Life cycle assessment of Italian citrus-based products. Sensitivity analysis and improvement scenarios

Journal of Environmental Management 91 (2010) 1415e1428

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Life cycle assessment of Italian citrus-based products. Sensitivity analysis and improvement scenarios Marco Beccali a, Maurizio Cellura a, *, Maria Iudicello a, Marina Mistretta b, * a b

Dipartimento di Ricerche Energetiche e Ambientali (D.R.E.AM.), Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy Dipartimento di Arte, Scienza e Tecnica del Costruire (D.A.S.TE.C.), Università Mediterranea di Reggio Calabria, Salita Melissari, 89124 Reggio Calabria, Italy

a r t i c l e i n f o

a b s t r a c t

Article history: Received 16 June 2009 Received in revised form 7 January 2010 Accepted 7 February 2010 Available online 15 March 2010

Though many studies concern the agro-food sector in the EU and Italy, and its environmental impacts, literature is quite lacking in works regarding LCA application on citrus products. This paper represents one of the first studies on the environmental impacts of citrus products in order to suggest feasible strategies and actions to improve their environmental performance. In particular, it is part of a research aimed to estimate environmental burdens associated with the production of the following citrus-based products: essential oil, natural juice and concentrated juice from oranges and lemons. The life cycle assessment of these products, published in a previous paper, had highlighted significant environmental issues in terms of energy consumption, associated CO2 emissions, and water consumption. Starting from such results the authors carry out an improvement analysis of the assessed production system, whereby sustainable scenarios for saving water and energy are proposed to reduce environmental burdens of the examined production system. In addition, a sensitivity analysis to estimate the effects of the chosen methods will be performed, giving data on the outcome of the study. Uncertainty related to allocation methods, secondary data sources, and initial assumptions on cultivation, transport modes, and waste management is analysed. The results of the performed analyses allow stating that every assessed ecoprofile is differently influenced by the uncertainty study. Different assumptions on initial data and methods showed very sensible variations in the energy and environmental performances of the final products. Besides, the results show energy and environmental benefits that clearly state the improvement of the products eco-profile, by reusing purified water use for irrigation, using the railway mode for the delivery of final products, when possible, and adopting efficient technologies, as the mechanical vapour recompression, in the pasteurisation and concentration of juice. Ó 2010 Elsevier Ltd. All rights reserved.

Keywords: Citrus Life cycle assessment Water Energy Improvement scenarios Sensitivity analysis

1. Introduction Recent studies on the agro-food sector have shown that it is one of the most relevant contributors to environmental impacts, via resource depletion, land degradation, air emissions, and waste generation (Beccali et al., 2009). The intensification of agricultural practices has substantially increased water and fertiliser consumption (Carlsson-Kanyama et al., 2003). Fertiliser production significantly contributes to the Global Warming Potential (GWP), essentially from CO2, CH4, and N2O emissions. Fertiliser use causes nitrogen emissions (as NH3 and N2O), nitrate leaching, and potassium and phosphorus losses to water. Freshwater consumption for agricultural use accounts for about 70% of the total water use in the EU (Chapman, 2006). In

* Corresponding authors. Tel.: þ39 91 236139; fax: þ39 91 484425. E-mail address: [email protected] (M. Mistretta). 0301-4797/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2010.02.028

particular, about 60% of the ground water in southern Europe is used for irrigation at an unsustainable rate, contributing heavily to the potential depletion of aquifers in the medium- and long-terms (Beccali et al., 2009). The following key goals towards sustainability for the agro-food chain are highlighted from current literature: - lowering the use of fossil fuels in cultivation and manufacturing by introducing renewable energy sources and energy efficiency optimisation to reduce the related carbon footprint (Wiedmann and Minx, 2008)1; - reducing freshwater consumption in food processing by water recycling (Ardente et al., 2008);

1 Carbon footprint for a production process is defined as the amount of produced greenhouse gases over the life cycle of a product or service, measured in units of carbon dioxide (CO2) (Parliamentary Office of Science and Technology, 2006).

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- reducing waste generation along the food chain and increasing waste reuse/recycling (i.e., feed for animals) (van Weenen, 1995). Due to the complexity of the actions involved, Life Cycle Assessment (LCA) is suitable for estimating the environmental and energy performances at all stages of the life cycle of products (Andersson and Ohlsson, 1999; Foster et al., 2006). LCA provides benchmarks for eco-profiling of food products and a systematic basis for developing suitable indicators of sustainability for different foods. However, developing an LCA for the agro-food chain is extremely difficult. Moreover, LCA is complicated by the nature of the processes involved. Although modern farming can be compared to the industrial systems in which LCA has become well-known and accepted, agriculture should be considered more as a sequence of natural and industrial processes not completely controllable by humans. Therefore, the environmental impacts of agricultural processes are highly variable depending on the climate, soil type, farming practice, and many other inter-related factors, which must be taken into account when carrying out an LCA for an agro-food chain (Blengini and Busto, 2009). Detailed research studies have focused on the harmonising of LCA applications in agriculture (Audsley et al., 1997), and many reports deal with the life cycles of the most important agricultural commodities, such as the detailed report on the LCAs of ten key agricultural commodities by Williams et al. (2005). However, even if there are many studies concerning the agrofood sector in the EU and Italy and its environmental impacts, the literature is quite lacking in studies regarding the application of LCA to citrus products. This paper represents one of the first studies on the environmental impacts of citrus products from cradle to gate in order to suggest feasible strategies and actions to improve their environmental performance. It includes the analysis of the environmental burdens associated with the essential oil, natural juice and concentrated juice from oranges and lemons. The next sections synthesise the results of the life cycle assessment for each citrus product, which was more extensively published by Beccali et al. (2009). Then a sensitivity analysis estimates the variation in the energy and environmental performances of the final product, taking into account varying allocation methods, uncertainty related to secondary data sources, and initial assumptions on cultivation, transport modes, and waste management. Starting from the LCA results, which highlight significant environmental issues in terms of energy consumption, associated CO2 emissions, and water consumption, we modify the baseline scenario of production to investigate the potential for improvement in the ecoprofile of each citrus product. Therefore, scenarios for saving water and energy are proposed to reduce the environmental impacts of the examined products. Particular attention is paid to hot spots of production, such as primary energy consumption and water exploitation. 2. Case study: life cycle assessment of three Italian citrusbased products 2.1. Goal and scope definition The paper aims to assess the environmental impacts of citrus production and transformation processes to identify the most significant issues and suggest suitable options for improvement. LCA methodology is applied to assess mass and energy inputs and outputs at each production step, including indirect environmental impacts related to energy generation and water and raw materials production (ISO 14040, 2006).

