotential impact on the environment. Once classification is complete, characterisationtakes place in order to quantify the potential contribution of an input or output, J, tothe impact, CIJ, allowing aggregation into a single score by means of the followingequation:

CIJ = AJWIJ,

where AJ is the amount of input or output and WIJ is the weighting factor. The total potentialcontribution of all inputs and outputs to the effect, CI, is the sum of each CIJ.

Afterwards, normalisation is intended to perceive the relative magnitude of each envi-ronmental indicator from a non-dimensional approach. This procedure transforms the resultof an indicator by dividing it by a selected reference value, such as the total emissions orresource use for a given area (ISO, 2000). In the present study, the situation in WesternEurope (data from the year 1995) was taken as the reference scenario for all the impactcategories as this is the most complete list available (Huijbregts et al., 2003).

Fig. 3 shows the results obtained from the normalisation phase.

5. Interpretation of results and discussion

5.1. Contribution analysis

Once the more significant impact categories were identified, a contribution analysisallowed us to identify the subsystems with the highest environmental loads. In fact, Fig. 3indicates that both acidification and global warming potentials are the impact categorieswhere efforts have to be directed in order to decrease the overall impact of canned tunamanufacture processing.


Fig. 3. Normalisation values per functional unit. EP: Eutrophication Potential, ODP: Ozone Depletion Potential,GWP: Global Warming Potential, AP: Acidification Potential, POFP: Photo-Oxidants Formation Potential, ADP:Abiotic resources Depletion Potential.

In both categories, processing represents the greatest contribution with almost 85 and95%, respectively. Fig. 4 shows a detailed analysis for these categories: Subsystem 8, mainlydue to tinplate production and transportation, was responsible for 60.85% of the total GlobalWarming Potential and 54.76% of the total Acidification Potential associated to processing.The next step implies the proposal of diverse improvement actions in order to reduce theenvironmental impact of the whole system.

5.2. Improvement actions

The first option proposed is related to the recycled percentage of packaging materials.As it only concerns managers in factories, it may be easy to implement. In the inventorytinplate in particular with 23% of recycled was considered as it is the most similar to the realtinplate used at the factory (15–20%). However, a higher percentage is achievable withoutrisking the required characteristics of the packaging and two values were compared with

Fig. 4. Contribution analysis for significant categories (characterisation values).


Table 10Comparative data associated to the improvement actions proposed

GWP AP

No action 100 100Action 1a 83.86 90.00Action 1b 69.70 80.81Action 2a 48.70 51.72Action 2b 44.68 44.95

the original one: 50% (named action 1a) and 100% (named action 1b). Comparative resultsfrom evaluation are displayed in Table 10, where the real percentage was established as thebaseline at 100 (called no action).

Another type of action proposed and evaluated is the substitution of packaging materials.In Spain, some canning factories have recently initiated some activities in this direction andplastic bags have been put on the market. In order to evaluate this alternative, three scenarioswere defined (Table 10):

• No action: The present situation where tinplate cans of 52 g (dry weight) grouped 3 by 3with cardboard are used.

• Action 2a: Plastic bags of 140 g (dry weight).• Action 2b: Plastic bags of 618 g (dry weight).

The former is the common option used for canned tuna and the last two are technolog-ically feasible as they are used nowadays for salads for individual consumers and cannedtuna for the catering sector, respectively.

Each scenario comprises the production of the packaging material, its transportationto the canning factory as well as the treatment of the waste generated after using it. Thistreatment consists of recycling and landfilling according to the average national recycledpercentages for each type of material.

As Table 10 shows, important reduction is likely to be achieved if changes related topackaging are carried out. However, and according to Dainelli (2003), three elements shouldbe taken into consideration when dealing with the recycling of packaging materials: (i)best environmental performance; (ii) economic balance of the whole processes, includingcollection, sorting and transportation; and (iii) consumer acceptance of recycled materials,particularly in sensitive applications such as food packaging. Here, only the environmentalperformance has been evaluated and, consequently, no general conclusions can be derived.

6. Conclusions

A detailed inventory was carried out to evaluate the environmental performance of theactivities, excluding fishery, necessary to have canned tuna ready for consumption in ourhouseholds. In particular, processing was pointed out as the greatest contributor to theenvironmental impact. Going further, production and transportation of tinplate, the primarypackaging material used here, was identified as the least environmentally-friendly aspectof the industrial process. As a result, improvement actions were focused on this point and


two alternatives were proposed and evaluated: an increase in the percentage of the recycledmaterial and the replacement of the triple pack of tinplate cans by another option, such asplastic bags.

Although both strategies have pointed to a beneficial outcome for the environment,consumers, at least in Spain, are not very keen on changing food habits and, specifically,canned products are linked to tinplate cans. As a consequence, an important marketingcampaign is necessary to bring nearer these results and all the stakeholders involved.

Acknowledgements

This work has been partially financed by the Xunta de Galicia (Project references:PGIDIT04TAL262003PR). Almudena Hospido would like to express her gratitude to theSpanish Ministry of Education for financial support (Grant reference: AP2001-3410).

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