There is an ever-increasing need to develop, produce, and use products that are robust, reliable, of high quality, supportable, cost-effective, environmentally sustainable from a total life cycle perspective, and that are able to respond to the needs of the user/customer, industry, and society in a more sustainable manner. Different definitions of sustainability have been used in literature, with up to eight or more dimensions of sustainability reported to date, including physical, environmental, economic, social, equity, cultural, psychological, and ethical. Nevertheless, it is widely accepted today that sustainability encompasses three main domains: (i) social; (ii) economic; and (iii) environmental.
Sustainable design addresses not only the functional and aesthetic requirements of products, but more importantly, aims to meet the needs of the present, without compromising the ability of future generations to meet their needs. With increases in the number, variety, and complexity of sports products traded globally and affecting more stakeholders, sustainable sports product design has gained increased importance. Fundamental to sustainable design is comprehensive treatment of the entire life cycle of the product. The life cycle of products is typically related to raw material extraction, production, use and end of life, whereby design impacts all life cycle phases 23. Inappropriate use and disposal can have negative impacts, even when products are reasonably produced. In the case of sports products, the greatest environmental impacts are associated with the production phase, as opposed to some other products, like cars, where the greatest impact is in the use phase. With the adoption of new, more advanced materials, the impact weighting is increasingly being shifted to the end-of-life (disposal) phase due to the environmental burden associated with such materials.
Interpretation of the LCA results could lead to particular product design improvement strategies, strategic planning of new product development, policy making, marketing, and others. Experience shows that the materials and processes used in products typically have the greatest impact on the LCA results. The following case study involving composite tennis racquets will illustrate the LCA process, type of results obtained, and typical recommendations for sustainable design stemming from such a study.
2.1 LCA of Composite Tennis Racquets
Composite tennis racquets consist of several different materials, depending on the model and the manufacturer. The manufacturing techniques used to produce tennis racquets are generally the same, with minor changes introduced from manufacturer to manufacturer, each having their own trade secrets. Although it is not possible to obtain or publish the details of these processes in full, the main steps that make up the majority of the construction can be retrieved from literature 18. In order to gather more accurate information on the materials, it is necessary to either work closely with a tennis racquet manufacturer or adopt a reverse engineering or forensic engineering approach.
In this case study, four different tennis racquets (with two different designs and two different manufacturing techniques used) will be assessed. The goal is to identify the materials and processes that give rise to the main differences in the respective environmental impacts of the racquets. The scope and boundaries, as well as the functional unit of the product system considered in this analysis, have been described in detail by Subic and Paterson 20. The functional unit is a measure of the function of the studied system, and it provides a reference to which the inputs and outputs can be related. Thus, two different products can be compared if they have the same functional unit. The functional unit of a tennis racquet requires assumptions to be made about how long it will be used for. For example, if an average casual player is considered, the average racquet's useful lifespan can be assumed to be 5 years, with each racquet requiring four replacement grips and two sets of replacement strings. A racquet will probably last much longer than this, but it is usual for new models to replace existing racquets before their useful life has been exceeded due to the changing personal preferences of the user.
A detailed material and process inventory for the four racquets has been completed, with Figure 1 showing the inventory tree (including the processing steps used for the construction of the racquets and estimates of the waste), whereby Table 1 indicates the weightings and types of materials found in the racquets (including estimations for the waste material and accurate data for packaging). There are many similarities between the materials used in the different racquets, as might be expected. For clarity, the materials that exhibit differences are indicated in bold.
Figure 1. Inventory tree for composite tennis racquets. CF, carbon fibers; GF, glass fibers; PA, polyacetylene; PET, polyethylene terephthalate; PUR, polyurethane; SMC, sheet molding compound; TT, polyamide-based finishing. Reprinted from Subic and Paterson 20. © 2008 Taylor and Francis. Reproduced with kind permission.
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Table 1. Materials inventory for four tennis racquets; model no. 1
| || ||Mass (g)|
|Part Name||Material||RAD LAQ 1A||RAD TT 1B||10 LAQ 2A||10 TT 2B|
|nylon parts||PA 6||23||23||23||23|
|frame rubber||nitrile rubber||1.8||1.8||1.8||1.8|
|neck foam||PUR hard||6||6||6||6|
|GF lams||SMC GF50||64.6||64.6||7.8||7.8|
|CF lams||SMC CF50||148.3||148.3||178.5||178.5|
|attach tape||PVC soft||1||1||1||1|
|TT finish||PA 6||N/A||16||N/A||16|
|pack plastic||PET bottle grade||21.8||21.8||21.8||21.8|
There are five main areas where the racquets differ in material weights. The bumpers, for example, are a plastic component used to protect the frame and attach the strings. The lead alloy tape is used as additional weight in various places around the frame. It is acknowledged that this tape would require an adhesive, as with many other components of the racquet. Because the adhesive mass is negligibly small, it is expected to contribute very little to the overall environmental impact of the racquet. The two materials that contribute significantly to the overall difference in racquet weight are the CF and glass fiber sheet molding compound (SMC) used in the frame. The final material that exhibits differences depending on design is the method B finish. A particular polyamide is used only in method B to provide a better, more resilient finish to the frame décor. The environmental impact of materials used and the waste by-products of the processes have been calculated in detail in this study.