2.2. Scope of the study: definition of functional unit and system boundary A detailed description of citrus production and industrial processing is presented in Beccali et al. (2009). Details of the production system examined are shown in Fig. 1. According to the UNI EN ISO 14040 standard, the functional unit (FU) is defined as the reference unit through which the performance of a product system is quantified in a life cycle assessment (ISO 14040, 2006). In the examined product system, six different FUs have been defined, 1 kg of each final product delivered by the manufacturer to distribution centres in Italy, Central Europe, the United States and Japan: -

oranges essential oil (FU1); oranges natural juice (FU2); oranges concentrated juice (FU3) lemons essential oil (FU4); lemons natural juice (FU5); lemons concentrated juice (FU6).

The energy and mass flows and the environmental impacts from the production of raw materials to the manufacturing of the end products have been assessed, following the “cradle to gate” approach. The following life cycle steps have been monitored and analysed: e cultivation and harvest of citrus fruit (lemons and oranges) in Sicily. e production and transportation of raw materials and fuels during all steps, via road lorries. e the processing of the citrus-derived products with regard to the production cycle of a Sicilian factory. The examined company is representative in size for its region; its yearly production is approximately the regional average for one year. e packaging. The sampled firm does not recover/recycle either the tanks containing the essential oil and concentrated juice or the tankers used for natural juice delivery; they are disposed as wastes. e transport of final products to distribution firms, using road tankers within Italy and Europe, and by sea freight within Italy and from Italy to the USA and Japan; The construction of facilities and equipment was not taken into account. Market phase, use, and end of life (disposal of organic residues and packaging) have been neglected. Since international rules for citrus products are not yet defined, we have followed the existing Product Category Rules for beverages, such as milk, wine, and mineral water (Beccali et al., 2009). 2.3. Life cycle inventory (LCI) analysis 2.3.1. Data quality Primary data were collected from the field, while secondary data have been taken from international literature and international databases (Beccali et al., 2009). The data complies with quality requirements of the European Platform on Life Cycle Assessment (European Commission, 2006a). The authors have collected the following yearly data from local investigation (reference year 2005): e Amount of citrus fruit (lemons and oranges) harvested; e Amounts of pesticides and herbicides used; e Amount of fruit (lemons and oranges) processed by the company;

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428

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Fertilizers Cultivation and crop

Water

Air emissions

Diesel Transport of citrus Electric energy Water

Primary Process (Citrus selection and washing, extraction)

Wastes (scraps, leaves, rejected citrus) Wastewater to purification plant

Recycled water

Water-oil emulsion

Electric energy

Secondary Process (Refining; Centrifugation)

Scraps

Juice line To pressing process

Essential oil line

Raw juice

Essential oil Packaging & Storage

Electric energy

Transport of final products

Secondary Process (Refining; Pasteurization and cooling) Steam

to purification plant

Air emissions

Juice

Wastewater Natural juice line

Concentrated juice line Electric energy

Electric energy

HFO, Diesel

Electric energy

Scraps Cooling water

Wet wastes, Wastewater

Methane

Refrigeration & Packaging

Concentration & cooling

Methane Steam

Natural juice HFO, Diesel

Air emissions

Air emissions Waste water to purification plant

Transport of final products

Concentrated juice

Cooling water

Electric energy

Packaging & Refrigeration

HFO, Diesel

Transport of final products

Air emissions

Air emissions Fig. 1. Flow chart related to citrus products life cycle.

e Water consumption for irrigation, estimated from the average rainfall in Sicily and the soil permeability; e Consumption of water, electricity, and methane in the production process, which were estimated from the working time and the power ratings of the machines; e Consumption of antiseptics, lubricating oils, and detergents; e Generation of solid wastes and wastewater. International databases were used to calculate the ecoinventories of raw materials and energy sources. In particular, the eco-profiles of chemical fertilisers were derived from Öko-Institut (2006), while the eco-profiles of pesticides, herbicides, diesel, water, electricity, and energy (Italian mix) and the environmental

impacts of methane supply and use were taken from PRè-Product Ecology Consultants (2006). The environmental impacts of energy sources (electricity, methane, diesel, and HFO2) were extracted from international environmental databases (Boustead, 2001; PRèProduct Ecology Consultants, 2006; Öko-Institut, 2006). 2.3.2. Allocation The multi-functional process under investigation is a coproduction process with six functional outflows. We applied the

