Volume 53, Issue 5

A literature review was executed to collect data on the resource consumption connected to domestic laundering processes. Data from literature on water and energy consumption were collected. The study focussed on Europe, as for Europe enough date could be collected for a thorough analysis. However, the limited data available for Japan and the USA were also included and discussed.

Washing laundry is one of the most widespread housework tasks in the world. Washing machines, performing this task already in many private households, are now responsible for about 2% of the global electricity consumption. Worldwide, more than 840 million domestic washing machines are in use, with an annual consumption exceeding 92 TWh of electricity and 19 billion m 3 of water as well as causing emissions of more than 62 megatons CO 2 eq. In North America, Western Europe and Pacific OECD countries, most households own a washing machine. In these economies standard and label policy programs already addressed and reduced the specific electricity and water consumption of washing machines per wash cycle. Nevertheless, in other world regions, the level of ownership for washing machines is still well below saturation and high growth rates can be observed in developing and newly industrialising countries. As washing machines use water, electricity, chemical substances and process time as resources, also the absolute worldwide resource consumption and emissions of these appliances are still on the rise. Due to different washing habits and practices as well as types of washing machines in different world regions, the specific consumption of resources for doing the laundry is varying to a large extent. On that score, this paper presents an overview of the current situation worldwide as well as respective saving potentials. Bottom-up scenario calculations, carried out for the 11 world regions according to the Intergovernmental Panel on Climate Change classification, show that large energy, water and greenhouse gas savings are possible with the ‘Best Available Technologies’ today, and even higher savings will be possible with next generation ‘Best Not yet Available Technologies’. According to model results, these savings are usually also very cost-effective. Following these calculations, it is highly advisable for policymakers world-wide to pay even more attention to improvement options in order to implement ambitious and product-specific policy packages, including minimum performance standards and labelling schemes.

A study was conducted to understand the impact of technological changes on household washing machines and how consumer behavior has adapted to such changes with respect to purchase drivers and laundry practices. To assess this aspect, from November 2014 until June 2015, 600 users were interviewed and from this group a sample was selected for a closer look on purchase decision and washing practices. Data were obtained through interviews and field visits with consumers in 3 different cities in Mexico. Results showed that consumer have changed their habits and practices through the years due to an improved income, increased women's participation in workforce, higher washing machine penetration and lowered prices/offers to acquire the appliance. Obtained results provide on the one hand an overview of how consumers evolve in case of purchasing a washing machine as well as the way of using the machine and on the other hand how their behavior was still influenced by the elderly.

Since the washing performance of household washing machines must comply with certain limit values, like the ecodesign requirements in Europe, the method of washing performance evaluation is crucial. Today, the washing performance is defined as an overall washing performance in IEC 60456:2010, constituting an calculation of the average sum of reflectance values of five different stain monitors. As a result, the different washing characteristics of each individual stain are totally neglected. This study investigates how the washing cycle affects the individual stains, when washing temperature, washing time and load size are varied systematically. The results show individual stains contribute differently to the overall washing performance. For a proper assessment of the washing performance, the individual stains’ contributions to the overall washing performance are required to be considered. A supplement of temperature sensitive stain monitors is suggested. E.g., as tea has a crucial contribution at higher temperature, this stain should have a higher influence in washing performance assessment when good bleaching or hygiene performance is requested.

Washing machines should not only deliver good removal of stains, but also take care of the garments. Mechanical action produced by the washing machine has a twofold impact: It supports the removal of stains, but it also influences the structure of the textiles negatively and is, therefore, critical to textile care. Most washing machines are currently assessed by consumer organisations and political regulations, such as energy labelling, just for their washing properties. However, a long programme may provide a good washing performance, but might also damage the textiles more than a shorter programme. Test specimens assessing the mechanical impact are well known and published, for example, IEC PAS 62473:2007, however, they are rarely used. Reasons may be poor knowledge about their effectiveness in assessing the mechanical action and their reaction to different washing conditions, for example, load size, temperature and duration of the washing programme. It was the task of this study to verify this relationship and confirm that the thread removal fabric, as specified in IEC PAS 62473:2007, adds additional information to the assessment of a washing process. As a result of a wide variation of washing parameters, it could be shown that this test fabric is almost independent of the washing temperature, but shows a clear correlation with the load size and the length of the washing process. The thread removal specimens add valuable additional information concerning a relevant parameter of the washing process.

