It did not all start at the Earth summit in Rio in 1992, but the writing in Agenda 21 has been extremely influential and spurred further research on the interrelationship of human activities, lifestyles, and the environment. In chapter 4 of Agenda 21, unsustainable patterns of production and consumption particularly in industrial countries, are identified as the major causes of the continued deterioration of the global environment. Agenda 21 calls upon developed countries to take the lead by developing national policies and strategies to achieve sustainable consumption patterns (United Nations, 1992).


The developed countries have responded to the call in Agenda 21. The measures taken have focused on influencing consumption directly, by changing consumer behaviour, and indirectly, by encouraging and in some cases forcing industry (the market) to shift production towards more environmentally benign goods and services. The concept “green consumers” has emerged and is today established (Wagner, 1997). The Swedish Environmental Protection Agency has published reports titled: “To eat for a better environment” (Naturvårdsverket, 1997), “To shop for the future” (Naturvårdsverket, 1998), etc. Although these titles are primarily chosen to be catchy, they reflect what the messages to consumers have been and still are: change the consumption pattern and there are “greener” alternative types of consumption. 


Historically, efforts put into improving the natural environment have often produced good results. In many ways the environment has improved considerably in Sweden and in other industrialised countries during the last decades (Bernes and Grundsten, 1992; Jernelöv, 1996). Especially, pollution detected by human senses has been reduced. Both air and water are much cleaner, rivers previously polluted are now clean enough to swim in and the smell of car-fumes is, in Sweden, nearly gone, even from the city-centres. 


A major unresolved issue today is the probable onset of rapid global warming caused by increased levels of greenhouse gases (carbon dioxide, methane and nitrous oxide) in the atmosphere (IPCC, 2001). Whether the warming of the earth is cause by human activity; primarily combustion of fossil fuels, deforestation and agricultural practices or cause by natural fluctuations in for example solar activity is a matter of scientific debate. Indisputable the level of greenhouse gases has increased in the atmosphere.


The greenhouse gas that has received the most attention is carbon dioxide (CO2). The reason for this is that CO2 is the green house gas that according to IPCC has contributed the most to the warming of the global climate since pre-industrial times (IPCC, 2001). Another reason is that CO2 emissions have a relatively long residence time in the atmosphere in the order of a century or more (IPCC, 1995). This means that even if net emissions were to be stabilised at current levels there would still be a constant rate of increase for at least two centuries. 


The reasons why CO2 emissions continue to increase are: (1) the carbon can not be efficiently filtered or captured as can most other pollutants, (2) the global energy supply relies heavily on fossil fuels (80%) as its main energy source and, (3) while economic growth has been a prerequisite for the reduction of many types of environmental problems the correlation between CO2 emissions and economic growth is the opposite. The latter is problematic and a source of obvious conflict as the reduction of CO2 is not the only target for the international community, governments and individuals. Increasing income levels, improving the quality of the education system, care for the elderly and reducing unemployment, etc. are in many instances considered a higher priority or at least more urgent. 


There are two ways of reducing CO2 emissions. One is to reduce the consumption of energy, preferably while maintaining or even increasing utility and performance, the idea behind the Factor 4[1] and Factor 10 concepts (Weizsäcker, Lovins et al., 1997). A second is to replace fossil fuels by new types of energy sources which either have lower CO2 intensities (CO2 per energy output) than current sources or result in no emission of carbon at all, for example renewable energy sources and nuclear power. 


These methods for reducing CO2 emissions have been applied. Technological improvements have increased energy efficiencies substantially, for example, fuel-efficiency in cars has improved, light bulbs are more energy efficient, whilst still providing the same amount of light, etc. New cleaner fuels have resulted in a substantial “decarbonisation” i.e. less carbon per energy output, and ongoing research is trying to find feasible carbon sequestration techniques. In spite of all these improvements, CO2 emissions are still increasing and in many cases offsetting the improvements. 