2 HFO is the acronym for Heavy Fuel Oil, a typical fuel oil for marine engines that requires preheating before use.

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allocation procedure for the six FUs, following a combined mass and economic criterion (Beccali et al., 2009). Natural juice is the functional unit with the highest mass but the lowest economic value, while essential oil has the highest market value but the lowest mass (see Table 3 of the sensitivity scenarios). For essential oil (FU1 and FU4 lines of production), the economic criterion is applied from the cultivation and harvest steps to primary extraction, according to the rates of sale proceeds shown in Table 3. No allocation procedure is required for the subsequent processes related to the essential oil FUs. For juice lines, the manufacturer suggested using the assumption that 50% of pasteurised juice is packaged and distributed as natural juice (FU2 and FU5 lines), while the remaining 50% is conveyed to the concentration and subsequent refrigeration steps (FU3 and FU6 lines). In accordance with this suggestion, we apply the combined mass and economic criterion from the cultivation and harvest steps to the primary extraction of raw juice, assigning equal rates of sales to FU2 and FU3 and to FU5 and FU6 (Table 3). From the refining to the pasteurisation and cooling of the juice, a mass-based allocation is performed for electricity, methane, and water and used for the steam production and juice cooling, according to the company's suggestion. 2.3.3. Inventory results According to the above criteria of allocation, the inventory was performed for each FU, accounting for energy and raw materials consumption and environmental releases. The eco-profiles of each citrus product per FU are presented in Table 1. The Cumulative Energy Demand (CED), valued as primary energy, was calculated along the examined life cycle of each functional unit (Beccali et al., 2009). The CED is mostly due to the fertilisers and fuels used in cultivation, the electricity consumption in essential oil manufacturing, and the consumption of methane in juice pasteurisation and concentration. Global transportation has a higher share in the CED of the lemon FUs than the orange ones, due to the greater amount of travel from the lemon crop sites to the processing company and from the company to distribution firms. More than 80% of the indirect energy consumption for FU2, FU3, FU5, and FU6 is due to fossil sources. Renewable energy accounts for 6e8% of the entire consumption. With regard to water, direct consumption for irrigation and processing and indirect consumption in the water supply, energy sources, and raw materials production (such as fuel, fertilisers, pesticides, herbicides, lubricants, electricity, packaging, and detergents) are estimated. Direct consumption is mostly due to irrigation rather than processing, accounting for about 45% of the entire water consumption (both direct and indirect) in the life cycle of the FU. The smallest contributor to the water use is the manufacturing process, where steam is used for washing the citrus fruits and equipment and for generating emulsions in the essential oil lines, and for steam generation and juice cooling in the pasteurisation and concentration steps of the juice lines.

AP FU1 10% 0% FU6

FU2

-10%

Base Scenario

-20%

Scenario 1 -30%

Scenario 2 Scenario 3

FU5

FU3

FU4 Fig. 2. Incidence of electricity production on AP.

Noteworthy is the significant contribution of the amount of water required for the water supply, looking at the whole resource consumption. In fact, the supply of the water used directly in the assessed system involves further water consumption, which amounts to about 50% of the total required flow. 2.4. Interpretation The eco-profiles of the citrus products per FU are presented in Table 1. The Life Cycle Impact Assessment (LCIA) of the studied production system showed the following critical issues for the ecoprofiles of the FUs (Beccali et al., 2009): - Direct water consumption is mostly due to cultivation in the citrus groves, rather than processing. - The CED and GWP impacts are largely due to the production of chemical fertilisers, pesticides, and herbicides, to transport steps, and to methane consumption in the pasteurisation and concentration of natural juice. The above considerations suggest that the eco-profile of each final product may be significantly improved by the pursuit of suitable strategies to: - reduce the use of fossil fuels in the cultivation, transportation, and manufacturing steps; - reduce the consumption of freshwater during cultivation, especially for irrigation.

Table 1 Eco-profile of the citrus products per FUs. Impact category

Unit

Essential oil

Natural juice

Concentrated juice

Oranges

Lemons

Oranges

Lemons

Oranges

Lemons

Cumulative energy demand (CED) Global warming potential (GWP100) Acidification potential (AP) Eutrophication potential (NP) Photochemical ozone creation potential (POCP)

[MJPrim] [kg CO2eq] [g SO2eq] [g PO3 4 eq] [kg CFC-11eq]

1086 72.5 480 187 15.6

675 43.0 307 99 10.3

14 0.9 6.5 2.0 0.2

9.8 0.6 4.7 1.4 0.16

108 5.7 39 11.0 1.4

76 4 27.5 6.4 1.0

Water consumption

[kg]

90 057

44 293

966

507

5095

2271

Wastes

[kg]

125

1.2

6.1

78.3

0.8

3.5

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428

2.4.1. Sensitivity analysis The results of LCA studies do not represent “exact” data, but they are affected by uncertainty that arises from different factors noted by Bjorklund (2002):

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POCP FU1 10% 0%

-

parameter and model uncertainty; uncertainty due to choices; spatial and temporal variability; variability between sources and objects.

FU6

FU2

-10%

Base Scenario

-20%

Scenario 1

-30%

ISO 14040 provides guidelines on how to treat the above items and suggests investigating all parameters that can strongly influence the final eco-profile (ISO 14040, 2006). Sensitivity Analysis (SA) is “a systematic procedure to estimate the effects of the choice made regarding methods and data on the outcome of a study” (ISO 14044, 2006). SA helps to judge whether the collected data and scientific assumptions of a model are valid. Many tools deal with the above-mentioned issues of uncertainty within LCAs, among which scenario modelling is especially useful in cases where uncertainty about choices occurs (Huijbregts et al., 1999). The authors carry out SA on the input data and assumptions of the study to estimate which data and assumptions lead to the most uncertainties in the eco-profiles (Ardente et al., 2005). Thus, the initial hypotheses and data on the life cycle steps of each product and assumptions (as system boundaries or allocation of impacts) have been revised following a scenario analysis for estimating their impact on the final eco-profiles. The uncertainties of a generic parameter have been shown as a range of variation in the energy and environmental indices. The uncertainty of the results has been analysed and the quality of data assessed. The applied procedure has been iterative and interactive with other phases of LCA. The strength and the limits of the scenarios have been considered and reported due to the fact that the choice of different scenarios has been important for the results of LCA. A scenario analysis was performed for the following elements, adopting a linear model: -

Eco-profile of electricity. Transport of citrus products. Cultivation of citrus. Allocation rules. Scrap reuse.

