Energy is consumed at every stage of the cycle of water supply, treatment, use and disposal. The intensity of energy consumption (kW h/m 3 ) depends upon the specific technologies applied at each stage of the water cycle. For some technologies, the intensity may be relatively low, whereas the intensity of other technologies is substantially greater. This report surveys the available literature on energy intensity for water use in the municipal and agricultural sectors and separates the process into several stages. Water supply, water treatment, residential end use, wastewater treatment, and agriculture end use are considered. Representative values of the energy consumed per unit water are given for a broad range of processes. Water extraction and pumping from ground and surface sources is considered. The energy intensity of treatment required for different types of water source is found to vary widely between the extremes of relatively fresh surface waters, which use energy mainly in pumping, and seawater, which requires desalination. Energy usage for different methods of irrigation including pressurized as well as surface irrigation is studied. The energy intensity of residential end use is very high relative to other parts of the water supply cycle. Processes such as heating water, washing clothes and dishes, and cooking are briefly studied within the water end-use stage. Hot water usage is responsible for making end use the most energy intensive stage of the water cycle. Hot water use in different buildings is briefly reviewed. Wastewater treated with various processes is considered, and the energy intensity is found to be highest when advanced wastewater treatment methods are applied. Energy consumption in the agricultural sector, which is principally related to irrigation pumping, is generally of lower energy intensity than for the municipal treatment or end use.

Energy requirements for water production, treatment, end use, reclamation, and disposal

The purpose of this article is to discuss the role of social influence regarding sustainability in households. Several research studies show that individual and family recycling and e-consumption behaviours are more affected by people that the individual/family know than by outside influences such as government or advertising campaigns. Social influence theory, although prevalent in such diverse fields as communication, marketing, sociology including medical and rural sociology, management information science and education, has not been used as extensively in human sciences, home economics and human ecology, specifically in applications to household green behaviour. The origins of social influence are found in the ground-breaking work in opinion leadership by Lazarsfeld in sociology and in E.M. Rogers's diffusion of innovation theory. The present article makes a case for using social influence theory as a framework for future studies and academic work in environmentalism, and for those trying to increase or promote pro-environmental behaviour at the individual, family or household level.

Social influence and sustainability in households

Over the years, appliance manufacturers have been successful in developing dishwashers that enable consumers to save time, energy and water very conveniently. Within the last 20 years the savings in energy consumption exceed 30%, and the average water consumption per cycle has been more than halved. As a result, it is very hard for the majority of people to compete with the efficiency of a dishwasher when dishes are done by hand. However, consumer habits (e.g. regarding the use of the dishwasher load capacity, programme choice and particularly the additional pretreatment of dishes with water) are influencing the overall efficiency of the dishwashing process and resource use. Still, detailed information on consumer behaviour in everyday life concerning these issues is rare.

In order to improve the understanding of dishwashing habits and to fill the lack of information about dishwashing on the household level, an in-house consumer survey in four European countries (Germany, Italy, Sweden and the UK) was conducted between 2007 and 2008. Two hundred households with and without dishwasher were interviewed and comprehensively observed. For a period of 2 weeks, participants recorded every dishwashing process with the help of a dishwashing diary and pictures they took of their loaded dishwashers. In addition, an in-depth observation took place in 82 households where measurements and webcam observations were recorded at the kitchen sink. Actual resource consumption data for manual dishwashing and the pretreatment for the dishwasher were obtained.

The present paper reports on findings of this investigation and concentrates on consumer habits related to the use of the dishwasher. In general, the study showed that the households with dishwasher used on average 50% less water and 28% less energy per cleaned item compared with households not owning a dishwasher. Yet, there were still consumer habits, which indicate that a higher degree of sustainable dishwashing is achievable. The researchers found that in 20% of the dishwasher cycles, baskets were only slightly filled and consumers were likely to use higher amounts of energy than stated on the energy label because they have chosen mostly in favour of high cleaning temperatures (52% used 65°C and higher). Particularly in Italy and Sweden intensive pretreatment habits have been observed, resulting in an average additional water use of 11–20 L per dishwasher cycle.

Usage of dishwashers: observation of consumer habits in the domestic environment

Understanding usage patterns of electric kettle and energy saving potential

Plastic (PET) vs bioplastic (PLA) or refillable aluminium bottles - What is the most sustainable choice for drinking water? A life-cycle (LCA) analysis.

