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Life cycle assessment of gasoline production and use in Chile
Science of the Total Environment 505 (2015) 833–843
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Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
Life cycle assessment of gasoline production and use in Chile Marjorie Morales a,⁎, Sara Gonzalez-García b, Germán Aroca a, María Teresa Moreira b a b
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaiso, Av. Brasil 2085, Valparaiso, Chile Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
H I G H L I G H T S • A well-to-wheel LCA of gasoline production in Chile was carried out. • Volume, economic and energy allocations were considered for sensitivity analysis. • Refinery and car emissions were the main contributors to environmental impacts.
a r t i c l e
i n f o
Article history: Received 8 July 2014 Received in revised form 7 October 2014 Accepted 19 October 2014 Available online 7 November 2014 Editor: Simon James Pollard Keywords: Environmental assessment Passenger car Refinery Transportation fuel Well-to-wheel analysis
a b s t r a c t Gasoline is the second most consumed fuel in Chile, accounting for 34% of the total fuel consumption in transportation related activities in 2012. Chilean refineries process more than 97% of the total gasoline commercialized in the national market. When it comes to evaluating the environmental profile of a Chilean process or product, the analysis should consider the characteristics of the Chilean scenario for fuel production and use. Therefore, the identification of the environmental impacts of gasoline production turns to be very relevant for the determination of the associated environmental impacts. For this purpose, Life Cycle Assessment has been selected as a useful methodology to assess the ecological burdens derived from fuel-based systems. In this case study, five subsystems were considered under a “well-to-wheel” analysis: crude oil extraction, gasoline importation, refinery, gasoline storage and distribution/use. The distance of 1 km driven by a middle size passenger car was chosen as functional unit. Moreover, volume, economic and energy-based allocations were also considered in a further sensitivity analysis. According to the results, the main hotspots were the refining activities as well as the tailpipe emissions from car use. When detailing by impact category, climate change was mainly affected by the combustion emissions derived from the gasoline use and refining activities. Refinery was also remarkable in toxicity related categories due to heavy metals emissions. In ozone layer and mineral depletion, transport activities played an important role. Refinery was also predominant in photochemical oxidation and water depletion. In terms of terrestrial acidification and marine eutrophication, the combustion emissions from gasoline use accounted for large contributions. This study provides real inventory data for the Chilean case study and the environmental results give insight into their influence of the assessment of products and processes in the country. Moreover, they could be compared with production and distribution schemes in other regions. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Crude oil represents the leading fossil fuel in the world, accounting for 33% of global energy consumption. Its relevance is even more important in South America with more than 45% of the total energy consumed in 2012 (BP, 2013). This remarkable dependence on oil and its derivatives involves major environmental problems, mainly associated with the emission of greenhouse gases (GHG). Around 11 Gt CO2 were emitted globally in 2010 according to the last report of the International
⁎ Corresponding author at: Av. Brasil 2085, Valparaiso, Chile. Tel.: +56 992588315. E-mail address: [email protected] (M. Morales).
http://dx.doi.org/10.1016/j.scitotenv.2014.10.067 0048-9697/© 2014 Elsevier B.V. All rights reserved.
Energy Agency (IEA, 2012), with road transport as the largest contributing source (~5 Gt CO2). Within South American countries, Chile occupies the fifth position in terms of GHG emissions (IEA, 2012) associated with fuel use in industrial, transport and energy sector (Fig. 1a). These emissions are expected to increase by 400% in 2030 (O'Ryan et al., 2010). Around 70% of the total energy consumption in the transport sector is associated with road transport (O'Ryan et al., 2010). Fig. 1b reports the distribution of fuel products consumed in the Chilean transport sector, being diesel the most consumed fuel followed by gasoline (BNE, 2013). Passenger cars mainly run on gasoline (96%) and produce 32%, 24% and 20% of total NO x , NMVOC and CO emissions of the transport sector (OCDE and CEPAL, 2005). Beyond the tailpipe emissions related
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Fig. 1. (a) Chilean Energy Matrix (2012) (BNE, 2013); (b). Distribution of oil derivatives consumed in the Chilean transport sector (2012) (BNE, 2013).
with gasoline use, there are many other upstream processes (such as crude oil extraction, refining, transport, etc.) that need to be considered in the environmental profile of gasoline due to their associated environmental effects. Regarding solid and liquid emissions, the extraction stage of crude oil typically requires the removal of sludge and water in settling tanks, both streams polluted with hydrocarbons and heavy metals (Capelli et al., 2001). Moreover, the refining process is a large consumer of water for cooling, steam production, washing and reaction processes as well as it produces solid wastes such as petroleum coke and sludge from different process units (ENAP, 2012b). Both the extraction of crude oil as well as its transport and refining involve leaks of crude oil that cause pollution of groundwater and land (Al-Majed et al., 2012). Gaseous emissions (either direct or indirect) such as hydrocarbons, CO, SO x and NOx , are one of the main contributors to the environmental impacts in the refining related activities. These emissions are produced in different steps such as the topping, flaring or storage of refining products. In Chile, environmental management was institutionalized just over the last decade. Chilean governments have made remarkable progress in designing and implementing environmental policies and regulations for the industrial sector (CONAMA, 2010), which has positioned Chile as the Latin America leading country in terms of environmental protection. Moreover, Chile occupies the 29th position in the Environmental Performance Index (Esty et al., 2014). The promotion of new standards in order to control and reduce pollutant emissions in Chile has forced oil companies to make significant efforts to implement and improve environmental technologies. Chilean refineries have paid attention to the identification and control of environmental risks in order to accomplish with the general rules and regulations applicable to their processes. The crude oil extraction, production and refining in Chile are based on international environmental standards such as ISO 14001 (ENAP, 2012b). The quantification of the environmental profile associated with a process or product throughout its life cycle can be performed by means of the Life Cycle Assessment (LCA) methodology (ISO, 2006b). In agreement with numerous studies where the environmental profiles of fuel production and use have been quantified by LCA (Keesom et al., 2012; Restianti and Gheewala, 2012; Singh et al., 2010; Spatari et al., 2010), this methodology has been chosen to qualitatively evaluate the environmental loads of the gasoline production and use in Chile. Commonly, LCA studies for fuels have been performed from a wellto-wheel perspective (Borrion et al., 2012; Cherubini et al., 2009; González-García et al., 2010, 2012; Pont, 2007; Restianti and Gheewala, 2012), taking into account not only fuel production but
also its final use. Concerning gasoline, its environmental profile has been quantified under the same perspective in Europe (Furuholt, 1995; Keesom et al., 2012; Querini et al., 2011), USA (Skone and Gerdes, 2009; Unnasch et al., 2009) and Indonesia (Restianti and Gheewala, 2012). This study aims to perform an environmental analysis of the gasoline produced and used in Chile by means of the LCA methodology because no LCA study is available for gasoline in the Chilean or Latin-American context. In addition, the environmental hotspots (that is, the processes responsible of the largest contributions to the environmental profile) all over the life cycle will be identified in order to future improvement alternatives. 2. Methodology LCA evaluates the environmental burdens of a production system by identifying resource and energy consumptions as well as emissions to different environmental compartments. LCA allows identifying priority areas where improvement actions will have the greatest effects on reducing the environmental impacts (ISO, 2006a). In this study, the environmental profile was performed following ISO 14040 specifications (ISO, 2006a). The objective of this study was to perform the environmental analysis of the Chilean gasoline production and use in passenger cars, following the LCA methodology from a well-to-wheel perspective. The functional unit provides a reference to which the input and output process data are normalized. Generally, the results for transportation fuels are related with the distance traveled (Cherubini et al., 2009). The functional unit used in this study was 1 km driven by a middle size passenger car. An average consumption of 0.15 L gasoline per km was assumed (EPA/DOE, 2014). 2.1. System boundaries description All the processes or activities carried out from the crude oil extraction and production up to the gasoline use in a passenger car were considered within the system boundaries. Production of the different consumable materials (chemicals, electricity, machinery, etc.) as well as infrastructure construction and maintenance were also included. Fig. 2 shows an overview of the Chilean gasoline system under study. The system was divided into five subsystems, which will be described in detail below: crude oil extraction (Subsystem 1); gasoline importation (Subsystem 2); refinery (Subsystem 3); gasoline storage (Subsystem 4) and distribution and use (Subsystem 5).
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843
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Fig. 2. System boundaries corresponding to the life cycle of the gasoline.
2.1.1. Subsystem 1 (S1). Crude oil extraction The oil supply chain is mainly based on imports of crude oil (99% of the total) that comes from Latin America (92%), Europe (6%) and North America (1%), while the remaining crude oil is obtained from national extraction (ENAP, 2012b). The countries from where Chile imports crude oil are Brazil (30%), Ecuador (30%), Colombia (16%), Argentina (16%), the UK (6%) and Canada (1%), while national production represents 1%. The crude oil produced in Chile is exploited by National Oil Company1 (ENAP), which manages its exploration and production located in the Southernmost Magallanes region. Crude oil is transported to different refineries in Chile by tanker and/or pipeline. It was considered that the oil from Argentina is transported
1
www.enap.cl.
through the Trasandino pipeline, while oil from other sources is transported by sea. 2.1.2. Subsystem 2 (S2). Gasoline importation Regarding the importation of gasoline, 783,000 m3 of gasoline was imported in 2012 (SEC, 2012). It was considered that gasoline is imported from Brazil and Colombia (the two principal importing sources of crude oil in Chile) and transported by tanker. Thus, this subsystem includes the crude oil extraction and gasoline production in these countries. The different national refineries have the infrastructure for crude oil and co-products reception and storage in marine terminals. 2.1.3. Subsystem 3 (S3). Refinery This subsystem includes the reception of the crude oil (national and imported) in the different Chilean refineries to the production of
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Fig. 3. Refineries and pipelines involved in the Chilean gasoline production.