To ensure the completeness of the evaluation, several parameters should be assumed and combined, thus involving a larger uncertainty than using only one parameter. 2.4.1.1. Sensitivity analysis of the electricity eco-profile. Electricity consumption is essential in the manufacturing process for each FU, from the primary extractions of the watereoil emulsion from citrus peels and the raw juice from pulp to packaging, storage, and refrigeration of the final products. In particular, the highest contribution to the CED occurs in the processing of essential oils (22% for FU1 line and 32% for FU4), while the lowest occurs in the processing of natural juice (6% for FU2 and 8.5% FU5). To compute the uncertainty related to electricity production, the following scenarios of medium-voltage electricity production3 have been compared:

3 All the databases include production and transport of primary energy sources and exclude the infrastructure of energy systems. Transport and transformation losses at grid are considered.

Scenario 2 Scenario 3 FU5

FU3

FU4 Fig. 3. Incidence of electricity production on POCP.

- Base Scenario e ETH-ESU 96: Medium-voltage electricity production and supply refer to the average Italian energy mix (PRè-Product Ecology Consultants, 2006); - Scenario 1 e Ecoinvent data v.2.0: Medium-voltage electricity at grid refers to the average Italian energy mix (PRè-Product Ecology Consultants, 2006); - Scenario 2 e BUWAL 250 v.2.0: Medium-voltage electricity in Italy includes the production and transport of primary energy sources and excludes the infrastructure of energy systems. - Scenario 3 e Ecoinvent data v.2.0: Medium-voltage electricity refers to the average European energy mix (PRè-Product Ecology Consultants, 2006). From the comparison of the different scenarios it is possible to observe that: - The CED has a negligible variation (<1%) both for lemon and orange FUs. The impact of the electricity production process on the GWP depends on the citrus product; it is not relevant (3%) for the natural juice products (FU2 and FU5), while higher rates of reduction are possible for essential oils (from 2% in Scenario 2 to 8% in Scenario 3). With regard to concentrated juice, the influence varies from 3% in Scenario 2 to 8% in Scenario 3. The above outcomes imply that the variations affecting the values of CED and GWP are globally low (10%), and thus the electrical eco-profiles have acceptable reliability. - The AP and POCP result in the most variable impacts, while the outcomes regarding NP have very small variations for almost Table 2 Contribution to the global environmental impacts from transportation steps (%). Impact category

Essential oil

Natural juice

Concentrated juice

Oranges Lemons Oranges Lemons Oranges Lemons Cumulative energy 15.8 demand (CED) 8 Global warming potential (GWP100) Acidification 10.4 potential (AP) Eutrophication 2 potential (EP) Photochemical ozone 11 creation potential (POCP)

17

36

44.7

26

31

9

22

30

18

23.5

14

39

51

28.3

37.5

4.3

6.5

6

9.6

43.3

54.7

28.5

2.4 15

37

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Fig. 4. Variation (%) of CED from Base Scenario due to the different transportation scenarios.

all the FUs (3%). The variations in AP and POCP in each scenario are shown in Figs. 2 and 3, respectively.

2.4.1.2. Sensitivity analysis of transportation. The contributions to each FU eco-profile of the citrus transportation from the crop site to the manufacturing company and of final product delivery to the distribution centres are shown in Table 2. Fuel consumption (diesel and HFO) and the related air emissions have been estimated, depending on the mode of transport and the distance covered. The eco-profiles of each fuel used were taken from the Sima-Pro 7 database (PRè-Product Ecology Consultants, 2006) (Base Scenario). Uncertainty in the eco-profiles of the fuel production is assessed in the following scenarios: - Scenario 1: the eco-profiles of fuels are taken from the Boustead database (Boustead, 2001). - Scenario 2: the eco-profiles of fuels are taken from the GEMIS database (Öko-Institut, 2006).

- Scenario 3: the eco-profiles of fuels are taken from the GaBi database (PE International, 2006). It can be noted that the fuel eco-profiles do not significantly influence the CED or the GWP. The variation in these impacts is no higher than 5% in any FU eco-profile (Figs. 4 and 5). AP, EP, and POCP result in the most increased impacts by the fuel eco-profiles. Fig. 6 shows the range of variation for AP in each ecoprofile; POCP and EP follow a similar trend. 2.4.1.3. Sensitivity analysis of cultivation stage. Citrus groves generally grow better in well-drained medium soil, which has to be neither clayey nor calcareous (Base Scenario). Soil characteristics influence the amounts of fertiliser and water consumption in the cultivation phase, due to the variation in permeability (Goebes et al., 2003; Chinkin et al., 2003). The authors estimated this influence assuming different feasible scenarios. In scenarios 1, 2, and 3 the citrus groves are in medium, clayey soil, medium, sandy soil, and dry, sandy soil, respectively.

Fig. 5. Variation (%) of GWP from Base Scenario due to the different transportation scenarios.

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428

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Fig. 6. Variation (%) of AP from Base Scenario due to the different transportation scenarios.

