This research performs life-cycle assessments on two products-plastic bags and paper bags. The two products are considered to be substitutes for one another, and the end objective of the life-cycle assessments performed on the two products is to compare the life-cycle costs of the two products for the purpose of recommending a production strategy for a company that produces bags.
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A life-cycle assessment for paper bags is presented in the following section, and this presentation is followed by a presentation of a life-cycle assessment for plastic bags in the succeeding section. Following the presentations of the two life-cycle assessments, the two substitute products are compared with the emphasis being placed on the full costs of the products for the manufacturing company. Recommendations and conclusions based on this comparison are then presented.
Life cycle assessment attempts to measure the total environmental effects of a product “from cradle to grave.” Proponents contend that life-cycle assessment can provide the information to assess tradeoffs throughout the life of every product.
Life-cycle assessment permits producing organizations to determine the environmental impact of both their products and the manufacturing processes used in the production of those goods. As manufacturing companies have experienced increasing pressures to minimize adverse environmental effects of all types, therefore, life-cycle assessment has assumed greater importance in manufacturing management.
The initial step in a life-cycle assessment involves the establishment of the purpose of the study and defining the objectives of the study. This step for this current examination was established in the initial paragraph of this “Introduction.”
The second step of a life-cycle assessment is the life-cycle inventory. In the life-cycle inventory, energy and raw material requirements and environmental emissions of the product and its manufacturing process are quantified. Precise and extensive calculations are involved in this step. Totals for all material requirements and environmental emissions are presented for all stages of production, from raw materials acquisition to waste management.
The third step is an impact assessment, which attempts to translate the life-cycle inventory data into effects on human health, ecological health, and resource depletion, which are the impacts of the product and its manufacturing process on the environment. The impact assessment is accomplished by classifying the inventory items into condition groups that may lead to an environmental impact.
The final step in a life-cycle assessment is an improvement analysis. The improvement analysis develops recommendations based on the results of the life-cycle inventory and the life-cycle impact assessment. Such recommendations may include the modification of a production process, the use of different raw materials, or choosing one product over another, as is the case in this current study.
The steps of the life-cycle assessment process from life-cycle inventory through life-cycle improvement analysis are addressed in this current study in the following two sections. In these two sections, these steps of the life-cycle assessment process are developed for both plastic bags and paper bags.
Life-Cycle Assessment: Plastic Bags
The life-cycle assessment of plastic bags is presented in relation to life-cycle inventory, life-cycle impact assessment, and life-cycle improvement analysis.
Life-Cycle Inventory
The life-cycle inventory analysis is a technical, data-based process of quantifying energy and raw material requirements, atmospheric emissions, waterborne emissions, solid wastes, and other releases for the entire life cycle of a product, package, process, material, or activity. In this section, the life-cycle inventory is developed for plastic bags.
In the broadest sense, a life-cycle inventory analysis begins with raw material extraction and continues through final product consumption and disposal. The scope of the life-cycle inventory refers to the setting of boundaries for the life-cycle inventory of a specific product.
A flow chart of the life cycle of plastic bags is presented in Exhibit 1. The exhibit may be found on the following page.
The flow of the life cycle of plastic bags is illustrated in Exhibit 1. This flow begins (PE) petroleum extraction, and progresses through (PR) petroleum refining, (Pl-E) plastic extrusion, (Pl-F) plastic fabrication, (PB-M) plastic bag manufacture, (Tr) transportation of plastic bags to initial users, (IU) initial use, (SU) secondary use, (UD) user disposal, and thence to either (Rcy) recycling or (LFD) landfill disposal.
The life-cycle inventory of environmental factors for plastic bags is presented in Table 1. The table may be found on the following page.
Table 1: Life-Cycle Inventory Plastic Bags
Environmental Factor
Emissions [metric tons]
SO2
0.07037
CO
0.01655
NO2
0.04692
VOC
0.27504
Lead
0.00001
PM10
0.00241
MTCO2E
58.76522
Non-Point Air
0.02432
Point Air
0.03892
Air Releases
0.04723
Water Releases
0.00225
Land Releases
0.00106
Underground Releases
0.01568
The life-cycle inventory of plastic bags indicates that several environmental factors are involved in the production and use of the product. These factors come into play at every stage of the life cycle of plastic bags.
Life-Cycle Impact Assessment
Qualitative aspects of the life-cycle are addressed through the life-cycle impact assessment. The life-cycle impact assessment, however, also includes technical and quantitative data to assess the effects of the resource requirements and environmental factors (atmospheric emissions, waterborne emissions, and solid wastes) identified in the life-cycle inventory.
The life-cycle impact assessment for plastic bags developed in this section considers ecological and human health impacts, and resource depletion. Other effects, such as habitat modification and heat and noise pollution, also are included in the life-cycle impact assessment.
The key concept in the life-cycle impact assessment is the environmental stressor. The environmental stressor concept links the life-cycle inventory and the life-cycle impact assessment through identified conditions that tie resource consumption and environmental factors. Thus, a stressor is a set of conditions that may lead to an impact.
The life-cycle impact analysis does not attempt to quantify any specific actual impacts associated with a product or process. Rather, the life-cycle impact assessment seeks to establish a linkage between the product or process life cycle and potential impacts.
The substance releases associated with the manufacture, distribution, use, and disposal of plastic bags create a number of stressors. These stressors, in turn, have an impact on the ecology, human and other animal welfare, and resource conservation. The magnitude of releases into the air, water, and land are not enormous; however, the are nevertheless substantial.
