Sustainability 2011, 3, 1234-1249; doi:10.3390/su3081234
A Carbon Consumption Comparison of Rural and Urban Lifestyles
Jukka Heinonen * and Seppo Junnila
Aalto University School of Engineering, P.O. Box 11200, 00076 AALTO, Finland;
* Author to whom correspondence should be addressed; E-Mail: email@example.com;
Received: 4 May 2011; in revised form: 23 July 2011 / Accepted: 8 August 2011 /
Published: 16 August 2011
Abstract: Sustainable consumption has been addressed from different perspectives in
numerous studies. Recently, urban structure-related lifestyle issues have gained more
emphasis in the research as cities search for effective strategies to reduce their 80% share of
the global carbon emissions. However, the prevailing belief often seen is that cities would
be more sustainable in nature compared to surrounding suburban and rural areas. This paper
will illustrate, by studying four different urban structure related lifestyles in Finland, that the
situation might be reversed. Actually, substantially more carbon emissions seem to be
caused on a per capita level in cities than in suburban and rural areas. This is mainly due to
the higher income level in larger urban centers, but even housing-related emissions seem to
favor less urbanized areas. The method of the study is a consumption-based life cycle
assessment of carbon emissions. In more detail, a hybrid life cycle assessment (LCA)
model, that is comprehensive in providing a full inventory and can accommodate process
data, is utilized.
Keywords: life cycle assessment; carbon; climate change; lifestyle; consumption;
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Cities have been both blamed for climate change [1,2] and defended  in comparison to rural and
semi-urban areas. The per capita carbon emissions in cities have been reported as substantially lower
than those of the surrounding rural and suburban areas and the country average in several
studies [4-6]. In addition, high density areas, based on multi-storey buildings, have been reported to
cause significantly less carbon emissions on a per capita basis than low-density low-rise areas .
However, almost completely opposite results have been reported recently .
Unquestionably, the importance of cities in the search for effective climate change mitigation
strategies is high, as cities have been estimated to produce up to 80% of global greenhouse gases
(GHGs) . However, the approaches utilized in a vast majority of earlier studies are not sufficient to
conclude cities or rural areas as more sustainable in preventing climate change. The approaches have
two notable deficiencies. First, they have concentrated on the producer perspective, allocating the
GHG emissions for a city or region that can occur inside the borders of the region. This seems to favor
cities as heavy industries and energy production are often located outside of the city borders. Second, a
relevant question left unanswered in them, is how the type of a region, city or rural, affects the
consumption habits, i.e., the lifestyle. If cities accommodate more consumption-intensive lifestyles, the
possible advantage of high density and dwelling-based housing might easily be lost in comprehensive
carbon emission calculations.
This paper presents an empirical consumption-based assessment of the carbon emissions caused by
consumers living in different types of communities. We utilize the life cycle assessment (LCA) method
to assess the GHGs (CO
O and HFC/PFCs) attributable to private consumption. This
approach enables global comparisons as no regional borders need to be set. Also, the approach allows
an analysis of the relations between consumption habits and the area or habitation type.
The study utilizes urbanization rate-based samples from rural to metropolitan areas taken from a
large consumer survey representing different consumer profiles in Northern Europe. The consumer
profiles offer a possibility to assess the carbon consumption, the GHG emission associated with
consumption of commodities in carbon equivalents, related to the lifestyles in different area types.
In the paper we will demonstrate that, when a change from rural to urban area type leads to upgrade
in the income level, and thus in the consumption volume, urbanization might lead to significantly
higher carbon emissions instead of diminishing of the emissions. We argue that this perspective will be
of high importance in the future in the search for effective climate change mitigation strategies.
Together with the more common regional production-based assessments, the two perspectives provide
sustainable basis for strategic decision making in an urban development.
The study is conducted utilizing the LCA method. The method includes two main approaches:
input-output-LCA (IO-LCA), process-LCA, and a combination of the two, namely hybrid-LCA. The
three approaches together with the main solutions are shortly presented below.
