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Critical evaluation of the European diesel car boom - Global comparison, environmental effects and various national strategies

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Background On the way to a more sustainable society, transport needs to be urgently optimized regarding energy consumption and pollution control. While in earlier decades, Europe followed automobile technology leaps initiated in the USA, it has decoupled itself for 20 years by focusing research capacity towards the diesel powertrain. The resulting technology shift has led to some 45 million extra diesel cars in Europe. Its outcome in terms of health and environmental effects will be investigated below. Results Expected greenhouse gas savings initiated by the shift to diesel cars have been overestimated. Only about one tenth of overall energy efficiency improvements of passenger cars can be attributed to it. These minor savings are on the other hand overcompensated by a significant increase of supply chain CO2 emissions and extensive black carbon emissions of diesel cars without particulate filter. We conclude that the European diesel car boom did not cool down the atmosphere. Moreover, toxic NOx emissions of diesel cars have been underestimated up to 20-fold in officially announced data. The voluntary agreement signed in 1998 between the European Automobile industry and the European Commission envisaging to reduce CO2 emissions has been identified as elementary for the ensuing European diesel car boom. Four factors have been quantified in order to explain very different dieselization rates across Europe: impact of national car/supplier industry, ecological modernization, fuel tourism and corporatist political governance. By comparing the European diesel strategy to the Japanese petrol-hybrid avenue, it becomes clear that a different road would have both more effectively reduced CO2 emissions and pollutants. Conclusion Europe's car fleets have been persistently transformed from being petrol-driven to diesel-driven over the last 20 years. This paper investigates on how this came to be and why Europe took a distinct route as compared to other parts of the world. It also attempts to evaluate the outcome of stated goals of this transformation which was primarily a robust reduction in GHG emissions. We conclude that global warming has been negatively affected, and air pollution has become alarming in many European locations. More progressive development scenarios could have prevented these outcomes.
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D I S C U S S I O N Open Access
Critical evaluation of the European diesel car
boom - global comparison, environmental effects
and various national strategies
Michel Cames
1*
and Eckard Helmers
2*
Abstract
Background: On the way to a more sustainable society, transport needs to be urgently optimized regarding
energy consumption and pollution control. While in earlier decades, Europe followed automobile technology leaps
initiated in the USA, it has decoupled itself for 20 years by focusing research capacity towards the diesel powertrain.
The resulting technology shift has led to some 45 million extra diesel cars in Europe. Its outcome in terms of health
and environmental effects will be investigated below.
Results: Expected greenhouse gas savings initiated by the shift to diesel cars have been overestimated. Only about
one tenth of overall energy efficiency improvements of passenger cars can be attributed to it. These minor savings are
on the other hand overcompensated by a significant increase of supply chain CO
2
emissions and extensive black
carbon emissions of diesel cars without particulate filter. We conclude that the European diesel car boom did not cool
down the atmosphere. Moreover, toxic NO
x
emissions of diesel cars have been underestimated up to 20-fold in
officially announced data. The voluntary agreement signed in 1998 between the European Automobile industry and
the European Commission envisaging to reduce CO
2
emissions has been identified as elementary for the ensuing
European diesel car boom. Four factors have been quantified in order to explain very different dieselization rates across
Europe: impact of national car/supplier industry, ecological modernization, fuel tourism and corporatist political
governance. By comparing the European diesel strategy to the Japanese petrol-hybrid avenue, it becomes clear that a
different road would have both more effectively reduced CO
2
emissions and pollutants.
Conclusion: Europe's car fleets have been persistently transformed from being petrol-driven to diesel-driven over the last
20 years. This paper investigates on how this came to be and why Europe took a distinct route as compared to other parts
of the world. It also attempts to evaluate the outcome of stated goals of this transformation which was primarily a robust
reduction in GHG emissions. We conclude that global warming has been negatively affected, and air pollution has become
alarming in many European locations. More progressive development scenarios could have prevented these outcomes.
Keywords: Diesel; Diesel car boom; Dieselization; NO
x
;CO
2
;PM;Soot;Blackcarbon;Globalwarming;Healtheffects;
Voluntary agreement; Taxation; Emissions; Fuel
Background
The clout of the transport sector
By 2007, the share of energy demand for transport purposes
made up 28.7% of final delivered energy on a global scale
[1]. Worldwide transport was responsible for 23% of world
energy-related greenhouse gas (GHG) emissions with road
traffic representing 74% of this sector (IPCC data from
2007, as summarized in [2]). The transport sector includes
airplanes, ships, trains and all types of street vehicles (e.g.
trucks, busses, cars, two-wheelers). Vehicles sometimes are
also separated into light-duty vehicles (automobiles, motor-
cycles, light trucks) with a kerb weight of up to 3,850 kg
and the class of heavy-duty vehicles. In a business-as-usual
scenario, a further doubling of automobile CO
2
emissions
is to be expected by 2050 due to the enormous increase in
automobile use in the developing world (particularly Asia,
* Correspondence: michel.cames@gmail.com;e.helmers@umwelt-campus.de
1
University of Luxembourg, 162a, avenue de la Faïencerie, 1511 Luxembourg,
Luxembourg
2
Institut für angewandtes Stoffstrommanagement (IfaS) am Umweltcampus
Birkenfeld, Trier University of Applied Sciences, P.O. Box 1380, 55761 Birkenfeld,
Germany
© 2013 Cames and Helmers; licensee Springer. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Cames and Helmers Environmental Sciences Europe 2013, 25:15
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see [3]). Improving fuel efficiency by 50% could however
stabilize world automobile CO
2
emissions by 2050 [4].
Strategically as well as environmentally, automobiles
play a particular role due to several reasons: first, cars
dominate road traffic in most countries. Eighty million
motor vehicles were produced in 2008 worldwide, 60
million of these being cars [5]; second, car sales exhibit
the largest growth rates in the world (see below); third,
unlike for trucks, the automobile market offers various
propulsion technologies as well as carbon-based fuels
[6]; fourth, besides the climate-relevant CO
2
emissions,
toxic emissions of cars negatively affect the air quality in
many regions, predominantly, those of the world's
densely populated. The World Health Organization
(WHO) [7] identified particulate matter (PM), nitrogen
oxides (NO
2
), ozone and sulphur dioxide (SO
2
) as being
the most dangerous air contaminants causing 1.3 million
premature deaths per year due to urban outdoor air pollu-
tion. However, PM (by number) and NO
x
emissions as well
as ozone production are largely caused by traffic emissions.
