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Journal of Cleaner Production 37 (2012) 162e171

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Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

A life cycle assessment comparison between centralized and decentralizedbiodiesel production from raw sunflower oil and waste cooking oils

Loreto Iglesias, Adriana Laca, Mónica Herrero, Mario Díaz*

Department of Chemical Engineering and Environmental Technology, Faculty of Chemistry, University of Oviedo, C/ Julián Clavería s/n., 33071 Oviedo, Asturias, Spain

a r t i c l e i n f o

Article history:Received 17 October 2011Received in revised form1 June 2012Accepted 2 July 2012Available online 10 July 2012

Keywords:LCABiodieselSunflower oilWaste cooking oilsBiofuelsScale productionPlant distribution

* Corresponding author. Tel.: þ34 985 103439; fax:E-mail address: mariodiaz@uniovi.es (M. Díaz).

0959-6526/$ e see front matter � 2012 Published byhttp://dx.doi.org/10.1016/j.jclepro.2012.07.002

a b s t r a c t

In this study, a comparative Life Cycle Assessment has been performed with the aim of finding out howthe environmental impact derived from biodiesel production (using raw sunflower oil or waste cookingoils) could be affected by the degree of decentralization of the production (number of production plantsin a given territory). The decentralized production of biodiesel has been proposed for several reasons,such as the possibility of small scale production, the fact that there is no need to use high technology ormake large investments, and because small plants do not need highly specialized technical staff. Thus,hypothetical territories (considering scenarios in which the production and area were theoreticallymodified), as well as real territories, have been analyzed to determine which environmental indicatorswere most affected. Results showed that the optimum degree of centralization was different for eachanalyzed case. In general, in small territories centralized production was more suitable for the envi-ronment, decentralization being more advisable as the territory increased in area. For each of the casesanalyzed, an optimum number of plants, which minimized the environmental impacts, was found. Thiswork illustrates the importance of considering the number of industrial plants in the production design,not only from an economic aspect but also from an environmental point of view.

� 2012 Published by Elsevier Ltd.

1. Introduction

The European Directive 2009/28/EC on the promotion of theuse of biofuels (i.e. biodiesel and bioethanol) for transport, estab-lished a substitution corresponding to 10% of biofuels in the totalconsumption by the year 2020 (EC, 2009). The near completedependence of the transportation sector on oil products generatesconcerns on supply security and on climate change. Currently,there is an emerging interest in replacing fossil feedstock bybiomass-based raw materials. Since the use of biodiesel must beincreased, leading to significant opportunities in the market, it isimportant to evaluate the environmental loads associated to itsproduction. As reported (Blottnitz von and Curran, 2007), movingtowards sustainability requires a re-thinking of our systems ofproduction.

Biodiesel is a diesel fuel defined as the mono-alkyl esters ofvegetable oils or animal fats. It is recommended as a substitute forpetroleum-based diesel mainly because it is a renewable fuel, withan environmentally friendly emission profile and is readily biode-gradable. The use of biodiesel as a fuel has beenwidely investigated

þ34 985 103434.

Elsevier Ltd.

(Sheehan et al., 1998; Ma and Hanna, 1999; Srivastava and Prasad,2000; Fukuda et al., 2001; Dorado et al., 2003; Knothe et al.,2003). Compared to petroleum-based diesel, the high cost of bio-diesel is themajor barrier to its commercialization. Its cost, which isapproximately one and a half times that of petroleum-based diesel,depends on feedstock oils (Zhang et al., 2003). It is reported thatapproximately 70e95% of the total biodiesel production cost arisesfrom the cost of raw material, that is, vegetable oil or animal fats(Connemann and Fischer, 1998; Kulkarni and Dalai, 2006; Helwaniet al., 2009). Moreover, it should be considered that arable land isa scarce resource in most of Europe (Ponton, 2009).

Waste cooking oil (WCO) is a domestic waste generated as theresult of cooking and frying foodwith edible vegetable oil. WCO hasbeen identified as an alternative source of fatty materials for theproduction of biofuels (Canakci and Van Gerpen, 2003). WCO andfats produce significant disposal problems in many parts of theworld. The growing problem of wastes affects the daily lives ofmillions of people (Dovi et al., 2009). This environmental problemcould be solved by proper utilization and management of WCO toenable it to be used as a fuel. Many developed countries have setpolicies that penalize the disposal of WCO in the waste drainage(Kulkarni and Dalai, 2006). The estimated amount ofWCO collectedin Europe is about 700,000e100,000 tons/year (Supple et al., 2002;Kulkarni and Dalai, 2006). The amount of WCO collected in

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171 163

a territory is proportional to the number of inhabitants, just as thedemand for biodiesel.