A Scenario 4 is performed, assuming that the needed quantity of water for irrigation is directly drawn from artesian wells by suitable electric pumps. In this way the further water consumption involved in the water eco-profile is not computed. In Scenario 5, the CO2 balance is calculated taking into account the yearly amount of CO2 absorbed by the citrus groves. Research on traditional Sicilian groves estimates an average of 520 kgC/ha is absorbed yearly (Inglese and Liguori, 2007). With regard to pesticide-based treatment, uncertainty depends on the “exact” applied quantity of the active ingredients (organic phosphorus compounds). Initially the authors supposed an average amount (5.35 kg/ha for the orange groves; 4.32 kg/ha for the lemon groves) (Base Scenario). The eco-profiles of pesticides were taken from PRè-Product Ecology Consultants (2006). The calculations have been repeated assuming application of the minimum quantities of herbicides and pesticides (3.55 kg/ha for orange groves; 3.20 kg/ha for lemon groves) (Scenario 6) and the maximum quantities (6.39 kg/ha for orange groves; 5 kg/ha for lemon groves) (Scenario 7) (CORERAS, 2006). The scenario analysis shows that: - The impact on the CED is negligible in Scenarios 6 and 7 (<1%), while it is reduced by about 1e2% in Scenario 1. Scenarios 2, 3, and 4 have the greatest impacts on the CED. Both Scenario 2 and Scenario 3 consistently increase the CED,

mostly due to the greater amount of fertilisers needed. On the contrary, Scenario 4 involves the greatest reduction of the CED in the eco-profiles of all the FUs. Globally, the impact on the CED varies from 16% (Scenario 4, FU1) to 12% (Scenario 3, FU1). - A similar trend of variation has been obtained for the GWP. Obviously, Scenario 5 would produce the highest reduction of the GWP in comparison with the other analysed scenarios. Such a reduction amounts to 20e25% in both the essential oil FUs (FU1 and FU4) and in the natural juice FUs (FU2 and FU5), while it accounts for 11% in FU3 and 17% in FU6. - AP, NP, and POCP resulted in the greatest influences on the impacts. The range of variation is quite large, when different FUs are considered. Fig. 7 shows the influence of the assumed scenarios on EP. The hypothesis of dry sandy soil (Scenario 3) induces the highest increase in AP (up to 16% e FU6). A similar trend has been obtained for the influence of the scenarios on POCP (Fig. 8). - The influence of Scenarios 6 and 7 on water consumption is negligible (<1%), while other scenarios have a greater influence (Fig. 9a and b). Scenario 1 would reduce water use by nearly 5% for every FU, while Scenario 3 would increase it by about 29%. Intermediate outcomes were obtained in Scenario 2. Scenario 4 causes the highest reduction in water consumption (about 50% in each eco-profile).

Fig. 7. Influence on EP from the soil permeability scenarios for each functional unit.

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POCP

20%

10% Scenario 1

0% FU1

FU2

FU3

FU4

FU5

FU6

Scenario 2 Scenario 3

-10%

Scenario 4

-20%

-30% Fig. 8. Incidence on POCP from the soil permeability scenarios with respect to the Base Scenario.

a

Water variation

FU3

Scenario 4 Scenario 3

FU2

Scenario 2 Scenario 1

FU1

-60%

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

Water variation

b

FU6

Scenario 4 Scenario 3

FU5

Scenario 2 Scenario 1

FU4

-60%

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

Fig. 9. Incidence on the water use from the most affecting scenarios for the (a) orange final products and (b) lemon final products.

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428 Table 3 Allocation factors in the different scenarios. Co-products

From oranges Essential oil Natural juice Concentrated juice Scraps

Functional units [kg/y]

13 0.2 0.4

40.40 FU1 24 167 FU2 1 654 920 29.80b FU3 330 984 29.80

0

Total From lemons Essential oil Natural juice Concentrated juice Scraps

b

1.2 82.3 16.5

0.3 23.9 4.8

0

0

71

100

100

100

2 78.4 19.6

0.5 22 5.5

0

0

72

100

100

100

52.20 FU4 57 725 FU5 2 292 025 23.90b 23.90 FU6 573 000

13 0.2 0.4 0

Total a

Base Scenario 1a Scenario 2 [%] Scenario [%] [%]

Economic value [V/kg]

Mass rates for each final product as regards the total ones. The amounts of natural juice and concentrated juice are assumed equal.

2.4.1.4. Sensitivity analysis of allocation rules. Many production systems have multiple outputs. The associated environmental burdens must be allocated to each product to accurately reflect their individual contributions to the environmental impact of the investigated system (Guinée, 2001; Guinée et al., 2004). According to ISO 14044 standards, the life cycle inventory is based on material balances between inputs and outputs of the system, and the allocation procedure should follow these fundamental relationships. This standard states that when it is possible to apply different procedures of allocation, a sensitivity analysis should be performed to assess the effects of each of these procedures on the results of the study (ISO 14044, 2006). Further, the ISO standard outlines the following steps for dealing with co-products allocation (Weidema, 2001; Weidema et al., 2004): 1. Allocation of the environmental burdens associated with the system under study should be avoided by dividing the multifunctional process into more sub-processes and collecting data related to them. 2. Where allocation cannot be avoided, the environmental burdens should be allocated according to a fundamental physical relationship that reflects how the inputs and outputs are changed by mass allocation.