Following all that, it is essential to optimize automobiles
with respect to fuel efficiency, fuel type and emissions [8].
Astonishingly, these challenges are addressed in very differ-
ent ways: Europe strongly favours diesel-type combustion
cars, while diesel cars in USA are a side issue only. More
astonishingly, while since the late 1990s, the European
diesel car market boomed, diesel vehicles were removed
from the Japanese market. Possible backgrounds and ef-
fects of these oppositional strategies will be discussed in
this paper. Also, the European diesel car boom constitutes
a profound technology change. Presently, another automo-
bile technology change is being planned for the near future:
several western states and China seek to introduce electric
cars on large scale, which are much more energy efficient
and have local zero emissions [8]. Experiences in success-
fully dieselizingcar markets may help to launch electric
cars.
Global automobile market
The European Union (EU), USA and Japan own the
world's biggest car fleets (Table 1). Within the EU,
Germany (over 40 million) hosts most cars (Table 1),
followed by Italy (36 million) and France (31 million),
the UK and Italy (figures as of 2008, [9]). A fleet of
altogether 530 million cars are to be found on the eight
biggest car markets including as well Russia, China,
Brazil, South Korea and India ([9], data as of 2008).
According to the IPCC [10], the number of vehicles may
double until 2030 and triple by 2050 amounting to 2 bil-
lion light-duty vehicles worldwide. Over the past ten
years, China witnessed the largest annual car fleet
growth up to 23%, followed by India (13%) [9]. In 2011,
60 million new cars were manufactured worldwide
according to ACEA [5] and annual vehicle production is
believed to grow by 3% per annum until 2030 [11].
Sixty-five million vehicles were produced in 2010 while
worldwide production is expected to be 93 million in
2020 and 114 million in 2030 [11]. To date, the largest
markets and fleets are to be found in the EU, USA and
China (Table 1). All in all, the EU, USA and Japan domin-
ate car markets worldwide and own the largest car fleets,
with China following suit (third biggest market in 2011).
Automobile production is spread more widely (Table 1).
However, as for turnover (2008) and production (2010)
figures, the world's 15 largest car manufacturers are all sit-
uated in Europe, USA or Japan. Accordingly, EU, US and
Japanese development of automobile technology as well as
emission standards continue to dominate worldwide auto-
mobile standards, car production and fleet development.
For example, Asian countries widely adopt EU automobile
emission standards however with considerable time lag.
European cars exported to emerging markets have to
comply with much weaker emission standards than those
established in Europe [12]. The European diesel car boom
needs to be considered in this context as well.
Table 1 Key automobile figures worldwide (in millions of cars)
Largest car fleets (2010)
a
Largest markets (car registrations by 2011)
a
Largest producers (2011)
Country/region Cars Country/region Cars Country/region Cars
EU
27
239 EU
25
13.1 EU
27
15.7
a
USA 132 USA 12.7 China 14.5
b
Japan 58 China 11.3 Japan 7.2
a
China 44 Japan 4.2 Germany 5.9
b
Germany 42 Brazil 3.3 South Korea 4.2
b
Russia 34 Germany 3.2 USA 3.0
b
Brazil 26 India 2.5 India 3.0
b
(India) 12 France 2.2
a
ACEA [5];
b
http://www.oica.net/category/production-statistics/ (26.9.2012).
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Putting the European diesel car boom in a global context
In the early 1990s, the ratio of diesel cars in both Europe
and Japan did not differ much and accounted to about
10% of the fleet (Figure 1). It further increased until the
mid of the decade. Since then, the development com-
pletely diverged. Japan began to phase out diesel cars
while at the same time EU diesel car registrations began
to take off and grew steadily. Only the influence of the
economic crisis in 2008/2009 disturbed this longstanding
increase in Europe when gradually smaller and signifi-
cantly less diesel-driven cars were purchased (e.g. in
Germany, a temporary scrappage bonus strongly pro-
moted small car sales). At that time, diesel car fleet ratios
amounted to 1.4% in Japan compared to 35.3% in Europe
(2010), respectively, 58% as for new registrations (2011)
(Figure 1).
We assume that the long-term diesel car share in
Europe would have stabilized at around 15% since the
mid 1990s without incisive interventions by the Euro-
pean Commission to promote diesel cars (e.g. diesel
car emission concessions), Member State tax advan-
tages to support diesel car sales and provisions taken
by the European car industry. Asserted interventions
are being discussed below. These days, 238.8 million
cars are registered in EU-27 (figures as of 2011, [5]).
Theincreaseofdieselizationfromanon-intervention-
ist scenariofigure of 15% to 35.5% as calculated for
the EU-15 results in about 45 million extra on-road
diesel cars as compared to the mid 1990s. Provided a
different political course would have been taken, these
diesel-fuelled cars could have run on petrol or
equipped with alternative powertrains such as petrol-
electric hybrids like in Japan, as discussed below. As for
the territory covered by the European Environmental
Agency (30 European countries, including Turkey), the
share of diesel cars among the entire fleet increased from
14.2% in 1995 to 33.2% in 2009 [17] which amounts to an
extra 46.95 million diesel cars in absolute terms. These
extra diesel cars impact air pollution levels for a long time:
\the average life span of a 1990-built car in Western
Europe has been reported to be 16.1 years [18].
We will raise the question whether European diesel
technology or Japanese petrol hybridization have been
environmentally more efficient and what have been the
reasons for this very different development. Interestingly
enough, the level of diesel car penetration is far from
uniform within Europe (Figure 2).
While the overall EU diesel car penetration follows the
trend shown in Figure 1, the ratio of diesel cars remained
very low in some European countries (Figure 2). Also, die-
selization developed heterogeneously over time in differ-
ent countries. The fastest dieselization increase occurred
in Italy where the share of diesel cars quadrupled between
1995 and 2009 (Figure 3). This is to be discussed to under-
stand underlying political and economic mechanisms, as
we will see below.
