Comparative environmental assessment of wood transport models

Science of the Total Environment 407 (2009) 3530–3539

Contents lists available at ScienceDirect

Science of the Total Environment j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / s c i t o t e n v

Comparative environmental assessment of wood transport models A case study of a Swedish pulp mill Sara González-García a,⁎, Staffan Berg b, Gumersindo Feijoo a, Ma Teresa Moreira a a b

Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, 15782-Santiago de Compostela, Spain The Forestry Research Institute of Sweden (Skogforsk), Uppsala Science Park, SE-751 83 Uppsala, Sweden

a r t i c l e

i n f o

Article history: Received 27 February 2008 Received in revised form 5 February 2009 Accepted 10 February 2009 Available online 9 March 2009 Keywords: Environmental impacts Energy use LCA Pulp mill Secondary hauling Sweden

a b s t r a c t Wood transportation from forest landing to forest-based industries uses large amounts of energy. In the case of Sweden, where forest operations are highly and efficiently mechanized, this stage consumes more fossil fuels than other elements of the wood supply chain (such as silviculture and logging operations). This paper intends to compare the environmental burdens associated to different wood transport models considering a Swedish pulp mill as a case study by using Life Cycle Assessment (LCA) as an analytical tool. Five scenarios (the current one and four alternative reliable scenarios) were proposed and analysed taking into account two variables. On the one hand, the influence of imported pulpwood share from Baltic countries and on the other hand, the use of rail transportation for wood transport. In particular, the following impact categories were assessed: Eutrophication, Global Warming, Photochemical Oxidant Formation, Acidification and Fossil fuel extraction. The environmental results indicate that transport alternatives including electric and diesel trains, as well as the reduction in Baltic wood imports should present better environmental performance than the current scenario in terms of all the impact categories under study. Remarkable differences were identified with regard to energy requirements. This divergence is related to different longdistance transport strategies (lorry, boat and/or train) as well as the relative import of wood selected. The combination of lorry and train in wood transportation from Southern Sweden plus the reduction of wood imports from 25% to 15% seems to be more favourable from an environmental perspective. The results obtained allow forecasting the importance of the wood transport strategy in the wood supply chain in LCA of forest products and the influence of energy requirements in the results. © 2009 Elsevier B.V. All rights reserved.

1. Introduction The European Union (EU-15) is one of the largest producers, traders and consumers of forest products in the world (European Commission, 2007a). The forest sector (forestry, forest-based and related industries) comprises several industrial sectors: woodworking, pulp, paper and paperboard manufacturing and converting, printing industries and furniture. The annual production value of this sector reached 335 billion € in 2001, employing about 3.4 million people (European Commission, 2007b). In addition, EU-15 is a net importer of forest products. Roundwood from Russia and Eastern European countries and pulpwood mainly from North and South America are key imports in the sector. However, forest-based products consumed in EU-15 are mainly of domestic supply, especially the more highly value-added products, such as quality papers and wood-based panels. EU-15 is even a leading exporter in this kind of products. Paper is necessary for most human activities (education, communication, business, culture, hygiene, food and beverage packaging, ⁎ Corresponding author. Tel.: +34 981563100x16776; fax: +34 981547168. E-mail address: [email protected] (S. González-García). 0048-9697/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2009.02.022

medicine, …). Paper is a natural product, manufactured from a renewable raw material: wood. Paper pulp (the basic ingredient for the manufacture of paper and board) is produced from fresh wood, wood chips from sawmills, recovered paper and sometimes, from textiles and agricultural products or industrial crops. Nowadays, wood constitutes the main virgin paper pulp raw material in developed countries (Sigoillot et al., 2005) and pulp manufacture is the largest non-food industrial use of plant biomass (Gutierrez et al., 2001), since virgin fibres are necessary in paper-, pulp- and board products due to quality requirements. The pulp and paper industries are also highly energy and water intensive (EUROSTAT, 2007). However, it is important to remark that the EU pulp, paper and board industry tends to use energy from renewable energy sources. In fact, biomass energy corresponded to half of the thermal energy and electricity consumption in these industries in the year 2000 (European Commission, 2006). Worldwide consumption of pulp and paper is steadily increasing. The European pulp and paper industry had in the year 2003 a capacity over 41 million metric tonnes1/year of pulp and 95 million tonnes/year

1

All tonnes in this report are metric tonnes hereafter referred as tonne(s).