The traditional way of conducting an LCA, process-LCA, assesses the emissions based on energy
and mass flows in the production and supply chain processes inside the selected assessment
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boundaries [10-12]. The accurateness of the method is potentially very high as the emissions are
measured as they are generated. However, even by including multiple upstream processes into the
assessments, the approach suffers from truncation error from the boundary selection that always needs
to be made. The amount of processes that add emissions to a certain good or service is normally very
high if all production and supply chain processes are calculated. These boundary selection-based
cutoffs may potentially significantly affect the result of the assessment . Also, a comprehensive
process-LCA is inherently laborious and time consuming to conduct [10,11] due to the described
nature of the assessment.
IO-LCA, in turn, assesses the emissions based on monetary transactions, the basic idea being that
every monetary transaction is related to production of a good or service that causes emissions . The
IO method is based on transaction tables that describe the connections between different industries,
normally within a certain national economy . The tables show the emissions that each sector
causes related to a monetary transaction on one sector. The tables capture both the energy and non-
energy related GHG emissions from each industry sector in the supply chain related to production and
distribution of a product over its lifetime, thus including the embedded as well as the production phase
emissions. Together these form a comprehensive carbon footprint of a certain good or service
independent of the geographic place where the production or the consumption occurs. The carbon
footprint referred in this paper is thus in accordance with several definitions, i.e., Pandey et al.
The IO method does not suffer from the truncation error described above. The method is
comprehensive, always providing a full inventory of the emissions attributable to a certain
good [11,14], except for the end of life stage, which should be added to the calculations . Input
output method is also quick and rather easy to use .
There are three types of inherent problems related to IO method. The first is a high level of
aggregation of industry classifications. Even in the most disaggregated model, the number of industry
sectors is less than 500 , significantly lower than in an economy in reality. The second include
possible temporal (inflation and currency rate differences) and regional (industry structure differences)
asymmetries between the data and the model. The models available are not updated annually, and the
industry structure of the model might deviate from that of the region studied. Third, the models
generally assume domestic production of imports, meaning that the emissions intensities are always
the same for each sector [10,11,16].
Although both of the described approaches have weaknesses, the inherent problems differ from
each other. This creates space for the approach combining the strengths of the two approaches and
reducing the weaknesses related to them; hybrid-LCAs [10,17]. The hybrid-LCA method allows life
cycle assessments with lacking information, and enables creation of models that significantly reduce
the truncation error inherent in process-LCAs while reaching to process specificity. In addition,
hybrid-LCAs suit well for assessments within the context of the built environment, where
the studied systems tend to be complex in nature . Three different approaches can be distinguished
in hybrid-LCAs: tiered hybrid LCA, IO-based hybrid analysis and integrated hybrid analysis .
In this study we exploit an IO-based application of tiered hybrid-LCA, utilized also earlier by
Heinonen and Junnila , to assess the GHGs related to private consumption. The model retains the
comprehensiveness of IO approach while reaching for the accurateness of a process approach. The
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model is based on IO tables to maintain full coverage of the inventory. To increase the accuracy, the
key emission sources are assessed with local process data. The utilized model and its construction is
further described in the next section.
3. Research design
3.1. Rural, Semi-Urban, City and Metropolitan Consumers
Four representative samples of consumers from Finland were selected for the study covering a
range of types of living from rural to metropolitan to assess the carbon consumption of an average
consumer of each living type.
The first sample consists of consumers living in Finnish rural regions. These consist of regions
where less than 60% of the inhabitants live in urban areas with the largest urbanization smaller than
15,000 inhabitants, or of regions where 60 to 90% of the inhabitants live in urban areas with a
maximum of 4,000 inhabitants. The second sample, the semi-urban regions, comprises consumers
from municipalities where 60 to 90% of the inhabitants live in urban areas with 4,000–15,000
inhabitants. The third sample, the cities, consists of consumers of municipalities where a minimum of
90% of the inhabitants live in urban areas, and those where the largest urbanization is larger than
15,000 inhabitants. The Helsinki metropolitan area forms the fourth sample. The region consists of the
capital of Finland, Helsinki, and the three large cities surrounding Helsinki, the region together having
around 1,000,000 inhabitants. In addition, the Finnish average carbon consumption was assessed to
support the analysis.
