Comparative Study of Life Cycle Assessment of Polypropylene and Polylactic Acid for Food Packaging
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International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Vol-7, Iss-1, Spl. Issue-2 Mar.-2019, http://iraj.in COMPARATIVE STUDY OF LIFE CYCLE ASSESSMENT OF POLYPROPYLENE AND POLYLACTIC ACID FOR FOOD PACKAGING 1SYAMIM FAUZI, 2HAZLEEN ANUAR 1,2Manufacturing and Material Engineering IIUM Malaysia E-mail: [email protected], [email protected] Abstract - Synthetic polymers caused depletion of the petroleum. Development of PLA as food packaging is frequently done to reduce the environmental impact due to its characteristic of easily degraded. Cradle-to-grave analysis of PLA indicates that even though PLA packaging is easy to degrade, it will still be considered as waste after disposal. However, biodegradability of PLA enabled the cradle-to-cradle analysis to be made where no unwanted excess material produced as it can be recuperated or reused as the packaging decomposes into nutrients. System boundary is first developed. PLA gives lesser GWP where PP gives 203.0 Kg CO2 eqv. Due to implementation of cradle-to-cradle, the GWP value of PLA is reduced to 161.37 Kg CO2 eqv from 164.6 Kg CO2 eqv. AP value of PLA is lower than PP packaging with amount of 4.89 x -1 -1 10 Kg SO2 eqv and 4.89 x 10 Kg SO2 eqv for PLA. PP packaging gives lesser environmental impact through ODP and EP with 7.09 x 10-12 Kg CFC-11 eqv and 1.10 x 10-4 Kg P eqv each as compared to PLA with 6.22 x 10-10 Kg CFC-11 and 1.79 x 10-4 Kg P eqv. As the major contributor towards the environmental impact is GWP which covered about 97% over others, PLA packaging gives better environmental impact as compared to PP packaging. Keywords - Life Cycle Assessment, Cradle-to-Cradle, Polypropylene, Polylactic acid, Food packaging, Environmental Impacts I. INTRODUCTION terms of global warming potential (GWP)[4]. To date however, there is none of the researchers have Synthetic polymers are well known in many human conducted cradle-to-cradle assessment on polylactic activities along with industrial development. These acid as it is biodegradable that decompose into artificial substances are basically made up from nutrients that help in new crop production [5]. Thus, petroleum which define the non-degradable properties the aim of this study is to quantify the environmental that cause harm and problem to the environment impacts on food packaging of polypropylene (PP) and which is not subtle for temporary use [1]. As a polylactic acid (PLA)fabricated.Both PP and PLA countermeasure to the environmental problems such were assessed using GaBi Software. Cradle-to-gate as pollution towards the landfills, researchers are system boundary was developed for PPwhereas consistently developing and enhancing the properties cradle-to-cradle system was developed for PLA.The of the biodegradable polymer of PLA to make it environmental impact quantified were global competitive with other synthetic polymers which are warming, ozone depletion, eutrophication and well known for their good mechanical properties such acidification. as PP. Environmental impacts can be assessed by sustainability tool of Life Cycle Assessment (LCA) as II. METHODOLOGY it is an approach which is used to evaluate environmental impacts potential. Interpretation of 2.1. Definition of Scope LCA comprises the assessment of the environmental Scope of cradle-to-cradle is used for the PLA and impacts starting with the early stage of the product cradle-to-grave for PP.The raw pellets of both PP and that consists of raw materials towards the end of the PLA were obtained from suppliers accordingly where product‟s life [2]. In order to develop LCA, system it has been transported to the manufacturing plant that boundary must be identified. System boundary is what later on transported to consumer defined as use phase defines the unit processes that need to be included in and lastly to the landfill where landfill site for PLA the modeled system. There are different types of scope serves as a nutrients settling. that defined the system boundary which are cradle-to- 2.2. Functional Unit for Production of Packaging grave, cradle-to-gate and gate-to-gate in LCA [3]. Functional unit used for producing food packaging of Cradle-to-cradle assessment on the other hand defined both PP and PLA was 50 units where the weight for as another sustainability tool with certification system each unit of PLA food packaging is defined to be that provides an informative methodology. As 0.0106 kg while the weight for each unit of PP food compared to LCA scopes, cradle-to-cradle assessment packaging is 0.0073 kg. provides a definitive analysis that covers a closed 2.3 Transportation system as the status of the resources is For this project, PP required only land transportation maintained.PLA packaging gives lesser environmental of a car as it is obtained from Penang while PLA impact compared to other synthetic packaging in required air and land transportation as it is obtained Comparative Study of Life Cycle Assessment of Polypropylene and Polylactic Acid for Food Packaging 37 International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Vol-7, Iss-1, Spl. Issue-2 Mar.