gasoline and other refining products. National and imported crude oil is transported by tanker and/or pipeline and received in the ENAP oil refineries. ENAP owns three different refineries: Refinery Aconcagua (Refinery A), Refinery Bio-Bio (Refinery B) and Refinery Gregorio (Refinery C), located in Central-Zone, Southern-Zone and Austral-Zone of Chile, respectively, where crude oil is processed. The location and volume of crude oil annually processed at each refinery are shown in Fig. 3 and Table 1, respectively. The refining process consists of a complex and highly integrated process where the equipment and unit operations are tailored to specific feed properties. The basic operations that are performed in the ENAP refineries are the following: topping, vacuum distillation, ethylene plant, catalytic reforming, alkylation, isomerization, hydrocracking, visbreaking, catalytic cracking, coking, desulfurization/hydrotreating acid recovery plant and a sulfur recovery unit (ENAP, 2014). The total volume of petroleum refining co-products produced in Chile in 2012
Table 1 Volume of crude oil processed in ENAP Refineries in 2012 (thousand m3) (SEC, 2012). Origin of crude oil
Refinery A
Refinery B
Refinery C
Imported National
4668 27.8
4501 68.5
13.4 249
(ENAP, 2012a) are: diesel 3349 Mm3, gasoline 3290 Mm3, fuel oil 1275 Mm3, kerosene 846 Mm3, LPG 668 Mm3 and other refining products 10 Mm3. 2.1.4. Subsystem 4 (S4). Gasoline storage The gasoline produced at each refinery is stored in its own facilities. However, a part is also stored in storage plants located between V and VIII Regions. Gasoline is transported by pipeline from refineries to storage plants (see Fig. 3). The storage plants I, II, III and IV are located in the Central zone of Chile, between the Metropolitan region and Bio-Bio region (see Fig. 3). 2.1.5. Subsystem 5 (S5). Distribution and use The gasoline is distributed from the storage plants to the consumption centers located across the country. The gasoline distribution was assumed to be carried out by 32 ton diesel lorries. The refineries A and B produce gasoline to the northern part and southern part of the country respectively. It was assumed that there are also four storage plants located in the Central Valley to supply gasoline to the most populated cities. Refinery C provides gasoline to the southernmost region (Magallanes). The distribution from the storage plants to the service station was assumed to be carried out by 16 ton diesel lorries, covering an average distance of 50 km (Spielman et al., 2007).
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843
2.2. Allocation procedure The refining process is a very complex system, giving a large number of co-products that are strongly correlated (Furuholt, 1995; Restianti and Gheewala, 2012). Allocation is the partitioning of input or output flows of a unit process to the product under study. In this study, allocation was required and the partition was performed considering a volume criteria (ENAP, 2012a). Allocation approach based on market prices (CNE, 2014) and energy content (BNE, 2013) of the refining co-products were also considered in a sensitivity assessment which will be discussed below. Table 2 briefly reports the allocation factors considered. 3. Life cycle inventory The quality of an environmental life cycle study considerably depends on the inventory data managed. In this study, primary inventory data were managed for the Chilean sector, which were taken from official data sources (BNE, 2013; ENAP, 2012a, 2012b; SEC, 2012). These data were completed, when necessary, with secondary data from the ecoinvent® database v2.0 (Jungbluth, 2007; Spielman et al., 2007). SimaPro software v8 was used for the analysis (Prè-Consultants, 2014). As previously reported, part of the crude oil processed in the Chilean gasoline system is imported from different countries. It was not possible to collect real and valuable inventory data corresponding to each exporter country. Therefore, inventory data were taken from the ecoinvent® database, considering a world average (Jungbluth, 2007). The onshore oil extraction is the common practice for crude oil extraction in Chile. The inventory data for the oil extraction (Table 3) was obtained from the 2012 annual report (ENAP, 2012b). The production of infrastructure, the wells for crude oil extraction and the onshore platform was considered within the analysis. Inventory data for infrastructure was obtained from the ecoinvent® database (Jungbluth, 2007). Inventory data concerning imported gasoline production as well as combustion emissions derived from tanker transport were obtained from the ecoinvent® database (Jungbluth, 2007; Spielman et al., 2007). Table 4 shows the volume of crude oil (per functional unit) transported by tanker from each exporting country to each Chilean refinery. The same proportion of crude oil from the importing countries to each refinery was assumed. Concerning the crude oil imported from Argentina across pipeline, Table 5 shows the volume of crude oil (per functional unit) transported by pipeline from Argentina to each Chilean refinery. Inventory data obtained for pipeline transport in Chile are shown in Table 6. Data concerning distances as well as inputs and emissions for each pipeline transport were obtained from literature for 2012 (ENAP, 2012b). Inputs and outputs correspond to average data from the three refineries by year 2012 (Table 7). These inventory data were taken from literature (ENAP, 2012b) and included refining products, energy supply, materials, air emissions, wastewaters, spills and solid wastes. The water used in the refineries is continuously taken from nearby rivers and the effluent after treatment is discharged into the sea. Wastewater treatment inventory was taken from the ecoinvent® database (Doka, 2007). The energy required at the stage of refinement comes from Chilean national grid and/or sub-products from refining,
Table 2 Allocation factors corresponding to the different co-products from the gasoline production system. Allocation Method
Volume Economic Energetic
Table 3 Relevant inputs and outputs for crude oil extraction in Chile (per 1 km driven by a passenger car).
Inputs Materials Water Gas lift Energy Electricity Natural gas Diesel Gasoline Kerosene Outputs Products Crude Oil Natural gas Air emissions CH4 CO2 CO NOX SO2 Hydrocarbons gases Soil emissions Oil spills Water emissions Waste water Wastes to treatment Solid wastes not dangerous to landfill Solid wastes hazardous to incineration Sludge from excavation
Liquefied petroleum gas
Kerosene
Diesel
Fuel oil
Other refining products
34.9 44.6 32.7
7.1 8.1 5.5
8.9 8.2 9.3
35.5 32.2 37.3
13.5 6.9 15.1
0.1 0.1 0.2
Value
Unit
1.6 70.7
L L
9.3 38.4 1.2 0.02 1.5
kJ MJ MJ MJ MJ
0.42 2.5
L L
0.08 0.73 0.013 0.23 0.03 0.44
mg mg mg μg mg μg
3.2
mL
1.3
L
1.04 0.40 12
g g g
such as fuel oil and refinery gas (which is completely consumed in the refinery). Air emissions from refining activities account for indirect emissions associated with the production and combustion of fuels at the refinery, flaring, venting and fugitive emissions. Inventory data corresponding to the infrastructure production and maintenance for three refineries were taken from the ecoinvent® database (Jungbluth, 2007). The gasoline transport from the refineries to storage plants considers pipeline transport. Inventory data corresponding to this subsystem (S4) are reported in Table 6. Distributing distances are detailed in Table 8. The volume of gasoline distributed in each region across the country was obtained from Superintendency of electricity and fuel for 2012 (SEC, 2012). The electricity required in the inventories of the crude oil extraction (see Table 3) and pipeline transport (see Table 6) are shown in Table 9. Data for the electricity production in 2012 were collected from the Chilean Ministry of Energy (BNE, 2013). Inventory data concerning the different energy sources used in the electricity production process was obtained from the ecoinvent® database (Jungbluth, 2007) and adapted to the Chilean context. Table 4 Volume and distance of crude oil transported by tanker between country of origin and marine terminals in Chilean refineries (per functional unit). Country of origin
Refinery of destination
Volume of crude oil (L)
Brazil
Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C
7.8 7.5 2.2 6.4 6.2 1.8 3.4 3.3 9.8 1.3 3.1 6.1
Ecuador
Refining products Gasoline
837
Colombia
Chile
· · · · · · · · · · · ·
10−2 10−2 10−4 10−2 10−2 10−4 10−2 10−2 10−5 10−3 10−3 10−4
Distance (km) 7026 6562 4722 3673 4118 6336 4462 4907 7131 2913 2451 0
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Table 5 Volume and distance of crude oil transported by pipeline between country of origin and refineries in Chile (per functional unit). Country of origin
Refinery of destination
Volume of crude oil (L)
Distance (km)
Argentina
Refinery A Refinery B Refinery C
3.4 · 10−2 3.3 · 10−2 9.8 · 10−5
773a 163 163b
a b
Considering Trasandino pipeline + national pipelines. Considering only Trasandino pipeline, then is transported by tanker.
4. Results Characterization factors from the ReCiPe 2008 method (Goedkoop et al., 2009) in the hierarchic perspective were considered for the environmental impact assessment. The impact categories considered were climate change (CC), ozone depletion (OD), human toxicity (HT), photochemical oxidation formation (POF), terrestrial acidification (TA), freshwater eutrophication (FE), marine eutrophication (ME), terrestrial ecotoxicity (TET), freshwater ecotoxicity (FET), marine ecotoxicity (MET), water depletion (WD), mineral depletion (MRD) and fossil depletion (FD). Table 10 summarizes the LCA characterization results per subsystem according to a volume-based allocation (base case). Fig. 4 shows the contribution to the impact categories from each subsystem involved all over the life cycle of the gasoline system. According to the results, two subsystems played a major role: refinery and distribution and use. Distribution and use was responsible for 50% of the impact in the CC followed by refinery (40%), being CO2 emissions the main responsible substance. Refinery and distribution and use also represented 54% and 46% in the OD respectively, being Halon 1301 emissions the main pollutant contributing in this category. Refinery was the main stage contributing to HT, accounting for 70% of the total impact mainly due to heavy metals emissions derived from the refining activities, followed by refinery (19%) and distribution and use (11%). Refinery played a significant role with a contribution of 97% and 51% to POF and TA, respectively. SOx and NOx were the main pollutants affecting POF and TA impact categories. Phosphate emissions derived from refinery (65%) and distribution and use (27%) affected FE. Nitrogen based pollutants emitted from refinery (87%) affected ME. Regarding ecotoxicity related categories, the principal subsystem contributing to TET and MET was refinery (62% and 44% respectively) due to the emissions of heavy metal (nickel and copper). In FET, distribution and use was the main contributor (79%) due to bromine and nickel emissions. Nearly all the contributions to WD were accounted for refinery (99%) due to the water requirements in the refining activities. Moreover, this subsystem summed up to 83% of the total MRD due to the materials used in the pipeline infrastructure. Finally, FD was mainly affected by crude oil extraction and refinery due to the fossil fuels required in the crude oil extraction and refining Table 6 Relevant inputs and emissions for pipeline transport in Chile (per 1 km driven distance by a passenger car).