As endorsed by the scientific community, LCA is one of the bestmethodologies for assessing the environmental burdens associatedwith biofuels production, allowing quantification of energy andmaterials as well as waste and emissions released to the environ-ment (Consoli et al., 1993; Lindfors et al., 1995). Recently, a numberof studies have been focussed on LCA approaches related to bio-diesel, including general studies, comparisons with conventionaldiesel, and the use of different production methods or differentraw materials, among others (Bernesson et al., 2004; Kim andBruce, 2005; Harding et al., 2007; Niederl-Schmidinger andNarodoslawsky, 2008). As reported by Gwehenberger et al.(2007), the dominant aspects influencing their ecological impactare, together with the process, the rawmaterial used and the size ofthe production facilities. Another relevant point is related to thedistribution of the production plants, their capacity and physicallocation, comparing the environmental burdens associated withsmall- or large-scale production. Nevertheless, these aspects havehardly been considered for biodiesel production from a LCAperspective.

Although biodiesel production has followed the example of theoil industry (by investing in big centralized facilities), this strategyis being questioned owing to the simplicity of the biodieselproduction process. Unlike fossil fuels, biodiesel can be obtainedfrom different rawmaterials on a small scale, locally, since biodieselproduction does not require high technology or great economicinvestment (Bernesson et al., 2004). Another positive aspect is thata small, decentralized facility does not require highly specializedstaff and offers greater opportunities for rural development, animportant point in many countries’ economies. Therefore, theutility of small biodiesel plants and their distribution zone iscurrently being evaluated. The degree of centralization of biodieselproduction implies economic but also environmental impacts. Thetrend with regard to economic factors is that the higher theproduction capacity of a plant, the lower the production costs. Itshould be noted, however, that this statement is less clear withregard to environmental concerns (Gwehenberger et al., 2007).Recently, the viability of a small-scale biodiesel plant (10,000 ton/year) has been analyzed in detail in terms of its design and oper-ation, estimating capital investment and operational costs (Skarliset al., 2012). As shown, the investment had good financial resultsprovided that the raw materials were kept in acceptable prices andbiodiesel sales were ensured in the local market.

A decentralization of the production would lead to transportsavings, although it is expected that it would also lead to lossesrelated to the energetic efficiency of the production process. Byusing LCA methodology, this study aims to assess and quantify theenvironmental impacts of biodiesel produced from raw sunfloweroil (RSO), and alternatively, from waste cooking oils (WCO),comparing centralized and decentralized distribution and the zonedistribution of the plants.

Fig. 1. Location of production plants in hypothetical territories (indicated by black dots), w

Previous studies, comparing centralization/decentralizationalternatives for a production process, have been done for othersystems. In the case of sewage treatment plants (Benetto et al., 2009)the study focused on the advantages and disadvantages of thedecentralized Ecological Sanitation Systems, in comparison withthe traditional centralized systems. Results obtained showed that thedecentralized sanitation scenario had a significant advantage interms of the reduced contribution to the damage of ecosystemquality. Similarly, a comparative LCAwas used to assess the potentialreduction in greenhouse gas (GHG) emissions in small dumpingplaces as opposed to big centralizedwastes sites (Shabbir, 2009). Theconclusion obtainedwas that, in termsof transport, small centralizedwastes siteswouldbe thebestoption,whereas bigwastes siteswouldbe the best option in terms of economy and total GHG emissions.

Thus, LCA methodology has been applied in this study to assessand quantify the environmental impacts of biodiesel productionfrom RSO and from WCO, comparing centralized production witha fragmented distribution of plants closer to the supply andconsumption points.

2. Methodology

In this study, LCA methodology is used as a tool for thecomparative evaluation of centralized production and differentdegrees of decentralization, in hypothetical and real territories, byusing RSO and alternatively, WCO, as raw materials.