-2019, http://iraj.in from Nature Works located in China. PP required an III. RESULTS AND DISCUSSION estimated distance of 276 km from supplier to manufacturing plant. For PLA, the distance from the 3.1. Global Warming Potential supplier is estimated to be 4004 km of airway and The result of GWP for PP is shown in Figure 3. The 77 km of roadway while the distance for transporting presence of recovery section in the plotted graph the used product to the landfill site for both PP and indicated the material recovery of PLA due to PLA are estimated to be 10 km. implementation of cradle-to-cradle method in assessing the environmental impact. It can be seen 2.4 Electricity that GWP of PP is higher compared to PLA where the For PP, the electrical energy was only used for the amount of GWP for PP is 203 Kg CO2 eqv. The fabrication of the food packaging through amount of GWP of PLA is reduced from 164.6Kg compression molding. PLA required higher electrical CO2 eqv to 161.037 Kg CO2 eqv due to the energy due to drying and compression molding implementation of cradle-to-cradle method of PLA processes. For PP, 847.22 MJ amount of electrical where the material recovery is considered. This can consumed while for PLA, 10.80 MJ for drying and be seen as similar to the study made by (GPI, 2007) 678.96 MJ was used for compression molding where cradle-to-cradle results in reduction of global process. warming potential.Manufacturing process of compression molding for PP and extra process of 2.5 Life Cycle Impact Assessment drying for PLA is the major cause of global warming Potential environmental impact of Global Warming for both PP and PLA that indicates the major cause of Potential (GWP), Ozone Layer Depletion Potential global warming for food packaging production is due (ODP), Eutrophication Potential (EP) and to the usage of electricity followed by transportation, Acidification Potential (AP) with unit of Kg CO2 eqv, obtaining raw pellets which include the production of Kg CFC-11 eqv, Kg P eqv and Kg SO2eqv each were raw pellets and lastly deposition to landfill. The assessed and interpreted as the system boundary been process of obtaining that includes production of raw developed. The impact was analysed up to the pellets for PLA is lesser which 0.311 Kg CO2 eqv midpoint level that covers the environmental problem over PP which is 0.718Kg CO2 eqv. This is due to the that were positioned between the inventory and presence of carbon dioxide, nitrous oxide, sulphur endpoint level. The impacts were assessed using hexafluoride, and greater methane gas emission as ReCipe (1.08) as LCIA method provided by the compared to PLA that contributed to GWP. Greater GaBisoftware.Figure 1 and Figure 2 show the system amount of GWP contributed in producing PP boundary developed for both PP and PLA food compared to PLA was due to the process of packaging. extraction from petroleum that required higher amount of energy used thermally and electrically where production of PP granules gives high GWP than biodegradable plastics [7]. Landfilling activity of PP is simply lesser than PLA due to composting reaction as high amount of methane is produced by bacterial decomposition when an organic material of PLA is disposed towards landfill [8]. However, due to cradle-to-cradle implementation, the amount of greenhouse gases are sequestered and absorbed by the plants as the new material are recovered by new crop production that later on deduce the overall amount of global warming to 161.037 Kg CO2eqv. Figure 1. Developed system boundary for PP in the GaBisoftware Figure 2. Developed system boundary for PLA in the GaBi software Figure 3. Global Warming Potential of PP and PLA packaging Comparative Study of Life Cycle Assessment of Polypropylene and Polylactic Acid for Food Packaging 38 International Journal of Advances in Science Engineering and Technology, ISSN(p): 2321 –8991, ISSN(e): 2321 –9009 Vol-7, Iss-1, Spl. Issue-2 Mar.-2019, http://iraj.in 3.2. Ozone Depletion Potential required in order to shape PP packaging. Excess Figure 4 shows the ODP value in producing PP and emission of phosphorus and phosphates caused by PLA packaging. Process of obtaining raw pellets greater electricity generation to support electrical serves as a major contributor to ozone depletion as demand will induce environmental problem due to the ODP value in producing PLA food packaging is high coal combustion[12].Both polylactic acid and 6.03 x 10-10 Kg CFC-11 eqv with no ozone depletion polypropylene, process of producing PLA produces caused by producing PP pellets.