The described selection of lifestyle-based samples enabled us to demonstrate the changes in carbon
consumption from three perspectives: growth of the urban density, change in the dominant type of
habitation from detached houses to apartment buildings, and growth in the income level. In rural areas,
detached housing is dominating and the areal structures are loose. On the other end, in the Helsinki
metropolitan area, the urban structure is substantially denser and apartment buildings dominate
housing. Semi-urban areas and cities fall between the two extremes. In addition, the differences in the
income levels and the consumption volumes are significant. In rural areas the annual consumption
volume an average consumer is 12,200 € whereas that of an average consumer in the Helsinki
metropolitan area is 17,600 €. Again, semi-urban areas and cities fall between these values .
Table 1 gathers together the important figures related to the four samples.
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Table 1. The key figures of the four studied samples on the reference year 2006.
2,200 inhab. 1,600 inhab. 4,700 inhab. 1,100 inhab.
<60% live in
urban areas with
60–90% live in
urban areas with
60–90% live in
urban areas with
>90% live in
and Vantaa, the
Dominant types of
mainly detached detached and
2.33 2.27 2.01 1.93
Annual volume of
12,200 € 13,800 € 15,200 € 17,600 €
3.2. Input Data
The four samples forming the exploited input data were taken from the Finnish consumer survey
2006 . The consumer survey 2006 data describes the consumption of an average Finnish consumer.
The survey presents the consumption of an average consumer in very detailed form as it includes
around 1,000 categories and sub-categories of goods and services. The sample size, nearly 10,000
participants on a national level (0.2% of the Finnish population), can also be considered representative.
Smaller samples can be produced based on diverse variables, type of areal structure and region being
the ones used in this study. This survey data were used as inputs in the carbon consumption
assessments of the study.
The utilized process data include the average Finnish emissions of heat and electricity production,
fuel combustion emissions of private driving and public transport, disaggregation of the public
transport sector according to the local profiles of public transport use, and a regional price level
correction on property prices. The data are described in more detail in the next section.
3.3. Tiered Hybrid-LCA Model
The study consists of two calculation phases, a direct IO assessment and a hybrid assessment. For
the calculations, the original 1,000 categories were aggregated down to 43 consumption sectors
representing the region and lifestyle-related consumption. After this, two different assessment models
were utilized to calculate the carbon consumption of an average Finn: the Carnegie-Mellon EIO-LCA
US Industry benchmark 2002 based model  as the primary model, and the Finnish ENVIMAT 
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to evaluate the result. The Finnish average consumption volumes in the above-mentioned 43
consumption sectors were utilized as inputs for both models. The overall results of the two assessments
were very similar, within a 5% range of each other, supporting the use of the Carnegie Mellon
EIO-LCA as the basis of our hybrid model. The EIO-LCA output matrices are publicly available,
which enables construction of tiered hybrid applications. The emissions included in the model are CO
O and HFC/PFCs calculated in carbon equivalents (100 years equivalency). Furthermore, the
model is the most disaggregated model available, providing output tables for 428 industry sectors,
reducing thus the aggregation error inherent in IO approaches. This was given high importance as the
input data utilized in the study is highly complex. The problem of high level of aggregation of the
industry sectors, inherent in all IO models, has been addressed by a number of studies. Of these,
Lenzen et al. (2004) state that the level of disaggregation has significant impact on the results and thus
the most disaggregated model should be utilized . The Finnish economy is also a small and open
economy with over 50% of the value of total consumption oriented to import goods , a significant
part of the emissions attributable to Finnish consumption thus originating abroad. Of the model
dimensions, the first tier utilized to accommodate local process data, the production or combustion
phase, complies the WRI (2009)  Scopes 1 and 2 definitions. The whole model, in turn, is in
accordance with the Scope 3 definition.
