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issue: April 2006 APPLIANCE Magazine

Engineering - Energy Consumption
Assessment of the Environmental Impact of Household Appliances


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by Reinhard Otto, Arno Ruminy and Herbert Mrotzek, BSH Bosch und Siemens Hausgeräte GmbH

The following reveals the results of a life-cycle assessment (LCA) on dishwashers, washing machines, dryers, and refrigerators. The different factors responsible for the environmental impact are discussed.

Figure 1. Development of Energy and Water Consumption of BSH Appliances

Over the years, appliance manufacturers have been successful in saving energy and the conservation of resources. As an example, Figure 1 illustrates the savings in energy and water consumption of products manufactured by BSH Bosch und Siemens Hausgeräte GmbH. For refrigerators, energy consumption decreased by more than 70 percent. For dishwashers and washing machines, the savings in energy consumption exceed 30 percent. The water consumption of front-loader washing machines has been reduced from 30 L/kg in 1970 to 13.6 L/kg in 1990 to 7.2 L/kg today.

The new European Eco-Design Framework-Directive (2005/32/EC) will require an assessment of all significant environmental aspects of energy-using products. To identify the significance, it is necessary to appraise the entire life cycle of the product. The life-cycle observation presented here provides a means of identifying and measuring significant environmental aspects. By looking at the complete life cycle, the best trade-offs between different environmental impacts caused by production, the use phase, and recycling can be estimated.

Table 1. Specification of Assessed Products

Methodology

The main parameters that were taken into account include primary energy, material depletion, water consumption, and global warming potential (GWP). Eco-indicators beyond this scope, such as ozone depletion potential (ODP) or heavy metals regulation schemes, are already in existence. Recent studies demonstrated that these impact parameters were not relevant for the products under assessment [1]. According to the Montreal Protocol and the European Regulation (2037/2000/EC), ozone-depleting substances are banned in appliance products. In compliance with the European RoHS legislation (Directive 2005/95/EC), a phase-out of certain heavy metals in the electronics will be achieved by July 1, 2006.

The assessment included a broad range of the most widely used large appliances, including dishwashers, washers, dryers, and refrigerators. Cooking units with their multifaceted technology and wide scope of consumer behavior are not considered in this study. The appliances chosen for the assessment are those typically found in the European market and belong to a segment with high sales figures. Table 1 summarizes the specification of the selected products.

The full cradle to grave life cycle was covered (see Figure 2). In the production period, the bill of materials, transport of materials and consumption of resources by BSH and suppliers were evaluated. The material assessment included 98 percent of the total mass of the appliances. The second phase is transport to the customer, covering the mode of transport, distance and load as its input parameters. Throughout a period of 10 to 20 years of usage by the customer, electrical energy, water and chemicals are consumed. After that, the appliances become waste. They are collected from the households and treated. The treatment process separates the waste from appliances into different material flows for reuse, recycling, energy recovery, or disposal.

The first and most time-consuming step in an LCA is the compilation of the bill of materials. Thus, this aspect is given much attention. For the assessment of refrigerators and dishwashers, appliances were dismantled and weighed, yielding a list of components with the weights of all parts, a material description and composition details. For dryers and washing machines, a different approach was adopted. The products were only present as prototypes, so the bill of materials had to be listed from a computer-aided design (CAD) model. The latter approach appears to be slightly less accurate; however, it is a less time-consuming method that can be realized in the development state.

For each material, the environmental parameters per kg were recorded in a list. These “eco-profiles” were provided by Life Cycle Simulation GmbH and were based on commercially available life-cycle databases and their calculations.

Figure 2. Input and Boundaries of LCA Life-Cycle Phases

Results

Several scenarios with different intensities of use were investigated. For all appliances evaluated, the use phase dominated the life-cycle impact, with a proportion of more than 90 percent. Production represented less than 8 percent of the overall environmental burden. Logistics (i.e., transport from appliance producer to customer) and recycling are not displayed in Figure 3 because they amounted to less than 1 percent. For the use phases, a lifetime of 15 years was assumed. The number of cycles per year was estimated at 300 for dishwashers, 260 for washing machines and 200 for dryers.

The energy demand for production is between 4,300 MJ and 6,100 MJ for the different appliances. Plastics and metals are the main materials of the products. Figure 4 shows the influence of production factors on the chosen set of parameters.