The USA and China are two further world-leading car
markets (Table 1). In the USA, as a response to the 1973
and 1979 oil crises, several hundred-thousand diesel cars
were sold. However, from the 1980s onwards, diesel cars
became marginalized, and its market share later shrank
to some 0.3% in the early 2000s [16]. Since 2008, again,
diesel car sales achieve double-digit growth in the USA
reaching 1.3% market share in 2011 [16]. Analysts be-
lieve it could grow to 6% by 2015. Within the world's
largest car markets, China has the lowest diesel car ratio
with only 0.04% of new registrations in 2005 [20]. India,
the next-fastest growing car market on the contrary ex-
hibits a registration share of 35% [4].
Discussion
Climate change mitigation effects of the European diesel
car boom
GHG emissions
The UN Intergovernmental Panel on Climate Change
(IPCC) was established in 1988. Its creation may be con-
sidered as the beginning of a global political commit-
ment to combat the threat of climate change. The
political efforts of the 1990s years resulted in the Kyoto
protocol adopted in 1997, where particularly European
countries committed themselves to significant reduc-
tions of GHG emissions. The European Union signed
the Kyoto protocol with the commitment to save 8%
GHG by 2012. During the elaboration of the target, the
European Commission devised an allocation plan of the
envisaged savings.
Figure 1 Diesel car penetration in major world markets.
Expressed as percentages, either annual new car registrations or
annual entire car fleet composition. Data sources: EU registration
data [5,13]; data 1990 to 1993 (Western Europe, including Iceland,
Norway, Switzerland); data 1994 to 2011 (EU-15); EU fleet data for
2006, 2008 and 2010 (ACEA, http://www.acea.be); EU fleet data 1990
to 2005 [14]; Japan fleet data [15]; US registration data 2000 to 2011
([16], data extrapolated back to 1990).
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Traffic and particularly road traffic had early been
identified as one of the main GHG emission sources (see
above). However, since heavy-duty vehicles (trucks) are
propelled by diesel engines with hardly any alternative
(despite busses and local heavy-duty traffic), the automo-
bile sector has been identified early as the sector in
which a technology shift from gasoline to diesel engines
may ensure significant GHG savings. GHG emitted by
automobiles are expressed in CO
2
equivalents, which are
usually quantified by summarizing the three GHG CO
2
,
CH
4
and N
2
O emitted by fuel provision and combustion.
However, CH
4
- plus N
2
O-related CO
2
equivalents
amount to less than 2% of CO
2
emissions [21]. The
European Environmental Agency (EEA) considers only
one parameter of both CH
4
and N
2
O in calculating the
CO
2
equivalents of road transport diesel oil and gasoline
fuel, respectively, resulting in only around 1% deviation of
CO
2
emissions [22]. Direct CO
2
passenger-car emissions
Figure 2 Diesel penetration by country in EU-15 plus EFTA (in %) of new cars registered by 2011 [5]. NO, Norway; CH, Switzerland; IS,
Iceland; IE, Ireland; EL, Greece.
Figure 3 Dieselization in 1995 (blue columns) and 2009 (purple columns) according to EEA [17]. Percentage of diesel cars in the total
passenger car fleet. Threshold exceedances (in %, red) according to the Gothenburg protocol for NOxemissions in 2010 [19].
Cames and Helmers Environmental Sciences Europe 2013, 25:15 Page 4 of 22
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may thus be considered here since they equal GHG emis-
sions with a low error rate.
CO
2
emission of diesel as compared to petrol-driven
passenger cars
Generally, diesel cars are believed to be (much) more
fuel efficient compared to their gasoline alternative. In
its fourth assessment report, IPCC [3] announced an
outstanding 25% well-to-wheel CO
2
emission advantage
of a diesel car compared to its petrol equivalent.
According to the report, Direct injection diesel engines
yield about 35% greater fuel economy than conventional
gasoline engines, enhancing thereby the market value of
diesel cars. The US federal office of transportation quan-
tifies the fuel economy advantage of diesel cars over
gasoline cars as up to 63% [23]. All too often, however,
the higher calorific value of diesel fuel is not taken into
account. Diesel fuel contains, dependent to fuel quality,
about 14% more carbon per litre [6]. This effect reduces
the CO
2
emission advantage of diesel cars suggested by
favourable fuel efficiency measured in volumetric terms
(l/100 km or miles gal
1
). Thus, the emission intensity
(in g CO
2
km
1
) is a much more precise indicator to
measure the efficiency of fuels with competing engine
technologies than the fuel consumption efficiency.
Lutsey [24] compared the fuel economy increase as
well as the CO
2
emission reduction advantage of 23 dif-
ferent electric hybrid gasoline cars and 16 diesel cars to
their gasoline model equivalents. On average, the hybrid
models offered a 45% fuel efficiency advantage and 30%
CO
2
savings whereas diesel models only brought about a
35% fuel efficiency advantage and 15% CO
2
savings dur-
ing operation [24]. Also, Schipper and Fulton [25] con-
clude that the diesel car CO
2
advantage appears to be
no more than 15% to 18% for vehicles of similar size
class.
Diesel car engines have been tremendously improved
over the last 2 decades: the diesel engine with direct in-
jection has been introduced, fuel pressure has been con-
tinuously increased by common rail direct fuel injection
and turbo charging has become common in modern
passenger car diesel engines. Fuel economy of diesel
cars has been improved considerably by these mea-
sures. However, the much higher diesel fuel injection
pressure continuously increased NO
x
emissions (see
below), whereas soot emissions were decreased - but
only by weight [26]. Without post-treatment, how-
ever, the remaining soot is composed of much smaller
particles [27].
In contrast, the advancement of the petrol-fuelled en-
gine has received considerably less attention during the
past 20 years. For example, there were a few automakers
only early offering cars with downsized turbocharged
petrol-fuelled engines like Mitsubishi and Volkswagen.
Just recently, other automobile manufacturers have
marketed downsized petrol engines.
