Elsevier

Environment International

Volume 91, May 2016, Pages 168-179
Environment International

Personal Metabolism (PM) coupled with Life Cycle Assessment (LCA) model: Danish Case Study

https://doi.org/10.1016/j.envint.2016.02.032Get rights and content

Highlights

  • Personal Impact Profiles (PIPs) of urban residents were estimated.

  • Environmental and human health impacts of urban residents were estimated.

  • Personal Metabolism (PM) coupled with the LCA approach was developed and applied.

  • Food and energy consumption impacts found to be the major contributors to the PIPs

  • Behavioral factors (different diets, personal car, household size) affect the PIPs.

Abstract

Sustainable and informed resource consumption is the key to make everyday living sustainable for entire populations. An intelligent and strategic way of addressing the challenges related with sustainable development of the everyday living of consumers is to identify consumption-determined hotspots in terms of environmental and health burdens, as well as resource consumptions. Analyzing consumer life styles in terms of consumption patterns in order to identify hotspots is hence the focus of this study. This is achieved by taking into account the entire value chain of the commodities consumed in the context of environmental and human health burdens, as well as resource consumptions. A systematic commodity consumption, commodity disposal, and life style survey of 1281 persons living in urbanized Danish areas was conducted. The findings of the survey showed new impact dimensions in terms of Personal Metabolism (PM) patterns of residents living in urbanized areas of Denmark. Extending the PM analysis with Life Cycle Assessment (LCA) provided a clear picture of the per capita environmental and human health burdens, as well as resource consumptions, and the exact origin hereof.

A generic PM-LCA Model for all the 1281 persons was set-up in Gabi 6. The assessment results obtained applying the model on all 1281 personal consumption scenarios yielded the 1281 Personal Impact Profiles (PIPs). Consumption of food and energy (electricity and thermal energy) proved to be the primary impact sources of PM, followed by transport. The PIPs further revealed that behavioral factors (e.g. different diets, use of cars, household size) affect the profiles. Hence, behavioral changes are one means out of many that humanity will most likely have to rely on during the sustainable development process. The results of this study will help the Danish and other comparable populations to identify and prioritize the steps towards reducing their environmental, human health, and resource consumption burdens.

Introduction

Persistent population growth and urbanization have led to an increased demand for man-made resources. This inevitably puts tremendous pressure on the global environment and natural resources. In particular, the increasing natural and man-made resource consumption rates and associated emissions are becoming more and more problematic. In the period 1900 to 2005, the extraction of construction materials grew by a factor of 34, ores and minerals by a factor of 27, fossil fuels by a factor of 12, and biomass by a factor of 3.6 (UNEP, 2011). The convenient and modern life styles prevailing in high population density urban areas are, just as rural life styles, both directly and indirectly associated with environmental, human health impacts. However, urban life styles compared to rural life styles lead to an increased consumption of both natural and man-made resources. In other words, not only is the increasing population adding to environmental and human health burdens, as well as resource consumptions related with human activities, but also the increasing urbanization (Parikh et al., 1991). Due to the complexity of the supply-chains, humans tend not to clearly perceive and realize the impacts entailed with specific life styles. This further makes it more difficult to relate to the environmental and human health impacts induced at a global level.

Private consumption plays an important role in relation to the impacts posed by various life styles. EEA (2010) reveals that private consumption expenditures grew by 35% in the EU-27 Member States between 1990 and 2007 with the greatest growth in the EU-12 Member States (75%). The complexity of the consumption increase in terms of increased consumption of specific goods is illustrated by the same report (EEA, 2010). For example, meat imports to the EU-15 increased by 120% from 1990 to 2007, cereal imports increased by 83%, frozen vegetables by 174%, and bananas by 92% over the same period. This suggests that specific goods follow specific consumption patterns. One of the factors contributing to the overall increased consumption is the growing tendency of households to become smaller in terms of persons per household. This decrease in household size inevitably cause more energy and water use along with increased waste generation per person, due to the general decrease in consumption benefits of economies of scale (EEA, 2005). The increasing urbanization, growing consumption, and decrease in household size are factors that need to be analyzed in the context of environmental and human health burdens, as well as resource consumptions, in order to quantify the various impacts of urban systems and residents.

The path towards quantification of the environmental, human health, and resource burdens of urban residents requires a holistic approach accounting for the impacts across the life cycle of the products covering all the upstream and downstream resource use and material interventions. The Personal Metabolism (PM) notation used here is simply a synonym used when a study focuses on individual/resident consumption, rather than city/system scale consumption, such as quantified in Urban Metabolism (UM). PM refers to estimation of annual consumption patterns (also called metabolic flows) of the individuals residing in particular localities. PM provides a holistic framework for analyzing the environmental burden of urban residents. Material Flow Accounting (MFA) and non-mass based methods (i.e. emergy, exergy concepts) of analysis are considered conventional methods applied for quantification of resource and environmental burdens (Pincetl et al., 2012). MFA studies take into account only direct mass and energy exchanges and hence ignore the embedded upstream and downstream processes required to provide a unit of resources consumed by the urban resident (Goldstein et al., 2013). Raw material equivalents (RME) based on economy-wide material flow accounts (EW-MFA) and Input output tables attempt to account for upstream raw material consumption in MFA (Barles, 2009, Eurostat, 2015). Emergy (embodied energy) assessment methods attempt to take a more comprehensive approach than MFA by further taking into account embodied energy of the metabolic flows across city system boundaries (Liu et al., 2011). Limitations have been identified in these approaches, invalidating the application of such methods for sustainability assessment of cities/city systems (Pincetl et al., 2012). The present state of art of sustainability assessment of large-scale systems, such as urban systems, suggests that it is essential to couple system consumption and emissions with holistic environmental assessment methods, such as UM studies coupled with Life Cycle Assessment (LCA). LCA is a well-established methodology for quantifying environmental burdens of common products, technologies and services (Finnveden et al., 2009, Guinée et al., 2011, Pennington et al., 2004, Rebitzer et al., 2004). Coupling of well-established and/or standardized methods allows for accounting of up- and down-stream impacts of associated with the urban system being assessed and hence provides an expanded environmental burden estimate beyond direct mass and energy accounting (Goldstein et al., 2013, Ulgiati et al., 2011). PM coupled with the LCA (PM-LCA) approach accounts for upstream as well as downstream resource use and impacts. Hence, for the purposes of the present study, PM-LCA is considered the best-suited approach for assessing environmental impacts of urban residents. Basically, PM-LCA is a special LCA defined as consumer/lifestyle LCA (Hellweg and Milà i Canals, 2014).