The model selection includes some potential sources of bias in addition to those inherent for the IO
approach in general. First, as in all IO-based LCA assessments, the number of included processes is
infinite within the system boundary defined by the scope of the model . However, the problem that
arises is an assumption of domestic production of imports. In this study, this means US industry
emissions intensities for all the commodities outside of the utilized Finnish process data. The potential
industry structure and emissions asymmetry error between a US based model and Finnish consumption
profiles was assessed as not very significant according to the comparative assessment with the
ENVIMAT model. Larsen and Hertwich (2009) also employ the same type of EIO-LCA based tiered
hybrid LCA model in their study concerning the public sector in Norway arguing for the suitability of
EIO-LCA in a similar northern country context . However, Weber and Matthews (2008) report a
15% increase in the US household carbon emissions when the international trade is explicitly
modeled . This uncertainty is further discussed later in the paper.
Second, to decrease the temporal asymmetry problem arising from inflation and currency rate
differences between the US and the Finnish economies, and the base years of the model and the input
data, the model was adjusted with purchasing power parity (PPP) multiplier , a method that was
utilized by Weber and Matthews in their fairly recent study of the global and distributional aspects of
the American household carbon footprint .
Third, as inherent in all IO-based models, the output tables exclude the emissions from the use and
the end of life phases. However, the use of total private consumption as the input data reduces this
problem significantly. The costs related to these phases are embedded either in the consumer prices of
goods and services or included in the input data as waste and recycling costs.
The final problem that needs to be assessed in IO method-based calculations is the accuracy
problem arising from the use of the use of industry averages in the output matrices. In this study, the
use of a hybrid assessment model reduces this problem as the utilization of the US industry averages
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can be avoided. The sectors enhanced with local process data cover more than 50% of the total carbon
emissions, and all the most significant emission sources, as is further described below.
In the second phase the direct IO assessment was used for the design of the tiered hybrid-LCA
model. In the tiered hybrid-LCA the most important processes creating carbon emissions according to
the IO model were enhanced with local process data, but the rest of each output matrix, the EIO-LCA
result matrices describing the emissions of each industry sector related to a monetary transaction on a
certain sector, was left untouched to maintain the full coverage of the model.
In the direct IO assessment, four sectors were found to cover two thirds of the carbon consumption
in all the samples. These four sectors were emissions related to housing energy use (heat and
electricity), building related emissions and transport-related emissions divided into public transport
and private driving. According to this assessment these four key sectors were enhanced with
Concerning housing energy, the production phase emissions, the first tier in the output matrix, were
replaced with process data. We utilized the average Finnish emission profiles for electricity, district
heat and oil assessed with energy method, that allocates the production phase emissions of combined
heat and electricity production directly according to the distribution of the total production between the
two. According to Kurnitski and Keto  the carbon intensities in Finland are 240 g CO
electricity, 286 g CO
/kWh for district heat and 267 g CO
/kWh for oil. For private use of firewood,
zero carbon emissions were assumed. The Finnish electric power production profile behind the figures
is: nuclear power 28%, fossil fuels 36%, peat 8% and renewable energy sources 28%.
The consumption survey, the input data, distinguishes in detail the maintenance charges of privately
owned detached houses, but the maintenance paid as housing management charges or rents are
embedded within these costs. To increase the reliability of the assessment, the communal building
energy, normally paid with rent or housing management charges in apartment buildings and row-
houses, was added to the energy consumption of a consumer by disaggregating the consumption
sectors of housing management charges and rents. The average shares of communal heat and
electricity attributable to each inhabitant were calculated in a study including eight housing
corporations from the Helsinki metropolitan area . Furthermore, all the other operation and
maintenance costs included in rents and housing management charges, water, waste, cleaning,
maintenance and repair construction, etc., were re-allocated under appropriate consumption categories
according to the results of Kiiras et al. .
