Environmental evaluation of valorization options for used cooking oil

Transcription

1 Environmental evaluation of valorization options for used cooking oil ANA CLÁUDIA DIAS, MARIA ISABEL NUNES, ELMA FERREIRA, LUIS ARROJA Department of Environment and Planning & CESAM University of Aveiro Campus Universitário de Santiago, Aveiro PORUGAL Abstract: - his study aims to compare the potential environmental impacts derived from two alternative options for the valorization of used cooking oil (), in order to provide supporting information for the establishment of management strategies for this urban waste. Life cycle assessment (LCA) methodology is applied for this purpose. Since the systems under study are multifunctional (they treat and simultaneously deliver a useful product), a system expansion approach was adopted so that both systems deliver the same functions. hus, the functional unit was defined as the provision of 0.87 t of biodiesel and t of soap, which are the amounts produced with 1 t of. he system that produces biodiesel from was expanded in order to include the of t of soap using virgin oils, whereas the system that produces soap from was also expanded to include the of 0.87 t of biodiesel from virgin oils. he results show no significant differences (not exceeding 10%) between the two valorization options. herefore, other aspects should be considered in the improvement of the management strategy for, such as economic and social issues. he results also indicate that methanol and thermal energy are the hotspots in biodiesel from, whereas virgin oils is the hotspot in soap from. hus, the optimization of the consumption and of these materials as well as the energy should be a priority for the mitigation of the environmental impacts associated with valorization. Keywords: - biodiesel, life cycle assessment (LCA), soap, used cooking oil, waste management 1 Introduction Used cooking oil () is a waste produced in the domestic sector, canteens, hotels, restaurants and food industy, consisting in edible vegetable oil used in frying food. Inappropriate disposal of may generate significant problems, such as blockages and operational problems in wastewater treatment plants when discharged into sewerage systems. In Portugal, there is legislation prohibiting the discharge of into sewerage systems as well as the deposition in landfills, and encouraging recycling. is thus seen not as a problem, but as a resource, being a raw material that can be used in the of valuable products. has been considered as an interesting raw material for biodiesel. Compared with virgin oils, the use of avoids the competition between food and energy. Other possible application for is the of soap. he valorization of generates several environmental impacts. One methodology that has been applied to evaluate those impacts is Life Cycle Assessment (LCA). Several LCA studies have been carried out for biodiesel produced from [1-7], whereas for soap made with this kind of studies is very scarce [6]. LCA is an internationally standardized methodology that studies the environmental aspects and potential impacts throughout a product life cycle from raw material extraction through, use, recycling and disposal [8,9]. LCA is generally considered the most suitable methodology for assessing the environmental impacts of products since it addresses both the entire life cycle (avoiding problem shifting) and a great variety of environmental impacts. he objective of this study is to compare the environmental impacts of biodiesel and soap from using LCA, in order to get insights about what is the best option, from an environmental point of view, for management in Portugal. 2 Methodology 2.1 LCA phases LCA is structured in four phases: (1) goal and scope definition, (2) inventory analysis, (3) impact assessment, and (4) interpretation. ISBN:

2 he goal and scope definition is very important as the study will be carried out according to the statements made in this phase. It must describe the goal of the study, functional unit, system boundaries, allocation procedures, impact assessment methodologies, data quality requirements and assumptions, among other items. he inventory analysis involves data collection on inputs (raw materials, ancillary materials and energy) and outputs (products, emissions to air, water and soil, and solid waste generation) for each process included within the system boundary. he impact assessment phase assigns inventory results to specific impact categories and quantifies the system s potential contribution to different environmental impacts. Finally, in the interpretation phase, the inventory analysis and impact assessment results are discussed and the significant environmental issues are identified to reach conclusions and recommendations consistent with the goal and scope requirements. 2.2 Function and functional unit he comparison of the two alternative options for valorization of should be based on the same functions. Each option represents a multifunctional system, because, at least, two functions are delivered: to treat the and to produce a new valuable product (biodiesel or soap). herefore, the functional unit was defined as the provision of 0.87 t of biodiesel and t of soap. hese are the amounts that are produced from 1 t of. In the case of the system that produces biodiesel from, the system was expanded in order to include the of t of soap using virgin oils. On the other hand, the system that produces soap from was also expanded to include the of 0.87 t of biodiesel from virgin oils. As biodiesel from soybean and rapeseed oil are the most representative in the Portuguese market, these two types of biodiesel were selected for analysis. 2.3 Systems boundaries Fig.1 shows the systems boundaries for the two valorization options. For the system where biodiesel is produced from, the processes considered were: - of biodiesel from ; - and transport of chemicals, water, fuel oil and electricity consumed in the biodiesel process; - of soap from virgin oils; - and transport of virgin oils, chemicals, packaging materials, water, fuel oil and electricity consumed in the soap process. For the system where is used for soap, the processes considered include: - of soap from ; - and transport of oils other than, chemicals, packaging materials, water, fuel oil and electricity consumed in the soap process; - of biodiesel from virgin oils (soybean/rapeseed) - and transport of virgin oils, chemicals, water, natural gas and electricity consumed in the biodiesel processes. he collection was excluded since it was assumed to be the same in the two valorization alternatives. he and maintenance of capital goods (equipment, buildings, etc.) was also excluded. 2.4 Inventory data Inventory data for the of biodiesel and soap from are real data provided by Portuguese factories. Data for the of soap from virgin oils were adapted from the dataset of soap from by considering that is replaced by coconut oil. Data for biodiesel from soybean and rapeseed oils were taken from the Ecoinvent database [10]. his database was also the source of the data for the of chemicals, packaging materials, fuel and electricity. Regarding transports, data on the distances travelled and transport modes are real data provided by the factories, whereas data on inputs and outputs for each transport mode were retrieved from the Ecoinvent database. 2.5 Allocation During the of biodiesel there is also the of glycerol as co-product. An economic allocation based on market prices was applied to divide the environmental burdens of biodiesel between biodiesel and glycerol. Following this criterion, 99% of the burdens were allocated to biodiesel. 2.6 Impact assessment he midpoint characterisation factors recommended by the International Reference Life Cycle Data System (ILCD) [11] were considered in the impact assessment phase. he following impact categories ISBN:

3 were addressed: climate change (CC), photochemical ozone formation (POF), acidification (A), freshwater eutrophication (FEu), and mineral and fossil resource depletion (MFRD). 3 Results able 1 summarizes the results obtained for the two valorization options. As referred above, when is used for soap, two alternative virgin oils were considered for biodiesel : soybean and rapeseed. 1 t = transport Biodiesel from Soap from Packaging materials 0.87 t biodiesel t soap Packaging materials + Soap from virgin oils + Biodiesel from virgin oils Natural gas System of biodiesel t soap 0.87 t biodiesel System of soap Fig.1 Systems boundaries. able 1 Impact assessment results expressed per functional unit. for biodiesel for soap for soap Impact Biodiesel Soap from otal Soap Biodiesel otal Soap Biodiesel otal category from virgin oils from soybean oil from rapeseed oil (*) CC 2.88E E E E E E E E E+01 POF 1.40E E E E E E E E E-01 A 2.68E E E E E E E E E-01 FE 3.36E E E E E E E E E-03 MFRD 2.89E E E E E E E E E-03 (*) Units: CC - kg CO 2 eq; POF - kg NMVOC eq; A - mole H + eq; FE - kg P eq; MFRD - kg Sb eq ISBN:

4 he results show that the differences between the two valorization options are small, not exceeding 10%, regardless the type of biodiesel (soybean or rapeseed) considered in the system boundaries of valorization into soap (able 2). Valorization of into biodiesel seems to be favorable for the impact category of MFRD due to lower resources consumption during the biodiesel process itself when compared to biodiesel from virgin oils. In contrast, valorization of into biodiesel generates higher total impacts than valorization of into soap for the impact category of POF. In this case, although the biodiesel process from itself has lower impact than biodiesel from virgin oils, the effect of a higher impact associated with soap from virgin oils is prevalent. For the remaining impact categories, the most favorable option depends on the virgin oil considered for biodiesel. able 2 Deviation of the total impacts of valorization into soap in relation to valorization into biodiesel. Impact category Considering biodiesel from soybean oil Considering biodiesel from rapeseed oil CC +1.6% -1.0% POF -1.5% -2.5% A -3.2% +6.3% FE +10.0% -2.7% MFRD +5.8% +0.2% A more detailed analysis of the biodiesel process from indicates that the main contributions to the impacts assessed are associated with methanol and thermal energy (i.e. extraction, processing and combustion of fuel oil) (Fig.2). Methanol dominates all impact categories except POF, with contributions ranging from 40 to 96%, whereas thermal energy has the largest contribution to POF (52%). Regarding the soap process from, the largest contribution comes from the of virgin oils that are consumed together with (Fig.3). he of these oils accounts for 72 to 99% of the total impacts, depending on the impact category. About 75% of the total oils consumed in soap is palm oil and 17% is coconut oil. represents only 8% of the total oils consumed. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% CC POF A FE MFRD ransport Sodium hydroxide Methanol hermal energy and wastewater treatment Fig.2 Relative contribution of each source to the impacts associated with biodiesel from. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% CC POF A FE MFRD ransport and packaging hermal energy Fig.3 Relative contribution of each source to the impacts associated with soap from. 4 Conclusions his study compares, from an environmental point of view, two current alternatives in Portugal for valorization: biodiesel and soap. he results show that there are no significant differences in the environmental impacts associated with these alternatives. herefore, other aspects should be taken into account in order to better support a management strategy for, such as economic and social aspects. A life cycle sustainability assessment, which incorporates these aspects, is thus recommended. he results also indicate that methanol and thermal energy are the hotspots in biodiesel from, which means that optimization of methanol and thermal energy consumption should be a priority in order to decrease the environmental impacts of this process. he soap from has the largest impacts in the virgin oils, meaning that, in this case, the priority should be in the optimization of virgin oils. ISBN:

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