CED FU1 150% 100% FU6

50%

FU2

0%

Base Scenario

-50%

Scenario 1

-100%

Scenario 2

FU5

FU3

1423

3. Where such a relationship cannot be identified, the allocation should reflect other relationships between the inputs and outputs of the systems, such as economic value. The system under study is a multiple-output process. Methodologically it was divided into six sub-processes, and an LCA was performed for each. Consequently, the allocation procedure was applied to the six FUs following a combined mass and economic criterion (Base Scenario). The choice of the allocation method is controversial in LCA studies, mostly due to its large influence on the final results (Weidema, 2001). We compare two different allocation methods with the Base Scenario. In Scenario 1, a mass-based allocation, rather than an economic one is used for all six functional flows. Despite their current recovery as semi-manufactured products, scraps were considered as residuals in the Base Scenario, due to their negligible role in the firm earnings. In Scenario 2, the calculations of the eco-profiles of the FUs have been repeated considering the scraps as a functional output, and a mass allocation was applied. Essential oil products have the highest price but the lowest mass, while natural juice products are the functional units with the highest mass but the lowest economic value. Consequently: - Scenario 1 has a relevant influence on each FU eco-profile. In particular it reduces all the environmental impacts for the essential oil products (50%) and the concentrated juice products (30e40%). The environmental impacts of the natural juice products (FU2 and FU5) are significantly increased in Scenario 1 (>100%); - the assumption of scraps as functional output (Scenario 2) affects the eco-profiles of all the FUs to a large extent due to their great mass and reduces each environmental impact. The relevance of the results is apparent in Table 3. Figs. 10e13 show the influence of the choice of the allocation method on the eco-profiles of the FUs. 2.4.1.5. Sensitivity analysis of scraps. Though scraps arise in large volumes from the production system, they have been considered as no more than wastes in the Base Scenario. They do not provide significant income to the processing company, but they can provide a social function, depending on their potential reuses. At the moment the company does not recycle scraps t, but they are pretreated and conveyed to landfill. Hence, the following scenarios of reuse are supposed: - Scenario 1: Methane required in the manufacturing process is extracted from the biogas produced by anaerobic digestion of scraps. The required amount of biogas is calculated from data in the international literature (Borjesson and Berglund, 2006; Jungbluth et al., 2007). - Scenarios 2 and 3 e Scraps are reused in animal feeds after a drying process. In particular, in Scenario 2 we suppose that scraps are conveyed to open build-up areas and dried naturally, while in Scenario 3 the scraps are conveyed to a methane dryer within the company studied. - Scenario 4: untreated scraps are reused for animal feed, without being dried. From a comparison of the sensitivity scenarios it is possible to observe that (Figs. 14e16):

FU4 Fig. 10. Incidence on CED by allocation methods.

- The waste reduction in Scenario 1 is the lowest in comparison with the other scenarios, depending on the significant amount

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GWP

200% 150% 100%

Scenario 1

50%

Scenario 2 0% -50%

FU1

FU2

FU3

FU4

FU5

FU6

-100% Fig. 11. Variation of GWP by the allocation methods.

of exhausted wastes from the scraps digestion. With regard to the essential oil FUs, it is negligible (<1%), while it is higher in the natural juice FUs (about 2%) and the concentrated juice FUs (9% in FU3 and 12% in FU6). Considerable waste reduction can be obtained with the other scenarios, which have the greatest range of reduction, from 70% in the eco-profiles of the orange FUs to 90% for the eco-profiles of the lemon FUs. - Scenarios 2 produces negligible variation in all the environmental impacts (1%) for each FU eco-profile. - The CED and the GWP are more significantly affected by Scenarios 1 and 3. The change in the CED varies from 9% (Scenario 1) in FU6 to nearly 60% (Scenario 3) in FU4, and in the GWP varies from nearly 16% (Scenario 1) in FU6 to 32% (Scenario 3) in FU4. In Scenario 3, the high rates of variation are due to the methane consumption in the drying process. Such rates also take into account the transportation of dried scraps to existing zootechnic companies. On the contrary, Scenario 2

does not involve any fuel consumption for the scraps treatment, thus affecting the CED and the GWP in a negligible way (<1%).

2.4.1.6. Discussion of main results. Sensitivity analysis has shown quite different variations in the eco-profiles of the assessed products. Table 4 shows the ranges of variation of the CED and the GWP. In the sensitivity scenarios of electricity production, there is a global reduction of the environmental impacts with respect to the baseline scenario. The low variations in the CED and the GWP in the different scenarios of electricity production suppose a good reliability of the electrical eco-profiles. In detail, Scenario 2 is the one with the least effect and produces variation lower than 3% for each impact indicator. Scenarios 1 and 3 have the highest reduction for every indicator, in particular the AP and POCP. However,

AP 150% 100% 50% Scenario 1 Scenario 2

0% -50% FU1

FU2

FU3

FU4

FU5

FU6

-100% Fig. 12. Variation of AP by the allocation methods.

EP

250% 200% 150% 100%

Scenario 1

50%

Scenario 2

0% -50% -100%

FU1

FU2

FU3

FU4

FU5

-150% Fig. 13. Variation of EP by the allocation methods.

FU6

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428

1425

Wastes 0.00 FU1

-0.20

FU2

FU3

FU4

FU5

FU6 Scenario 1

-0.40

Scenario 2 Scenario 3

-0.60

Scenario 4 -0.80 -1.00 Fig. 14. Incidence of scraps reuse scenarios on wastes with respect to the Base Scenario.

(AP: from 10.5% in FU1 to 34% in FU6; EP: from 3% in FU1 to 25% in FU6; POCP: from 5% in FU2 to 18% in FU6). The scenario analysis of the cultivation step has shown that soil characteristics significantly affect the environmental impacts of the assessed FUs. The higher the permeability of soil, the more fertilisers and water for irrigation are required. The higher influence on the eco-profiles of the orange products is due to the greater amount of fertilisers and water employed in orange groves than in lemon groves. An important reduction in the GWP has been obtained from the estimation of the CO2 fixed by Sicilian citrus groves. Drawing water directly from wells could significantly reduce the share of the resource consumption in the eco-profile of the FU, but it could deplete local freshwater sources.

this reduction is not necessarily due to the low reliability of databases but to the different reference energy mix. In fact Scenarios 1 and 3 are the most up-to-date, thus reflecting the changing Italian and European power mix, which is moving towards replacing oil substantially with natural gas. In particular, the highest variations induced by Scenario 3 are due to the different reference energy mix. Regarding transportation, the fuel eco-profile does not significantly influence the CED or the GWP (less than 5%), while AP, EP, and POCP are the most impacted by the fuel eco-profiles. In particular, Scenario 1 has the greatest influence on all the FUs because it overestimates the amounts of SOx and NOx (Boustead Model Ver. 4. 4). There is a large range of variation in such impacts

CED 2,000

1,600

FU1 FU2

1,200 MJ

FU3 FU4

800

FU5 FU6

400

0 Base Scenario

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Fig. 15. CED per functional unit in each scenario of scrap reuse.