In addition to various technical solutions, the demand side has therefore received increasing attention. Most reports dealing with the question of how to reduce emissions by policy and/or technological change argue that in addition to technological change, “changes in lifestyles and consumption patterns” are of crucial importance (Duchin, 1998; OECD, 1998; Lundgren, 1999). However in most cases it is not clear what is meant by changed lifestyles, changed consumption patterns or “the need to change peoples values and attitudes”. What is unclear is if these changes involve changes in the level of consumption and/or changes in the pattern of consumption. This distinction is vital as the level of consumption (income) is probably one of the most important determinants of energy consumption and CO2 emissions. 


Most earlier studies on the environmental impact of different lifestyles or consumption patterns at the household level have either focused on attitudes towards the environment without any data on actual impact or have used a “thematic approach” i.e. have studied “isolated” sources of emission, primarily due to lack of comprehensive data. The thematic studies indicate fairly high potentials for reducing energy consumption from, for example, the housing or transport sector, through changes in behaviour. 


Life cycle assessment (LCA) studies have been developed during the last decade allowing for analyses of the environmental impact of products throughout their life cycle i.e. throughout the entire production process up to the point of consumption. LCA studies have shown that similar products can differ substantially in terms of environmental impact including energy requirements and related CO2 emissions. Thus through behavioural changes that lead to individuals choosing products with lower environmental impact, for example, lower embodied energy requirements and CO2 emissions compared to other products, energy requirements and CO2 emissions from this type of consumption can be reduced. 


However LCA studies are only a limited systems analysis and do not cover the whole system. For instance costs (prices) are not included, nor an analysis of the household budget. By not considering costs one fails to capture second order effects related to a changed pattern of consumption. If making a green choice not only reduces energy requirements and CO2 emissions but also reduces costs, the analysis should include an analysis of what happens to the saved money. Assuming that household expenditures are not reduced then this means that the saved money will be used on other consumption, which will take back some of the initial savings in energy requirements and CO2 emissions.  If a consumer reduces car-travel and instead uses public transport, walks or cycles for short distance trips the consumer not only reduces fuel consumption but also saves money. How the household uses this saved money determines the net effect of adopting a green consumption pattern. If the saved money is spent on a holiday trip abroad, a large part of the energy savings are “taken back” resulting in a substantially smaller net saving. If the reduced consumption item has a lower energy intensity than the substitute the result is a net increase in energy consumption.


The first (to my knowledge) quantitative study on household lifestyles and CO2 emissions, including both direct and indirect energy consumption and using a systems analysis approach, was conducted in the course of the Dutch National Research Programme on Global Air Pollution and Climate Change between 1990 and 1995. Within the project a method for calculating the energy requirements for more than 350 household consumption categories was developed. As household consumption is measured in expenditures in the Netherlands (CBS) the same as in Sweden (SCB) the methodological development involved a translation of “money into energy”, expressed as energy intensities (energy per monetary unit), later extended to include CO2 emissions equally expressed as CO2 intensities (CO2 per monetary unit). 


This methodology was used to study the relationship between household expenditures and energy intensities (Vringer and Blok, 1995) and to study the potential for CO2 emission reductions by changing lifestyles and/or consumption patterns (Biesiot and Moll, 1995). Biesiot and Moll’s study approached the question of the potential to reduce CO2 emission by looking at empirical differences in energy consumption between households at similar levels of consumption and the future effects of changes in the energy intensities of goods and services given unchanged production structures and consumption patterns. This thesis builds on the basic methodology developed in the Netherlands but extends its scope by modelling the effect of changes in the pattern of consumption by simulating the effect of adopting hypothetical green consumption patterns.


The core idea of the thesis is to explore the potential for reducing energy requirements and CO2 emissions from altered consumption patterns, by implementing the energy and CO2 intensity concept into a microsimulation model that models individual household consumption while keeping total consumption constant. 


By modelling individual households the demographic and geographic constraints and possibilities of each household can be taken into account. Types of geographic constraint are, for example, climatic differences inhibiting the possibility of reducing heating consumption for households in cold regions and lack of access to public transport for households not living in municipal areas.