How To Understand The Purpose Of Life Cycle Assessment

Transcription

1 Life-Cycle Assessment Lesson 1 Overview This is the first lesson on life cycle assessment in this module. In this lesson, the framework for conducting life-cycle assessments is described and examples of the ways in which life-cycle assessments have been applied are provided. The second lesson provides a more detailed overview of the inventory process in life-cycle assessment, and the third lesson discusses potential methods for assessing the impacts of a product life-cycle. 1

2 Why do life-cycle assessment? minimize the magnitude of pollution conserve non-renewable resources conserve ecological systems develop and utilize cleaner technologies maximize recycling of materials and waste apply the most appropriate pollution prevention and/or abatement techniques To begin the lessons, we ask the question: "Why do life-cycle assessment?" A great deal of waste is generated through human activities -- approximately 40 tons/year per person in the United States. This represents lost resources as well as results in environmental degradation. The most important goal of LCA, according to a survey of organizations actively involved in LCA, is to minimize the magnitude of pollution (S. Ryding, "International Experiences of Environmentally Sound Product Development Based on Life Cycle Assessment," Swedish Waste Research Council, AFR Report 36, Stockholm, May 1994.) This chart lists some of the other goals: conserve non-renewable resources, including energy; ensure that every effort is being made to conserve ecological systems, especially in areas subject to a critical balance of supplies; develop alternatives to maximize the recycling and reuse of materials and waste; and apply the most appropriate pollution prevention and/or abatement techniques; 2

3 How is life-cycle assessment used? By manufacturers: product development product improvement product comparison Life cycle assessment has been applied in many ways in both the public and private sectors. This is a list of some of the uses manufacturers have for LCA. Product comparisons have received the most attention from the press but according to the Swedish survey the most important uses for manufacturers are 1) to identify processes, ingredients, and systems that are major contributors to environmental impacts, 2) to compare different options within a particular process with the objective of minimizing environmental impacts, and 3) to provide guidance in long-term strategic planning concerning trends in product design and materials. 3

4 How is life-cycle assessment used? By public policymakers: environmental labeling LCA is also used in the public sector. Some of the most visible of the applications of life-cycle assessments are environmental or eco-labels. Examples of ecolabels from around the world are shown here. Besides environmental labeling programs, public sector uses of life-cycle methodologies include use as a tool for making procurement decisions and developing regulations. Policymakers report that the most important uses of LCA are in 1) helping to develop long-term policy regarding overall material use, resource conservation and reduction of environmental impacts and risks posed by materials and processes throughout the product life-cycle, 2) evaluating resource effects associated with source reduction and alternative waste management techniques, and 3) providing information to the public about the resource characteristics of products or materials. 4

5 What is life-cycle assessment? energy raw materials human activities products wastes and emissions This is a simplified diagram of the inputs and outputs associated with human activities. Opportunities for reducing waste outputs and energy and raw material requirements in this system can be analyzed from several perspectives. For example, studies of wastes and emissions at a large scale can show the industries and regions where large volumes of waste or highly toxic wastes are generated. In the field of industrial ecology, the fate of materials as they move through processes and into products and wastes are studied. Life-cycle assessment looks at this system from the perspective of products. In LCA, the processes required to make, use, and dispose of a product are analyzed to determine the raw materials, energy requirements, wastes, and emissions associated with the product's life cycle. 5

6 What is a product life-cycle? raw material acquisition energy material manufacture raw materials wastes and emissions transport product manufacture use product reuse product remanufacture materials recycle disposal This is a simplified diagram that shows the major stages of a product life cycle. First, there is raw material acquisition. For the case of paper products, raw material acquisition would include timber harvesting. For plastic products, it would include crude oil extraction. After raw material acquisition is the material manufacture stage. This is where raw materials are processed into basic materials of product manufacture. Felled trees are processed into lumber and paper, for example. Crude oil is processed into polymers that can be made into plastics. These materials move to the product manufacture stage where they are made into products such as paper and plastic cups. After this, they are used and disposed of or recycled. Recycling can occur in several ways. A product might be reused, which is what happens when a plastic cup is washed and reused instead of being thrown away. It could be sent to product remanufacture, where the materials it contains are used to make another product. A paper cup, for example, might be shredded and used for animal bedding. Finally, it might be recycled to materials manufacture, where it is fed as a raw material for a process. As shown in the diagram, all of these stages, along with the transport required to move products and materials, can require raw materials and energy and all of them can produce wastes and emissions. Life-cycle stages include raw-material acquisition, production, use, and disposal. LCA is a new and evolving concept, and definitions and terminology as well as more fundamental practice aspects are still developing. Students of life-cycle assessment will find that differences exist among practitioners as they learn more about LCA. 6