GWP 100

[kg CO2 eq]

80

FU1 FU2

60

FU3 FU4

40

FU5 FU6

20 0 Base Scenario

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Fig. 16. GWP per functional unit in each scenario of scrap reuse.

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Table 4 Range of variation of CED and GWP.

Table 6 Option of purified wastewater reuse: induced variation in the current eco-profiles of the citrus products (%).

eq/FU]

CED [MJ/FU]

GWP [kg CO2

Min

Referring value Max

Min

Referring value Max

Orange products Essential oil (FU1) Natural juice (FU2) Concentrated juice (FU3)

277 11.7 72

1086 14 108

1594 28 136

13.5 0.6 3

74 0.9 6.0

89 2 12

Lemons products Essential oil (FU4) Natural juice (FU5) Concentrated juice (FU6)

261 7.6 60.4

1092 21 95.6

12.6 0.4 2.6

43.0 0.6 4

57 1.4 8.1

Impact category

Essential oil

Natural juice

Concentrated juice

Oranges Lemons Oranges Lemons Oranges Lemons

675 9.8 76

In the scenario analysis of the scraps, the strong increases of impacts in the scenario of biogas production and use essentially arise from the environmental releases in the anaerobic digestion. The other analysed scenarios involve the greatest range of waste reduction, and, in particular, Scenario 3 (assumption of a methane dryer) affects noticeably the CED and the GWP due to the consumption of methane during the drying process. While the scenarios of scraps reuse represent an entry point to the assessment of the potential related benefits, this approach is not a full evaluation of them. An exhaustive analysis should assess not only the environmental burdens associated with the production of substitute animal feed, but also the avoided costs of waste disposal and the incomes from the feed sale. The allocation of environmental burdens is a significant methodological problem in LCAs. Allocation is an artefact of applying LCA to individual products rather than to the whole productive system. The allocation procedure should either be avoided by expanding system boundaries or disaggregating the process into different sub-processes, or it should be solved by a suitable and consistent method (ISO 14044, 2006). The scenario analysis shows that the environmental loads associated with citrus products depend to a large extent on the method used for the life cycle allocation. Since the products with the lowest masses are the FUs with the highest economic value, while the products with the highest masses are the FUs with the lowest economic value, the two hypotheses of mass allocation reduce the environmental impacts of the essential oil and concentrated juice products, while increasing the environmental impacts of the natural juice products. 3. Improvement options of the citrus products eco-profiles Starting from the results of the above LCA study, we propose scenarios for water and energy savings to reduce the environmental burdens of the production system. Direct consumption is mostly due to the cultivation of the citrus groves rather than processing (Table 5). The significance of this consumption is apparent when looking at the water used. The

Cumulative energy demand (CED) Global warming potential (GWP100) Acidification potential (AP) Eutrophication potential (EP) Photochemical ozone creation potential (POCP) Water consumption

2.9

2.3

2.4

1.8

1.6

1.01

16.9

14

15.7

12.6

11.5

7.5

15.5

11.8

12.4

8.8

10.2

6

271.4

262.2

267.4

256

254

228

3

3.4

2

94.8

90.5

84.3

5.5

95

4

94.2

4.3

95.4

production of the water used directly for irrigation involves further water consumption, which accounts for about 50% of the total flow required for cultivation (Beccali et al., 2009). With an efficient irrigation system, i.e., a drop system, the total amounts of water required for cultivation are 452 kg/kgcropped oranges and 308 kg/kgcropped lemons, including the consumption for the irrigation steps (206 kg/kgcropped oranges and 141 kg/kgcropped lemons), the water eco-profile (235 kg/ kgcropped oranges and 160 kg/kgcropped lemons), and the production of fuel, fertilisers, herbicides and pesticides (11 kg/kgcropped oranges and 7 kg/kgcropped lemons). The water required for citrus cultivation could be completely replaced by treated wastewater from the neighbouring existing plants, including both the direct consumption for irrigation and the further quantity involved in the water eco-profile. Assuming this hypothesis and taking into account the eco-inventory of a mediumsized wastewater treatment plant, each FU eco-profile changed according to the variation rates shown in Table 6. The consumption of freshwater is reduced by nearly 95% for almost all the life cycles of the FUs. The rates of reduction are lower for the concentrated juice (91% for orange juice and 84% for lemon juice), depending on the higher quantity of water used in the concentration step. The introduction of purified water instead of freshwater consistently increases the environmental impacts for each final product. This is essentially due to the eco-inventory of the wastewater purification plant that includes data regarding infrastructure materials for medium size, transport, dismantling and land use burdens. The life cycle of the pipe from the plant to irrigation points was not taken into account. Table 7 shows the incidence of the chosen wastewater treatment plant on the eco-profiles of FUs. In comparison with the achievable freshwater savings by the direct reuse of purified water in the irrigation step (more than 90% in each FU life cycle as above described), the freshwater consumption in the wastewater treatment is negligible, resulting less than 1% of the total saving.