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

of paper and cellulose-based products, occupying the second position in world production of pulp and paper after North American countries. In Europe, this industry consists of over 1000 paper mills and 220 pulp mills. Germany is the largest paper producer followed by Finland, Sweden and France. Regarding pulp production, Finland and Sweden are the main pulp-producer countries (European Commission, 2007b). Annual wood pulp production in 2005 was 191 million metric tonnes, including dissolving pulp and other pulps (Skogsstatistisk Årsbok, 2007). The Swedish pulp and paper industry is organising itself to be globally competitive. It is made up of around 30 paper pulp mills with a total annual pulp production of more than 12 million tonnes (Reciclapapel, 2002; Skogsstatistisk Årsbok, 2007). Approximately 34% of the total wood pulp production is for market pulp. Almost 50% of the wood harvested in Swedish forests is delivered to this sector. In 2006, 5 million tonnes (7% of total use) of wood for forest industries were imported mainly from Baltic countries and Russia (Skogsstatistisk Årsbok, 2007). These imports are relevant for the Swedish industrial sector, especially for the pulp and paper sectors. Exports of secondary products, such as paper, paperboard and wood pulp and recovered paper, were approximately 10.9 million tonnes and 3.6 million metric tonnes, respectively. The resulting net product has a huge surplus, because imports of wood pulp, recovered paper, paper and paperboard accounted for only 2.3 million metric tonnes. The contribution from the forest sector is important for the national economy, the same year 11% of total exports were derived from the forest industry sector. It is evident that the massive use of wood as a raw material needs an appropriate management in order to reduce the associated environmental impacts. This study aims to complete a previous study where the environmental impacts associated to forest operations for softwood supply to a pulp mill, carried out in Swedish and Baltic stands, were analyzed from stand establishment to wood delivery at mill gate (González-García et al., 2008). In that study, the chain of forest management practices was divided in three main systems: silviculture operations, logging operations and secondary hauling and evaluated according to the Life Cycle Assessment (LCA) methodology (ISO 14040, 2006). According to the results, secondary hauling (transport of wood from forest landing to pulp mill gate) was identified as the main hot-spot for all the environmental impact categories analyzed (Global Warming, Eutrophication, Acidification and Photochemical Oxidant Formation) and energy used by that subsystem was around 60% compared with 37% by logging and only 3% by silviculture. This result fits in with other similar studies carried out mainly in Nordic countries (Schwaiger and Zimmer, 2001; Berg and Karjalainen, 2003; Lindholm and Berg, 2005a,b; Berg and Lindholm, 2005) where energy use associated with timber hauling is 50–65% of total energy requirements in the wood supply chain. In this study, five reliable scenarios of secondary hauling were analyzed from an environmental point of view. The current scenario was compared with four reliable alternative scenarios in order to identify the best way for pulpwood supply to a specific pulp mill placed in Northern Sweden. For the environmental evaluation, the application of LCA was again considered. There are several LCA studies that have addressed forest systems (Aldentun, 2002; Berg and Karjalainen, 2003; Berg and Lindholm, 2005; White et al., 2005) as well as the Swedish road transport (Eriksson et al., 1996). LCA studies have not only been carried out to compare different products, but also to obtain information about material and energy flows linked to products and systems. 2. Methodology Life cycle Assessment (LCA) methodology has proved to be a valuable tool for documenting and analysing environmental impacts from product and service systems that need to be part of decision-

3531

making process towards sustainability (Baumann and Tillman, 2004). In addition, LCA may give insight on areas in the forest-wood chain which need improvements, but also show environmental application of wood for industry and consumer markets (González-García et al., 2008, 2009; Karjalaimen et al., 2001; Rivela et al., 2006; Werner and Nebel, 2007). The forest sector has environmental relevance not only due to its low fossil fuel use, low emissions to air, water and soil, but also due to its potential as storage for carbon (Goodale et al., 2002; Liski et al., 2001; Lindholm and Berg, 2005b). LCA is compiled of several interrelated components: goal and scope definition, inventory analysis, impact assessment and interpretation of results (ISO 14040, 2006). SimaPro 7.1 designed by PRéConsultants was the software used in this study (PRé-Consultants, 2007). 2.1. Goal and scope definition This study aims to propose alternative scenarios to the current situation of wood supply to a Swedish pulp mill located in Northern Sweden. Secondary hauling (transport of wood from landing to endpoint) was identified as the most important hot-spot in Swedish forest operations in a previous study (González-García et al., 2008) and this result is in agreement with other related studies (Berg and Karjalainen, 2003; Berg and Lindholm, 2005; Lindholm and Berg, 2005a,b; Karjalaimen et al., 2001). The study presented here aims to compare several reliable alternative scenarios of wood delivery. Therefore, operations related to forest operations were not included within the system boundaries. Several transport system combinations will be analyzed (lorry, boat and diesel and electric trains), as well as the influence of the amount of wood imported from elsewhere. The Swedish pulp mill under study can be considered representative of the ‘state of art’ with an approximate process production of 210,000 tonnes of dissolving cellulose and an annual consumption of 1.30 million m3 of wood. 2.2. Functional unit The functional unit (FU) provides a reference to which the inputs and outputs are referred (ISO 14040, 2006). In this study, 1 m3 of fresh wood solid under bark (s.u.b.) was selected as the functional unit in order to make a straightforward comparison between scenarios as well as with other related works. This timber has an average basic density of around 400 kg/m3 (Sveriges Skogsvårdsförbund, 1994). The fresh wood contains more water than dry mass. The water content varies with the shipping season. For this study, the average raw weight was, on average, 825 kg/m3. 2.3. Description of the scenarios under study Currently, there are three main long-distance wood transport strategies to supply wood to wood-based industries in Europe: road, railway and waterway. Road transport is the dominant means of transport used and represents more than 80% of the total wood supplied to wood industries in Europe (Schwaiger and Zimmer, 2001). The transport work related to wood harvested in the forest and delivery to the pulp mill is extensive. In the case of Sweden, almost 55 million tonnes of roundwood were supplied by lorries in 2005 and the average distance to mill was 94 km. Other means of transport are necessary due to costs, distance, environmental impacts and geography. Average distance by rail is about 290 km. Rail transport is the second most important means of transport. Transport by ship is mainly used for long-distance domestic transport and imported wood (from the Baltic countries and Russia). In waterways there is an important variation in the average distance. The distance considered