Inputs Materials Water (groundwater) Drinking water Energy Electricity Outputs Transport (product) Transport by pipeline Soil emissions Oil spills Water emissions Waste water
Value
Unit
20.2 2.0 · 10−4
L L
0.10
Wh
3.0 · 10
−2
tkm
2.6 · 10
−7
L
2.3 · 10−3
L
Table 7 Global inventory for refining gasoline in Chile (per 1 km driven distance by a passenger car). Value Inputs Materials Crude oil Water Energy Fuel oil Liquefied natural gas Electricity Transport Crude oil by tanker Crude oil by pipeline Outputs Product Gasoline Co-products LPG Kerosene Diesel Fuel oil Other refining co-products Air emissions CO2 NOx NMVOC CO SO2 PM10 Hydrocarbons gases Water emissions Waste water Oils (unspecified) Hydrocarbons unspecified Sulfide Suspended solids Soil emissions Oil spills Wastes to treatment Solid wastes not dangerous to landfill Solid wastes hazardous to incineration
Unit
0.42 4.4
L L
0.02 9.0 0.40
MJ MJ MJ
1.6 0.03
tkm tkm
0.15
L
0.03 0.04 0.15 0.06 0.50
L L L L mL
95 138 8.52 24.5 190 40.3 15.9
g mg mg mg mg mg mL
4.2 72 41 2.0 286
L mg mg mg mg
4.2
mg
0.10 2.1
mL mL
activities (as energetic sources). A detailed description per impact category is reported below. 4.1. Climate change The emission of GHGs all over the life cycle of the system under study per functional unit was 0.39 kg CO2 eq (Table 10). Fig. 5 details the contributions from the key processes (hotspots) involved in each subsystem. According to this figure, the hotspots in terms of CC are the refining related activities due to the use of fuel oil and natural gas in the steam production process and in the torches as well as the gasoline use in the car. The detailed analysis of GHGs emissions is shown in Fig. 6. Emissions were mainly due to two global warming gases: CO2 (94%) and CH4 (5%). CO2 emissions mostly derive from the refinery related activities and gasoline combustion. CH4 emissions are mainly produced on the crude oil extraction. N2O emissions are almost negligible compared to CO2 and CH4 emissions.
Table 8 Transport by pipelines between refineries and storage plants in Chile (per functional unit). Refinery of origin
Storage plant of destination
Volume of gasoline (L)
Refinery A Refinery B
Storage plant I Storage plant II Storage plant III Storage plant IV
6.8 8.3 1.5 1.3
· · · ·
10−5 10−6 10−6 10−5
Distance (km) 127 350 175 82
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843 Table 9 Global inventory for electricity production in Chile (per 1 kWh electricity generated).
Inputs Primary energy Natural gas Coal Biomass Hydro-power Wind-power Crude oil products Diesel Fuel Oil Petroleum coke Outputs Electricity
Value
Unit
0.23 0.34 0.02 0.30 0.01
kWh kWh kWh kWh kWh
0.06 0.01 0.03
kWh kWh kWh
1.0
kWh
839
(involved in S3) the environmental hotspots (44%, 29% and 21% of total, respectively). Two different eutrophication potentials were evaluated: freshwater eutrophication (FE) and marine eutrophication (ME). The only one significant pollutant contributing to FE was phosphate mainly derived from gasoline combustion in the passenger car, transport of crude oil by tanker (involved in S3) and the refining activities. Fig. 5 shows that the refinery and transportation by tanker represent 44% and 19% of total, respectively; while the gasoline combustion in the car contributed with 26% of total. In the case of ME, this impact is mainly derived from the emission of nitrogen-based contaminants. The total value obtained in this category was 0.02 g N eq·km−1 (Table 10). The most significant processes contributing to ME were refining activities and gasoline use in passenger car, 10% and 87% respectively, principally due to NOx emissions (Fig. 5). 4.6. Ecotoxicity related potentials
4.2. Ozone depletion potential The key processes contributing to OD were the refining activities (38% of the total), the transport of crude oil by pipeline (15%) involved in refinery and the transport of gasoline by lorries (46%) included in refinery (Fig. 5) due to the production of the fossil fuels required in this stages (diesel and fuel oil). The main substance contributing to OD was Halon 1301 involved in the electricity production. 4.3. Human toxicity In HT, 70% and 15% of total contributions were due to the emissions from refining activities and transportation of crude oil by tanker (involved in S3) (see Fig. 5). Remaining contributions to HT were related with tailpipe emissions as well as emissions from crude oil extraction in the importing countries. This impact category was fully dominated by emissions of mercury and arsenic emitted to air related mainly to the electricity production required in the refinery. 4.4. Photochemical oxidant formation potential The POF impact (9 mg NMVOC eq·km−1) was mainly affected by emissions of NOx (Table 10). Fig. 5 shows that the emissions derived from the refining activities represent a percentage higher than 90% of the total contributions. 4.5. Acidification and eutrophication potentials Total terrestrial acidification (TA) per functional unit was 1.21 g SO2 eq, which comprises SO2 and NOx emissions (Table 10). Fig. 5 details the main processes involved in TA, being the gasoline use in the car, the refining activities and the transport of crude oil by tanker Table 10 LCA characterization results (per 1 km driven distance by a passenger car) for the potential impact categories under study. Impact category
Unit
Value
Climate change Ozone depletion Human toxicity Photochemical oxidant formation Terrestrial acidification Freshwater eutrophication Marine eutrophication Terrestrial ecotoxicity Freshwater ecotoxicity Marine ecotoxicity Water depletion Mineral depletion Fossil depletion
kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg NMVOC kg SO2 eq kg P eq kg N eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq m3 kg Fe eq kg oil eq
3.9 1.1 1.1 9.0 1.2 3.5 1.9 1.1 1.7 9.6 4.1 9.5 3.1
· · · · · · · · · · · · ·
10−1 10−9 10−3 10−6 10−3 10−4 10−5 10−5 10−4 10−4 10−1 10−4 10−1
Three different potentials related with ecotoxicity were assessed: terrestrial ecotoxicity (TET), freshwater ecotoxicity (FET) and marine ecotoxicity (MET). Detailed results for each one are shown in Table 10 and the main environmental hotspots, which contribute in these categories, are shown in Fig. 5. Activities related to refining were the main contributing to TET and MET, 62% and 44% respectively. However, in FET the most significant contributor was the emissions derived from the gasoline combustion in the car with 44% of total contributions to this category. 4.7. Water, mineral and fossil depletion potentials Table 10 shows the results corresponding to water, mineral and fossil depletions (WD, MRD and FD respectively). The total WD per functional unit was 0.4 m3. The refinery played a major significant role in this category, accounting for 99% (see Fig. 5) due to the water required in the process of petroleum refining and waste treatment. The principal contributing source to MRD was refinery, mainly due to the materials used in the pipeline and refinery infrastructure, representing 67% and 16% of MRD (see Fig. 5). Concerning FD, it was 0.3 kg oil per functional unit attributed mainly to refinery and distribution and use, 55% and 44% respectively. 5. Discussion The large dependence of gasoline in the transport sector imposes the need of reporting environmental data of its life cycle. This study can be considered as an opportunity to resolve the environmental concerns concerning gasoline production and use in passenger cars. LCA can be considered as a valuable tool in the process of strategic transportation planning, since it takes into account environmental, technical and economic considerations. Moreover, the results from the present study can be used as a base case for comparison with other fuels (e.g. bioethanol) as well as in decision-making strategies for the proposal of improvements in the production system. 5.1. Comparison with other gasoline studies assessed from a LCA perspective We have considered six reports available on gasoline production and use that managed real primary data for comparison with the results reported in this study (Furuholt, 1995; Keesom et al., 2012; Querini et al., 2011; Restianti and Gheewala, 2012; Skone and Gerdes, 2009; Unnasch et al., 2009). Although these studies provided detailed inventories, most of them were focused on quantifying GHG emissions and energetic requirements related to gasoline production and use while discarding other environmental impacts. Only the study carried out by Restianti and Gheewala (2012) considered other different impacts categories such as acidification or eutrophication. A comparison at an inventory level, only is possible with the values reported by Restianti
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Fig. 4. Contributions to the various impacts categories for each gasoline life cycle subsystem. Acronyms: CC — Climate change, OD — Ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion.
and Gheewala (2012), they reported its data using as a base 1 m3 of gasoline. In this study the inventory values are up to 45% lower for the production of co-products (Table 7) for the same base. Regarding the emissions of CO, CO2 and NOx, these were two, four and nine times higher in our study respectively, while for SO2, the emissions were six times lower. Moreover, there are several studies reporting environmental results in different impact categories for gasoline production system using inventory data from databases. These studies were taken into account for the comparison between the production and use of gasoline and bioethanol from an environmental perspective (Borrion et al., 2012; Cavalett et al., 2013; González-García et al., 2012; Luo et al., 2009). However, information concerning the gasoline production process was not reported in any of them since they were mainly focused on the bioethanol production technology. In addition, different characterization methods were used in these studies: ReCiPe (Goedkoop et al., 2009) and CML (Guinée et al., 2001). Depending on the method,
different characterization factors and reference units for some impact categories can been used. Hence, it is not possible to directly compare the results in all the impact categories. However, the environmental profiles could be compared in terms of four impact categories (climate change — CC, acidification — TA, Ozone layer depletion — OD, human toxicity — HT) and energy, considering the same functional unit and system boundaries for the Chilean and case studies (Borrion et al., 2012; Cavalett et al., 2013; González-García et al., 2012; Le et al., 2013; Luo et al., 2009; Restianti and Gheewala, 2012). According to the results shown in Table 11, it is possible to find some remarkable differences between our study and others available in the literature. These differences are related with the databases and the consideration of both different characterization methods (ReCiPe or CML) (Goedkoop et al., 2009; Guinée et al., 2001). The relevance of an LCA study is highly connected to the quality of the inventory analysis. For this reason, the management of inventory data representative of the production system is required. In our study,
Fig. 5. Contributions of the key processes to the impact categories under study. Acronyms: CC — Climate change, OD — Ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion.