We believe that the CO
2
advantage of petrol cars
would have been nearly or about the same if the same
effort had been invested in improving petrol engines. This
can be illustrated with two examples: in 2009, a
Volkswagen, model Passatwith turbocharged downsized
petrol engine (110 kW) emitted 157 g CO
2
km
1
, while its
pendant Passatwith 105-kW-diesel engine emitted only
3% less, i.e. 152 g CO
2
km
1
[2]. Fuelled by natural gas;
however, the Passatwith the same performance engine
emitted only 119 g CO
2
km
1
[2]. Another case in
point, a Ford, model Focus, with modern turbo-
charged downsized petrol engine (1.0 l, 3-cyclinder,
73.5 kW) emits 112 g CO
2
km
1
while the pendant car
with 70 kW turbocharged diesel engine emits 109 g
CO
2
km
1
, not even 3% less (according to Ford data).
We conclude that CO
2
emission advantages of diesel
cars can be close to absent if gauged against modern-
ized petrol-driven engines.
European diesel versus gasoline car CO
2
emissions
While the former chapter discussed whether there is a
fundamental efficiency, i.e. GHG emission advantages of
diesel cars versus petrol-fuelled cars, on-road CO
2
emis-
sions of new passenger cars are analyzed subsequently.
Between 1995 and 2005, a significant emission gap of 5%
to 10% CO
2
persisted in Europe between newly regis-
tered diesel and petrol cars (Figure 4).
However, while petrol-fuelled cars emitted continu-
ously less CO
2
over time, diesel cars in Europe stalled
emission intensity improvements between 2000 and
2005. New diesel passenger cars in Europe therefore lost
most of their CO
2
emission advantage over gasoline cars
(Figure 4). Since 2009, diesel car CO
2
emission advan-
tage over petrol cars in Europe became marginal and
went down to 1.5% in 2010 (Figure 4). Since 2006, CO
2
emissions of new diesel cars in Germany even continu-
ously increased as compared to gasoline cars [33]. CO
2
emissions of new diesel cars registered in Germany had
increased since 2001 while at the same time gasoline
cars lowered their CO
2
-emission intensity [34]. A con-
tinuous increase of engine power has been one reason.
CO
2
emissions are clearly increasing with growing en-
gine power [35]. Engine power of new passenger cars in
Europe grew continuously in the past. However, while
engine power of gasoline cars grew only by 7.5% be-
tween 2001 and 2011 among new cars in Europe, diesel
car engine power increased by 22% in the same period
[36]. By 2011, new diesel passenger car engines were
21% more powerful than gasoline cars in Europe [36].
Some authors have pointed in this context to the re-
bound effect [25,37,38]. In conclusion, the EU
Commission's thrust to boost diesel car technology
Cames and Helmers Environmental Sciences Europe 2013, 25:15 Page 5 of 22
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with the aim of reducing overall CO
2
emissions has
failed by mismanagement.
Based on comparable data as shown in Figure 4,
Ajanovic [14] argues that the largest part of saving over
time was brought about by overall efficiency improve-
ments for both gasoline and diesel cars. Due to better effi-
ciency of cars in general, between 1980 and 2007, about
9% of energy was saved of which about an eighth - 1% -
was saved due to the switch to diesel. Given this very
moderate result, we can conclude that the fuel tax incen-
tives provided of about 10% to 50% lower taxes in differ-
ent European countries for diesel than for gasoline were
not at all justified[14].
At the same time, Japan managed to decrease CO
2
emissions of new cars much faster (Figure 4) without
resorting to diesel technology. By increasing the hybrid
car market share in Japan continuously from 0.4% in
2001 to 9.3% in 2010 (numbers calculated with data
from http://www.greencarcongress.com/sales and JAMA
data [31,32]), Japanese CO
2
car emissions declined no-
ticeably since 2001 (Figure 4). In 2010, 1.4 million hybrid
cars circulated on Japanese roads [32], amounting to
2.4% of the whole car fleet.
In the USA, Canada and Australia, car CO
2
emissions
are much higher than in the EU and Japan [39] as a con-
sequence of larger average car size.
Supply chain CO
2
emissions
Tank-to-wheel CO
2
emissions as discussed above are
nonetheless only one side of the coin. Supply chain fuel
emissions are in the order of 18% of aggregate well-to-wheel
emissions ([8], based on [21]). Öko-Institut [21] quantifies
petrol-provisioned CO
2
emissions as being 7% higher than
for diesel. Bodek and Heywood [40] assert the opposite:
well-to-tank emissions of diesel fuel provision are 13.6%
higher than for petrol followed by another 7% CO
2
emis-
sion surcharge of diesel over petrol in the tank-to-wheel
phase (according to CONCAWE 2007 data [40]). Supply
chain CO
2
emissions are greatly depending on the source
and type of crude oil, the refinery location and transport
distances [41]. In addition, they are in continuous flux:
Pieprzyk et al. [41] claimed that the mean diesel and
petrol GHG emissions are 347.5 g CO
2
kWh
1
and there-
fore on average 15% higher than indicated by Global
Emission Model of Integrated Systems 4.5 (GEMIS, see
http://www.gemis.de). The consistently increasing diesel
fuel demand in Europe has considerably increased supply
chain emissions: diesel fuel supplies from Russia have
gradually supplanted EU production ensuing in higher
supply chain emissions. According to Pieprzyk et al. [41],
additional CO
2
emissions amount to some 25% as for
Russian compared to mean German diesel fuel. Moreover,
the European Petroleum Industry Association (EUROPIA)
believes that new environmental regulations to reduce
the sulphur content of fuels could lead to a 50% in-
crease in CO
2
emissions [42]. Dings [37] points out
that the high demand for diesel fuel resulting in a
sharp increase of the middle distillate/gasoline pro-
duction ratio from 1.7 to 3.7 will increase the CO
2
emissionsfrom0.18to0.29t/tproduct(+61%).Hy-
drocracking units necessary for this production shift in
order to maximize distillate fuel output is the case in
point. EUROPIA anticipates that despite assumed effi-
ciency improvements, the higher demand and enacted
or potential increased product quality specifications
will substantially increase refinery CO
2
emissions by
2020. Should the observed historic growth of diesel de-
mand in Europe continue, diesel market dynamics
would result in refinery-CO
2
-emission penalties even-
tually exceeding diesel vehicle benefits [43].