3532

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

Fig. 1. Transport scenarios under study: SC1 = Current scenario (base). SC2, SC3, SC4 and SC5 = alternative scenarios.

for Swedish shipping ports is 273 nmi, while the distance considered for imported wood is 700 nmi (Skogsstatistisk Årsbok, 2007). Five different scenarios (the existing one and four others) were considered (Fig. 1). The scenarios under study were designed according to the current main pulpwood suppliers to the mill under study. Therefore, the current main suppliers are the Baltic countries (25%) and Sweden (75%) (Domsjö personal communications). The scenarios are based on contemporary strategies by the pulp mill. The scenario is a created vision of the future situation, its realism cannot be evaluated and its consequences are analyzed. The advantage of using scenarios for this issue is due to the fact that import–export situations in the Baltic States are extremely volatile due to Russian wood trading policies on the one hand and due to global energy process on the other. Therefore, the scenarios reflect variations of raw material origin and energy use for transport (Fig. 2a). Inside each scenario, three systems were considered depending on the origin of pulpwood processed in the mill: Southern Sweden,

Central Sweden and Baltic countries (imported wood). The different scenarios were defined when varying a series of parameters. The percentage of pulpwood imported was varied from 10% to 40% and the means of transport was also changed, interchanging train and boat for wood supplied from Southern Sweden. Associated inventory data was modified correspondingly. The different scenarios are described below: 2.3.1. Scenario 1 (SC1) This scenario is the current situation in the pulp mill under study. Pulpwood processed is mainly from Swedish forest and only 25% is imported from Baltic countries (Fig. 2b). Around 30% comes from Southern Sweden and wood transportation by road and boat is combined due to the location of the pulp mill near the coast (the mill has its own shipping port). Pulpwood is loaded onto a lorry at forest landing and transported 100 km to a wood terminal, where the pulpwood is unloaded and loaded onto a boat with a capacity of 3200 m3. The distance travelled is 368 nmi. A share of 45% comes

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

3533

Fig. 2. (a) Energy requirements (in %) of SC1 depending on the origin of wood processed (b) Origin of pulpwood processed in the pulp mill under study.

from Central Sweden and is transported by road vehicles. Pulpwood is loaded onto a lorry and transported 100 km to the pulp mill gate where it is finally unloaded. The remaining 25% is imported from Baltic countries which breaks down to 58% from Latvia (428 nmi),

23% from Estonia (340 nmi) and 19% from Lithuania (461 nmi). In all cases, pulpwood is loaded in lorries, transported 100 km and finally unloaded and loaded onto the boat (cargo capacity is 3200 m3). A brief summary of features of wood transport is in Table 1.

3534

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

Table 1 Specifications of the models of wood transport from forest landing to pulp mill gate considered in the four scenarios under study. Transport models Contribution Truck Maximum weight Cargo capacity Load factord Distance Ship Cargo capacity Load factor Distance Electric train Wagons number Load per wagon Distance Load factor Diesel train Wagons number Load per wagon Distance Load factor

Unit

SC1

SC2

SC3

SC4

SC5

SSa

CSb

BCc

SS

CS

BC

SS

CS

BC

SS

CS

BC

SS

CS

BC

%

30

45

25

30

45

25

24

36

40

36

54

10

34

51

15

tonne tonne % km

60 40 57 100

60 40 50 100

40 25 50 100

60 40 57 100

60 40 50 100

40 25 50 100

60 40 57 100

60 40 50 100

40 25 50 100

60 40 57 100

60 40 50 100

40 25 50 100

60 40 57 100

60 40 50 100

40 25 50 100

m3 % nmi

3200 50 368

xe x x

3200 50 414f

x x x

x x x

3200 50 414

3200 50 368

x x x

3200 50 414

3200 50 368

x x x

3200 50 414

x x x

x x x

3200 50 414

tonne km %

x x x x

x x x x

x x x x

40 35 776 50

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

40 35 776 50

x x x x

x x x x

tonne km %

x x x x

x x x x

x x x x

20 35 187 50

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

x x x x

20 35 187 50

x x x x

x x x x

a

South Sweden. Central Sweden. c Baltic countries (58% Latvia, 23% Estonia, 19% Lithuania). d Distance driven with a full load (100%) per round trip. e There is not this kind of transport model in this scenario. f Average distance from Baltic countries travelled by boat from corresponding shipping port to pulp mill shipping port. Shipping ports considered are: Riga (Latvia), Pernu (Estonia) and Klaipeda (Lithuania). b

2.3.2. Scenario 2 (SC2) In this alternative scenario, the pulpwood processed comes from Southern Sweden (30%), Central Sweden (45%) and Baltic countries (25%). However, wood transport by rail is considered for wood supply from Southern Sweden instead of marine transport. The Swedish railway network comprises roughly 12,000 km, enabling transport in all directions in the South of Sweden. In addition, the majority of the railway network is electrified and trains are supplied with electricity, which has a modest environmental impact, “Green Cargo” supplies via contact lines (Banverket, 2007). This railway network is unique in Europe and for this reason it has been considered an interesting alternative of study for current scenario to combine transport by road and rail in order to determine if this option can reduce or not the associated environmental impact. Pulpwood is transported by lorry until the wood station (100 km), where it is loaded onto an electric train and transported 776 km to the second wood terminal. Then, a diesel train is used (187 km) due to the fact that it is not possible to perform this distance with an electric train. Train characteristics are shown in Table 1. It was assumed that loading and un-loading steps in trains use the same energy use as lorries (Löfroth and Rådström, 2006). The remaining wood supply and conditions are the same as in SC1. 2.3.3. Scenario 3 (SC3) As mentioned above, Sweden imports large quantities of wood from pulp mills in Russia and the Baltic countries. In the current scenario, 25% of pulpwood processed in the pulp mill comes from Baltic countries. Therefore, the influence of wood imports on the environmental results was evaluated. Wood transport systems considered are the same as in SC1 for South and Central Sweden and for Baltic countries (Table 1). However, percentages have been changed: 40% of total wood is now imported (from Latvia, Estonia and Lithuania in the same shares) and only 60% is from Swedish forests (36% from Central Sweden and 24% from Southern Sweden). 2.3.4. Scenario 4 (SC4) A reduction in imported wood was taken into account in this scenario. In this case study, only 10% of total wood processed is