Table 5 Contribution of each FU life cycle step to water consumption (%). Step

Irrigation Eco-profile of water for irrigation Manufacturing process (included water eco-profile) Raw materials production (Fuels, fertilisers and pesticides production, lubricants, electricity, packaging, detergents)

Oil essential

Natural juice

Concentrated juice

FU1

FU4

FU2

FU5

FU3

FU6

44.7 51.1 0.4

44.6 50.6 0.5

44.9 51.3 0.4

44.7 51 0.6

42.6 48.6 1.2

39.7 45.3 2.1

3.8

4.5

3.4

3.7

7.6

12.9

M. Beccali et al. / Journal of Environmental Management 91 (2010) 1415e1428 Table 7 Incidence (%) of the chosen wastewater treatment plant on the improved products eco-profiles. Impact category

Essential oil

Natural juice

Concentrated juice

Cumulative energy demand (CED) Global warming potential (GWP100) Acidification potential (AP) Eutrophication potential (NP) Photochemical ozone creation potential (POCP)

24

18.6

27.8

18.4

15

38

31.7

41.7

31.8

28.4

20

30

23.9

34.4

23

19

12

75.5

75

75.6

75

74.6

73.3

36.4

27.4

43.5

26.3

20.6

12.4

Table 9 Option of railway mode: induced variation on the current eco-profiles of the citrus products (%). Impact category

Oranges Lemons Oranges Lemons Oranges Lemons 9.5

The quantities of freshwater required for the resource and raw materials production and the processing steps (washing fruits and equipment, generation of the watereoil emulsion, and juice pasteurisation and concentration) do not change. The consumption of methane for the steam generation in the pasteurisation and concentration steps affects CED for about 20% and GWP for 11e13% in the FU3 and in the FU6 eco-profiles, respectively. Currently, pasteurisation and concentration of natural juice occurs by Thermal Vapour Recompression (TVR), which is characterised by a high expenditure of thermal energy and water to produce saturated or overheated steam. Growing concern over fuel availability and rising energy costs have created an increasing interest in the application of Mechanical Vapour Recompression (MVR) to citrus juice processing (European Commission, 2006b). In this process, steam at low pressure is mixed with an additional steam flow and conveyed to a compressor, which creates a steam flow at high pressure and temperature. In the case of insufficient enthalpy content of the steam leaving the compressor, a boiler is only used to start the process and to integrate heat. The consumption of water, thermal energy, and electricity may be considerably reduced in comparison with thermal recompression. The introduction of MVR in the examined production process may reduce the CED and the GWP in the eco-profiles of FUs, at the rates presented in Table 8. Given the significance of the contribution of the transportation steps to the global environmental impacts of the FUs (Table 2), we investigate the replacement of transportation by road tankers within Italy and Europe with the rail tankers. As presented in Table 9, this scenario improves the eco-profiles of every product. In particular, the highest rates of reduction are in the natural juice products, depending on the highest current distances covered by road hauling. Table 8 Option of MVR: induced variation on the current eco-profiles of the citrus products (%). Impact category

Natural juice

Concentrated juice

Oranges

Lemons

Oranges

Lemons

Cumulative energy demand (CED) Global warming potential (GWP100) Acidification potential (AP) Eutrophication potential (EP) Photochemical ozone creation potential (POCP)

6.4

7.6

19

20

3.7

5

12.5

14

1.0

1.5

2.7

3.0

0.3

0.5

1.2

2

1.9

2.4

5.7

6

1427

Essential oil

Natural juice

Concentrated juice

Oranges Lemons Oranges Lemons Oranges Lemons Cumulative energy demand (CED) Global warming potential (GWP100) Acidification potential (AP) Eutrophication potential (EP) Photochemical ozone creation potential (POCP)

2.0

3.6

16.1

22.5

19

9.6

0.9

2.0

8.3

12.0

12.5

5.4

2.9

5.3

26.5

35.0

2.7

3.6

0.2

0.4

1.7

3.0

1.2

4.5

3.3

5.9

29.3

37.4

5.7

2.0

4. Conclusions The results of LCA do not represent rigorous and precise data, i.e. difficulty in the collection of data, lack of detailed information sources, and data quality affected by uncertainty, mostly due to the lack of the knowledge about the actual value of a quantity, and by variability due to the heterogeneity of values and entailed into processes. The results of the sensitivity analysis allow stating that every assessed eco-profile is differently influenced by the uncertainty study. Even if in some cases different assumptions on initial data and methods showed sensible variations in the energy and environmental performances of the final products, the essential oil FUs have always the highest impacts, while the natural juice FUs result the less impacting products. Questions concerning the choice of the allocation method are controversial in LCA studies, mostly due to its large incidence on the final results. This is reflected in this study, where the scenario analysis of allocation shows that the eco-profiles of the citrus products depend to a large extent on the chosen method. It is not always obvious what kind of approach must be used. In order to establish it, the system behaviour must be well understood and detailed data on the sub-processes in the system must be available. The improvement analysis has been carried out to propose sustainable scenarios of water and energy saving for reducing environmental burdens of the examined production system. Water footprint represents a key environmental impact of the agro-food sector. Its effects may be severe in Mediterranean countries, where water scarcity is a particularly significant problem. In such a context, strategies of water recovery are needed for water recycling. From the performed LCA study the step with the highest water footprint is cultivation, due to the direct consumption in the irrigation and the indirect consumption for the water supply. The production of the required amount of water involves further water consumption, which amounts to about 50% of the total flow required for cultivation. Then, the authors have assumed to replace the required quantity for irrigation by the treated wastewater in the neighbouring existing plants, including both the direct consumption for irrigation and the further quantity involved in the water eco-profile. Re-use of municipal purified water for irrigation is a feasible hypothesis in Sicily to reduce freshwater consumption, employing water supplies from purification plants equipped of existing or under construction biological treatment, which are located near irrigation districts. It would means to recycle large amounts of water that anyway would be discharged in the sea. Globally the improvement analysis could involve relevant decreases on CED and GWP. The resulting freshwater saving in

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