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Brazil (Cavalett et al. 2013) with a value 25 times inferior, which is attributed to the data sources considered. Concerning the key processes contributing to the environmental profile, our study found that the refining activities and the tailpipe emissions from the passenger car were the environmental hotspots. Other studies (Borrion et al., 2012; González-García et al., 2012; Luo et al., 2009; Restianti and Gheewala, 2012) also reported the same contributing processes for the gasoline system (production and use), which is in agreement with our results. 5.2. Influence of the allocation approach
Fig. 6. Contributing GHG to each stage involved in the gasoline life cycle under assessment.
we have tried to use whenever possible representative inventory data for the Chilean gasoline production system (e.g. for crude oil extraction, transport, refinery, etc.). Regarding climate change, the results reported by Borrion et al. (2012) for the UK, Cavalett et al. (2013) for Brazil and Restianti and Gheewala (2012) for Indonesia ranging from 0.33 to 0.37 kg CO2 eq·km−1 were similar to this work: 0.39 kg CO2 eq·km−1. Lower values for this category were reported by González-García et al. (2012) for Spain, Luo et al. (2009) for USA and Le et al. (2013) for Vietnam ranging from 0.22 to 0.26 kg CO2 eq·km− 1. The environmental results in terms of terrestrial acidification showed similarities between our system and studies from Borrion et al. (2012), Cavalett et al. (2013) and Restianti and Gheewala (2012). In contrast, the results obtained by González-García et al. (2012) for Spain and Luo et al. (2009) for the USA were considerably lower, which could be due to differences in the characterization factors as well as the databases used. On the contrary, very large variations were identified between all the gasoline production systems concerning to OD and HT (Table 11). It is expected that these differences are the result of different calculation methods, sources of inventory data, allocation approaches as well as the scheme of production system. Moreover, a flow indicator such as energy use (expressed here in terms of MJ) has also been considered due to the relevance of this indicator in some studies (Furuholt, 1995; Le et al., 2013). The result from our study (12.9 MJ·km−1) is situated in the range of values obtained in other studies performed in the UK and Vietnam (Borrion et al., 2012; Le et al., 2013). However, large differences were found for
The allocation procedure assumed for assessment considerably affects the environmental results of a LCA study. The ISO standard for LCA (ISO, 2006a) recommends an order of priority to apply the allocation method. This order consists firstly on trying to avoid the allocation by dividing the process into sub-processes. Then, if allocation cannot be avoided, the application of physical principles for allocation is required (volume, mass, energetic). Finally, economic based allocation could be considered (Luo et al., 2009). In the case of a crude oil refinery, it is really difficult to split the production process into sub-processes, due to its high complexity and interactions between the streams (Tehrani, 2007). Initially, the allocation method developed in this paper was volume based allocation, taking into account the production volume of the different refined oil co-products in the Chilean refineries. The volume based allocation procedure presents the advantage to be relatively constant. However, in the case of oil refined co-products, mass residues of distillation processes generally are the most important, especially for high economic value added products (Chen et al., 2010). For this case, an economic based allocation is suggested. However, this approach could involve the disadvantage of fluctuations of market prices (Chen et al., 2010). The National Energy Commission (CNE, 2014) monthly published average prices in Chile. The economic data considered was obtained in January 2014 for metropolitan region: gasoline 1.6 USD/L, LPG 1.4 USD/L, kerosene 1.2 USD/L, diesel 1.2 USD/L, fuel oil 0.6 USD/L and others refining products 0.6 USD/L. This study compares the effect of using economic and energetic based allocations in the environmental performance. The effect of the allocation approach on the different impact categories per functional unit is shown in Table 12. The highest impacts were obtained in the economic allocation, due to the highest allocation factor assigned to the gasoline followed by the volume allocation and energetic allocation. The economic allocation shows a percentage of change respect to the case base between 4% and 28% depending on the category. However, the use of economic allocation is based in the Chilean market prices. Despite the various stabilization prices mechanisms established by the Chilean government, the Chilean prices for the refining co-products have high fluctuation in the time, especially gasoline, presenting an upward trend (CNE, 2014). Therefore it is difficult to project future prices of
Table 11 Comparative LCA results for gasoline production and use (well-to-wheel analysis). Acronyms: CC — Climate change, TA — Terrestrial acidification, OD — Ozone depletion, HT — Human toxicity. Country Chile UK Brazil Spain USA Vietnam Indonesia
CC (kg CO2 eq) 3.9 7.5 3.3 6.4 3.7 7.3 2.6 4.9 2.5 4.9 2.2 4.2 3.6 7.0
· · · · · · · · · · · · · ·
10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2
TA (kg SO2 eq) 1.2 2.4 1.0 2.0 1.0 2.0 7.4 1.4 7.0 1.4 – – 8.8 1.7
· · · · · · · · · ·
10−3 10−4 10−3 10−4 10−3 10−4 10−4 10−4 10−4 10−4
−4
· 10 · 10−4
OD (kg CFC-11 eq) 1.1 2.0 1.1 2.1 4.9 9.6 3.1 6.1 1.5 2.9 – – – –
· · · · · · · · · ·
10−9 10−10 10−7 10−8 10−8 10−9 10−8 10−9 10−2 10−3
HT (kg 1,4-DB eq) 1.1 · 2.2 · – – 1.4 · 2.7 · 1.4 · 2.8 · 1.6 · 3.1 · – – 40.7 7.9
10−3 10−4
−2
10 10−3 10−2 10−3 10−4 10−5
Energy (MJ)
FU
Reference
12.9 2.5 10.1 2.0 0.5 0.1 – – – – 14.9 2.9 – –
Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ
Case study Borrion et al. (2012) Cavalett et al. (2013) González-García et al. (2012) Luo et al. (2009) Le et al. (2013) Restianti and Gheewala (2012)
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Table 12 LCA characterization (per functional unit) for the potential impact categories under study. Effects of allocations methods in the impacts categories. Acronyms: CC — climate change, OD — ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion. Category
Volume allocation
CC (kg CO2 eq) OD (kg CFC-11 eq) HT (kg 1,4-DB eq) POF (kg NMVOC) TA (kg SO2 eq) FE (kg P eq) ME (kg N eq) TET (kg 1,4-DB eq) FET (kg 1,4-DB eq) MET (kg 1,4-DB eq) WD (m3) MRD (kg Fe eq) FD (kg oil eq)
3.9 1.1 1.1 9.0 1.2 3.5 1.9 1.1 1.7 9.6 4.1 9.5 3.1
Economic allocation Value
· · · · · · · · · · · · ·
10−1 10−9 10−3 10−6 10−3 10−4 10−5 10−5 10−4 10−4 10−1 10−4 10−1
4.4 1.3 3.9 1.4 1.4 1.2 5.04 2.04 1.3 1.8 5.2 1.2 3.9
· · · · · · · · · · · · ·
10–1 10−9 10−3 10−3 10−3 10−5 10−5 10−5 10−5 10−4 10−1 10−3 10−1
Energy allocation % Change
Value
+14.2 +28 +19 +16 +23 +28 +20 +4 +22 +6 +28 +28 +28
3.7 9.8 3.1 1.2 1.1 8.5 4.03 2.0 1.01 1.7 3.8 8.9 2.9
· · · · · · · · · · · · ·
% Change 10–1 10−10 10−3 10−3 10−3 10−6 10−5 10−5 10−5 10−4 10−1 10−4 10−1
–3.1 −6.1 −4.1 −3.4 −5 −6.1 −4.3 −1 −5 −1.3 −6.1 −6.1 −6.1
gasoline related to others refining co-products, for this reason the use of economic allocation could vary the LCA results depending of the period in which the data was obtained. The variability among the volume allocation and energetic allocation in the environmental impacts is low (differences between 1% and 6% depending on the category). The volume and energetic allocation approaches present the advantage of being relatively constant with the time. Thus, both allocation methodologies are preferred for this study.
is gratefully acknowledged. The authors (S. González-García and M.T. Moreira) belong to the Galician Competitive Research Group GRC 2013-032, program co-funded by FEDER. Dr. S. González-García would like to express her gratitude to the Spanish Ministry of Economy and Competitiveness for the financial support (Grant reference JCI-2012-11898).
6. Conclusions
Al-Majed A, Abedayo A, Hossain M. A sustainable approach to controlling oil spills. J Environ Manage 2012;113:213–27. BNE. Balance Nacional de Energía 2012. Division de Prospectiva y Política Energética. Comision Nacional de Energía (CNE). Ministerio de Energía. Gobierno de Chile, Santiago, Chile, 2013. Borrion AL, McManus M, Hammond G. Environmental life cycle assessment of bioethanol production from wheat straw. Biomass Bioenergy 2012;47:9–19. BP. BP Statistical Review of World Energy London, UK; 2013. Capelli S, Busalmen J, Saánchez S. Hydrocarbon bioremediation of a mineral-base contaminated waste from crude oil extraction by indigenous bacteria. Int Biodeter Biodegr 2001;47:233–8. Cavalett O, Ferreira M, Seabra J, Bonomi A. Comparative LCA of ethanol versus gasoline in Brazil using different LCIA methods. Int J Life Cycle Assess 2013;18:647–58. Chen C, Habert G, Bouzidi Y, Jullien A, Ventura A. LCA allocation procedure used as an incitative method for waste recycling: an application to mineral addition in concrete. Resour Conserv Recycl 2010;54:1231–40. Cherubini F, Bird ND, Cowie A, Jungmeier G, Schlamadinger B, Woess-Gallasch S. Energyand greenhouse gas-based LCA of biofuel and bioenergy systems: key issues, ranges and recommendations. Resour Conserv Recycl 2009;53:434–47. CNE. Sistema de información en línea de precios de combustibles en estaciones de servicio. Daily. Gobierno de Chile, Chile; 2014. CONAMA. Chile: Ejemplos de desarrollo sustentable. Gobierno de Chile, Chile: Comisión Nacional del Medio Ambiente; 2010. Doka G. Life cycle inventories of waste treatment services. Ecoinvent Report no 13. Dübendorf: Swiss Centre for Life Cycle Inventories; 2007. ENAP. Memoria anual 2012. Chile: Empresa Nacional de Petroleo; 2012a. ENAP. Reporte de Sustentabilidad 2012. Energía para un Chile más limpio. Chile: Empresa Nacional del Petróleo; 2012b. ENAP. Líneas de Negocios. Refinación, Procesos de Transformación. Chile: Empresa Nacional de Petroleo; 2014. EPA/DOE. Fuel economy guide. Model year 2014. USA: US Environmental Protection Agency and US Department of Energy; 2014. Esty D, Levy M, Kim C, de Sherbinin A, Srebotnjak T. Environmental performance index. Yale Center for Environmental Law and Policy, Center for International Earth Science Informacion Network at Columbia University; 2014. Furuholt E. Life cycle assessment of gasoline and diesel. Resour Conserv Recycl 1995;14: 251–63. Goedkoop M, Heijungs R, Huijbregts M, De Schryver A, Struijs J, Zelm R. ReCiPe 2008, a life cycle impact assessment method which comprises harmonised category indicators at the midpoint and the endpoint level, report I: characterization. Holland: PRé Consultants; CML, University of Leiden; Radboud University and RIVM; 2009. González-García S, Moreira MT, Feijoo G. Comparative environmental performance of lignocellulosic ethanol from different feedstocks. Renew Sustain Energy Rev 2010;14. González-García S, Moreira MT, Feijoo G. Environmental aspects of eucalytus based ethanol production and use. Sci Total Environ 2012;438:1–8. Guinée JB, Gorrée M, Heijungs R, Huppes G, Kleijn R, Koning A, et al. Life cycle assessment: an operational guide to the ISO standards. Leiden: Ministry of Housing, Spatial Planning and the Environment and Centre of Environmental Science/Lieden University; 2001. IEA. CO2 Emissions from fuel combustion. Highlights. France: OECD/IEA; 2012.