2.1. Goal and scope definition

2.1.1. Objectives and functional unit definitionThe goal of this work is to compare different options for bio-

diesel production (centralized/decentralized) in specific territories(hypothetical and real territories) from an environmentalperspective. Biodiesel is mainly used as transportation biofuel, sothe functional unit chosen in this work was the amount of biodieselneeded to cover 1000 km in a standard diesel engine vehicle (i.e.50 kg of biodiesel).

2.1.2. System description and boundariesThe scenarios analyzed in this work were the results of

combining defined territories (hypothetical and real territories)with different degrees of centralization of production.

2.1.2.1. Biodiesel production from sunflower oil. For biodieselproduction based on RSO, the hypothetical territories were consid-ered to have a square geometry and their area and seed productionvarying between 94,000 and 940,000 km2 and between 21,200 and1,047,000 tons per year. Both sunflower production points and bio-diesel consumption points were considered to be homogeneouslyspread through the considered territory. Both centralized anddecentralized production have been analyzed in these territories(Fig. 1). The centralized system consisted of one production plant

hen using RSO, according to different levels of decentralization (1, 2, 4 and 9 plants).

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171164

which obtained the rawmaterial (sunflowers seeds) from thewholeterritory and distributed the produced biodiesel to biodiesel stationsspread homogenously throughout the same territory. The number ofbiodiesel stations has been calculated by taking into considerationthe total production of biodiesel and the volume of biofuel usuallyserved per year by stations of average size. Decentralized systemsconsisted of a number of biodiesel plants spread through a territory,which was divided in different areas. Each plant obtained the rawmaterial (sunflower seeds) and distributed the produced biodieselthroughout its corresponding area.

When the analyzed scenarios corresponded to real cases, tworeal territories were chosen. Firstly, the Castilla-La Mancha region(located in the centre of Spain), with 79,000 km2 and a seedproduction of 137,000 tons per year; and secondly, Spain (consid-ering only the peninsular territory) with an area corresponding to493,518 km2 and a total seed production of 703,000 tons per year(source: Spanish Ministry of Environment, Rural and MarineEnvirons, data from the 2007e2008 season). Biodiesel productionwas calculated considering that 2.4 kg of sunflower seeds produces1 kg of RSO, yielding 0.96 kg of biodiesel (52.0 kg of RSO and125.0 kg of sunflower seeds are needed per FU).

The location of the different plants according to the level ofdecentralization in the Castilla-La Mancha region is shown inFig. 2a. The location of the plants according to the different levels ofcentralization in the territory of Spain (peninsular territory) isshown in Fig. 2b (the plants were located taking into account theareas with greater sunflower crops, with the objective of savingcosts in seed transport). In the case of the Castilla-La Manchaterritory, biodiesel stations have been homogenously distributedthroughout this region; in the case of Spain, stations have beendistributed heterogeneously throughout the peninsular territorytaking into account the population of each province (more inhab-itants demand more fuel).

2.1.2.2. Biodiesel production from waste cooking oils. Similarly, forbiodiesel production based on WCO, hypothetical territories wereconsideredwith a square geometry and homogeneous oil collectionand biodiesel distribution. The area and hypothetical scenarios forthe collection of waste oil varied between 94,000 and 506,000 km2

and between 2365 and 430,000 tons per year. On the other hand, inthe case of real scenarios, the geometry was irregular and oilcollection and biodiesel distribution were heterogeneous, since oilcollection and biodiesel distribution will depend on the number ofinhabitants of each zone. The territory chosen was Spain, where oilconsumption was 895,000 tons/year in 2004 (source: SpanishMinistry of Agriculture, Fisheries and Food) of which 71% wasdomestic use, 26% hotel use and 3% use by institutions. Of the oilconsumed in Spain, 16% is cooked, of which, once used, 30% iscollected for recycling. The amount of raw material which could beprovided to produce biodiesel can be estimated as being43,000 tons/year. Based on this data and considering that in orderto produce 1 kg of biodiesel about 1.09 kg of waste oil is needed(54.5 kf of WCO are needed per FU), the total biodiesel productionin Spain from WCO would be 40,000 tons/year. To determine theamount of WCO collected in each region, the number of inhabitantsin each province was taken into account (Table 1). In this case, theinsular territories (Canary Islands and Balearic Islands) were alsoconsidered for the study.

