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green design in the automobile industry Leigh Holloway Leigh Holloway is a Lecturer in Environmental Engineering with the School of Engineering at Sheffield Hallam University. He graduated in Mechanical Engineering in 1992 and is currently in the closing stages of a PhD in Design for the Environment. He has published numerous articles in this field and is currently working in the areas of integrating environmental concerns into the design process and the use of LCA within design. David Walker is a Lecturer in the Faculty of Technology at the Open University and founding editor of co-design. The key to effective clean design is the identification of the main areas of environmental impact and the use of appropriate design strategies. This paper looks at some current practices within the automobile industry and attempts to analyse whether the environmental strategies there are reaping the greatest environmental rewards. The automobile industry has been the target of much recent environmental legislation, such as regulations for tail-pipe emissions, waste minimisation, and future Producer Responsibility obligations. Therefore under sustained pressure, the industry has begun to reduce the environmental impact of their operations. Yet automobiles have very long and complicated life-cycles which require the adoption of many diverse design approaches during development. Manufacturers are dealing with environmental problems by the adoption of strategies such as Design for Disassembly, Design for Recycling and the use of engine technologies which improve fuel consumption, heat efficiency and reduce emissions. For example, many car manufacturers use recycled plastic body parts to make components requiring lesser mechanical and aesthetic properties. Thus bumpers can be converted to wheel arch liners, which help prevent body corrosion. Similarly, high grade but used tyres are converted to low grade crash barriers. (see figure 01) The retrievals game In fact the automobile industry in general has a very good record in component and materials retrieval. The current practices of car breaking are already quite efficient, and profitable, with well established practices of recycling metals. A derelict car is sold to a car breaker who takes out the re-useable parts such as tyres, batteries, starter motors, and alternators. The car breaker would hold a stock of major items such as gearboxes and engines for resale. The cars would be held at the merchant for about a month in order to sell individual items such as doors, wings, boot lids. After that time the breaker would remove the inoperable engines (normally of cast iron ) for direct recycling, and the remaining shell, including the upholstery and major plastic assemblies, is compressed. The small scrap dealer is likely to sell on the pressed cars to a more sophisticated operator where the compressed sandwich is pressed further into a dense cube and then shredded in a fragmentiser. Metallic materials are separated by various means - magnets, air and water. The value of the separated steel to the smelter is between £30-£40 per tonne. A medium sized car weighs about 1 tonne, so this compares well to the initial scrap value of the car of £15 - £25 (1992 figures). About 80 per cent by weight of the total materials of the car are retrieved by these crude but effective processes. The proportion for metals retrieval is higher still. However, as the proportion of plastic materials in cars increases, this presents a new range of problems. Retrieving lightweight materials by labour intensive methods is likely to be uneconomic for the car breakers. As the amount of plastics used in car construction grows the profitability of disassembly declines. Currently, plastics account for about 15 per cent by weight of modern cars. Some experiments have been made into plastic recycling. In 1989 at the German Automotive Technology Research Association, a Volkswagen Passat was disassembled in just over 74 minutes. Fifty one plastic components weighing 91 kilograms were retrieved. It took another 47 minutes to classify and sort the plastics into their main groups. Almost half the plastic components were thermoplastics. 1 The following conclusions came from this study and others that followed it:
There are clear eco-benefits in making cars lighter, principally in improved fuel consumption. Yet with current designs, automotive technology and infrastructure, it is much harder to make money from retrieving plastics then retrieving metals. The right priorities? This well established tradition of recycling, although desirable, leaves important questions hanging in the air. Should manufacturers be addressing other areas? What should shape the environmental priorities? Clearly, if one domain of a product creates a disproportionate amount of environmental damage, then it would make sense to target this area first! 2 . It has been shown in industry sectors such as transport, that energy requirement is a good indicator of overall environmental impact. 