imported from Baltic countries (from Latvia, Estonia and Lithuania in the same shares). The remaining 90% is from Sweden (54% and 36% from Central and South Sweden respectively). Wood transport systems considered are the same as in SC1 (see Table 1). 2.3.5. Scenario 5 (SC5) This scenario is a combination of SC1, SC2 and SC4. In this case, the original shares were changed, reducing by 15% wood imports and increasing Swedish wood proportion from 75% to 85%. In addition, wood from Southern Sweden (34% of total) is transported by lorry (100 km) and by train (as the same way as in SC2) instead of by boat. Wood from Central Sweden (51%) is again transported by lorry (100 km). Wood transport systems are summarized in Table 1. 2.4. Data quality High quality data is essential to make a reliable evaluation. Information regarding the current scenario of pulpwood transportation from forest landing to pulp mill gate was supplied by employees of the pulp mill by means of inventory tables, company visits and personal communications during a one year period. The production of capital goods (machineries, buildings and roads) and transport of energy carriers were not included within system boundaries according to the principle of excluding identical activities for comparative assessments (Jungmeier et al., 2002) and there was no data available. 3. Life Cycle Inventory Analysis Life Cycle Inventory Analysis involves the collection and computation of data to quantify relevant inputs and outputs of a product system, including the use of resources and emissions to air, water and soil associated with the system (ISO 14040, 2006). All data related to energy use (fossil fuels and electricity) in pulpwood supply from forest landing to pulp mill gate in all the scenarios is summarized in Table 2. Only average values for wood imported from Baltic countries are shown in this table. Change represents impacts of substituting SC1 for any of the four alternative scenarios. A negative change implies a

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539 Table 2 Energy use (MJ/m3sub) per scenario. Scenario

Loading

Truck

Boat

Electric train

Diesel train

Unloading

Total

% change

SC1 SC2 SC3 SC4 SC5

4.0 6.1 4.3 3.7 6.2

96.6 96.6 104.4 88.8 91.4

118.6 57.3 140.7 96.4 34.4

– 29.4 – – 33.4

– 19.7 – – 22.4

3.1 5.0 3.4 2.9 5.1

222.3 214.2 252.8 191.8 192.7

– − 3.6 + 13.7 − 13.7 − 13.3

reduction in energy use compared to the current scenario and a positive value implies an increase in energy use. Life cycle inventory (LCI) data for fuels (petrol and diesel) used in this study was taken from Frischknecht et al. (1996) and Dones et al. (2007), and lubricants were assumed to have the same LCI as petrol according to Uppenberg et al. (2001). Electricity use by electric trains was taken from Lindholm and Berg (2005a). The electricity profile is of major importance as it broadly affects the environmental performance in scenarios SC2 and SC5. The electricity supply was taken from the Swedish grid mix. Currently, hydro power and nuclear power dominate the electricity production in Sweden (Uppenberg et al., 2001; Wang, 2006). According to data from Uppenberg et al. (2001), the electricity generation profile in Sweden is: 48% of hydroelectric energy, 44% of nuclear energy, 3% from biomass, 2% from coal, 1% from oil and the remaining 2% is from natural gas and wind. Regarding diesel trains, fossil fuel consumption and emissions factors for diesel trains were taken from Frees and Weidema (1998) and the Network for Transport and the Environment (NTM, 2007a). Emission factors associated to heavy lorries were taken from the NTM (2007b). Emission factors associated to ship transport were taken from Frees and Weidema (1998) and NTM (2007c). Sulphur maximum legal content in Swedish fuel considered in this study was 2 ppm (NTM, 2007b). Information regarding the characteristics of transport systems (lorries, ships and trains) were taken from ECMT (2007), Forsberg (2002), Löfroth and Rådström (2006), NTM (2007a, b,c) and information supplied by the Swedish pulp mill under study. 4. Results Impact assessment is a technical, quantitative and/or qualitative process to characterize and assess the effects of the environmental