In past studies attempting to establish resource consumption patterns in urban areas a variety of approaches have been applied. Gilg and Barr (2006) studied the water consumption patterns by sampling 1600 households from Devon, England. Cluster analysis of the data from the 1600 households was used to identify groups with varying commitment towards the environment. The study concludes that, if policies aimed at water and energy conservation take into account behavioral complexity, behavioral groupings, and lifestyle types, then there is greater chance of success in implementation of these policies. Lähteenoja et al. (2007) carried out a detailed resource consumption study on 30 Finish households by accounting for material inputs to accommodation, food and beverage, transport, leisure time activities, tourism, household goods, and electronic appliances. The study estimated the Material Input Per Service unit (MIPS) for the typical Finish household. Baiocchi et al. (2010) analyzed consumer data on lifestyles in the United Kingdom (UK) using an Input–Output model to estimate Carbon Dioxide (CO2) emissions. In total, 56 UK lifestyles were analyzed. The UK study reveals the importance of considering the effects of lifestyles in relation to determining CO2 emissions. Newton and Meyer (2012) present a comprehensive urban resource consumption study of 1250 households in Melbourne, Australia. The Melbourne study seeks to assess how much of the resource consumption is attributed to cities and accommodation and how much is directly associated with the individual behavior of the consumer. Five parameters (water, energy, domestic appliances, travel, and accommodation space) were considered in the study. Newton and Meyer (2012) conclude that urban resource consumption is affected more by contextual and locational factors (household, dwelling, and location) than individual (structural and attitudinal) factors.

Schmidt and Muños (2014) report the hybrid Input Output (IO) study on Danish production and consumption. The study applies the FORWAST model (Schmidt et al., 2010) covering Danish production and consumption across 145 product groups (physical products, service products, waste treatment services and household uses). Additionally the FORWAST model takes into account emissions associated with imports and exports of products, direct land use change, and radiative forcing from aviation. Druckman and Jackson (2009) applied a socio-economically disaggregated quasi-multi-regional IO model to estimate the carbon footprint of UK households. The study included CO2 embedded in goods and services purchased by UK households; CO2 emissions caused by fuel use by the households; CO2 emissions due to personal vehicle use, and; CO2 emissions related with personal air transport.

Most of the above studies apply an IO approach and only cover a fraction of the consumption related metabolic flows across urban residential areas. In addition, the majority of these studies only report the carbon footprint of urban resource consumption. There is no study which addresses a wider range of environmental impact categories.

This is the first study of its kind focusing on estimation of Personal Impact Profiles (PIPs) by applying the PM-LCA approach to analyze resource consumption and waste disposal patterns of 1281 persons in urban areas of Denmark, as well as the associated environmental impacts. The study is part of a larger work on environmentally sustainable wellbeing from the Psychological Institute at Aarhus University named “Values, Ecologically Sustainable Behavior and Individual Wellbeing. This paper reports solely on the environmental impacts of resource consumption and waste disposal patterns on the individual level.

Section snippets

Methodology

The work comprises several steps starting from designing and distributing a comprehensive questionnaire for estimation of metabolic flows. Fig. 1 illustrates the methodology adopted. From the metabolic flows quantified via the questionnaires, the PM-LCA approach was subsequently used to estimate the impacts related with the metabolic flow. The PM-LCA is the only assessment approach, which takes into account the related upstream and downstream impacts of the individual consumption. The

Results and discussion

The sample size of 1281 is a good sample size (99.96% confidence level with 5% margin of error) to represent Denmark population for the year 2013. The average per person income and average per household income after tax of the sample was found to be 223,302 DKK/year and 362,014 DKK/year, respectively. In addition, the average age of the respondents was found to be 49.2 years with 75 percentile of respondents in the sample being < 63 years. Such a sample was assessed using the PM-LCA model to

Conclusions

The study presented here reports on the environmental burden of Danish urban residents. The computation was based on the PM-LCA approach, which is one out of several ways (consequential LCA and pure IO may also be used) to calculate the burden of Danish urban residents. No matter the approach used; assessment method specific uncertainties are introduced. For the primarily attributional based LCA approach applied here, the main uncertainty is the parts of the systems that have been cut off. On

Acknowledgements

The first author acknowledges Postdoctoral fellowship received from Technical University of Denmark (DTU) under the HC Ørsted Postdoc Programme co-funded by Marie Curie Actions (Grant agreement No. 609405).

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