3 Therefore, looking at the overall energy needs of a vehicle's life-cycle provides a clue to focused design effort 4 . Figure 03 shows that over 70 per cent of a vehicles energy requirement is in use through the burning of hydrocarbon based fuel (about 18,000 litres in an average lifetime). Other studies have suggested that the figure for in-use energy may well be over 80 per cent 5. It is the use stage in the life-cycle of a vehicle that manufacturers should be addressing with the greatest urgency. This becomes particularly evident when one considers that there are over 27 million vehicles on Britain's roads, a figure expected to reach 40 million by 2020. Current activities such as recycling materials and disassembly studies can only reduce the total energy requirement of a vehicle by very small amounts. Indeed it has been suggested that even if a vehicle were totally recycled the resultant net energy return would only be 5 per cent of that used in total 6. It seems that the main strategies that car manufacturers should be adopting are those of improving engine efficiency and reducing weight. In automobile design the lightest always wins out 7. Using materials which consume less energy in manufacture produce few environmental gains unless they save energy over the whole life-cycle. This introduces a number of paradoxes in automotive design which makes reducing environmental impact a very complex exercise. For example, the use of catalytic converters reduces engine emissions but also increases fuel consumption. Most new cars use side impact protection bars, seat belt tensioners, safety cages and so on, all of which have unarguable benefits for the occupants of the vehicle, but also increase weight which again raises fuel consumption. Equally, consumers now expect higher levels of trim and equipment, such as electric windows; central locking; improved sound proofing and power steering. These extras again all add weight to the car. This in turn makes the fuel consumption increase and so makes it even more difficult for the engine designers to achieve gains in efficiency (see table 1) 8. For example, in the 10 years from 1982 to 1992 the weight of a standard BMW saloon increased slightly , while giving only marginal increases in performance and fuel consumption. An alternative approach is taken in the new Audi series - A4, A6 and A8 - which make extensive use of aluminium in space frame chassis, bodies and mechanical parts. Using aluminium for high mass systems like bodies and engines allows further weight reduction in related systems, in the transmission, steering , suspension, brakes wheels, tyres and shock absorbers. 'This cumulative weight saving reduces emissions by lowering fuel requirements' 9 In such an aluminium bodied car the energy invested in the materials is nearly 5 times that of the steel equivalent. However when the life cycle energy costs are calculated, every kilogram reduction in weight will correspond to a fuel saving worth 290 megajoules over the life of the vehicle. More than that nearly 65 per cent of the energy held within the material can be recovered through recycling, using aluminium seems a good choice in environmental terms. There seems to be a good case for continuing and improving the metals retrieval infrastructure. Conclusions There are some fundamental dilemmas raised by ecological design of automobiles. At one level arising from design manufacture rules - whether assembly, disassembly or dat-assembly. Such rules need to be prioritised and intelligently applied. Beyond that, such a priority ranking, and assessment of the trade-offs between various rules, can only be made by criteria which come from the wider context of environmental management, and from higher social goals - such as reduction in energy use, in pollution, coupled with improvements in safety, recycling and waste reduction. One expert puts it this way: 'Without a guiding strategy, there is no way to tell what suggestions for improvement really support long-range goals. Some product design techniques depend too much on rules, including rule-based systems stemming from expert systems. These are no substitutes for experienced people.' 10 These initiatives are very important when viewed in a wider perspective. We generate about 140 million tonnes of waste in Britain each year. Our waste industry is already worth £5 billion per year. 11 All industries, not just the car industry, are being compelled to rethink the supply chain, in order to minimise resource consumption, energy use, and production of wastes. 12 It is clear that energy use of automobiles has by far the greatest impact. Moreover there has developed, in recent years, external pressure for the automotive industry to clean-up its operations. It may be led by legislation or consumer demand, but designers should not loose sight of the underlying reason - reducing environmental impact. It is easy to pander to the expectations of the marketing department and use 'green' design strategies in product development, but there is little point in cleaning one small part of the process if the whole is inherently environmentally damaging. In automobile design, as in many other areas, some of the strategies manufacturers promote as 'eco friendly' may not be as effective in reducing overall environmental life-cycle damage as they first appear. The important point for designers is to:
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