120
130
140
150
160
170
180
190
1995 1997 1999 2001 2003 2005 2007 2009 2011
petrol cars EU
Diesel cars
EU
cars Japan
/kmg CO2
Figure 4 CO
2
-emission time trend of new registered cars (comparison EU - Japan). (Sources: EU-15 figures 1995 to 1999 [28]; EU-27 figures
[29,30]; Japan 1995 to 2006 figures recalculated by JAMA [31] data; Japan 2007 to 2010 figures recalculated by JAMA [32] data.)
Cames and Helmers Environmental Sciences Europe 2013, 25:15 Page 6 of 22
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Standardized versus real life fuel consumption
As yet, the new European driving cycle(NEDC) has
been applied to quantify fuel consumption and GHG
emissions under standardized but artificial test cycle
conditions. It has become common understanding how-
ever that the test cycle is unable to represent real-life
driving. Almost all cars consume some 20% to 25% extra
fuel than NEDC estimates and as a result emit more
CO
2
than certified [8]. Most of the 100 cars investigated
by auto-testers exceeded test values by up to 40%, while
a few percent of the vehicles in this spot check revealed
fuel consumptions even up to 70% higher than certified,
according to the European test scheme [44].
What is more, diesel cars have been reported to show
higher deviations from test cycle results than gasoline
cars (reviewed in [6]). In a recent study published by the
European car magazine AutoBild (German Edition no.
23, June 8, 2012), real life fuel consumption deviations
of 19 diesel cars and 32 gasoline cars have been ana-
lyzed. Diesel cars revealed surplus consumption of +39%
while gasoline cars merely consumed +30% more fuel on
average compared to NEDC (plug-in hybrids were not
considered). It must be said however that the car classes
chosen such as SUVs, vans, green or sportive cars gener-
ally exhibit the highest deviations from certified fuel
consumption.
According to a real life assessment of 250 cars by the
German automobile club ACE between 2000 and 2008,
petrol cars recorded an average surplus fuel consump-
tion of 16.9% while diesel cars consumed 23.8% more
[6]. With regard to the above reasoning, we ultimately
believe that the European diesel car boom permitted
only small CO
2
savings from a book-keeping point of
view, yet it might have saved none at all or even boosted
aggregate CO
2
emissions.
Other climate change effect caused by diesel emissions:
NO
x
, ozone and black carbon
Beyond the previously mentioned greenhouse active spe-
cies (CO
2
,N
2
O, CH
4
) there are two more important
traffic-related warming agents emitted or induced by
road traffic: ozone and black carbon. Nevertheless, EEA
[45] calls PM (particulate matter) and ozone as being
just the most problematic pollutants in terms of harm
to health. Annual mean ozone concentrations in Europe
have been reported to be fairly constant since measure-
ments have begun in 1997 [45]. However, ozone is pro-
duced from the precursor groups VOC (volatile
organic carbons), CO and NO
x
. The latter is emitted
by traffic and particularly by diesel engines (see below).
EEA [29] reports that ozone concentrations remain
stable at a high level even that precursor emissions
have decreased considerably. However, reported pre-
cursor emissions are only modelled [45] and may not
reflect reality (see below). Radiative forcing by tropo-
spheric ozone has been quantified by IPCC [46] as be-
ing +0.35 ± 0.15 W·m
2
,whichis21.9%ofthenet
positive radiative forcing effect of all-human activities
since 1750 [47].
Nevertheless, EEA does not quantify the excess radia-
tive effect of ozone immission in Europe according to
their anthropogenic precursor emissions. The reason
nottodosoisitslackofcommitment:bothozoneand
black carbon are not covered by United Nations
Framework Convention on Climate Change and Kyoto
protocols [22].
Modelling ozone dynamics with respect to their pre-
cursor groups is difficult. In the USA, atmospheric re-
searcher Jacobson runs suitable models exhibiting, e.g. a
widespread ozone increase in consequence of excess
CO
2
emissions [48]. A reduction of ozone is most effi-
ciently achieved by reducing its precursor group, the ni-
tric oxides [49]. However, particularly NO
2
triggers
excess ozone production and the NO/NO
2
ratio de-
creased by oxidation catalysts in modern diesel cars of
recent years (e.g. [50]). Lemaire [51] points to a high
positive correlation of NO
2
and ozone in European-
polluted environments.
The biggest concern with regard to the effect of the
European diesel car boom towards the heat balance of
the atmosphere is however related to excess black car-
bon (BC) emissions of diesel cars. Jacobson [52] esti-
mates the anthropogenic black carbon direct forcing to
be higher than estimated by IPCC [10] and summing up
to +0.55 W·m
2
. According to Jacobson [52], it makes
up 16% of the total anthropogenic global warming. A
joint group of experts presently assisting IPCC in the
preparation of the forthcoming report concluded that in
the industrial era (1750 to 2005), direct radiative forcing
of atmospheric black carbon would be twice as high than
previously believed (+0.71 W·m
2
, [53]).
Jacobson [52] and his group modelled the atmospheric
effect of a theoretical conversion of the entire US car
fleet from gasoline to diesel. They based their calcula-
tions on the strictest EU emission thresholds (EU 5
and 6) with 5 mg of PM km
1
and European-type cars.
Jacobson [52] concludes that finally, even with a par-
ticle trap, diesel vehicles still emit more particles than
do gasoline vehicles(Jacobson did not consider recent
direct injection petrol-fuelled engines). Actually, EU
regulations do not require cars to be equipped with
particulate filters but PM must not exceed 5 mg·km
1
.
A diesel car equipped with particulate filter emits 1 to
5mgPMkm
1
[2].
Jacobson [52] concludes that given a (realistic) 15%
higher diesel car fuel efficiency as compared to petrol-
fuelled cars, no cooling effect will be observed in the at-
mosphere over 100 years. Given an (unrealistic) 30%
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higher fuel efficiency of diesel cars, Jacobson [52] pre-
dicts a warming of the atmosphere within the first 10
years, followed by an overall cooling, based on less than
6mgPMkm
1
of a single car.