Centralized and decentralized production have been consideredin these territories. The centralized system consisted of oneproduction plant which obtained the raw material (WCO) from allterritories and distributed the produced biodiesel to biodieselstations through the considered territory. Decentralized systemsconsisted of a number of biodiesel plants spread through theconsidered territory, which is divided in different areas. The degree

of decentralization has been analyzed in different scenarios, bothhypothetical and also in the real territory.

The decentralization scheme of plants in Spain was carried outas follows. Firstly, a centralized system with a sole biodieselproduction plant located in Madrid was analyzed, so raw material(oils) and biodiesel were considered to be transported to, or fromthis place to the other provinces. Then, a decentralized systemwithfive plants was considered, dividing the peninsular territory intofour zones and placing a plant in the Canary Islands. The nextsystem that was analyzed examined a degree of decentralization of11 zones (10 in the mainland and one in the Canary Islands), andthen, a further system of 20 zones (19 in the mainland and one inthe Canary Islands). Finally, the case in which each province had itsown biodiesel processing plant (50) was analyzed, plus the optionof splitting the production between two biodiesel plants in thoseprovinces where the amount of collected oil was over 1000 tons peryear (Fig. 3).

2.1.2.3. Production stages. The biodiesel production system fromRSO could be divided in different stages (Fig. 4a). The initial stage,the agricultural phase, includes the entire life cycle of the plant,comprising: planting, fertilizing, treatment with different pesti-cides and plant collection. It has been reported that bio-basedsystems have possible ecological drawbacks since agriculturalproduction of biomass is relatively land intensive, and there is a riskof pollutants entering water sources from fertilisers and pesticidesthat are applied to the land to enhance plant growth (Blottnitz vonand Curran, 2007). This phase, which according to various LCAstudies is responsible for the greatest environmental impact, wasnot included in this work since this was a common step to all thecentralized and decentralized systems analyzed here. For thisreason, effects of growing sunflower either on soil or on emissionsreleased were not considered. Thus, the first stage taken intoaccount in this study is the transportation of seeds to the produc-tion plant, where the second phase of the process is carried out,that is, oil extraction. The seeds are subjected to a process ofwashing, peeling, drying by air blown at base pressure andbleaching using calcium bentonite. The prepared seeds passthrough a series of rotating screws, where they are crushed andpressed. This milling process does not extract all the oil in the seed,so the resulting paste is treated with the solvent hexane, which ismixed into the paste. Once all the oil has been obtained, the hexaneis condensed and separated from the water to be reused in theprocess, while the oil obtained is decanted and centrifuged toremove impurities and to continue to the next production stage.Crude oils are subjected to a refining process where neutralizationand degumming, bleaching and dewaxing are performed. At thisstage, fatty acids, phosphatides and waxes contained in the oil areremoved in order to obtain the refined oil. The next stage is thetransesterification reaction converting the oil into biofuel by reac-tion of the triglyceride with an alcohol (methanol) in the presenceof a catalyst, producing a mixture of fatty acid alkyl esters (bio-diesel) and glycerin. The crude methyl ester is washed to removetraces of methanol, glycerin, catalyst, etc. (not considered in theinventory) and then dried to obtain biodiesel. Finally, biofuel isdistributed to the different stations for sale. For biofuel distributionin real territories, in order to calculate the transportation distancesto the biodiesel stations, it was considered that the number ofstations in each territory depended on its population and on theusual amount of biodiesel served per year in a biodiesel station(150e400 m3 year�1). In this study, the environmental loadsassociated with the use of biodiesel have not been taken intoaccount, since they do not have any influence on the comparativestudy of different degrees of centralization in the productionsystem.

Fig. 2. Location of production plants in real territories (indicated by black dots), when using RSO, according to different levels of decentralization: a) Castilla- La Mancha region(1, 5 and 10 plants) b) Spain (peninsular territory) (1, 4, 6, 11 and 20 plants).

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171 165

The phases described are common to all systems, the differencesdepending mainly on the size of the extraction, refining andtransesterification plants, and the transportation distances of seedsand biodiesel.

When using WCO as rawmaterial, the first stage in the life cycleis collecting the used cooking oil (Fig. 4b). The used oil is trans-ported to the treatment plant where it is unloaded and passedthrough a mesh to remove any solid residue. The solid-free oil is

Table 1Estimated oil collected in Spain in 2004 per provinces.