This study presents an overview of the washing up behaviour of consumers in the UK. Peoples' individual attitudes were observed as were the amount of water and energy used, the time taken and the cleaning performance. Additionally, manual dishwashing was compared with the use of automatic dishwashers. Participants were recruited to represent all geographic regions of the UK as well as forming a representative cross-section of the population. Each of the 150 participants washed a full load of soiled tableware based on the standard EN 50242 ‘Electric Dishwashers for Household Use – Methods for Measuring the Performance’. For comparison, the best selling dishwasher in the UK in 2007 was tested under the same conditions as those in the consumer trial. Additionally, consumers who owned a full-size dishwasher were asked to load it to the point when they decided that the dishwasher was full.

The study shows that these consumers, on average, used 49 l of water and 1.7 kWh of energy, whereas the dishwasher used 13 l of water and 1.3 kWh of energy on average for the same amount of dishes under the conditions tested. Statistical analysis showed that these differences are significant. The dishes washed by hand were found to be slightly less clean than dishes washed in a dishwasher. For washing a full dishwasher load by hand, the participants needed, on average, 60 min, while they only took 9 min on average to load and unload the same amount of dishes in a dishwasher. The average participants were able to fill almost the full load into the dishwasher (96% of the items as used in a test following EN 50242).

Manual dishwashing habits: an empirical analysis of UK consumers

This laboratory study presents an overview of the global manual dishwashing behaviour. The focus of the investigation was to analyse individual attitudes towards manual dishwashing and to determine the amount of water and energy used, as well as the cleaning performance achieved. Additionally, manual dishwashing was compared with automatic dishwashers. Two hundred eighty-nine participants from 29 countries took part in this investigation. Each consumer had to wash up a complete soiled dishwasher load consisting of 12 place settings based on both international and local performance test standards for automatic dishwashers. Country-specific aspects such as tableware, food residues or washing up equipment were considered. In order to analyse individual consumer's behaviour, each participant was recorded on video and had to fill out a questionnaire. The resource consumption for washing up dishes was measured during the tests. At the end of each trial, the cleaning result of the washed up tableware was assessed. To compare manual with automatic dishwashing, country-specific dishwasher models were tested in parallel with three different programmes with the same soiled dish samples. The study provides comprehensive data about the average resource consumption for manual dishwashing for a specific load for each country. The average water consumption per country reached 34.7 l up to 160.1 l, and individual values ranged from 18.3 l to 472.8 l. The lowest used average heat quantity accounted for 0.9 kWh per country, while the highest amount was five times higher. The cleaning results did not differ much between the countries: the average test results were between 2.2 and 2.8 on a scale between 0 and 5. The automatic dishwasher tests showed differences between both the machines and the programmes. All machines achieved lower water consumption values than the average consumers with about 9.6 l to 26.7 l of water on average. The energy consumption ranged from 0.5 kWh on average up to 2.0 kWh. The cleaning results of the dishwasher tests varied highly ranging from 1.1 in a quick programme to 4.4 in an intensive programme. The study comes to the conclusion that automatic dishwashing is more superior as compared with manual dishwashing in terms of performance and resource consumption under the tested conditions. Furthermore, it points out that washing up dishes under running tap water is the most water-consuming manual dishwashing method of all investigated ones. A high lack of knowledge about the benefits of automatic dishwashing compared with manual dishwashing can still be identified among consumers.

Comparative analysis of global consumer behaviour in the context of different manual dishwashing methods

Global studies have observed many techniques of manual dishwashing causing different levels of performance and using quite different amounts of water, energy, time and detergent. It is not known, however, if these techniques are pre-assigned to a person and persist when dishes are washed under different conditions, or are adapted to the specific type of dish-cleaning process. Here we explored this question in a study with 40 test subjects selected equally from Germany and East European countries by asking them to wash two place settings of dishes with different amounts of soil three times. The results showed that the test subjects did not adapt their washing-up behaviour to the amount of soil. In general, no significant differences were found in the water, energy and detergent consumption for all test subjects. Only the time used by the German test subjects to wash the fully soiled dishes was significantly longer compared with the dishes with only a quarter the quantity of soil, and no significant difference was observed for all other parts. The only significant difference found between the level of soiling of the dishes was the cleaning result achieved: The less soiled the dishes were, the better the final cleaning result was, and this related to all test subjects. This lends support to the proposition that the consumers did not adapt their washing-up behaviour to the specific circumstances of the dishwashing job to be done but retained some pre-assigned behaviour.

Petra Berkholz

Papers

Manual dishwashing habits: an empirical analysis of UK consumers

Comparative analysis of global consumer behaviour in the context of different manual dishwashing methods

Manual dishwashing process – a pre‐assigned behaviour?