3535

burdens identified in the Inventory (ISO 14040, 2006). Energy use in transport systems impacts the environment by means of emissions with a global warming effect, acidifying and eutrophying as well as emitting gases with the capacity to create photochemical ozone (Eriksson et al., 1996). In this study, a quantitative impact assessment was performed for four impact categories: Global Warming for the time horizon 100 years (GWP), Eutrophication (EP), Photochemical Oxidant Formation (POP) and Acidification (AP). To do so, the characterisation factors were taken from the literature (Derwent et al., 1998; Heijungs et al., 1992; IPCC, 2007; Lindfors et al., 1995; Uppenberg and Lindfors, 1999). In addition, fossil fuel extraction (FF) was also evaluated in terms of crude oil, natural gas and coal. Neither normalization nor weighting between categories were carried out in order to get a subjective approach. Fig. 3 shows the results from the characterisation phase at the life cycle impact assessment. In this figure, values were indexed using SC1 as baseline (Index = 100 for each impact category). 4.1. Eutrophication Alternative scenarios proposed in this study: SC2, SC4 and SC5, attain to reduce the total eutrophying emissions by approximately 26%. In the current scenario (SC1), wood transport by ship causes more than 53% of total eutrophying emissions (Fig. 4), being transport from Southern Sweden the main delivery model responsible. NOx emissions dominate the contributions to EP (~ 98% in all scenarios) followed by far by NH3. The introduction of a combination of electric and diesel trains in this stage, although slightly reduces the total energy use (see Table 2) up to 13% in SC5, allows to reduce total eutrophying emissions up to 24% and 38% in SC2 and SC5, respectively (Fig. 3). In both alternative scenarios, the use of electric trains (excluding loading and un-loading steps) represents a contribution of less than 0.5% to this impact category. The reduction of wood imports from Baltic countries, from 25% to 10%, reduces NOx emissions (the key contributor to EP) up to 15%. 4.2. Global Warming The rapid rise of atmospheric carbon dioxide (CO2) and other greenhouse gases (GHGs) concentrations causes a variety of environmental, social and economic problems, and is, therefore, one of the most pressing environmental issues facing society today (IPCC-NGGIP,

Fig. 3. Relative environmental profile of the compared scenarios, with SC1 being the baseline (Index = 100). Impact categories: EP = Eutrophication, GWP = Global Warming, POP = Photo-Oxidants formation, AP = Acidification, FF = Fossil fuels extraction. Acronyms: SC1 = Scenario 1 (current scenario); SC2 = Scenario 2; SC3 = Scenario 3; SC4 = Scenario 4; SC5 = Scenario 5.

3536

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

Fig. 4. Relative contributions to Eutrophication (EP) in all scenarios under study depending of the kind of wood transport model. Acronyms: SC1 = Scenario 1 (current scenario); SC2 = Scenario 2; SC3 = Scenario 3; SC4 = Scenario 4; SC5 = Scenario 5.

2003). In SC1, CO2 emissions are the main contributions to GWP (96%), followed by CH4 (3%) and N2O (1%). The main responsible of these emissions is marine transport (53%) and transport by lorry (44%) as shown in Fig. 5. Pulpwood imported from the Baltic countries figures 42% of total contributions to GWP, closely followed by transportation from Southern Sweden (40%) according to Fig. 6. Increased imports raise emissions. Therefore, when wood imports increase from 25% to 40% (SC3), both energy use and GWP are higher than in SC1 (up to 14%). On the contrary, when wood imports are reduced from 25% to 10% (SC4), both energy use and GWP decrease up to 14%. Use of train instead of boat (combination of electric and diesel powered trains) in wood transportation from Southern Sweden (SC2) allows reducing GWP emissions by almost 14%. In addition, if wood imports are slightly reduced (from 25% to 15%), GWP decreases more than 25% compared to SC1 (Fig. 3). Loading and un-loading steps in all scenarios under study contribute to less than 1% of total contributing emissions. 4.3. Photochemical Oxidant Formation Among the impact categories typically considered by LCA studies related to forest operations, Secondary hauling has the largest

contribution to the potential impact of photo-oxidant formation (Berg and Lindholm, 2005). Results obtained in this paper are considerably higher than results reported by other authors (Berg and Lindholm, 2005; Schwaiger and Zimmer, 2001). However, these differences are mainly due to the wood import considered in this paper. POCP emissions are closely related with energy use due to the fact that this impact category is affected by hydrocarbon emissions associated to the incomplete combustion of fossil fuels. SC3 has the largest impact in terms of Photochemical Oxidant Formation, followed by SC1 (Fig. 3). On the contrary, SC5 has the lowest impact due to the lower energy use (Table 2). 4.4. Acidification NOx emissions are the main acidifying emissions in all scenarios under study and represent more than 85% of total emissions. Again, the scenarios considering electric train transport (SC2 and SC5) get the lowest contributions to this impact category. SC5 involves reductions of up to 36% due to the combination of transport by train and the reduction of the amount of wood imported (only 15% of total wood processed). On the contrary, if the importation share is

Fig. 5. Relative contributions to Global Warming (GWP) in all scenarios under study in terms of wood transport models. Acronyms: SC1 = Scenario 1 (current scenario); SC2 = Scenario 2; SC3 = Scenario 3; SC4 = Scenario 4; SC5 = Scenario 5.