In private driving, the first tier emissions, the direct emissions from fuel combustion, were also
replaced with process data. The process data utilized was taken from The Technological Centre of
Finland’s LIPASTO study, the emissions per passenger kilometer (pkm) being 179 g CO
Next, the emissions from expenditure on building and property were enhanced with regional data.
These expenditures are separated from the management costs in the input data, except of the share
embedded in the rental payments. The embedded share was distinguished from the rental payments by
assuming that the division of the costs between management charges and payments of building and
property is similar to the privately owned apartments. Of these, the share of the price of property has
substantial regional variations, and as the emissions related to building and property differ heavily,
regional price adjustments were utilized according to the property price statistics of The Housing
Finance and Development Centre of Finland (ARA) . After the adjustment, the building share of
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the expenditure was allocated to construction of residential buildings, whereas the emissions related to
the property were assessed with a low-intensity office work sector.
Finally, while emissions related to public transport had minor significance in the IO calculation,
they were enhanced with Finnish industry-based data as the sector forms an important substitute for
private driving, and the emissions profile of EIO-LCA significantly differs from that of Finland. The
enhancement method was full replacement of the EIO-LCA output matrix with that of the respective
Finnish ENVIMAT study.
After the construction of the hybrid model, we further combined the 43 consumption categories
down to 10 consumption areas, which indicate the type of region and income level-related carbon
consumption. The utilized consumption areas are:
1. Heat and electricity;
2. Building and property;
3. Maintenance and operation;
4. Private driving;
5. Public transportation;
6. Consumer goods;
7. Leisure goods;
8. Leisure services;
9. Travelling abroad;
10. Health, nursing and training services.
Of the 10 consumption areas, Heat and electricity contain all housing energy use, including both
household heat and electricity and the share of communal building energy. Building and property is
dominated by construction, whereas Maintenance and operation comprise emissions of maintenance
and repair construction, water and waste water, waste and cleaning. Private driving, in addition to
gasoline combustion, includes all activities related to driving, purchases and maintenance of private
vehicles. Public transportation mostly consists of travelling by coach or train.
Goods and services classes comprise daily consumption and consumption of durable goods, so that
leisure-related expenses are separated for demonstration of the allocation of emissions and lifestyle
differences. Travelling abroad include all private flying and accommodation abroad. Finally, health,
nursing and training services are put together as they only include private services, which in Finland
form a minor share of all the services of these sectors.
The study produced an unconventional but really interesting outcome. The results indicate that the
level of carbon consumption is determined by income level and the area, and habitation types have
little significance. According to the study, the carbon consumption of an average consumer in rural
areas is 9.0 tons of carbon dioxide equivalents (t CO
-eqv.), in semi-urban areas 9.9 t, in cities 10.9 t
and in the Helsinki metropolitan area 12.5 t. The Finnish average was assessed as 10.3 t CO
would thus seem that in rural areas, significantly less emissions are caused on per capita level
compared to city living. Also, all the different types of areas studied follow the same pattern as
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the lifestyle of semi-urban and city consumers falls between rural and metropolitan lifestyles. Figure 1
shows the annual per capita carbon consumption of different lifestyles together with the private income
and the consumption volume.
Figure 1. The annual per capita carbon consumption (t CO
-eqv.) in the reference year
2006, together with net income (€) and the volume of private consumption (€) of the
average consumers of the four area types.
As the Figure 1 shows, carbon consumption is closely related to the income level (the red line
indicating annual net income per capita). However, as the green line of annual private consumption
shows, only a diminishing share of the earnings is consumed as the level of earnings grow. This has an
equaling effect on the carbon consumption of different lifestyles.
If we further analyze the components of the carbon consumption, very interestingly, the carbon
emissions grow in each category but one as the degree of the urbanization grows. Energy related to
housing is the largest single sector of carbon emissions. Quite surprisingly, it would seem that also the
emissions related to housing energy grow as the type of region changes from detached house
dominated rural regions to denser and more apartment building dominated city and metropolitan areas.