Provinces Inhabitants Oil collected(tons/year)

Provinces Inhabitants Oil collected(tons/year)

La Coruña 1,121,842 1058 Soria 93,064 88Lugo 346,759 327 Zamora 194,412 184Orense 328,086 309 Valladolid 521,279 492Pontevedra 941,411 888 Segovia 161,013 152Madrid 6,245,883 5890 Salamanca 347,651 328Oviedo 1,059,089 999 Ávila 169,274 160Santander 573,758 541 Guadalajara 231,681 218Vizcaya 1,139,079 1074 Toledo 646,104 609Guipúzcoa 692,171 653 Cuenca 213,830 202Álava 307,203 290 Ciudad Real 514,945 486Pamplona 610,384 576 Albacete 395,083 373Logroño 313,772 296 Cáceres 406,315 383Huesca 221,396 209 Badajoz 673,410 635Zaragoza 939,706 886 Murcia 1,430,986 1349Teruel 145,529 137 Huelva 500,043 471Barcelona 5,346,715 5042 Sevilla 1,840,055 1735Tarragona 781,065 737 Córdoba 784,797 740Lérida 423,813 400 Jaén 655,045 618Gerona 718,875 678 Cádiz 1,205,692 1137Castellón 584,455 551 Málaga 1,548,424 1460Valencia 2,499,834 2358 Almería 672,619 634Alicante 1,866,277 1760 Granada 898,933 848León 483,781 456 Mallorca 1,058,668 998Palencia 170,965 161 S.C. Tenerife 997,348 941Burgos 365,015 344 Las Palmas 1,064,151 1004

Total (Spain) 45,593,835 43,000

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171166

pumped into settling tanks where oil temperature is increased to60 �C. The oil is separated fromwater by decanting and transferredto the final storage tank to be used as feedstock in biodieselproduction. WCO, before being collected and conditioned, isconsidered as a waste so its collection has no impact and its recy-cling prevents carbon emission (2.8 kg CO2/kg oil). The quality ofthe oil received from the pre-treatment plant is defined by itsacidity, expressed in grams of free acid per 100 g of oil. Whenacidity exceeds 4%, esterification is the selected process; otherwisetransesterification is the next step. After these processes, washwater (with free fatty acids and methanol) and glycerine areobtained. The fatty acids obtained are fed back into the trans-esterification stage for increased production of biodiesel. Methanolis directed into a rectification column where it separates fromwater, to be recovered and reused in the transesterification stage.Finally, the produced biodiesel is distributed to biodiesel stations tobe used by consumers. In both cases it is considered that glycerin issold as a co-product and the main wastes generated during theproduction process are sent to landfill.

2.2. Life cycle inventory (LCI) and impact assessment (LCIA)

In the inventory phase, information is gathered as inputs andoutputs (emissions) for all the processes involved in the systemunder study.

The inputs and outputs for each of the stages have beenobtained from different sources: bibliographic sources in the caseof data related to the production process stages (Lechón et al., 2006;Sanz Requena et al., 2010) and software resources to evaluate thetransport distances. In order to obtain the water and energyconsumption for each considered plant, data corresponding to realplants of a specific size have been extrapolated to plants of differentsizes using the Williams method (Williams, 1960), which makes itpossible to calculate the cost of a set of equipment taking intoaccount the cost of equipment with similar characteristics butdifferent production capacity.

I2 ¼ I1ðq2=q1ÞM (1)

Where M is the correlation coefficient (0.68), q is the productioncapacity and I is the value of the equipment.

Considering that equipment cost is directly proportional to itswater and energy consumption, this formula, which uses theavailable information related to a real plant of a specific size, hasbeen used to calculate the water and energy consumption of a plantof the same nature but with different capacity. The consumption ofrawmaterials and products generationwere assumed to be directlyproportional to the capacity of the plant.

Comparison of the different distribution of biodiesel productionwas performed with the LCA software package SimaPro v7, usingthe Eco-indicator 99 (H) V2.05/Europe EI 99 H/A methodologywhich belongs to the LCIA damage-oriented methodologies orendpoint methodologies in ISO terminology. These methodologiesinclude the impact categories in three types of damage: damage tohuman health (including the following categories of impacts:carcinogenesis, organic respiratory effects, inorganic respiratoryeffects, climate change, ionizing radiation, and reduction of theozone layer), damage to ecosystem quality (ecotoxicity, acidifica-tion/eutrophication, and land use) and resources damage(including minerals and fossil fuels) (Blottnitz von and Curran,2007; Sanz Requena et al., 2010). Briefly, the outcome of the Eco-indicator 99 damage modelling for environmental impacts isa human health damage score expressed as Disability Adjusted LifeYears (DALY) and an ecosystem quality damage score expressed asPotentially Disappeared Fraction (PDF). The weighing method usedmeans that the result obtained with this method is expressed asa single ecoindicator score (as ecopoints), where one ecopoint canbe interpreted as one thousandth of the annual environmental loadof one average European inhabitant (Dreyer et al., 2003). Databasesemployed in this work are indicated in Table 2.