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

3537

Fig. 6. Relative contributions (in %) to GWP taking into account the origin of wood processed in the pulp mill. Acronyms: SC1 = Scenario 1 (current scenario); SC2 = Scenario 2; SC3 = Scenario 3; SC4 = Scenario 4; SC5 = Scenario 5.

increased (SC3), acidifying emissions increase approximately 15% (Fig. 3). The same as in GWP, in SC1 the highest contributions to AP are associated to imports of wood from Baltic countries (44%), followed closely by Southern Sweden (43%). In SC2 contributions from Baltic countries add up to 57%, due to the introduction of transport by electric train in Southern Sweden. In SC3 contributions from Baltic countries represent 61% of total due to the increase of the imports share in the second one (Fig. 7). In SC4, the 61% of total contributions to this impact category is associated to transport from Southern Sweden due to import reduction and the increase in Swedish wood. Central Sweden shows a higher contribution to acidifying emissions in SC5 (24%) compared to its contribution to the remaining scenarios. It is due to the reduction of wood processed from Baltic countries in the mill, the use of train instead of boat for transport in Southern Sweden and the increase of wood share transported from Central Sweden. 4.5. Fossil fuel extraction Fossil fuel extraction (FF) refers to the depletion of energetic resources such as coal, crude oil or natural gas. The contributions of crude oil, natural gas and coal to fossil fuel extraction (expressed in kg coal equivalent) are summarized in Table 3 for each scenario under

study. It can easily be seen that crude oil contributes largely to the fossil fuel extraction, followed by natural gas. In SC1, the contribution to fossil fuel extraction is 272.4 kg coal equivalent per 1 m3sub. The introduction of a combination of electric and diesel trains (SC2) reduces fossil fuel requirement up to 16%. In contrast, if the importation ratio is increased (SC3), contributions to FF increase up to 14%. Combining the reduction of the ratio of wood imported from Baltic countries and the transportation by train of wood from Southern Sweden (as the same way as SC2) should be possible to reduce the contributions to FF up to 28%. 5. Discussion Consumption of fossil fuels and the corresponding emissions to air, water and soil depend on the transport distances as well as on the transport system used. Research on timber haulage (Forsberg, 2002) suggests that there are many ways of decreasing the energy demands in the secondary road transport, such as reducing the transport distance, adjusting the load factors, design better route-planning systems, improving the standards of roads (curve geometry and surfaces), adopting more fuel efficient driving techniques and using the best available transport carriers.

Fig. 7. Relative contributions (in %) to Acidification (AP) taking into account the origin of wood processed in the pulp mill. Acronyms: SC1 = Scenario 1 (current scenario); SC2 = Scenario 2; SC3 = Scenario 3; SC4 = Scenario 4; SC5 = Scenario 5.

3538

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539

Table 3 Contributions to fossil fuel extraction (kg coal eq) per functional unit (1 m3sub).

6. Conclusions

Scenario

Crude Oil

Natural gas

Coal

Total

SC1 SC2 SC3 SC4 SC5

271.7 227.4 308.8 234.6 196.8

0.66 0.72 0.75 0.58 0.66

– 2.10 · 10− 3 – – 2.40 · 10− 3

272.4 228.1 309.6 235.2 197.4

In this paper, different scenarios of pulpwood supply to a Swedish pulp mill were compared in order to identify a more environmental friendly wood transport strategy. Scenarios in which electric trains are introduced for wood delivery reduce considerably environmental impact due the Swedish electric profile which considerably depends on renewable sources. In addition, reduction of wood imports seems to be an interesting alternative in order to reduce energy requirements and negative environmental effects. The results of this study show the large influence of the geographical origin of wood processed not only in a pulp mill but also in any forest-based industry. In conclusion, this kind of comparison is useful for providing insights into the environmental preference of different wood sources. Although this study was focused on Sweden, the results could be extended to other regions or countries. In addition, this study can serve as a basis to make possible improvements in LCA studies of wooden products regardless of the area under scrutiny. In this aspect this study has a general result.

In the Swedish pulp mill under study, 25% of the wood comes from Baltic countries (Lithuania, Estonia and Latvia), 30% from Southern Sweden and 45% from Central Sweden. Lorry and lorry-boat are the current means of transport considered for delivering from forest landing to mill gate. Wood transportation by boat is the largest contributor to energy requirements in the current scenario of wood supply to the pulp mill and adds up to 53% of the total energy use (Table 2). Boat transport is considered when wood processed comes from Southern Sweden (due to the location of the pulp mill near the coast) and the Baltic countries. The influence of the average transport distances by road was not considered in this study due to the fact that the average distance travelled in all systems (Central and Southern Sweden and, Baltic countries) is set to 100 km which fits in with average distances in other European countries. Replacing imported timber with timber from Southern Sweden would cause changes due to the choice of transport with ship or railway. Shipping by rail within Sweden combined with less import has a beneficial impact on all impact categories However, when train was considered (in SC2 and SC5), electric train was combined with diesel train as there is not electric train connection for the whole distance (963 km). SC2 involves lorry and train transport in Southern Sweden and the remaining systems do not change compared to SC1. The alternative scenario SC2 has lower potential impact in all impact categories analyzed (from 13% in POP to 24% in EP). These considerable environmental reductions are related to the nature of the energy used. The electricity used by electric trains in Sweden is mainly of hydroelectric origin (48%). SC3 and SC4 have opposite performances (Fig. 3). Wood imports are raised from 25% to 40% in SC3 and they are reduced up to 10% in SC4. Energy requirements increase by approximately 14% in SC3 due to the increase in the distance assigned per FU. In SC1, 496 km is the average distance travelled per FU and in SC3 adds to 570 km. Regarding SC4, travelling distance assigned to FU is reduced up to 422 km and therefore, energy use. SC5 seems to be the most favourable scenario under an environmental perspective. The combination of lorry and train transport and reduction of imported wood (up to 15%) reduce the contributions to all impact categories analyzed. In fact, EU is almost reduced by 40% and combustion related emissions decrease by 25%. The use of hydroelectric and nuclear energy (in the electricity profile generation) does not cause combustion emissions (e.g. CO2, NOx and SOx), therefore reducing the contributions to GWP, POP, EP and AP. However, other environmental problems are generated such as damage to the ecosystems which are not evaluated in this paper (Lior, 2008). In addition, it would be interesting to change the use of fossil fuels in transport models (mainly diesel) to renewable fuels since it should be a potential option in order to reduce their contributions to GWP. This study penetrates a specific case with three raw material sources and three means of transportation. The study shows that the source and choice of means of transportation have different impacts on environmental performance but a general interpretation is not possible as the impact might depend on aspects not analysed here, such as choice of ship vessel size, fuel, energy source for railways and electricity mix in the grid.