The same 2.9 t CO
-eqv. carbon emissions are caused by energy use in rural and semi-urban areas with
670 € and 650 € annual expenditures, whereas in cities the figure is 3.3 t and in the Helsinki
metropolitan area 3.7 t with purchases of 630 € and 650 €. While the level of energy consumption
varies only slightly between the different area types, the carbon content of the energy used is slightly
better in rural and semi-urban area types explaining the result. Figure 2 presents the annual energy
consumption in monetary terms divided according to the utilized fuels.
Global warming potential
Private consumption per
Net earnings per capita
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Figure 2. The annual per capita fuel purchases (€) in the reference year 2006 in the four
Emissions from the construction and maintenance of the building (Building and property and
Maintenance and operation) together form another significant entity of the total carbon consumption.
In rural areas, 1.8 t CO
-eqv. emissions relate to these two categories with annual purchases of 3,000 €,
whereas in the Helsinki metropolitan area the figure is as high as 2.9 t the average consumer spending
5,200 € on the commodities of these categories. In semi-urban areas the carbon consumption in these
categories is 2.3 t (3,790 €) and in cities 2.6 t (4,350 €). The spending on acquisition of homes is on a
substantially higher level in more urbanized areas, and the same applies to a majority of all operation
and maintenance costs, explaining the differences.
The only exception in the pattern are the emissions related to private driving, which follow earlier
studies i.e., [32,33] in having a growing tendency as the density of the region diminishes from the
metropolitan to the rural type. In rural and semi-urban areas, the carbon consumption from private
driving is 2.0 t, but in cities it is 1.6 t and in the Helsinki metropolitan area, only 1.4 t. The acquisition
of vehicles equals the figures as the differences in the emissions from vehicle production are almost
equal between the regions. The overall purchases on the category are 2,210 € in rural and 2,180 € in
semi-urban areas, 1,910 € in cities and 1,860 € in the Helsinki metropolitan area.
Public transport slightly affects little the overall carbon consumption, but is an important low-
carbon substitute for private driving. It would seem that a denser urban structure leads to higher level
of public transport use, as the emissions grow from 0.05 (70 €) and 0.06 t CO
-eqv. (80 €). in rural and
semi-urban areas to 0.15 (200 €) and 0.24 t (320 e) in cities and the Helsinki metropolitan area.
The rest of the categories comprise carbon emissions from consumption on goods and services. The
share of these of the total carbon consumption varies from 25% in rural areas to 33% in the Helsinki
metropolitan area, and the consumption volumes from 6,260 € to 9,270 €. The high positive connection
between income and carbon consumption is also seen in these categories. In fact, these are a key
explanation as to the growth in carbon consumption as the income level grows despite the region type.
The pattern is very clear, as Figure 3 shows. In Figure 3, the carbon consumptions of the average
consumers of the four different area types are shown sector by sector. The figure demonstrates that the
emissions increase, following the growth in the volume of consumption as the income increases
together with the urbanization size, in virtually every consumption sector leading thus to substantially
higher overall carbon consumption in larger urbanizations.
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Figure 3. The annual per capita sectoral emissions (t CO
-eqv.) in the reference year 2006
of the average consumers of the four area types.
The purpose of this study was to conduct a consumption-based analysis of consumer carbon
footprints for comparing the carbon emissions of average inhabitants living in different types of urban
structures. This was done with four samples of consumers from Finland representing types of regions
from rural to semi-urban, city and metropolitan areas. The study was conducted utilizing an application
of tiered hybrid-LCA method that notifies all life cycle emissions including production and delivery
chains without boundary cutoffs. We argue that this type of consumption-based modeling of emissions
is of high importance and adds valuable information to more common regional production-based
assessments. Especially, when seeking solutions for low-carbon living and low-carbon areal structures,
consumption-based assessments of the emissions are essential.