The present study shows the environmental results of an LCA performed for gasoline produced and used in the Chilean context. The study identified the key subsystems within the life cycle of the gasoline (production and use), which could help in future improvement technologies on gasoline production and transport sector. According to the results from this study, the main environmental hotspots were refining activities and gasoline use in the passenger car. The refining processes contribute in a number of impact categories with ratios higher than 45%: human toxicity, photochemical oxidant formation, freshwater eutrophication, terrestrial and marine ecotoxicity, water depletion and fossil depletion. Gasoline combustion emissions affect the categories of climate change, acidification, marine eutrophication and freshwater ecotoxicities (ranging from 44% to 79%). Transport of gasoline by lorry was the main responsible of ozone depletion. Distribution of crude oil by pipelines was the main source affecting the mineral depletion potential. The outcomes are highly sensitive to the allocation approach considered. The highest impacts were obtained in the economic allocation, followed by the volume allocation and energetic allocation. The high impacts resulting from the economic allocation were due to the high price assigned to the gasoline in the Chilean market. Despite the detail maintained in the study, there are limitations in the life cycle inventories by the lack of information from official sources. These include the uncertainty related to crude oil extraction and production from importing countries as well as the transportation distances. This study provides the basis for a comparative assessment for strategic decision-making concerning the use of alternative fuels (e.g. biofuels) that the Chilean government may propose in order to reduce their dependence on fossil fuels and/or the environmental impacts derived from the transport sector. Acknowledgments Financial support granted to M. Morales by CONICYT scholarship program (Comisión Nacional de Investigación Científica y Tecnológica)
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Contents lists available at ScienceDirect
Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
Life cycle assessment of gasoline production and use in Chile Marjorie Morales a,⁎, Sara Gonzalez-García b, Germán Aroca a, María Teresa Moreira b a b
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaiso, Av. Brasil 2085, Valparaiso, Chile Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
H I G H L I G H T S • A well-to-wheel LCA of gasoline production in Chile was carried out. • Volume, economic and energy allocations were considered for sensitivity analysis. • Refinery and car emissions were the main contributors to environmental impacts.
a r t i c l e
i n f o
Article history: Received 8 July 2014 Received in revised form 7 October 2014 Accepted 19 October 2014 Available online 7 November 2014 Editor: Simon James Pollard Keywords: Environmental assessment Passenger car Refinery Transportation fuel Well-to-wheel analysis
a b s t r a c t Gasoline is the second most consumed fuel in Chile, accounting for 34% of the total fuel consumption in transportation related activities in 2012. Chilean refineries process more than 97% of the total gasoline commercialized in the national market. When it comes to evaluating the environmental profile of a Chilean process or product, the analysis should consider the characteristics of the Chilean scenario for fuel production and use. Therefore, the identification of the environmental impacts of gasoline production turns to be very relevant for the determination of the associated environmental impacts. For this purpose, Life Cycle Assessment has been selected as a useful methodology to assess the ecological burdens derived from fuel-based systems. In this case study, five subsystems were considered under a “well-to-wheel” analysis: crude oil extraction, gasoline importation, refinery, gasoline storage and distribution/use. The distance of 1 km driven by a middle size passenger car was chosen as functional unit. Moreover, volume, economic and energy-based allocations were also considered in a further sensitivity analysis. According to the results, the main hotspots were the refining activities as well as the tailpipe emissions from car use. When detailing by impact category, climate change was mainly affected by the combustion emissions derived from the gasoline use and refining activities. Refinery was also remarkable in toxicity related categories due to heavy metals emissions. In ozone layer and mineral depletion, transport activities played an important role. Refinery was also predominant in photochemical oxidation and water depletion. In terms of terrestrial acidification and marine eutrophication, the combustion emissions from gasoline use accounted for large contributions. This study provides real inventory data for the Chilean case study and the environmental results give insight into their influence of the assessment of products and processes in the country. Moreover, they could be compared with production and distribution schemes in other regions. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Crude oil represents the leading fossil fuel in the world, accounting for 33% of global energy consumption. Its relevance is even more important in South America with more than 45% of the total energy consumed in 2012 (BP, 2013). This remarkable dependence on oil and its derivatives involves major environmental problems, mainly associated with the emission of greenhouse gases (GHG). Around 11 Gt CO2 were emitted globally in 2010 according to the last report of the International
⁎ Corresponding author at: Av. Brasil 2085, Valparaiso, Chile. Tel.: +56 992588315. E-mail address: [email protected] (M. Morales).
http://dx.doi.org/10.1016/j.scitotenv.2014.10.067 0048-9697/© 2014 Elsevier B.V. All rights reserved.
Energy Agency (IEA, 2012), with road transport as the largest contributing source (~5 Gt CO2). Within South American countries, Chile occupies the fifth position in terms of GHG emissions (IEA, 2012) associated with fuel use in industrial, transport and energy sector (Fig. 1a). These emissions are expected to increase by 400% in 2030 (O'Ryan et al., 2010). Around 70% of the total energy consumption in the transport sector is associated with road transport (O'Ryan et al., 2010). Fig. 1b reports the distribution of fuel products consumed in the Chilean transport sector, being diesel the most consumed fuel followed by gasoline (BNE, 2013). Passenger cars mainly run on gasoline (96%) and produce 32%, 24% and 20% of total NO x , NMVOC and CO emissions of the transport sector (OCDE and CEPAL, 2005). Beyond the tailpipe emissions related
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Fig. 1. (a) Chilean Energy Matrix (2012) (BNE, 2013); (b). Distribution of oil derivatives consumed in the Chilean transport sector (2012) (BNE, 2013).
with gasoline use, there are many other upstream processes (such as crude oil extraction, refining, transport, etc.) that need to be considered in the environmental profile of gasoline due to their associated environmental effects. Regarding solid and liquid emissions, the extraction stage of crude oil typically requires the removal of sludge and water in settling tanks, both streams polluted with hydrocarbons and heavy metals (Capelli et al., 2001). Moreover, the refining process is a large consumer of water for cooling, steam production, washing and reaction processes as well as it produces solid wastes such as petroleum coke and sludge from different process units (ENAP, 2012b). Both the extraction of crude oil as well as its transport and refining involve leaks of crude oil that cause pollution of groundwater and land (Al-Majed et al., 2012). Gaseous emissions (either direct or indirect) such as hydrocarbons, CO, SO x and NOx , are one of the main contributors to the environmental impacts in the refining related activities. These emissions are produced in different steps such as the topping, flaring or storage of refining products. In Chile, environmental management was institutionalized just over the last decade. Chilean governments have made remarkable progress in designing and implementing environmental policies and regulations for the industrial sector (CONAMA, 2010), which has positioned Chile as the Latin America leading country in terms of environmental protection. Moreover, Chile occupies the 29th position in the Environmental Performance Index (Esty et al., 2014). The promotion of new standards in order to control and reduce pollutant emissions in Chile has forced oil companies to make significant efforts to implement and improve environmental technologies. Chilean refineries have paid attention to the identification and control of environmental risks in order to accomplish with the general rules and regulations applicable to their processes. The crude oil extraction, production and refining in Chile are based on international environmental standards such as ISO 14001 (ENAP, 2012b). The quantification of the environmental profile associated with a process or product throughout its life cycle can be performed by means of the Life Cycle Assessment (LCA) methodology (ISO, 2006b). In agreement with numerous studies where the environmental profiles of fuel production and use have been quantified by LCA (Keesom et al., 2012; Restianti and Gheewala, 2012; Singh et al., 2010; Spatari et al., 2010), this methodology has been chosen to qualitatively evaluate the environmental loads of the gasoline production and use in Chile. Commonly, LCA studies for fuels have been performed from a wellto-wheel perspective (Borrion et al., 2012; Cherubini et al., 2009; González-García et al., 2010, 2012; Pont, 2007; Restianti and Gheewala, 2012), taking into account not only fuel production but
also its final use. Concerning gasoline, its environmental profile has been quantified under the same perspective in Europe (Furuholt, 1995; Keesom et al., 2012; Querini et al., 2011), USA (Skone and Gerdes, 2009; Unnasch et al., 2009) and Indonesia (Restianti and Gheewala, 2012). This study aims to perform an environmental analysis of the gasoline produced and used in Chile by means of the LCA methodology because no LCA study is available for gasoline in the Chilean or Latin-American context. In addition, the environmental hotspots (that is, the processes responsible of the largest contributions to the environmental profile) all over the life cycle will be identified in order to future improvement alternatives. 2. Methodology LCA evaluates the environmental burdens of a production system by identifying resource and energy consumptions as well as emissions to different environmental compartments. LCA allows identifying priority areas where improvement actions will have the greatest effects on reducing the environmental impacts (ISO, 2006a). In this study, the environmental profile was performed following ISO 14040 specifications (ISO, 2006a). The objective of this study was to perform the environmental analysis of the Chilean gasoline production and use in passenger cars, following the LCA methodology from a well-to-wheel perspective. The functional unit provides a reference to which the input and output process data are normalized. Generally, the results for transportation fuels are related with the distance traveled (Cherubini et al., 2009). The functional unit used in this study was 1 km driven by a middle size passenger car. An average consumption of 0.15 L gasoline per km was assumed (EPA/DOE, 2014). 2.1. System boundaries description All the processes or activities carried out from the crude oil extraction and production up to the gasoline use in a passenger car were considered within the system boundaries. Production of the different consumable materials (chemicals, electricity, machinery, etc.) as well as infrastructure construction and maintenance were also included. Fig. 2 shows an overview of the Chilean gasoline system under study. The system was divided into five subsystems, which will be described in detail below: crude oil extraction (Subsystem 1); gasoline importation (Subsystem 2); refinery (Subsystem 3); gasoline storage (Subsystem 4) and distribution and use (Subsystem 5).
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843
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Fig. 2. System boundaries corresponding to the life cycle of the gasoline.