After the inventory, characterization is the next step in animpact assessment. This step associates the magnitude of thepotential impacts of each inventory flow with its correspondingenvironmental impact. Characterization factors translate differentinventory inputs and outputs into directly comparable impactindicators. Characterization is completed with a weighting, whichrepresents the magnitude of the impact of different processes thatcompose the LCA of biofuel production and shows how this impactis distributed in each category. The units in which values areexpressed are points (Bare et al., 2003; Sanz Requena et al., 2010).

3. Results and discussion

3.1. Biodiesel production from sunflower oil as raw material

The total environmental effect of the production process ofbiodiesel from RSO was assessed, taking into account each impactcategory considered in the method. It has been highlighted thatmost current publications regarding the environmental perfor-mance analyses of agricultural-based biofuels published focus onGHG emissions but exclude other important impact factors(Reinhard and Zah, 2009). In addition, it should be noted that theyoften present contradictory results related to greenhouse gas (GHG)reductions, energy efficiency, impact on biodiversity, water pollu-tion and water depletion (Borjesson and Tufvesson, 2011). As anexample, the explanations for these contradictory results regardingthe sustainability of biofuels in the GHG performance have beenconsidered as due to differences in local conditions and in thedesign of the specific production systems, and/or different calcu-lation methods and systems boundaries (Borjesson and Tufvesson,2011). In this work, upon considering the whole production process(except for the agricultural phase), themost heavily affected impact

Fig. 3. Location of production plants in Spain (indicated by black dots), when using WCO, according to the different levels of decentralization (1, 5, 11, 20, 50 and 60 productionplants).

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categories in the system turned out to be fossil fuels and respiratoryinorganics. The components responsible for these environmentalburdens were the extraction of refined oil, methanol used as rawmaterial, transportation and energy consumption.

3.1.1. Hypothetical territoriesFirstly, to assess the environmental impacts of the different

biodiesel systems (considering 1, 2, 4 and 9 production plants),hypothetical territories were taken into account (modifyingproduction capacity and area).

Fig. 5a shows the single score graph when different levels ofcentralization were compared, in a square geometry territory witha biodiesel production of 84,000 tons per year, an area of94,000 km2 and homogeneous distribution. As shown, the envi-ronmental impact increased with decentralization.

3.1.1.1. Effect of variation in production. Hypothetically, for a givenarea, increased or decreased levels of production were considered.Fig. 5b represents the single score graph obtained when differentlevels of centralization were compared for a production of419,000 tons of biodiesel per year in a territory of 94,000 km2.Fig. 5c shows the results when different levels of centralizationwere compared for a production of 8400 tons of biodiesel per yearin a territory of 94,000 km2. As shown, for territories with the same

area but different production capacities, the environmental impactrelated to the produced fuel would be smaller as the productioncapacities increase and decentralization decreases. These resultsagree with previously reported results, indicating that increasedefficiency of larger plants usually reduces not only the operationalcosts but also the ecological impacts (Gwehenberger et al., 2007).

3.1.1.2. Effect of variation in area. In this case, for a given productioncapacity, a hypothetically increased area was considered. Fig. 5dshows the single score graph obtained when different levels ofcentralization were compared for a production of 84,800 tons ofbiodiesel per year in a territory of 940,000 km2. If Fig. 5a and d arecompared, it can be observed that when the surface area of theterritory considered increased, the environmental impactincreased, especially in the case of centralized production, due tothe increase in fuel consumption for transportation of raw mate-rials and biodiesel. For the bigger territory, the impact was inde-pendent of the degree of decentralization, although it was observedthat there was a minimum impact when the production wasdivided into 4 plants.