Black carbon is a strong warming agent expressed by
its global warming potential (GWP): For fossil fuel emis-
sions, Jacobson [52] quantifies a mean BC-GWP of
1,870 for the 100-year horizon and a GWP of 4,470 for
the 20-year horizon, respectively. Bond and Sun [54] cal-
culated a BC-GWP of 680 for the 100-year horizon and
a GWP of 2,200 for the 20-year horizon. A GWP of 680
means that 1 kg of BC produces as much forcing as 680
kg of CO
2
[54]. BC is an impressive warmer because it
absorbs most of the intercepted visible light whereas the
impact of CO
2
occurs over a limited range of infrared
wavelengths [54].
Due to its much shorter atmospheric lifetime in com-
parison to CO
2
, it is more efficient to reduce BC emissions
in order to cool down the atmosphere quickly concomi-
tantly reducing global outdoor air pollution [55].
With these data, CO
2
-equivalent radiative effects of
BC can be calculated: diesel PM contains 50% to 80%
carbon [56]. Andreas Mayer [57] specifies 58% BC in
diesel PM emissions, resulting in a mean of 61.5% if ag-
gregated with NREL [56] figures. The BC content of
petrol combustion emissions is much lower with only
20% [56], which has been confirmed by US-EPA [58].
Based on a mean 100-year GWP (averaged according to
Jacobson and Sond and Sun, see above) of 1,275 and
61.5% BC emitted within diesel PM, an emission of 1 mg
PM as achievable by particulate filters, would result in a
CO
2
-equivalent of 0.78 g·km
1
due to its radiative effect.
The most stringent PM thresholds (Euro 5, Euro 6),
however, allow 5 mg PM km
1
emission resulting in a
radiative effect of 3.9 g CO
2
equivalents km
1
. However,
prior to Euro 5 standards mandatory since 2009, the
European Commission allowed diesel cars to emit 25 mg
PM km
1
emission according to Euro 4. This corre-
sponds to 19.5 g of CO
2
emissions, which is largely
exceeding the maximum pre-2007 CO
2
emission ad-
vantage new diesel cars possessed over petrol cars
(Figure 4). Prior to 2005, the Euro 3 threshold was at
50 mg PM km
1
resulting in a CO
2
equivalent of 39.2
gCO
2
km
1
. However, the diesel car boom in Europe
already took off in 1997. Black carbon's global
warming potential relative to a 20-year time frame is
equivalent to the 2.6-fold potential relative to a 100-
year time frame.
Petrol car PM emissions were not regulated before
Euro 5 (then limited to 5 mg·km
1
), yet they were gener-
ally in the range of 5 mg·km
1
as shown, e.g. on a 2001
model car [59]. This quantity of PM emitted by a petrol
car corresponds to a radiative effect in the order of 1.3 g
CO
2
equivalents km
1
only due the much lower BC
content of the emitted PM. It has to be emphasized that
the above-generated radiative effects of emitted black
carbon have to be added to CO
2
fuel combustion emis-
sions. In conclusion, millions of diesel passenger cars
were allowed by EU authorities to be brought onto
European roads after 1996 (Euro 3 allowing 100 mg
PM km
1
)emittingupto20timesmorePMaswellas
up to 60 times more BC compared to petrol cars (European
Union automobile emission thresholds available here:
http://www.dieselnet.com/standards/eu/ld.php).
On a voluntary basis and to get hold of the first-mover
advantage, Peugeot Citroën (PSA; French) equipped
some of its new cars with particulate filters in 1999 [60].
After several years of public pressure debate about its
necessity, car makers have followed suit since 2003 and
equipped most of their diesel vehicles with particulate
filters [60] yet often at an extra charge [61]. Figures
about the share of diesel cars within the fleet equipped
with particulate filters have not been recorded. However,
since the European diesel car boom started already be-
fore the millennium and only after 2009, almost all cars
became equipped with filters ex works is rather unlikely
that a majority of diesel cars own a filter so far. A small
share of pre-2009 diesel cars has been retrofitted with an
unregulated, open, and inefficient filter system.
Did the European diesel car boom mitigate climate change?
A quantitative assessment of the climate impact of the
European diesel car boom would necessitate a complex
computer modelling, yet even basic variables, such as
the number of diesel cars equipped with particulate fil-
ters for each individual year starting 1999 is not avail-
able. Some qualitative estimations however reveal a
rather clear picture: the CO
2
emission advantage of
diesel cars as compared to petrol cars between 1995 and
2003 based on standardized measurements mounts up
to 12.8 g km
1
(range: 8 to 17.1) (Figure 4). However,
when taking account of black carbon emissions, the pic-
ture changes: diesel cars were allowed to emit up to 50
mg PM km
1
prior to 2005 (Euro 3). Average black car-
bon contained in the emitted PM of a diesel car regis-
tered between 1995 and 2003 has an excess radiative
effect equivalent to 37.9 g CO
2
km
1
relative to a petrol-
fuelled car. These extra emissions of pre-2003 diesel cars
are threefold the relative advantage of diesel to petrol
cars (12.8 g CO
2
km
1
) between 1995 and 2003 when it
comes to direct CO
2
emissions.
When, however, equipped with a particulate filter, the
extra radiative warming effect of a mean diesel-fuelled
car turns into a minor additional diesel car advantage
relative to a petrol-fuelled car of about 0.5 g CO
2
equiv-
alents km
1
, based on a simplified estimate here (ele-
vated PM emissions of petrol-fuelled cars with direct
injection neglected). Aggregated with the combustion
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CO
2
emission advantages of solely 3.5 g·km
1
(Figure 4),
recent diesel cars in Europe theoretically exhibit a cli-
mate advantage of 4 g CO
2
equivalents km
1
. We how-
ever believe that the mere extra well-to-tank CO
2
emissions caused by the strong demand for this type of
fuel most likely overcompensates this minor aggregate
emission advantage of modern diesel cars in real-life sit-
uations. Moreover, the above estimate is true only for
new cars with properly working particle filtration sys-
tem. A certain share of cars however develops technical
defects over time in the particle filtration system [6].
Then, those systems have a certain life expectancy rarely
extending beyond 200,000 km resulting in higher mean
PM emissions. The incentive of high mileage car owners
to replace expensive filtration systems will be marginal.