7. Future outlook This study provides useful information that can assist the forestbased industries in the aim of increasing their sustainability. Future work will focus on the incorporation of biofuels (such as forest biomass and/or biodiesel) instead of fossil fuels. Acknowledgements This project was developed within the framework of the BIORENEW Integrated Project (project reference: NMP2-CT-2006026456). S. González-García would like to express her gratitude to the Spanish Ministry of Education for financial support (grant reference AP2005-2374). The authors would also like to thank Domsjö pulp mill for the published data provided as well as to Skogforsk staff for all the information supplied. The paper has also gained from the cooperation with workings in project number 518128 EFORWOOD within Thematic priority 6.3 Global Change and Ecosystems. References Aldentun Y. Life cycle inventory of forest seedling production — from seed to regeneration site. J Clean Prod 2002;10:47–55. Baumann H, Tillman AM. The hitch hiker's guide to LCA. An orientation in life cycle assessment methodology and application. StudenlitteraturSweden: Lund9144023642; 2004. p. 543. Banverket, 2007. http://www.banverket.se (November 2007). Berg S, Karjalainen T. Comparison of greenhouse gas emissions from forest operations in Finland and Sweden. Forestry 2003;76:271–84. Berg S, Lindholm EL. Energy use and environmental impacts of forest operations in Sweden. J Clean Prod 2005;13:33–42. Derwent RG, Jenkin ME, Saunders SM, Pilling MJ. Photochemical ozone creation potentials for organic compounds in northwest Europe calculated with a master chemical mechanism. Atmos Environ 1998;32:2419–41. Dones R, Bauer C, Bolliger R, Burger B, Faist Emmenegger M, Frischknecht R, et al. Life cycle inventories of energy systems: results for current systems in Switzerland and other UCTE Countries. Ecoinvent report No. 5. Dübendorf, Switzerland: Paul Scherrer Institut Villigen, Swiss Centre for Life Cycle Inventories; 2007. ECMT. European Conference of Ministers of Transport; 2007. http://www.cemt.org (November 2007). Eriksson E, Blinge M, Lövgren G. Life cycle assessment of the road transport sector. Sci Total Environ 1996;189–190:69–76. EUROSTAT Statistical books. Quarterly Panorama of European business statistics. European Communities; 2007. ISSN 1725-485X, Available at: http://europa.eu (November 2007). European commission. Enterprise. Industry sectors. Forest-based industries. 2006. http://ec.europa.eu/enterprise/forest_based/pulp_en.html (November 2007). European Commission. Agriculture. Forestry measures. Main characteristics of the EU forest sector. Forest ownership. http://ec.europa.eu/agriculture/fore/characteristics/index_en.html (November) 2007a. European Commission. Agriculture. Forestry measures. Main characteristics of the EU forest sector. The economic importance of the EU forest sector. http://ec.europa. eu/agriculture/fore/characteristics/index_en.htm#book2 (November) 2007b. Forsberg M. Transmit — Driftstatistik och vägstandardens påverkan på bränsleförbrukningen. Arbetsrapport Nr 515. Uppsala (Sweden): SkogForsk (The Forestry