Life-Cycle Improvement Analysis
The life-cycle improvement analysis is an evaluation of the needs and opportunities to reduce the environmental burden associated with energy and raw material use and waste emissions throughout the life cycle of a product or process, which in this section is a product-plastic bags. This analysis includes both quantitative and qualitative measures of improvements.
The economic costs associated with the use of plastic bags approximate $0.58710 per metric ton of environmental discharge. Electricity consumption in the production of plastic bags approximates 0.19 million kilowatt-hours per $1 million production of plastic bags.
Life-Cycle Assessment: Paper Bags
The life-cycle assessment of paper bags is presented in relation to life-cycle inventory, life-cycle impact assessment, and life-cycle improvement analysis.
Life-Cycle Inventory
As noted in the preceding life-cycle assessment of plastic bags, the life-cycle inventory analysis is a technical, data-based process of quantifying energy and raw material requirements, atmospheric emissions, waterborne emissions, solid wastes, and other releases for the entire life cycle of a product, package, process, material, or activity. In this section, the life-cycle inventory is developed for paper bags.
In the broadest sense, as stated in the life-cycle assessment of plastic bags, a life-cycle inventory analysis begins with raw material extraction and continues through final product consumption and disposal. The scope of the life-cycle inventory refers to the setting of boundaries for the life-cycle inventory of a specific product.
A flow chart of the life cycle of plastic bags is presented in Exhibit 2. The exhibit may be found on the following page.
The flow of the life cycle of paper bags is illustrated in Exhibit 2. This flow begins (TH) tree harvesting, and progresses through (LT) log transport, (Pm-O) pulp mill operations, (Pa-F) paper fabrication, (PB-M) paper bag manufacture, (Tr) transportation of paper bags to initial users, (IU) initial use, (SU) secondary use, (UD) user disposal, and thence to either (Rcy) recycling or (LFD) landfill disposal.
The life-cycle inventory of environmental factors for plastic bags is presented in Table 2. The table may be found on the following page.
Table 2: Life-Cycle Inventory Paper Bags
Environmental Factor
Emissions [metric tons]
SO2
0.80988
CO
0.51794
NO2
0.35931
VOC
0.30502
Lead
0.00010
PM10
0.03281
MTCO2E
91.28522
Non-Point Air
0.00471
Point Air
0.07472
Air Releases
0.07824
Water Releases
0.00362
Land Releases
0.00144
Underground Releases
0.00000
The life-cycle inventory of paper bags indicates that several environmental factors are involved in the production and use of the product. These factors come into play at every stage of the life cycle of paper bags.
Life-Cycle Impact Assessment
Qualitative aspects of the life cycle are addressed through the life-cycle impact assessment, a fact noted in the life-cycle assessment of plastic bags. The life-cycle impact assessment, however, also includes technical and quantitative data to assess the effects of the resource requirements and environmental factors (atmospheric emissions, waterborne emissions, and solid wastes) identified in the life-cycle inventory.
The life-cycle impact assessment for paper bags developed in this section considers ecological and human health impacts, and resource depletion. Other effects, such as habitat modification and heat and noise pollution, also are included in the life-cycle impact assessment.
The key concept in the life-cycle impact assessment, a previously noted in the life-cycle assessment of plastic bags, is the environmental stressor. The environmental stressor concept links the life-cycle inventory and the life-cycle impact assessment through identified conditions that tie resource consumption and environmental factors. Thus, a stressor is a set of conditions that may lead to an impact.
The life-cycle impact analysis, as stated in the life-cycle assessment of plastic bags, does not attempt to quantify any specific actual impacts associated with a product or process. Rather, the life-cycle impact assessment seeks to establish a linkage between the product or process life cycle and potential impacts.
The substance releases associated with the manufacture, distribution, use, and disposal of paper bags create a number of stressors. These stressors, in turn, have an impact on the ecology, human and other animal welfare, and resource conservation. The magnitude of releases into the air, water, and land are not enormous; however, the are nevertheless substantial.
Life-Cycle Improvement Analysis
The life-cycle improvement analysis is an evaluation of the needs and opportunities to reduce the environmental burden associated with energy and raw material use and waste emissions throughout the life cycle of a product or process, which in this section is a product-plastic bags. This analysis includes both quantitative and qualitative measures of improvements.
The economic costs associated with the use of paper bags approximate $0.57299 per metric ton of environmental discharge. Electricity consumption in the production of plastic bags approximates 0.27 million kilowatt-hours per $1 million production of plastic bags.
Comparative Assessment of Plastic Bags & Paper Bags
Comparing the life-cycle assessment of plastic bags with the life-cycle assessment of paper bags reveals that, from an environmental risk perspective, plastic bags are a lower risk product than are paper bags. With respect to life-cycle inventory comparisons, paper bags are superior to plastic bags only within the context of non-point air releases.
Comparing the life-cycle assessment of plastic bags with the life-cycle assessment of paper bags within a total cost context reveals that plastic bags consume less resources in production and distribution. Further, the total cost of production is lower for plastic bags than for paper bags.
Recommendations
For the company manufacturing bags, the recommendation is that plastic bags continue to be produced. Although the company does not now produce paper bags, the recommendations is that such production not be commenced.
Conclusions
One conclusion drawn from the findings of this study is that plastic bags are a more economic product for the manufacturer than are paper bags. A second conclusion is that plastic bags are less harmful to the ecology than are paper bags.
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