Besides, the diesel scenario strongly shifts towards the
negative when the radiative effect over a short time - 20
years instead of 100 years - is considered. The CO
2
equivalent effect of BC emitted by diesel cars is then tri-
pled (see above). Even worse, recent global BC radiative
effect quantification [53] seems to be even higher than
assumed by Jacobson [52] which would further increase
above presented figures of an additional radiative effect
of diesel car BC emissions in terms of CO
2
equivalents.
We therefore estimate the aggregate climate effect of
the general European powertrain switch from petrol to
diesel to be negative accordingly, mainly due to the
strong radiation effect of large numbers of diesel cars
without particulate filter registered in Europe after 1995.
Moreover, we would like to draw attention to the fact
that in the developing world, some countries (such as
India) continue to register large numbers of diesel cars
without particle filter systems. The most effective strat-
egy in minimizing global warming consists of increasing
the ratio of electric hybrid petrol-fuelled cars or, under
certain circumstances, electric cars [8]. Furthermore,
European citizens have been exposed to additional
toxic emissions due to less stringent diesel car emis-
sion thresholds than applied to petrol cars for some 20
years. This holds true as well for many developing
countries where less stringent European diesel emis-
sion standards are being applied with a time lag. India
is a case in point [62].
Toxic emissions of the European diesel car boom
Nitrogen oxides
According to the WHO, NO
2
, ozone and PM are among
the primary air contaminants threatening human health
[7]. WHO is the leading organization in quantifying and
evaluating adverse health effects resulting in air quality
guidelines [63].
In Europe, WHO points to traffic-borne NO
2
,excess
ozone and particulate matter values to some extent
above dangerous levels and resulting in hundreds of
thousands of premature deaths in Europe just in terms
of PM [64]. As for NO
x
, e.g. empirical research in
California [65] and Leicestershire, UK [66] has shown
that childhood asthma and exposure to traffic-borne
nitrogen dioxide clearly correlates.
Analogously to PM thresholds for passenger cars, EU
authorities adopted different NO
x
emission thresholds
for diesel than for petrol cars. NO
x
represents the sum
of NO plus NO
2
. Since Euro 3 and up to now (Euro 5),
NO
x
emission thresholds for diesel cars have been about
three times higher than for petrol cars. Noticeably,
this legal threshold limit between petrol and diesel
cars (factor of 3) is mistakenly used as a basis for
emission comparison even in high-quality scientific
reports (e.g. by [67]).
NO
x
emission levels as reported by the different EU
Member State using the New European Driving Cycle
reveal a large gap between diesel and petrol vehicles:
Euro 3 to 6 diesels are specified to emit 400, 200, 150,
and 50 mg NO
x
km
1
, which is about the 10-fold quan-
tity than what petrol cars emit (data starting 2001, [36]).
As a result of catalytic converters, NO
x
emissions from
petrol cars have been less than 45 mg NO
x
km
1
since
2001 respectively less than 30 mg NO
x
km
1
since 2005
[36]. Based on this assumption of a 10:1 NO
x
ratio of
diesel to petrol car emissions, Helmers [2] deduced that
just the additionally registered diesel cars in Germany
between 1995 and 2007 emitted 3% to 5% of traffic-
related NO
x
emissions, amounting to 1.5% of aggre-
gate NO
x
emissions by 2007 in Germany. Moreover,
T. Buetler (Swiss EMPA) quantified diesel car NO
x
emissions under dynamometer conditions and con-
cluded that current European NO
x
emission thresh-
olds are exceeded under the New European Driving
Cycle conditions on some vehicles with medium
mileage (T Buetler, personal communication). We
mayconcludethatemissionlevelsasrecordedbythe
New European Driving Cycle are not being met. How-
ever, there is more than that. Strong evidence sug-
gests that under real-life driving, NO
x
emissions of
diesels largely exceed threshold limits: a multitude of
data was recently published, exhibiting much higher
real-life NO
x
emissions (e.g. [68] claims two-to-fourfold
higher real-life NO
x
emissions). Outside the laboratory,
only marginal NO
x
emission reductions were recorded
over the last 10 years, i.e. from 650 (Euro 0) to 560 mg
NO
x
km
1
(Euro 5) due to Scholz [69]. Measurements of
the European Joint Research Center [70] point to real-life
NO
x
emissions of Euro 5 diesel cars about 4 times higher
than threshold limits suggest. Steven [71] recorded values
as high as 4000 mg NO
x
km
1
on present-day diesel cars
in urban driving conditions with a high share of uphill
rides within the city of Stuttgart (Southwest Germany). He
concludes that even under a forthcoming Euro 6 threshold
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regime, the EU NO
2
air quality threshold of 40 μg·m
3
for
ambient air valid since January 1, 2010 cannot be met for
the discrepancy between standardized cycle and real street
emissions [71].
Hagman et al. [72] mention that new cars with diesel
engines may emit 500 to 1,500 mg NO
x
km
1
, which is
20 to 40 times more than a similarly sized petrol engine
car. New heavy-duty vehicles with diesel engines emit
4,000 to 10,000 mg NO
x
km
1
[72]. They particularly
object that diesel car NO
2
emissions have continuously
increased since Euro 0 peaking at 450 mg NO
2
km
1
for
Euro 4 diesel cars and 350 mg NO
2
km
1
for Euro 5
diesel cars. Under urban and highway driving conditions,
Hagman et al. [72] expect 45 to 55 mg NO
2
km
1
, which
is still in the order of the NO
2
emissions of Euro 0 to
Euro 2 diesel cars while under congested conditions,
they expect not less than 100 mg NO
2
km
1
for Euro 6
diesel cars. These data easily explain why people are irri-
tated by the chlorine-like pungent odour of NO
2
emitted
by modern diesel cars [73]. Lemaire points out that within
diesel exhaust emissions, control strategies of NO
2
was
apparently forgotten as separate component of the NO
x
emissions from diesel vehiclesresulting in increased NO
2
and ozone pollution in a number of European cities [74].
It is worth recalling that Japanese petrol-electric hy-
brid technology managed to effectively reduce CO
2
emissions of passenger cars enabling even lower NO
x
emissions in the magnitude of 6 mg NO
x
km
1
(cf. [24]).