7 3 Steps in LCA 1) life-cycle inventory 2) life-cycle impact assessment 3) life-cycle improvement analysis There are three main steps in a life-cycle assessment: 1) Determine the emissions that occur and the raw materials and energy that are used during the life-cycle of a product. This is called a life-cycle inventory. 2) Assess what the impacts of these emissions and raw material depletions are. This is called a life-cycle impact assessment. 3) Interpret the results of the impact assessment in order to suggest improvements. When LCA is conducted to compare products this step may consist of recommending the most environmentally desirable product. This is called an improvement analysis. 7

8 Planning an LCA Project determine objectives Why is LCA being conducted? define product under study and its alternatives What is its function? What is an appropriate functional unit? choose system boundaries What inputs and outputs will be studied? How will data be collected? Because of the open-ended nature of life-cycle assessments, the planning phase of an LCA project is important. In the plan, the reasons for conducting the LCA are stated. Also, the product to be studied and its alternatives are defined. The functions of the system under consideration must be defined and a functional unit chosen that provides a basis for calculating inputs and outputs. The choice of function unit can be ambiguous and is discussed in more detail later in this lesson. Also in the planning phase, a choice of system boundaries is made, defining the scope of the project. A strategy for data collection is also determined and aggregation and evaluation methods are chosen. 8

9 The Functional Unit especially critical in LCAs conducted to compare products example: Paper versus. plastic grocery sacks function is to carry groceries so the functional unit could be a defined volume of groceries -- one plastic sack does not hold the same volume of groceries as a paper sack The functional unit determines equivalence between systems. Choosing a functional unit is not always straightforward and can have a profound impact on the results of the study. For example, if paper and plastic grocery sacks are to be compared in an LCA, the functional unit would be a given volume of groceries. Because fewer groceries, in general, are placed in plastic sacks than in paper sacks, the sacks would not be compared on a 1 to 1 basis. Instead, two plastic sacks might be determined as having the equivalent function of one paper sack. 9

10 Functional Unit Ambiguity Soft Drink Delivery Systems Functional Unit 12-oz. of soft drink one container number of functional units 12-oz. aluminum cans 16-oz. glass bottles 2-liter PET bottle As shown here, the functional unit of soft drink delivery systems (12- oz. aluminum cans, 16-oz. glass bottles, or 2-liter polyethylene terephthalate bottles), could be either a serving of soft drink consisting of a given amount (e.g. 12 oz.) or a given container. These two choices illustrate some of the difficulty in choosing a functional unit. Neither choice of functional unit is entirely satisfactory. Twelve ounce cans and 16-oz bottles are generally consumed as a single serving and comparing them on the basis of container count makes sense. It is only rarely, however, that a 2-liter bottle of soft drink would be consumed as a single serving. Notice from this table how influential the choice of functional unit is. If "one container" is chosen as the functional unit, values obtained for the life-cycle inventory of 2-liter bottles will be over five times more per functional unit than values obtained if a 12-oz serving is chosen as the functional unit. This example emphasizes that the results of LCA studies are heavily dependent on the decisions made during the planning phase. 10

11 Uncertainty in Results of Life- Cycle Inventories assumptions made when choosing system boundaries and data sources use of regional or global data poor quality data unavailable data Ambiguity in the choice of functional unit is only one possible source of error in conducting a life-cycle inventory. This is a list of some of the major sources of uncertainties inherent in the results of life-cycle inventories. It is important to understand the factors that affect the accuracy of the data so that the results are not over-interpreted and so that time and resources are not wasted in "fine-tuning" elements of the inventory process when the overall results cannot be precisely obtained. The inherent uncertainties in life-cycle inventory include the assumptions and choices for system boundaries and data sources. For example, if a life-cycle stage is excluded from the analysis because it is incorrectly assumed to contribute insignificantly to the overall impacts, the results of the inventory will be in error. Also, local conditions may not have been adequately addressed in a study that used regional or global data. Most importantly, available data on the processes being inventoried may be of poor quality or not available. 11

12 Product Comparisons generally sponsored by a stakeholder (e.g. plastics manufacturers sponsor a study comparing paper and plastic products) uncertainties and assumptions inherent in life-cycle inventories leave room for stakeholders in losing product to criticize results Perhaps the most widely publicized applications of LCA are those that were completed for the purpose of comparing products. Examples of assessments That received a great deal of press attention are one conducted to compare cloth and disposable diapering systems, one comparing plastic and paper cups, and one comparing polystyrene clamshells and paper wrappings for sandwiches. Comparison assessments are generally sponsored by an industry that has a vested interest in the results, and because of the open-ended nature of LCA, there is always room for criticism of the data. Because the results of these LCAs have generated a great deal of controversy and debate, these high-profile examples have created a great deal of skepticism about the value of LCA and diverted attention away from some of the other less controversial applications, such as LCAs conducted in order to improve products. 12