Several different approaches are commonly used to obtain information about the performance of laundry systems, e.g. washing machines. The evaluation of washing performance with soiled test fabrics is commonly done by measuring the reflectance of the washed test specimen. The absolute reflectance readings may be used if the results are only compared within a series of tests using the same batches of test materials for all runs. The inevitable uncertainty of any test results may be reduced if the results can be expressed as ratios compared to the performance of well-known or well-established reference systems tested in parallel. This approach is defined in IEC 60456:2010 and followed globally for assessing the performance of washing machines. With the current evaluation method the calculation of the overall wash performance test result cannot be adjusted to adequately reflect the characteristics of different wash programmes designed for different purposes – or different machine technology and global regions. It is therefore the task of this paper to develop an evaluation method for assessing the cleaning performance of washing machines which is scientifically sound and statistically complete and more flexible in its application to different programmes and/or regions. A new cleaning evaluation method is suggested in this paper and applied to two sets of available data. The new cleaning evaluation method shows to have a number of apparent advantages over the method currently used. As a straightforward approach the stain specific evaluation ensures full usage of generated information including reference machine and batch values to allow calibrating the test result. The full statistical evaluation gives a more complete picture and allows partial results to reflect different aspects of system performance as well as weighting factors allow adjustment to specific requirements.

This paper discusses consumers’ wool washing habits and the possibilities for improving the laundering process with the aim of reducing the total environmental impacts of clothing consumption. Wool has great potential when compared to other fibres, such as cotton, especially when the energy per day of use is compared to energy per washing cycle. Wool products can be used longer between washing cycles due to the natural soil repellence, some washing can be replaced by airing, and the wool wash programs have lower washing temperatures and shorter washing cycles. Two surveys supplemented with in-depth interviews were conducted to study consumers’ clothing maintenance habits in Norway and Sweden. Results confirm that consumers use woollen products longer between washes than similar products made from cotton. However, there is still a potential to reduce the energy consumption from wool wash further both through technical washing program development and through changes in consumer behaviour.

To further reduce energy consumption of dishwashing programmes and still obtain satisfying cleaning results, water temperatures in the programme steps are decreased and running times are prolonged. To which extent the cleaning factor duration is able to compensate for temperature has been insufficiently researched until now. This study quantifies the effects of a pre-rinse step, of the duration and water temperatures in different dishwashing programme steps on the cleaning performance and energy consumption in mathematical models. Using those models it is shown that even a (cold) pre-rinse step increases the cleaning performance and that energy consumption is reduced by 25–28% and the cleaning performance decreases, especially on heavily soiled load items and of fatty soilings on plastic surfaces, if the water temperature in the cleaning step is lowered to 30°C.

Lowering water temperatures in the cleaning step of a dishwashing program to 30°C leads to reduced energy consumption and decreased cleaning performances on persistently soiled dish- and cookware and of fatty soilings on hydrophobic surfaces. This study focusses on the question if the observed decline of the cleaning performance can be compensated for by aligning the formulation of the dishwashing detergent. A Design of experiments-method is used to quantify the effects of detergent components on the cleaning performance in mathematical models. The calculated models are used to adjust the amount of those components in a detergent formulation that increases the cleaning performance in low temperature electric household dishwashing. The modeled formulation has been verified in practical experiments.

Currently there is a lack of knowledge on how to scientifically and rapidly screen new detergent formulations. To address this, we employed the Quartz Crystal Microbalance with Dissipation technique which allows real-time acquisition of the cleaning process. Using an automated multichannel setup enabled rapid, simultaneous screening of eight formulations in regard to cleaning rate, soil swelling and soil removal. Herein, 9 commercially available dishwashing formulations are screened and ranked based on their ability to remove/swell standardized cooking grease soiled onto a silica surface. Moreover, we observed that soil swelling can be monitored via the dissipation factor. In summary, we present a real-time in-situ method for detergent formulation screening during the R&D phase of new detergents.

It is known that decreasing temperatures in laundry can have a significant impact on the hygiene efficacy of laundering. This study used suspension tests to investigate the microbicidal effects of heat, detergent and activated oxygen bleach and their contributions to laundry hygiene. The results indicate that heat at 60°C contributes significantly to the microbicidal action, while detergent only has limited effects. Activated oxygen bleach strongly enhances the microbicidal action and thus has the potential to compensate for the loss of antimicrobial efficacy due to temperature decrease. This effect varied with the test strain and the temperature, and further work is needed to determine whether it is possible to achieve a hygiene effectiveness equivalent to that at 60°C across both fungal and bacterial strains.

Enzymes and surfactants are both essential ingredients that determine the performance of modern laundry detergents. We have conducted an investigation of the interaction of surfactants and enzymes under laundry detergent application conditions in order to understand the influence of individual ingredients and to optimize detergent performance. We can show that for a given protease enzyme, individual surfactants in a constant detergent matrix have a significant impact on relevant stability and performance parameter. While certain anionic surfactants like e.g. linear alkylbenzene sulfonate show strong protease inactivation, nonionic surfactants did only show slight inactivation over time. On the other hand, proteolytic performance of protease on test stains was most driven by fatty alcohol ether sulfate. Knowledge about the impact of individual surfactants on proteases will enable the best choice of ingredients for mixed surfactant systems with optimized enzyme performance and stability.