2.1.1. Subsystem 1 (S1). Crude oil extraction The oil supply chain is mainly based on imports of crude oil (99% of the total) that comes from Latin America (92%), Europe (6%) and North America (1%), while the remaining crude oil is obtained from national extraction (ENAP, 2012b). The countries from where Chile imports crude oil are Brazil (30%), Ecuador (30%), Colombia (16%), Argentina (16%), the UK (6%) and Canada (1%), while national production represents 1%. The crude oil produced in Chile is exploited by National Oil Company1 (ENAP), which manages its exploration and production located in the Southernmost Magallanes region. Crude oil is transported to different refineries in Chile by tanker and/or pipeline. It was considered that the oil from Argentina is transported
1
www.enap.cl.
through the Trasandino pipeline, while oil from other sources is transported by sea. 2.1.2. Subsystem 2 (S2). Gasoline importation Regarding the importation of gasoline, 783,000 m3 of gasoline was imported in 2012 (SEC, 2012). It was considered that gasoline is imported from Brazil and Colombia (the two principal importing sources of crude oil in Chile) and transported by tanker. Thus, this subsystem includes the crude oil extraction and gasoline production in these countries. The different national refineries have the infrastructure for crude oil and co-products reception and storage in marine terminals. 2.1.3. Subsystem 3 (S3). Refinery This subsystem includes the reception of the crude oil (national and imported) in the different Chilean refineries to the production of
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Fig. 3. Refineries and pipelines involved in the Chilean gasoline production.
gasoline and other refining products. National and imported crude oil is transported by tanker and/or pipeline and received in the ENAP oil refineries. ENAP owns three different refineries: Refinery Aconcagua (Refinery A), Refinery Bio-Bio (Refinery B) and Refinery Gregorio (Refinery C), located in Central-Zone, Southern-Zone and Austral-Zone of Chile, respectively, where crude oil is processed. The location and volume of crude oil annually processed at each refinery are shown in Fig. 3 and Table 1, respectively. The refining process consists of a complex and highly integrated process where the equipment and unit operations are tailored to specific feed properties. The basic operations that are performed in the ENAP refineries are the following: topping, vacuum distillation, ethylene plant, catalytic reforming, alkylation, isomerization, hydrocracking, visbreaking, catalytic cracking, coking, desulfurization/hydrotreating acid recovery plant and a sulfur recovery unit (ENAP, 2014). The total volume of petroleum refining co-products produced in Chile in 2012
Table 1 Volume of crude oil processed in ENAP Refineries in 2012 (thousand m3) (SEC, 2012). Origin of crude oil
Refinery A
Refinery B
Refinery C
Imported National
4668 27.8
4501 68.5
13.4 249
(ENAP, 2012a) are: diesel 3349 Mm3, gasoline 3290 Mm3, fuel oil 1275 Mm3, kerosene 846 Mm3, LPG 668 Mm3 and other refining products 10 Mm3. 2.1.4. Subsystem 4 (S4). Gasoline storage The gasoline produced at each refinery is stored in its own facilities. However, a part is also stored in storage plants located between V and VIII Regions. Gasoline is transported by pipeline from refineries to storage plants (see Fig. 3). The storage plants I, II, III and IV are located in the Central zone of Chile, between the Metropolitan region and Bio-Bio region (see Fig. 3). 2.1.5. Subsystem 5 (S5). Distribution and use The gasoline is distributed from the storage plants to the consumption centers located across the country. The gasoline distribution was assumed to be carried out by 32 ton diesel lorries. The refineries A and B produce gasoline to the northern part and southern part of the country respectively. It was assumed that there are also four storage plants located in the Central Valley to supply gasoline to the most populated cities. Refinery C provides gasoline to the southernmost region (Magallanes). The distribution from the storage plants to the service station was assumed to be carried out by 16 ton diesel lorries, covering an average distance of 50 km (Spielman et al., 2007).
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843
2.2. Allocation procedure The refining process is a very complex system, giving a large number of co-products that are strongly correlated (Furuholt, 1995; Restianti and Gheewala, 2012). Allocation is the partitioning of input or output flows of a unit process to the product under study. In this study, allocation was required and the partition was performed considering a volume criteria (ENAP, 2012a). Allocation approach based on market prices (CNE, 2014) and energy content (BNE, 2013) of the refining co-products were also considered in a sensitivity assessment which will be discussed below. Table 2 briefly reports the allocation factors considered. 3. Life cycle inventory The quality of an environmental life cycle study considerably depends on the inventory data managed. In this study, primary inventory data were managed for the Chilean sector, which were taken from official data sources (BNE, 2013; ENAP, 2012a, 2012b; SEC, 2012). These data were completed, when necessary, with secondary data from the ecoinvent® database v2.0 (Jungbluth, 2007; Spielman et al., 2007). SimaPro software v8 was used for the analysis (Prè-Consultants, 2014). As previously reported, part of the crude oil processed in the Chilean gasoline system is imported from different countries. It was not possible to collect real and valuable inventory data corresponding to each exporter country. Therefore, inventory data were taken from the ecoinvent® database, considering a world average (Jungbluth, 2007). The onshore oil extraction is the common practice for crude oil extraction in Chile. The inventory data for the oil extraction (Table 3) was obtained from the 2012 annual report (ENAP, 2012b). The production of infrastructure, the wells for crude oil extraction and the onshore platform was considered within the analysis. Inventory data for infrastructure was obtained from the ecoinvent® database (Jungbluth, 2007). Inventory data concerning imported gasoline production as well as combustion emissions derived from tanker transport were obtained from the ecoinvent® database (Jungbluth, 2007; Spielman et al., 2007). Table 4 shows the volume of crude oil (per functional unit) transported by tanker from each exporting country to each Chilean refinery. The same proportion of crude oil from the importing countries to each refinery was assumed. Concerning the crude oil imported from Argentina across pipeline, Table 5 shows the volume of crude oil (per functional unit) transported by pipeline from Argentina to each Chilean refinery. Inventory data obtained for pipeline transport in Chile are shown in Table 6. Data concerning distances as well as inputs and emissions for each pipeline transport were obtained from literature for 2012 (ENAP, 2012b). Inputs and outputs correspond to average data from the three refineries by year 2012 (Table 7). These inventory data were taken from literature (ENAP, 2012b) and included refining products, energy supply, materials, air emissions, wastewaters, spills and solid wastes. The water used in the refineries is continuously taken from nearby rivers and the effluent after treatment is discharged into the sea. Wastewater treatment inventory was taken from the ecoinvent® database (Doka, 2007). The energy required at the stage of refinement comes from Chilean national grid and/or sub-products from refining,
Table 2 Allocation factors corresponding to the different co-products from the gasoline production system. Allocation Method
Volume Economic Energetic
Table 3 Relevant inputs and outputs for crude oil extraction in Chile (per 1 km driven by a passenger car).
Inputs Materials Water Gas lift Energy Electricity Natural gas Diesel Gasoline Kerosene Outputs Products Crude Oil Natural gas Air emissions CH4 CO2 CO NOX SO2 Hydrocarbons gases Soil emissions Oil spills Water emissions Waste water Wastes to treatment Solid wastes not dangerous to landfill Solid wastes hazardous to incineration Sludge from excavation
Liquefied petroleum gas
Kerosene
Diesel
Fuel oil
Other refining products
34.9 44.6 32.7
7.1 8.1 5.5
8.9 8.2 9.3
35.5 32.2 37.3
13.5 6.9 15.1
0.1 0.1 0.2
Value
Unit
1.6 70.7
L L
9.3 38.4 1.2 0.02 1.5
kJ MJ MJ MJ MJ
0.42 2.5
L L
0.08 0.73 0.013 0.23 0.03 0.44
mg mg mg μg mg μg
3.2
mL
1.3
L
1.04 0.40 12
g g g
such as fuel oil and refinery gas (which is completely consumed in the refinery). Air emissions from refining activities account for indirect emissions associated with the production and combustion of fuels at the refinery, flaring, venting and fugitive emissions. Inventory data corresponding to the infrastructure production and maintenance for three refineries were taken from the ecoinvent® database (Jungbluth, 2007). The gasoline transport from the refineries to storage plants considers pipeline transport. Inventory data corresponding to this subsystem (S4) are reported in Table 6. Distributing distances are detailed in Table 8. The volume of gasoline distributed in each region across the country was obtained from Superintendency of electricity and fuel for 2012 (SEC, 2012). The electricity required in the inventories of the crude oil extraction (see Table 3) and pipeline transport (see Table 6) are shown in Table 9. Data for the electricity production in 2012 were collected from the Chilean Ministry of Energy (BNE, 2013). Inventory data concerning the different energy sources used in the electricity production process was obtained from the ecoinvent® database (Jungbluth, 2007) and adapted to the Chilean context. Table 4 Volume and distance of crude oil transported by tanker between country of origin and marine terminals in Chilean refineries (per functional unit). Country of origin
Refinery of destination
Volume of crude oil (L)
Brazil
Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C Refinery A Refinery B Refinery C
7.8 7.5 2.2 6.4 6.2 1.8 3.4 3.3 9.8 1.3 3.1 6.1
Ecuador
Refining products Gasoline
837
Colombia
Chile
· · · · · · · · · · · ·
10−2 10−2 10−4 10−2 10−2 10−4 10−2 10−2 10−5 10−3 10−3 10−4
Distance (km) 7026 6562 4722 3673 4118 6336 4462 4907 7131 2913 2451 0
838
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Table 5 Volume and distance of crude oil transported by pipeline between country of origin and refineries in Chile (per functional unit). Country of origin
Refinery of destination
Volume of crude oil (L)
Distance (km)
Argentina
Refinery A Refinery B Refinery C
3.4 · 10−2 3.3 · 10−2 9.8 · 10−5
773a 163 163b
a b
Considering Trasandino pipeline + national pipelines. Considering only Trasandino pipeline, then is transported by tanker.
4. Results Characterization factors from the ReCiPe 2008 method (Goedkoop et al., 2009) in the hierarchic perspective were considered for the environmental impact assessment. The impact categories considered were climate change (CC), ozone depletion (OD), human toxicity (HT), photochemical oxidation formation (POF), terrestrial acidification (TA), freshwater eutrophication (FE), marine eutrophication (ME), terrestrial ecotoxicity (TET), freshwater ecotoxicity (FET), marine ecotoxicity (MET), water depletion (WD), mineral depletion (MRD) and fossil depletion (FD). Table 10 summarizes the LCA characterization results per subsystem according to a volume-based allocation (base case). Fig. 4 shows the contribution to the impact categories from each subsystem involved all over the life cycle of the gasoline system. According to the results, two subsystems played a major role: refinery and distribution and use. Distribution and use was responsible for 50% of the impact in the CC followed by refinery (40%), being CO2 emissions the main responsible substance. Refinery and distribution and use also represented 54% and 46% in the OD respectively, being Halon 1301 emissions the main pollutant contributing in this category. Refinery was the main stage contributing to HT, accounting for 70% of the total impact mainly due to heavy metals emissions derived from the refining activities, followed by refinery (19%) and distribution and use (11%). Refinery played a significant role with a contribution of 97% and 51% to POF and TA, respectively. SOx and NOx were the main pollutants affecting POF and TA impact categories. Phosphate emissions derived from refinery (65%) and distribution and use (27%) affected FE. Nitrogen based pollutants emitted from refinery (87%) affected ME. Regarding ecotoxicity related categories, the principal subsystem contributing to TET and MET was refinery (62% and 44% respectively) due to the emissions of heavy metal (nickel and copper). In FET, distribution and use was the main contributor (79%) due to bromine and nickel emissions. Nearly all the contributions to WD were accounted for refinery (99%) due to the water requirements in the refining activities. Moreover, this subsystem summed up to 83% of the total MRD due to the materials used in the pipeline infrastructure. Finally, FD was mainly affected by crude oil extraction and refinery due to the fossil fuels required in the crude oil extraction and refining Table 6 Relevant inputs and emissions for pipeline transport in Chile (per 1 km driven distance by a passenger car).