The values are calculated for a washing machine manufactured in Germany. The parameters of fossil and renewable energy are based on a German energy mix. Non-renewable energy resources are fossil fuels such as coal, gas or oil. Non-renewable material resources are metal ores and mining residue. “Water” incorporates cooling water for energy generation and process water. GWP is the combined global warming potential from the emission of carbon dioxide and volatile organic compounds (VOC) into the atmosphere. Take a washing machine as an example, where metals contribute almost 50 percent of the total impact. The impact of materials used in total adds up to 80 percent. The production processes at BSH and supplier factories require approximately 20 percent of the resources.

For the dishwasher life cycle, the assessment showed the dominance of the use phase with 95 percent of the total environmental burden. A surprising result of the study was the ecological effect of 1 kg of cotton fleece used for noise insulation in dishwashers. Contrary to the common belief that natural fabrics are environmentally friendly, the water consumption involved in cotton irrigation (12,000 L/kg cotton) dominates water usage in the production process.

In addition to the dishwasher, a washing machine was assessed. Again, the use phase dominates the overall life-cycle impact; however, due to complex design, more resources are necessary for production than for any other appliance.

The other extreme is the dryer. In this case, 97 percent of total primary energy is consumed during the use phase. In a scenario with 200 drying cycles per year, the dryer needs 180 GJ of primary energy over a period of 15 years.

Of all the appliances considered, refrigerators demonstrate the lowest lifetime energy consumption. This is a surprising result, which demonstrates the success of environmental friendly product design. (The tremendous savings in energy consumption over the last decade are evident in Figure 1.) Problematic refrigerants and blowing agents such as chlorofluorocarbons (CFCs) could be replaced by non ozone-depleting substances, and in this regard, the refrigerator is a model appliance, demonstrating the ecological design of modern white goods. Intelligent features such as auto-defrost and active warning systems combine environment-friendly technology with user convenience.

Another interesting result concerns the water consumption of washing machines and dishwashers. In Figure 5, the water used in the washing process and the water for energy supply are compared. Obviously, cooling water for energy supply is of the same magnitude as the process water for washing. In dishwashers, the amount needed for the supply of electrical energy is more than twice the volume of process water. Of course, these values should be compared with caution, since cooling water for energy supply is usually taken from surface water, while households use specially treated drinking water.

Figure 3. Primary Energy Consumption in Main Life-Cycle Phases

Discussion

Substitution of Materials in Production
Figure 6 shows the primary energy demand per kg for typical materials. Major fractions of the energy used are consumed in the production of aluminum and certain die-casting plastics. Looking at the energy need for aluminum and polyamide production, it might be expected that potential existed for minimizing cumulated life-cycle energy needs by substituting these materials. However, the aluminum content of a dishwasher, for example, is less than 1 percent. Die-casting plastic parts consume more energy in production, but save energy in the use phase. The reason for this is better forming technology for plastics compared to the alternative of stainless-steel sheets. An LCA conducted by BASF, Basell and BSH showed that the savings more than compensate for the energy investments in the production phase. [2]

Energy consumption for most of the materials is between 50 MJ/kg and 100 MJ/kg. That means, for example, that if 1 kg polypropylene was replaced by stainless steel, the savings in primary energy would be 25 MJ, a negligible figure compared to the data in Figure 3. Some basic materials such as sand and rock salt need only a minimum of energy, but of course, cannot be used for supporting parts. Cotton is a special case in that it shows the limits of pure energy assessment, because here, the irrigation water is the major environmental factor.

In summary, the use of alternative materials should be considered from the technological perspective to minimize resource allocation during the use phase. The potential savings from material substitution as such are secondary.

Energy Consumption
Energy supply is fundamental for the environmental impact of energy-using products such as home appliances. For this reason, the life-cycle impact of a refrigerator used in different European countries was calculated (see Figure 7). Germany, whose energy supply originates mainly from coal and nuclear power plants, is compared to France (mostly nuclear power) and Sweden (hydro and nuclear power). The measured impact parameters are fossil and renewable primary energy, non-renewable energy and material resources, cooling water, and GWP. To take one example, the refrigerator operated in France or Sweden causes only 20 percent or less of the global warming produced by its precise counterpart in Germany.

Water Consumption
Washing machines and dishwashers naturally use water for the cleaning process. The process water in dishwashers was reduced by 80 percent from 60 L in 1965 to 14 L in 2005. In washing machines, this process water was reduced by 70 percent throughout the last 30 years. With today’s washing process, no major decrease seems possible in the future. The reasons are the physical necessities of washing.