3.1.2. Application to real casesFig. 6a is the single score graph obtainedwhen different levels of

centralization were compared for a production of 54,800 tons of

Fig. 5. Single score graphs showing the environmental impact of hypothetical systems(using RSO) with 1, 2, 4 and 9 production plants: a) for a biodiesel production of84,000 tons per year and a territory area of 94,000 km2, b) for a biodiesel production of419,000 tons per year and a territory surface of 94,000 km2, c) for a biodieselproduction of 8400 tons per year and a territory surface of 94,000 km2 and d) fora biodiesel production of 84,000 tons per year and a territory surface of 940,000 km2.Units correspond to points (Pt).

RECYCLING PLANT

1) Oil collection and transport

5) Biodiesel Transport

BIODIESEL STATIONS

OIL CONSUMERS

2) Pre-treatment 3) Transesterification 4) Biodiesel purification

a

b

PRODUCTION PLANT

1) SeedsTransport

6) Biodiesel Transport

BIODIESEL STATIONS

SUNFLOWER CROPS

2) Extraction of crude oil 3) Refining of oil 4) Transesterification 5) Biodiesel purification

Fig. 4. Stages of the biodiesel production process a) from RSO and b) from WCO.

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171168

biodiesel per year in Castilla-La Mancha (surface area of79,000 km2). Fig. 6b is the single score graph obtained whendifferent levels of centralizationwere compared for a production of281,200 tons of biodiesel per year in Spain (area 493,518 km2).

In the case of Castilla-La Mancha, based on the single scoregraph it can be seen that a decentralized system for biodieselproduction would have a greater environmental impact thana centralized system. On the contrary, in the case of the wholeSpanish peninsular territory, the environmental impact decreasedas decentralization increased, until a point of inflection wasreachedwhere the impact began to increase again, and an optimumlevel of decentralization appeared. At this point, the number ofproduction plants was approximately 6.

Table 2Data based used in LCIA.

EnergyElectricity ETH-ESU 96Natural gas Ecoinvent

Water EcoinventTransport EcoinventChemical productsNaOH BUWAL 250HCl BUWAL 250H3PO4 IDEMA 2001CH4O EcoinventBentonite ETH-ESU 96

In this work, availability of arable land has been considered. Ithas been reported (Reinhard and Zah, 2009) that an increase inagro-biofuel consumption would have consequences such ascompetition with food production, fostering intensification andendangering natural areas. The increased production of biofuelscould merely shift or even increase the environmental impactscurrently related to the production and use of fossil fuels, unlessbiofuels production is decoupled from the global food and feedmarkets (by using biogenic waste or non-edible energy crops thatgrow specifically on degraded land) (Reinhard and Zah, 2009). Ithas been also reported (Upham et al., 2009) that the problem ofland-use change lends weight for slowing the incentivisation of‘first-generation’ biofuel production, redirecting support to‘second-generation’ research and development, maximising the

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Fig. 7. Weighting graph that shows the environmental impact of systems (using WCO)with different numbers of production plants: a) for a hypothetical territory of94,000 km2 and a biodiesel production of 2200 tons per year (1, 2, 4 and 6 plants), b)for a hypothetical territory of 506,000 km2 and a biodiesel production of 40,000 tonsper year (1, 6, 9, 18 and 36 plants) and c) for Spain (1, 5, 11, 20 and 50 plants). Unitscorrespond to points (Pt).

Fig. 6. Single score graphs showing the environmental impact of real systems (usingRSO) with different numbers of production plants: a) Castilla-La Mancha region (1, 5and 10 plants) and b) Spain (1, 4, 6, 11 and 20 plants). Units correspond to points (Pt).

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171 169

use of bio-wastes, as this does not prejudice soil quality. In relationto biofuels of second generation, energy efficiency have beenreported as a precondition for diverting cellulosic residues(Rethabile and von Blottnitz, 2011).

3.2. Biodiesel production from WCO as raw material

The impact categories most affected during the productionprocess turned out to be fossil fuels, inorganic pollutant emissionsand climate change (see Fig. 7). It should be noted that when usedfrying oil is disposed of as a waste, carbon dioxide emissions shouldbe considered, so in the WCO production process the impact on theclimate change category is negative (i.e. beneficial to the environ-ment). Obviously, this means that total impacts associated withbiodiesel production from WCO are much lower than those asso-ciated with biodiesel production from RSO. As reported (Uphamet al., 2009), although it is far from clear that biofuel productionat the large scale demanded would be environmentally or sociallybenign, only used cooking oil has guaranteed sustainability benefitsamong the feedstocks examined (for which the UK RenewableTransport Fuel Obligation supplies default carbon intensity values).In the case of bioethanol, it has been reported (Blottnitz von andCurran, 2007) that when it is made from a waste product, resultswill differ depending on how efficiently wastes are used and howthe industrial systems are configured, on a case-by-case basis.