In the study we assessed the carbon consumption of the different area types and the Finnish average
consumer with the hybrid model. This assessment showed slightly unconventional results, as an
average consumer of rural areas seems to cause significantly less carbon emissions than a city resident.
According to the assessment, in rural areas the annual carbon consumption of an average consumer is
9.0 t CO
-eqv., in semi-urban areas 9.9 t, in cities 10.9 t and in the Helsinki metropolitan area 12.5 t.
The explanation for the unconventional result seemed to be twofold. First, it would quite
unconventionally seem that the degree of urbanization, whether a rural region dominated by detached
housing , or a city or metropolitan area dominated by apartment buildings, barely affects the overall
emissions of an average consumer. Concerning energy consumption, which was considered to strongly
favor apartment building-based city residents, the per capita monetary consumption seemed in the end
to have only small variation between the different housing types. In addition, the pattern found was
that the housing related emissions actually grow as the structure gets denser and housing more
apartment building based due to rise in expenditure on building and maintenance following growth in
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the size of the urbanization. This contradicts some earlier studies, which have shown substantial
differences between the carbon emissions of detached houses and apartment buildings. The
explanations offered by the input data are clear, though. First, when also the communal building
energy was allocated to the consumer in addition to household energy, the total amount of energy used
was roughly equal in all types of regions. Second, the profile of energy sources explain the difference
in emissions, as in areas with detached housing a significant amount of wood is used for heating. Also,
as electricity dominates the total energy consumption in the rural areas, and has slightly better
emissions profile than district heat and oil, the emissions in rural areas are lower with equal
consumption volume. And third, the size of an average household is 2.33 persons in rural areas, 2.27 in
semi-urban areas, 2.01 in cities and 1.93 in the Helsinki metropolitan area . Even if there was
difference in energy use on building level, the per capita perspective would diminish this.
The second explanation for the overall result lies in the consumption volume, 12,200 € in rural areas
annually per capita, 13,800 € in semi-urban areas, 15,200 € in cities and 17,600 € in the Helsinki
metropolitan area. An important pattern found in the study was that the income level and, following
this, the level of consumption on goods and services grows together with the density of the structure.
The consumption volume grows as the density and size of the urbanization grow in virtually all
consumption sectors except private driving (see Figure 3). Now, as the volume of consumption grows,
the emissions related to consumption grow. This study strongly indicates that this effect of income
growth determines the volume of carbon consumption regardless of regional factors like density and
housing type. Whether the more consumption-intensive lifestyle is a consequence of the growth in the
size of the urbanization or not is not clear, however.
In private driving, the conventional, previously reported pattern, where emissions grow as the
density decreases, was found. However, the effect on the overall carbon consumption per capita is
quite weak when all the emissions related to driving are calculated, including car manufacturing,
deliveries and maintenance of vehicles. According to the hybrid model, the share of fuel combustion of
all private driving related emissions is 50 to 70%, the rest being dominated by car manufacturing-
related emissions. Thus, growth in trip generation due to decline in the density of the city structure has
only a relatively minor effect on the overall carbon consumption.
The reliability of the study was assessed from four perspectives. First, a positioning of the results
among earlier applicable studies was made. Of these, calculation with the Finnish ENVIMAT study
output tables showed an annual per capita carbon consumption of 10.1 t CO
-eqv. for an average
Finnish consumer, whereas the figure with the hybrid model of this study was 10.3 tons. Regarding the
results and the conclusions, the authors have published similar results in other recent papers [8,34]. On
the method level, a reference for the applicability of the method has been published quite recently by
Weber and Matthews, who used the EIO-LCA approach to study the global and distributional aspects
of the American household carbon consumption . Furthermore, the usefulness of the consumption-
based approach has been noted in several studies. Ramaswami et al. call for the importance of
exceeding the regional boundaries , whereas Kennedy et al. also bring up the issue stating that “it
is appropriate to attribute more than just the within-boundary emissions to cities, as the consumption
activities located in the cities cause the emissions” . The truncation error might also be significant,
i.e., , if boundary cutoffs are needed. Regarding this perspective the IO basis would seem very
suitable for a carbon consumption assessment, as the truncation errors of all the commodities would
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accumulate. However, also the uncertainty (discussed further below) of the IO-based model from the
utilization of industry average emissions accumulate, and create uncertainty to the results.