Experience shows that consumers will not tolerate poor washing results related to minimum water use. However, an additional effect is that users tend to use too much detergent, leading to a higher demand for water to rinse the fabric. This fact is considered in the development of new intelligent and efficient prototypes. In state-of-the-art washing machines, sensors monitor the washing process to keep the use of energy, water and detergent to a minimum. The electronics control the washing process to achieve the best cleaning results with the lowest water and energy consumption. A display can provide the user with information if the maximum weight is reached and can indicate how much detergent should be added.

Consumer Behavior and General Conditions
Consumer habits play an increasing role in the use of highly optimized products. Appropriate handling has benefits for the environment as well as the household budget. Events like the “Aktionstag Nachhaltiges Waschen,” sponsored by the German Ministry of the Environment, promote sustainable use and illustrate the benefits of state-of-the-art eco-features. For appliances older than 10 years, an economical and ecological gain can be realized by replacement with a new product [3-5]. Looking at the installed base of household appliances, early replacement may contribute significantly to the protection of resources. For dishwashers, the promotion of machine dishwashing instead of washing dishes by hand would lead to significant savings in energy and water consumption [6].

While usage may be influenced by educational advertising aimed at the general public, some technical parameters are connected with the installation site. Factors such as hard water may lead to 50 percent higher detergent consumption. In small kitchens, refrigerators are sometimes placed next to the oven or dishwasher, leading to higher energy consumption for cooling purposes. Some appliances, such as dryers or dishwashers, may be operated overnight, using low-rate electricity, to save primary energy. Primary energy use can further be decreased if a warm water tub for the washing machine is available.

Conclusion

Figure 4. Distribution of Parameters Relating to Factors of Washing Machine Production

The use phase dominates the overall life-cycle impact of large appliances with a proportion of more than 90 percent. Compared to 1990, contemporary appliances consume between 30 percent (washing) and 70 percent (refrigeration) less electric energy. The reduction in the consumption figures has a direct influence on the life-cycle impact. The potential for further reduction through design options seems limited given current technology. Due to the importance of the use phase, further efforts for improvements should be investigated.

The education of consumers, the promotion of existing environmentally friendly features and replacement of old, non-energy-efficient appliances provide plenty of potential for reducing the overall environmental impact. State-of-the-art appliances use sensor technology for process control and user guidance to achieve optimized consumption of energy and resources.

Furthermore, the way electric energy is generated in different regions has a large influence on the life cycle’s environmental impact of energy-using products. This has to be kept in mind when using LCA as a method for determining the environmental impact of energy-using products.

References
[1] Van Holsteijn en Kemna: European Commission Eco-design Methodology Project—MEEUP Product Cases Report, www.eupproject.org.
[2] G. Krotkine: “Forging Global Partnerships with Key Accounts,” Int. Appl. Manufacturing 2002.
[3] I. Ruedenauer, et al.: “Eco-Efficiency Analysis of Washing Machines,” Oeko-Institut e.V.; Freiburg 2004.
[4] I. Ruedenauer, C.-O. Gensch: “Environmental and Economic Evaluation of the Accelerated Replacement of Domestic Appliances,” Oeko-Institut e.V, Freiburg 2005.
[5] Y.A. Horie: “Life Cycle Optimization of Household Refrigerator-Freezer Replacement,” Center for Sustainable
Systems, Univ. of Michigan Report No. CSS04-13.
[6] R. Stamminger: “Is a Machine More Efficient than the Hand?”, Home Energy May/June 2004.

About the Authors
Reinhard Otto joined BSH Bosch und Siemens Hausgeräte GmbH in 2005. He is currently a management trainee in Engineering. Otto studied physics at Humboldt Universitaet zu Berlin and at the University of Toronto.

Dr. Herbert Mrotzek is director of Corporate Department for Environmental Protection Health and Safety at BSH Bosch and Siemens Hausgeräte GmbH. He has a Ph.D. in Chemistry from the University of Hamburg and completed post-doctorate studies at the University of California, U.S.

Dr. Arno Ruminy is environmental protection manager at BSH Bosch and Siemens Hausgeräte GmbH. Since graduating with a Doctor rerum naturae (Dr. rer. nat.) in Chemistry from the Technical University in Munich, Germany. He has worked in the field of industrial environmental protection for 20 years.

 

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