S. González-García et al. / Science of the Total Environment 407 (2009) 3530–3539 Research Institute of Sweden); 2002. ISSN 1404-305X. [in Swedish, with English abstract]. Frees N, and Weidema BP. Life cycle assessment of packaging systems for beer and soft drinks. Energy and transport scenarios. Technical report 7. Miljöprojekt vol. 406. Ministry of Environment and Energy, Denmark, 1998. Frischknecht R, Bollens U, Bosshart S, Ciot M, Ciseri L, Doka G, et al. Ökoinventare von Energiesystemen: Grundlagen für den ökologischen Vergleich von Energiesystemen und den Einbezug von Energiesystemen in Ökobilanzen für die Schweiz. 3. Gruppe Energie — Stoffe — Umwelt (ESU), Eidgenössische Technische Hochschule Zürich und Sektion Ganzheitliche Systemanalysen, Paul Scherrer Institut, Villigen, Bundesamt für Energie (Hrsg.), Bern (Switzerland), 1996. (in German). Goodale C, Apps M, Birdsey R, Field C, Heath L, Houghton R, et al. Forest carbon sinks in the northern hemisphere. Ecol Appl 2002;12(3):891–9. González-García S, Berg S, Feijoo G, and Moreira, MT. Environmental impacts of production and supply of pulpwood: Spanish and Swedish case studies. Paper submitted to Int J LCA 2008. González-García S, Berg S, Moreira MT, and Feijoo G. Evaluation of forest operations in Spain under a life cycle assessment perspective. Paper accepted in Scand J Forest Res 2009. Gutierrez A, del Río JC, Martínez MJ, Martínez AT. The biotechnological control of pitch in paper pulp manufacturing. Trends Biotechnol 2001;19:341–8. Heijungs R, Guinée JB, Huppes G, Lankreijer RM, Udo de Haes HA, Wegener Sleeswijk A, et al. Environmental life cycle assessment of products. Guide and backgrounds. Leiden (The Netherlands): CML, Leiden University; 1992. IPCC, Intergovernmental Panel on Climate Change. Climate change 2007 — the physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the IPCC; 2007. Available at: http://www.ipcc.ch/ipccreports/ar4-wg1.htm (January 2009). IPCC-NGGIP, Intergovernmental panel on climate change national greenhouse gas inventories programme. “Good practice guidance for land use, land-use change and forestry”, 2003. http://www.ipcc-nggip.iges.or.jp/public/gpglulucf (December 2007). ISO 14040. Environmental management — life cycle assessment — principles and framework. Switzerland, Geneva, 2006. Jungmeier G, Werner F, Jarnehammar A, Hohenthal C, Richter K. Allocation in LCA of woodbased products. Experiences of cost action E9. Part I. Methodology. Int J Life Cycle Assess 2002;7:290–4. Karjalaimen T, Zimmer B, Berg S, Welling J, Schwaiger H, Finér L, et al. Energy, carbon and other material flows in the life cycle assessment of forestry and forest products; achievements of the working group 1 of the COST action E9. European Forest Institute (EFI), Joensuu (Finland), 2001. Lindholm EL, Berg S. Energy requirement and environmental impact in timber transport. Scand J For Res 2005a;20:184–91. Lindholm EL, Berg S. Energy use in Swedish forestry in 1972 and 1997. Int J For Eng 2005b;16:27–37. Lindfors LG, Christiansen K, Hoffman L, Virtanen Y, Juntilla V, Hanssen OJ, et al. Nordic guidelines on life cycle assessment. Nord. Copenhagen: Nordic Council of Ministers; 1995. p. 20.

3539

Lior N. Energy resources and use: the present situation and possible paths to the future. Energy 2008;33:842–57. Liski J, Pussinen A, Pingoud K, Mäkipää R, Karjalainen T. Which rotation length is favourable to carbon sequestration? Can J For Res 2001;31:2004–13. Löfroth C, Rådström L. Fuel consumption in forestry continues to fail. Results from Skogforsk, vol. 3. Uppsala (Sweden): The Forestry Research Institute of Sweden; 2006. NTM-Environmental Data for International Cargo Transport. Calculation methods — modespecific issues. Rail transport. 2007a Gothenburg (Sweden), http://www.ntm.a.se (November 2007a). NTM-Environmental Data for International Cargo Transport. Calculation methods — modespecific issues. Road transport. 2007b. Gothenburg (Sweden), http://www.ntm.a.se (November 2007). NTM-Environmental Data for International Cargo Transport. Sea Transport. Calculation methods, emission factors, mod-specific issues. 2007c. Gothenburg (Sweden), http:// www.ntm.a.se (November 2007). PRé-Consultants. SimaPro 7—introduction to LCA with SimaPro 7. 2007. Amersfoort (The Netherlands), http://www.pre.nl/ (October 2007). Reciclapapel, 2002. http://www.reciclapapel.org/htm/info/tecnica/ciclo/dconsumopastas.asp (October 2007). Rivela B, Moreira MT, Muñoz I, Rieradevall J, Feijoo G. Life cycle assessment of wood wastes: a case study of ephemeral architecture. Sci Total Environ 2006;357:1-11. Schwaiger H, Zimmer B. A comparison of fuel consumption and Greenhouse gas emissions from forest operations in Europe. In: Karjalainen T, Zimmer B, Berg S, Welling J, Schwaiger H, Finér L, Cortijo P, editors. Energy, carbon and other material flows in the life cycle assessment of forestry and forest products — achievements of the working group 1 of the COST action E9. Joensuu (Finland): European Forest Institute (EFI); 2001. p. 33–53. Sigoillot C, Camarero S, Vidal T, Record E, Asther M, Pérez-Boada M, et al. Comparison of different fungal enzymes for bleaching high-quality paper pulps. J Biotechnol 2005;115:333–43. Skogsstatistisk Årsbok 2007 (Statistical yearbook of forestry 2007). Official statistics of Sweden. Swedish Forest Agency. Jönköping, Sweden [in Swedish, with English abstracts]. Sveriges Skogsvårdsförbund. Praktisk Skogshandbok; 1994. Djursholm. Uppenberg S, Lindfors LG. EPD Produktspecifika utgångspunkter för drivmedel, vol. 6. PSR; 1999. [in Swedish, with English abstract]. Uppenberg S, Almemark M, Brandel M, Lindfors LG, Marcus HO, Stripple H, et al. Bakgrundsinformation och Teknisk bilaga. Miljöfaktabok för bränslen, Del 2. — IVL Svenska miljöinstitutet AB, IVL Rapport B1334-2A, Stockholm (Sweden); 2001. [in Swedish]. Wang Y. Renewable electricity in Sweden: an analysis of policy and regulations. Environ Policy 2006;34:1209–20. Werner F, Nebel B. Wood & other renewable resources. Int J Life Cycle Assess 2007;12:462–3. White MK, Gower ST, Ahl DE. Life cycle inventories of roundwood production in northern Wisconsin: inputs into an industrial forest carbon budget. For Ecol Manag 2005;219:13–28.