Inputs Materials Water (groundwater) Drinking water Energy Electricity Outputs Transport (product) Transport by pipeline Soil emissions Oil spills Water emissions Waste water
Value
Unit
20.2 2.0 · 10−4
L L
0.10
Wh
3.0 · 10
−2
tkm
2.6 · 10
−7
L
2.3 · 10−3
L
Table 7 Global inventory for refining gasoline in Chile (per 1 km driven distance by a passenger car). Value Inputs Materials Crude oil Water Energy Fuel oil Liquefied natural gas Electricity Transport Crude oil by tanker Crude oil by pipeline Outputs Product Gasoline Co-products LPG Kerosene Diesel Fuel oil Other refining co-products Air emissions CO2 NOx NMVOC CO SO2 PM10 Hydrocarbons gases Water emissions Waste water Oils (unspecified) Hydrocarbons unspecified Sulfide Suspended solids Soil emissions Oil spills Wastes to treatment Solid wastes not dangerous to landfill Solid wastes hazardous to incineration
Unit
0.42 4.4
L L
0.02 9.0 0.40
MJ MJ MJ
1.6 0.03
tkm tkm
0.15
L
0.03 0.04 0.15 0.06 0.50
L L L L mL
95 138 8.52 24.5 190 40.3 15.9
g mg mg mg mg mg mL
4.2 72 41 2.0 286
L mg mg mg mg
4.2
mg
0.10 2.1
mL mL
activities (as energetic sources). A detailed description per impact category is reported below. 4.1. Climate change The emission of GHGs all over the life cycle of the system under study per functional unit was 0.39 kg CO2 eq (Table 10). Fig. 5 details the contributions from the key processes (hotspots) involved in each subsystem. According to this figure, the hotspots in terms of CC are the refining related activities due to the use of fuel oil and natural gas in the steam production process and in the torches as well as the gasoline use in the car. The detailed analysis of GHGs emissions is shown in Fig. 6. Emissions were mainly due to two global warming gases: CO2 (94%) and CH4 (5%). CO2 emissions mostly derive from the refinery related activities and gasoline combustion. CH4 emissions are mainly produced on the crude oil extraction. N2O emissions are almost negligible compared to CO2 and CH4 emissions.
Table 8 Transport by pipelines between refineries and storage plants in Chile (per functional unit). Refinery of origin
Storage plant of destination
Volume of gasoline (L)
Refinery A Refinery B
Storage plant I Storage plant II Storage plant III Storage plant IV
6.8 8.3 1.5 1.3
· · · ·
10−5 10−6 10−6 10−5
Distance (km) 127 350 175 82
M. Morales et al. / Science of the Total Environment 505 (2015) 833–843 Table 9 Global inventory for electricity production in Chile (per 1 kWh electricity generated).
Inputs Primary energy Natural gas Coal Biomass Hydro-power Wind-power Crude oil products Diesel Fuel Oil Petroleum coke Outputs Electricity
Value
Unit
0.23 0.34 0.02 0.30 0.01
kWh kWh kWh kWh kWh
0.06 0.01 0.03
kWh kWh kWh
1.0
kWh
839
(involved in S3) the environmental hotspots (44%, 29% and 21% of total, respectively). Two different eutrophication potentials were evaluated: freshwater eutrophication (FE) and marine eutrophication (ME). The only one significant pollutant contributing to FE was phosphate mainly derived from gasoline combustion in the passenger car, transport of crude oil by tanker (involved in S3) and the refining activities. Fig. 5 shows that the refinery and transportation by tanker represent 44% and 19% of total, respectively; while the gasoline combustion in the car contributed with 26% of total. In the case of ME, this impact is mainly derived from the emission of nitrogen-based contaminants. The total value obtained in this category was 0.02 g N eq·km−1 (Table 10). The most significant processes contributing to ME were refining activities and gasoline use in passenger car, 10% and 87% respectively, principally due to NOx emissions (Fig. 5). 4.6. Ecotoxicity related potentials
4.2. Ozone depletion potential The key processes contributing to OD were the refining activities (38% of the total), the transport of crude oil by pipeline (15%) involved in refinery and the transport of gasoline by lorries (46%) included in refinery (Fig. 5) due to the production of the fossil fuels required in this stages (diesel and fuel oil). The main substance contributing to OD was Halon 1301 involved in the electricity production. 4.3. Human toxicity In HT, 70% and 15% of total contributions were due to the emissions from refining activities and transportation of crude oil by tanker (involved in S3) (see Fig. 5). Remaining contributions to HT were related with tailpipe emissions as well as emissions from crude oil extraction in the importing countries. This impact category was fully dominated by emissions of mercury and arsenic emitted to air related mainly to the electricity production required in the refinery. 4.4. Photochemical oxidant formation potential The POF impact (9 mg NMVOC eq·km−1) was mainly affected by emissions of NOx (Table 10). Fig. 5 shows that the emissions derived from the refining activities represent a percentage higher than 90% of the total contributions. 4.5. Acidification and eutrophication potentials Total terrestrial acidification (TA) per functional unit was 1.21 g SO2 eq, which comprises SO2 and NOx emissions (Table 10). Fig. 5 details the main processes involved in TA, being the gasoline use in the car, the refining activities and the transport of crude oil by tanker Table 10 LCA characterization results (per 1 km driven distance by a passenger car) for the potential impact categories under study. Impact category
Unit
Value
Climate change Ozone depletion Human toxicity Photochemical oxidant formation Terrestrial acidification Freshwater eutrophication Marine eutrophication Terrestrial ecotoxicity Freshwater ecotoxicity Marine ecotoxicity Water depletion Mineral depletion Fossil depletion
kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg NMVOC kg SO2 eq kg P eq kg N eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq m3 kg Fe eq kg oil eq
3.9 1.1 1.1 9.0 1.2 3.5 1.9 1.1 1.7 9.6 4.1 9.5 3.1
· · · · · · · · · · · · ·
10−1 10−9 10−3 10−6 10−3 10−4 10−5 10−5 10−4 10−4 10−1 10−4 10−1
Three different potentials related with ecotoxicity were assessed: terrestrial ecotoxicity (TET), freshwater ecotoxicity (FET) and marine ecotoxicity (MET). Detailed results for each one are shown in Table 10 and the main environmental hotspots, which contribute in these categories, are shown in Fig. 5. Activities related to refining were the main contributing to TET and MET, 62% and 44% respectively. However, in FET the most significant contributor was the emissions derived from the gasoline combustion in the car with 44% of total contributions to this category. 4.7. Water, mineral and fossil depletion potentials Table 10 shows the results corresponding to water, mineral and fossil depletions (WD, MRD and FD respectively). The total WD per functional unit was 0.4 m3. The refinery played a major significant role in this category, accounting for 99% (see Fig. 5) due to the water required in the process of petroleum refining and waste treatment. The principal contributing source to MRD was refinery, mainly due to the materials used in the pipeline and refinery infrastructure, representing 67% and 16% of MRD (see Fig. 5). Concerning FD, it was 0.3 kg oil per functional unit attributed mainly to refinery and distribution and use, 55% and 44% respectively. 5. Discussion The large dependence of gasoline in the transport sector imposes the need of reporting environmental data of its life cycle. This study can be considered as an opportunity to resolve the environmental concerns concerning gasoline production and use in passenger cars. LCA can be considered as a valuable tool in the process of strategic transportation planning, since it takes into account environmental, technical and economic considerations. Moreover, the results from the present study can be used as a base case for comparison with other fuels (e.g. bioethanol) as well as in decision-making strategies for the proposal of improvements in the production system. 5.1. Comparison with other gasoline studies assessed from a LCA perspective We have considered six reports available on gasoline production and use that managed real primary data for comparison with the results reported in this study (Furuholt, 1995; Keesom et al., 2012; Querini et al., 2011; Restianti and Gheewala, 2012; Skone and Gerdes, 2009; Unnasch et al., 2009). Although these studies provided detailed inventories, most of them were focused on quantifying GHG emissions and energetic requirements related to gasoline production and use while discarding other environmental impacts. Only the study carried out by Restianti and Gheewala (2012) considered other different impacts categories such as acidification or eutrophication. A comparison at an inventory level, only is possible with the values reported by Restianti
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Fig. 4. Contributions to the various impacts categories for each gasoline life cycle subsystem. Acronyms: CC — Climate change, OD — Ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion.
and Gheewala (2012), they reported its data using as a base 1 m3 of gasoline. In this study the inventory values are up to 45% lower for the production of co-products (Table 7) for the same base. Regarding the emissions of CO, CO2 and NOx, these were two, four and nine times higher in our study respectively, while for SO2, the emissions were six times lower. Moreover, there are several studies reporting environmental results in different impact categories for gasoline production system using inventory data from databases. These studies were taken into account for the comparison between the production and use of gasoline and bioethanol from an environmental perspective (Borrion et al., 2012; Cavalett et al., 2013; González-García et al., 2012; Luo et al., 2009). However, information concerning the gasoline production process was not reported in any of them since they were mainly focused on the bioethanol production technology. In addition, different characterization methods were used in these studies: ReCiPe (Goedkoop et al., 2009) and CML (Guinée et al., 2001). Depending on the method,
different characterization factors and reference units for some impact categories can been used. Hence, it is not possible to directly compare the results in all the impact categories. However, the environmental profiles could be compared in terms of four impact categories (climate change — CC, acidification — TA, Ozone layer depletion — OD, human toxicity — HT) and energy, considering the same functional unit and system boundaries for the Chilean and case studies (Borrion et al., 2012; Cavalett et al., 2013; González-García et al., 2012; Le et al., 2013; Luo et al., 2009; Restianti and Gheewala, 2012). According to the results shown in Table 11, it is possible to find some remarkable differences between our study and others available in the literature. These differences are related with the databases and the consideration of both different characterization methods (ReCiPe or CML) (Goedkoop et al., 2009; Guinée et al., 2001). The relevance of an LCA study is highly connected to the quality of the inventory analysis. For this reason, the management of inventory data representative of the production system is required. In our study,
Fig. 5. Contributions of the key processes to the impact categories under study. Acronyms: CC — Climate change, OD — Ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion.