The impact assessment stage involves technical, quantitative, and qualitative efforts to determine the effects or impacts of the inventory, such as what type of damage the use of resources or output of emissions has on the environment. The main purpose of this stage is to allow a comparison of processes, emissions, and other waste on the same scale, thus determining an overall environmental impact of the product. The principal aim here is to provide a quantitative indicator of environmental impact that can be used for a relative comparison between different racquet designs. Figure 2 shows a comparison of the environmental impact determined for the four tennis racquets considered in this study. Racquet 1B is clearly the worst in terms of its environmental impact, followed by the other model 1 constructed by method A, and then the two model 2s in the same order.
Figure 2. Comparison of environmental impacts of the four composite tennis racquets of Table 1 (1A, 1B, 2A, 2B). EI-99 mPt, Eco Indicator 99 life cycle assessment in millipoint. Reprinted from Subic and Paterson 20. © 2008 Taylor and Francis. Reproduced with kind permission.
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Figure 3 shows how the various components contribute to the overall environmental impact of composite tennis racquets. The frame has the largest contribution to each racquet's overall environmental impact. The remaining components (end-cap, bumpers, handle) of the actual racquets contribute little, with the separate components, such as grip, strings, and packaging contributing slightly more. To put the impact in some perspective, the work of Goedkoop and Spriensma 17 should be considered. Simpson states that 1 EI-99 Pt is approximately equal to 1/1000th of the average European citizen's yearly environmental load, which equates to 114.2 mPts/h. Thus, the racquets analyzed can be equated with the average environmental load of a European citizen over a period of 3 h.
Figure 3. Environmental impact breakdown across racquets components. EI-99 mPt, Eco Indicator 99 life cycle assessment. Reprinted from , r 2008 Taylor and Francis. Reproduced by kind permission.
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The two B models include additional materials as part of the construction process to provide a better finish, which contributes to the higher environmental impact of the frames than the model A counterparts, but only by approximately 20 mPts. This is clearly not the largest contribution to the frames' environmental impact, as seen in Figure 4, which shows the environmental impact for the parts that make up the frame, with materials and secondary processes included.
Figure 4. Environmental impact breakdown for racquet frames. Anodiz, anodized parts; CF, carbon fibers; GF, glass fibers; MLD, molded; SMC, sheet molding compound; TT dec form, TT finishing process for forming; TT dec mat, TT finishing process for material. Reprinted from Subic and Paterson 20. © 2008 Taylor and Francis. Reproduced with kind permission.
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The study shows that the most significant material for all racquets is the CF SMC. The second-highest contributors to the frames' environmental impact are lead alloy, used for additional weight in model 1 racquets, and nylon, used in the blow-molding process of all racquets. The nylon material, plus the molding process, equals 26 mPt, and in model 1, where 37 g of lead alloy is present, the lead material, plus the rolling process, equals 31 mPt. Both of these materials with their respective secondary processes seem to be important.
The racquet frame represents the most important component with respect to the environmental impact. The strings, packaging, and the grips are also important. Although these components contribute much less to the overall environmental impact during the racquet life cycle, they have the important property of easy disposal because they are easily detached from the racquet by the user. This means that compared with the racquet frame, these components are easily separated and potentially recycled, which has the potential to improve the environmental design of the racquets. Design for end of life incorporates these types of objectives. There are already environmentally-friendly initiatives in the design of strings, and particularly packaging plastics. For example, Gosen's Bio-gut Multi-oil 16 biodegradable tennis strings, made partly from corn starch, are an environmentally-friendly option that would reduce the environmental impact considerably. Chlorine-free polythene packaging is suitable for recycling, as is cardboard and paper, both of which would improve the environmental design of the product system.
The frame is the most complicated of the components and not easily recycled. This means that the most common form of racquet disposal is most probably through municipal waste at present. More work is required to identify and evaluate the various end-of-life strategies for a tennis racquet, which should enable the feasibility of frame recycling to be considered. Specifically, the recycling chain would have to be analyzed, and specialist composite recycling plants would need to be involved, which is difficult because there are only few in existence. Ideally, this could also lead to improvements in the recyclability of the frame. Recycling of fiber-reinforced composites uses solvents to dissolve the resin matrix. Anastas and Lankey 16 notes that it might be possible to develop and use less chemically-hazardous solvents in conjunction with polymer matrices. The sustainability issues associated with the use of composites in sports equipment will be discussed in greater detail in the following section.