3.2.1. Hypothetical territoriesA production of 2200 tons of biodiesel per year in a hypothetical

territory of 94,000 km2 has been considered, and results are shownin Fig. 7a. This weighting graph compares different levels ofdecentralization (1, 2, 4 and 6 plants), and, as can be observed, inthis case, centralized production tuned out to be the best option.

3.2.1.1. Effect of increased production and area. A production of40,000 tons of biodiesel per year in a hypothetical territory of

506,000 km2 has been considered in the results shown in Fig. 7b.When the production and area increased, the best option turnedout to be decentralized production (in this case, into 18 plants). Ina similar way to this case, previous research (Gwehenbergeret al., 2007) highlighted that logistical factors may becomeincreasingly important, leading to situations where the expectedeconomy of scale and the environmental impact of scale are incontradiction.

3.2.2. Real territoryFig. 7c represents the weighting graph where different levels of

centralization were compared for a production of 40,000 tons ofbiodiesel per year in Spain (506,000 km2).

As shown, the production of biodiesel from WCO collectedthroughout the Spanish territory is less harmful to the environ-ment when some degree of decentralization is undertaken. Asignificant reduction in impact was observed when moving froma centralized to a decentralized system, which is mainly due to thefact that for decentralization, the location of a plant in the Canary

L. Iglesias et al. / Journal of Cleaner Production 37 (2012) 162e171170

Islands has been considered, saving transportation by ship (oil tothe peninsula, and biodiesel to the islands). For more than 5plants, it can be observed that the differences between differenttypes of decentralized distributions considered (11, 20, 50 and 60plants) were very low, indicating that the improvements achievedby transportation savings were offset by increased energyexpenditure (lower efficiency for smaller plants). Considering thetotal environmental loads, the less damaging option in this realcase would be to decentralize the production into 11 productionplants (one of them located in the Canary Islands, see Fig. 3).Furthermore, although it is out of the scope of this study, it hasbeen reported (Skarlis et al., 2012) that the regional developmentand the social benefits derived should always be taken intoaccount when a decision of such small-scale investment needs tobe taken.

4. Conclusions

The impact categories most affected by the production of bio-diesel from sunflower oils (ignoring the agricultural phase) werefossil fuels and respiratory inorganics. The system componentsresponsible for the highest environmental burdens were energyconsumption (electricity, natural gas, diesel oil), transportation andthe methanol used as a raw material. It was observed that thedegree of centralization of biodiesel plants influenced the impactsduring the stages of transportation of the raw material, biodieselprocessing and distribution of the product to the biodiesel stations.In this case, differences regarding the impact between centralizedand a decentralized distributionwill depend on various factors, likethe area of the studied territory, the total production capacity or thehomogeneity or heterogeneity of the distribution of crops andbiodiesel stations.

In general, in small territories centralized production was moresuitable for the environment, decentralization being more advis-able as the territory increased in area. For each of the casesanalyzed, an optimum number of plants, which minimized theenvironmental impacts, was found.

Being an alternative to waste management, processing of WCOinto biodiesel has a positive contribution to the environment in thecategory of climate change. Again, the degree of centralization isa key point in order to determine the best environmental option,which is different for each case analyzed. The production of bio-diesel from WCO collected throughout the Spanish territory(including the islands) is less harmful to the environment if it isperformed with some degree of decentralization, particularly if thesituation of plants and biodiesel stations is such that it avoidstransportation by ship between the Canary Islands and the main-land. This study illustrates the importance of considering thenumber of industrial plants in the production design, not only froman economic aspect but also from an environmental point of view.

Acknowledgement

This work has been funded by the Ministry of Education andScience of Spain, as part of the subproject “Logistics and environ-mental sustainability” included in the project “Promotion of thecompetitivity in the Spanish business network employing logisticsas a strategic factor in a global context” (GLOBALOG: MEC-09-PSE-370000-2008-8).

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