13 LCA for Product Improvement Average Gross Energy Required to Produce 1 kg of Polyethylene Fuel Type Electricity Oil Fuels Other Totals Fuel Production and Delivery (MJ) Delivered Energy (MJ) Feedstock Energy (MJ) Total Energy (MJ) Feedstock energy is defined as the caloric value of materials that are input into the processes required to produce polyethylene. From Ecoprofiles of the European Plastics Industry, Reports 1-4, PWMI, European Centre for Plastics in the Environment, Brussels, May LCAs conducted for product improvement can reveal processes, components, ingredients, and systems to target for environmental improvement. This was identified by product manufacturers as the most important application of LCA, according to a Swedish survey mentioned earlier. The results of an example of an LCA effort conducted for the purpose of product improvement are shown in this table, which gives the results of an inventory of the energy required to produce 1 kg of polyethylene. The table shows that the majority of fuel required to make polyethylene is in the organic matter that instead of being burned for energy is converted to polyethylene. The values in the column titled "Feedstock Energy" are about 3/4 of the total energy requirements. This inventory showed that the focus of efforts to reduce the life-cycle energy consumption of polyethylene are best spent on reducing the mass of polyethylene in products -- to make them as light as possible. 13

14 LCA for Product Improvement Polyester blouse life-cycle energy requirements: Production: 18% Use: 82% Disposal: <1% Energy requirements of use stage could be reduced by more than 90% by switching to cold water wash and line dry instead of warm water wash and drying in dryer. (See Franklin Associates, Ltd., Resource and Environmental Profile Analysis of a Manufactured Apparel Product, Prairie Village, KS, June 1993 for more details.) The results of another example of an LCA conducted for product improvement are shown here. This energy inventory of the life cycle of a polyester blouse showed that the majority of energy consumption in the life-cycle (82%) occurred during the product use life-cycle stage, during washing and drying of the blouse. In this case, low-energy use methods of washing and drying the blouse (cold water wash and line dry) have the greatest potential for lowering the energy requirements of a blouse's life cycle. 14

15 LCA for Product Improvement Transportation vs. Manufacturing Energy Consumption for a Garment % of Life-Cycle Energy Requirements for a Garment Delivery Mode Transport Manufacture Overnight Air 28% 72% Truck Truck + Rail 5% 1% 95% 99% From Hopkins, Allen, and Brown, Pollution Prevention Review, 4(4), The results of a life-cycle inventory of the energy required to manufacture a garment and deliver it to the customer are shown in this table. This study showed that in the case where next-day air shipping is used, the transportation and distribution life-cycle stages of a product can be significant contributors to its energy requirements. When customers were sent their orders by overnight air, transportation energy requirements were 28% of total life-cycle energy requirements. This finding is contrary to common knowledge: transportation and distribution of products generally contribute negligibly to the energy requirements of a product. Prior to this study, the garment manufacturer was unaware that the delivery mode could contribute significantly to the energy required over the life-cycle of their products. 15

16 LCA for Product Improvement A final example of LCA used for product improvement is one where the assessment was used to reveal which components are responsible for the majority of raw material usage, wastes, emissions, and energy consumption in a product manufactured from multiple components. In a life-cycle assessment of a computer workstation, life-cycle inventory data were compiled for diverse components such as semiconductors, semiconductor packaging, printed wiring boards and computer assemblies, and display monitors. The findings of the study showed that the majority of energy usage over a workstation life cycle occurs from operation of the display during the use stage of the life-cycle. Therefore, to reduce the overall energy usage of a computer workstation, efforts are best directed at the energy consumed by the monitor. Semiconductor manufacture was found to dominate hazardous waste generation and was also found to be a significant source of raw material usage, even though, by weight, semiconductors are a very small portion of a workstation. 16

17 Summary of Lesson 1 LCAs are a tool for assessing and minimizing the impact of human activities. Life-cycle stages of a product include raw material acquisition, manufacturing, use, and disposal. LCA techniques have been adopted in industry and the public sector to serve a variety of purposes. Choices made during the planning phase of an LCA have a profound impact on the results obtained. The choice of functional unit, particularly when LCAs are conducted to compare products, is especially influential. This concludes the first lesson on life-cycle assessment in this module. You have been introduced to the concepts and goals of LCA. Remember that a complete life-cycle assessment consists of three steps: 1) a life-cycle inventory of the wastes and emissions, raw materials, and energy requirements of a product over its life cycle, 2) an assessment of the impacts caused the wastes and emissions, raw materials and energy requirements of the product over its life cycle, and 3) an improvement analysis where recommendations for reducing the impacts are formulated. At this point, you should understand what factors to consider in choosing a functional unit and also understand how crucial the system boundaries of a life-cycle assessment are to the results. You should also be aware of some of the ways in which this powerful tool has been put into use by industry and by public policymakers. 17