Second, as a test of the sensitivity of the results regarding the building-related emissions, which
include some uncertainty on the allocation of the expenditure, we removed the Building and property
category from the results. While the change decreases the overall emissions, the interpretation of the
results remains the same. Without the sector the average annual per capita carbon consumptions of
each area type are 7.3 t in rural areas, 8.0 t in semi-urban areas, 8.9 t in cities and 10.3 t in Helsinki
The third source of possible biases is the hybrid model itself due to the inherent problems of all
LCA approaches. Based on the assessments and amendatory actions described in the method and
research design sections, we argue that we have substantially diminished these. However, especially
concerning the goods and services sectors, the output sector choices include some uncertainties, as
both the input data and the output sectors are quite diversified. However, the impact on the overall
results is low, and no adjustments were seen to be necessary. In addition, the previously mentioned
assumption of domestic production of imports is a potential source of bias. Regarding this study, this
means the US industry GHG intensities for all the commodities outside of the scope of the local
process data. A majority of the consumption commodities in Finland are imported, but a multi-regional
model would be needed to explicitly assess the emissions. Weber and Matthews (2008) found a 15%
increase in the US household carbon emissions when the imports were modeled in detail . Larsen
and Hertwich (2009) utilized the EIO-LCA model in Norway context, but without providing specific
assessment of the potential bias of the results .
Finally, the reliability of the input data was assessed. In this study, the Finnish consumer survey
provided the primary input data. The level of detail of the data is very high. The survey presents
private consumption divided into more than 1.000 categories of goods and services, thus providing an
excellent basis for IO based LCAs. Also, the sample size is representative, including roughly 10,000
subjects (0.2% of the Finnish population). In this study, the sub-samples remained sufficient (over
1,000 observations in each sample) and thus biases related to these were considered small.
Despite the very high quality input data, free public services and heavily subsidized services create
a source of bias in the Finnish economy system, as these form a noteworthy share of the total private
consumption. However, no amendatory actions were taken, since the assessment in the Finnish
ENVIMAT study showed that the bias predominantly concerns our comprised consumption class
"health, nursing and training services", which had minor significance in this study.
As the final test of the robustness of the results, we conducted a longitudinal study using preceding
consumer survey data from 2001. The test results were very similar, except for a scale difference due
to the change in the income levels between the two surveys. This test strongly supports the robustness
of our findings.
The study demonstrated that cities may not be more sustainable in nature compared to the
surrounding suburban and rural areas concerning climate change as is often suggested, when a
demand-based approach is taken. In fact, the study showed that the per capita emissions related to city
Sustainability 2011, 3
lifestyle are substantially higher than those related to rural and semi-urban lifestyles in the Finnish
context. This notion is very important when sustainable climate change mitigation strategies are sought
in the near future. However, it is very important to notify that this study only presents a static situation
of the reference year, and concluding that rural living would always be less carbon intense would be
misleading. Migration from city to rural areas would probably not have any carbon mitigation effect.
Thus, the main issue is to understand the huge effect of income on the overall carbon consumption, and
that the type of urbanization as such does not define the emissions. It should also be noted that a very
important factor behind the results of this study is the pattern of growth in the average income as the
size of the urbanization grows. There might be reverse situations on a global level which could limit
the generalizability of the results.
Despite the limitations, we argue that the type of consumption-based assessment approach presented
here should be given high value in national- as well as regional-level decision making regarding
climate change. In the future, the accuracy of the model could be further increased. In addition,
comparative global studies should be conducted to test the results in different contexts.
Conflict of Interest
The authors declare no conflict of interest.
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