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841
Brazil (Cavalett et al. 2013) with a value 25 times inferior, which is attributed to the data sources considered. Concerning the key processes contributing to the environmental profile, our study found that the refining activities and the tailpipe emissions from the passenger car were the environmental hotspots. Other studies (Borrion et al., 2012; González-García et al., 2012; Luo et al., 2009; Restianti and Gheewala, 2012) also reported the same contributing processes for the gasoline system (production and use), which is in agreement with our results. 5.2. Influence of the allocation approach
Fig. 6. Contributing GHG to each stage involved in the gasoline life cycle under assessment.
we have tried to use whenever possible representative inventory data for the Chilean gasoline production system (e.g. for crude oil extraction, transport, refinery, etc.). Regarding climate change, the results reported by Borrion et al. (2012) for the UK, Cavalett et al. (2013) for Brazil and Restianti and Gheewala (2012) for Indonesia ranging from 0.33 to 0.37 kg CO2 eq·km−1 were similar to this work: 0.39 kg CO2 eq·km−1. Lower values for this category were reported by González-García et al. (2012) for Spain, Luo et al. (2009) for USA and Le et al. (2013) for Vietnam ranging from 0.22 to 0.26 kg CO2 eq·km− 1. The environmental results in terms of terrestrial acidification showed similarities between our system and studies from Borrion et al. (2012), Cavalett et al. (2013) and Restianti and Gheewala (2012). In contrast, the results obtained by González-García et al. (2012) for Spain and Luo et al. (2009) for the USA were considerably lower, which could be due to differences in the characterization factors as well as the databases used. On the contrary, very large variations were identified between all the gasoline production systems concerning to OD and HT (Table 11). It is expected that these differences are the result of different calculation methods, sources of inventory data, allocation approaches as well as the scheme of production system. Moreover, a flow indicator such as energy use (expressed here in terms of MJ) has also been considered due to the relevance of this indicator in some studies (Furuholt, 1995; Le et al., 2013). The result from our study (12.9 MJ·km−1) is situated in the range of values obtained in other studies performed in the UK and Vietnam (Borrion et al., 2012; Le et al., 2013). However, large differences were found for
The allocation procedure assumed for assessment considerably affects the environmental results of a LCA study. The ISO standard for LCA (ISO, 2006a) recommends an order of priority to apply the allocation method. This order consists firstly on trying to avoid the allocation by dividing the process into sub-processes. Then, if allocation cannot be avoided, the application of physical principles for allocation is required (volume, mass, energetic). Finally, economic based allocation could be considered (Luo et al., 2009). In the case of a crude oil refinery, it is really difficult to split the production process into sub-processes, due to its high complexity and interactions between the streams (Tehrani, 2007). Initially, the allocation method developed in this paper was volume based allocation, taking into account the production volume of the different refined oil co-products in the Chilean refineries. The volume based allocation procedure presents the advantage to be relatively constant. However, in the case of oil refined co-products, mass residues of distillation processes generally are the most important, especially for high economic value added products (Chen et al., 2010). For this case, an economic based allocation is suggested. However, this approach could involve the disadvantage of fluctuations of market prices (Chen et al., 2010). The National Energy Commission (CNE, 2014) monthly published average prices in Chile. The economic data considered was obtained in January 2014 for metropolitan region: gasoline 1.6 USD/L, LPG 1.4 USD/L, kerosene 1.2 USD/L, diesel 1.2 USD/L, fuel oil 0.6 USD/L and others refining products 0.6 USD/L. This study compares the effect of using economic and energetic based allocations in the environmental performance. The effect of the allocation approach on the different impact categories per functional unit is shown in Table 12. The highest impacts were obtained in the economic allocation, due to the highest allocation factor assigned to the gasoline followed by the volume allocation and energetic allocation. The economic allocation shows a percentage of change respect to the case base between 4% and 28% depending on the category. However, the use of economic allocation is based in the Chilean market prices. Despite the various stabilization prices mechanisms established by the Chilean government, the Chilean prices for the refining co-products have high fluctuation in the time, especially gasoline, presenting an upward trend (CNE, 2014). Therefore it is difficult to project future prices of
Table 11 Comparative LCA results for gasoline production and use (well-to-wheel analysis). Acronyms: CC — Climate change, TA — Terrestrial acidification, OD — Ozone depletion, HT — Human toxicity. Country Chile UK Brazil Spain USA Vietnam Indonesia
CC (kg CO2 eq) 3.9 7.5 3.3 6.4 3.7 7.3 2.6 4.9 2.5 4.9 2.2 4.2 3.6 7.0
· · · · · · · · · · · · · ·
10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2 10−1 10−2
TA (kg SO2 eq) 1.2 2.4 1.0 2.0 1.0 2.0 7.4 1.4 7.0 1.4 – – 8.8 1.7
· · · · · · · · · ·
10−3 10−4 10−3 10−4 10−3 10−4 10−4 10−4 10−4 10−4
−4
· 10 · 10−4
OD (kg CFC-11 eq) 1.1 2.0 1.1 2.1 4.9 9.6 3.1 6.1 1.5 2.9 – – – –
· · · · · · · · · ·
10−9 10−10 10−7 10−8 10−8 10−9 10−8 10−9 10−2 10−3
HT (kg 1,4-DB eq) 1.1 · 2.2 · – – 1.4 · 2.7 · 1.4 · 2.8 · 1.6 · 3.1 · – – 40.7 7.9
10−3 10−4
−2
10 10−3 10−2 10−3 10−4 10−5
Energy (MJ)
FU
Reference
12.9 2.5 10.1 2.0 0.5 0.1 – – – – 14.9 2.9 – –
Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ Per km Per MJ
Case study Borrion et al. (2012) Cavalett et al. (2013) González-García et al. (2012) Luo et al. (2009) Le et al. (2013) Restianti and Gheewala (2012)
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Table 12 LCA characterization (per functional unit) for the potential impact categories under study. Effects of allocations methods in the impacts categories. Acronyms: CC — climate change, OD — ozone depletion, HT — Human toxicity, POF — Photochemical oxidant formation, TA — Terrestrial acidification, FE — Freshwater eutrophication, ME — Marine eutrophication, TET — Terrestrial ecotoxicity, FET — Freshwater ecotoxicity, MET — Marine ecotoxicity, WD — Water depletion, MRD — Mineral depletion, FD — Water depletion. Category
Volume allocation
CC (kg CO2 eq) OD (kg CFC-11 eq) HT (kg 1,4-DB eq) POF (kg NMVOC) TA (kg SO2 eq) FE (kg P eq) ME (kg N eq) TET (kg 1,4-DB eq) FET (kg 1,4-DB eq) MET (kg 1,4-DB eq) WD (m3) MRD (kg Fe eq) FD (kg oil eq)
3.9 1.1 1.1 9.0 1.2 3.5 1.9 1.1 1.7 9.6 4.1 9.5 3.1
Economic allocation Value
· · · · · · · · · · · · ·
10−1 10−9 10−3 10−6 10−3 10−4 10−5 10−5 10−4 10−4 10−1 10−4 10−1
4.4 1.3 3.9 1.4 1.4 1.2 5.04 2.04 1.3 1.8 5.2 1.2 3.9
· · · · · · · · · · · · ·
10–1 10−9 10−3 10−3 10−3 10−5 10−5 10−5 10−5 10−4 10−1 10−3 10−1
Energy allocation % Change
Value
+14.2 +28 +19 +16 +23 +28 +20 +4 +22 +6 +28 +28 +28
3.7 9.8 3.1 1.2 1.1 8.5 4.03 2.0 1.01 1.7 3.8 8.9 2.9
· · · · · · · · · · · · ·
% Change 10–1 10−10 10−3 10−3 10−3 10−6 10−5 10−5 10−5 10−4 10−1 10−4 10−1
–3.1 −6.1 −4.1 −3.4 −5 −6.1 −4.3 −1 −5 −1.3 −6.1 −6.1 −6.1
gasoline related to others refining co-products, for this reason the use of economic allocation could vary the LCA results depending of the period in which the data was obtained. The variability among the volume allocation and energetic allocation in the environmental impacts is low (differences between 1% and 6% depending on the category). The volume and energetic allocation approaches present the advantage of being relatively constant with the time. Thus, both allocation methodologies are preferred for this study.
is gratefully acknowledged. The authors (S. González-García and M.T. Moreira) belong to the Galician Competitive Research Group GRC 2013-032, program co-funded by FEDER. Dr. S. González-García would like to express her gratitude to the Spanish Ministry of Economy and Competitiveness for the financial support (Grant reference JCI-2012-11898).
6. Conclusions
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The present study shows the environmental results of an LCA performed for gasoline produced and used in the Chilean context. The study identified the key subsystems within the life cycle of the gasoline (production and use), which could help in future improvement technologies on gasoline production and transport sector. According to the results from this study, the main environmental hotspots were refining activities and gasoline use in the passenger car. The refining processes contribute in a number of impact categories with ratios higher than 45%: human toxicity, photochemical oxidant formation, freshwater eutrophication, terrestrial and marine ecotoxicity, water depletion and fossil depletion. Gasoline combustion emissions affect the categories of climate change, acidification, marine eutrophication and freshwater ecotoxicities (ranging from 44% to 79%). Transport of gasoline by lorry was the main responsible of ozone depletion. Distribution of crude oil by pipelines was the main source affecting the mineral depletion potential. The outcomes are highly sensitive to the allocation approach considered. The highest impacts were obtained in the economic allocation, followed by the volume allocation and energetic allocation. The high impacts resulting from the economic allocation were due to the high price assigned to the gasoline in the Chilean market. Despite the detail maintained in the study, there are limitations in the life cycle inventories by the lack of information from official sources. These include the uncertainty related to crude oil extraction and production from importing countries as well as the transportation distances. This study provides the basis for a comparative assessment for strategic decision-making concerning the use of alternative fuels (e.g. biofuels) that the Chilean government may propose in order to reduce their dependence on fossil fuels and/or the environmental impacts derived from the transport sector. Acknowledgments Financial support granted to M. Morales by CONICYT scholarship program (Comisión Nacional de Investigación Científica y Tecnológica)
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