In comparison, petrol-fuelled cars emit under real-life
situations 10 to 100 mg NO
x
km
1
as reviewed by Helmers
[2]. In conclusion, NO
x
emissions from current on-road
diesel cars are 10 to 100 times higher than petrol car NO
x
emissions if petrol-fuelled hybrid cars are considered.
Currently, European car manufacturers mind supple-
mentary NO
x
cleaning technology costs required to
comply with Euro 6 emission standards while simultan-
eously exporting clean dieselsoverseas (USA basically).
As a consequence, NO
2
pollution levels have increased
in those European countries with a high diesel car share,
yet even in heavy traffic hot spots in moderately diesel-
ized Germany, 34% of 489 measuring stations record
NO
2
mean pollution levels above the European Union
threshold of 40 μg·m
3
in 2010 [69]. Due to the city of
Stuttgart's setting in a valley inhibiting air exchange, ni-
trogen oxide records persistently exceed the EU annual
threshold. In the city of Luxembourg, Europe's diesel car
capital, annual mean NO
2
concentrations have increased
continuously from 46 to 60 μgm
3
since 1996 [75].
Paris, London and Florence are also among the highest
NO
2
pollution sites in Europe [76].
With the estimated extra 45 million newly registered
diesel engines in the European Union since 1995 emit-
ting at least the tenfold amount of NO
x
as the engines
they substituted, the EU is struggling to come to terms
with the Gothenburg multi-component protocol. This
protocol signed in 1999 is part of the stepwise process of
the Convention on Long-Range Transboundary Air Pollu-
tion and aims at protecting health and ecosystems [77]. It
became effective in 2005 and compels Member States to
effectively reduce SO
2
,NO
x
, VOC and NH
3
emissions.
The EEA and the European Member States follow these
obligations by modelling their individual emission targets.
However, national emission ceilings laid down in Euro-
pean Commission's Directive status reports are not based
on actual recorded pollution but on computed theoretical
modelling such as e.g. TREMOVE, TREMOD or COPERT
[78]. Modelling of toxic traffic emissions may thus be
based on overall national fuel consumption [19]. Even
that, any model acknowledges to comprise potential
errors - e.g. TREMOVE considers these to be 17% to 19%
of computed NO
x
emissions [78] - we believe those to be
much larger since models are based on artificial
laboratory-based emissions of cars (see above) while em-
pirical and real-world measurements reveal that diesel car
on-road NO
x
emissions are up to 20 times higher.
Lemaire [51] also points to numerous robust NO
x
immission underestimations ascribed to modelling.
Despite underestimations, some states have been iden-
tified to exceed their NO
x
emission quota granted by the
Gothenburg protocol [19]. NO
x
emission exceedances
and fleet dieselization rates of EEA Member States have
been displayed in Figure 3.
Even though non-traffic-related NO
x
can make up half
of the aggregate NO
x
emissions in most countries, a
prominent clustering of countries with both highest NO
x
threshold value exceedances and highest share of diesel
cars in their fleets is observed (Figure 3). Luxembourg, the
most dieselized European Member state, exceeds the
allowed NO
x
emission quota by even 87% which is how-
ever partly explained by its fuel tourismexport policy.
High NO
x
emissions of Ireland are related to the out-
standing increase of car registrations [79].
AvailabledataondieselcarNO
x
emissions in Europe
thus raises the question whether EU authorities are not
able to sufficiently keep control in this field. We believe
poor data causing considerable and persistent underesti-
mation of actual diesel car NO
x
emissions to be the cause.
In addition, the European public is hardly aware of the
actual NO
x
immission situation: generally, modelled data
computed with artificial data demonstrate (drastic) future
emission reductions dominate the public view. While
mean national (modelled) NO
x
levels are rarely exceeded,
many European cities increasingly experience NO
2
pollu-
tion levels above the EU threshold of 40 mg·m
3
in reality.
Health hazards of particulate matter
In June 2012, WHO's International Agency for Research
on Cancer classified diesel engine exhaust as carcinogenic
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to humans (group 1) based on sufficient evidence that ex-
posure is associated with an increased risk for lung cancer
[80] after it was classified as probably carcinogenic to
humans (group 2A) in 1988. Gasoline exhaust has
remained to be classified as possibly carcinogenic to
humans(group 2B) since 1989 [80]. WHO has thus criti-
cized the shift from gasoline to diesel vehicles commended
by the IPCC focusing merely on alleged CO
2
emission
reductions [81].
In the Netherlands, particulates have been classified as
the second highest risk for human life [82]. Wichmann
[83] reviewed that average life exposure to particulates
(23.5 μgPM
10
m
3
) reduces life expectancy by 0.6 years.
Moreover, 1% to 2% of annual fatal casualties can be at-
tributed to diesel vehicle emissions in Germany [83].
The equipment of all diesel cars with particulate filters
would prolong life expectancy in Germany by 1.9
months [83]. It has been claimed that the diesel particu-
late filter retains most of the particulates. While this is
true in terms of mass (weight basis), it does not hold in
terms of number concentration as particulate filters may
emit nanoparticles in much larger numbers [84] than
without filtering. Moreover, modern diesel engine tech-
nology has caused the number concentration of
nanoparticles to increase [85]. We wish to recall that
probably a majority of diesel cars with modern engine
technology registered in Europe since 1995 - with a life
span beyond 15 years (see above) - have not been
equipped with a particulate filter trap. Health costs for
excess direct CO
2
emissions may as well be quantified
(e.g. [48]). However, we are not going to compare CO
2
and toxic emissions health costs in this paper, which is a
complex but important question [86]. We have to point
out all the more that due to the European diesel car
boom, citizens in Europe have been exposed to excessive
toxic emissions and associated health costs while the cli-
mate could not benefit.
The European Commission has unilaterally promoted
diesel car technology evidenced by higher toxic emission
threshold legislation since 1996 (Euro 2). We believe this
is a violation of the principles of a sustainable society as
defined in 1991 by IUCN, UNEP and WWF [87].
Quest for the origin of the European diesel car boom
Impact by the European oil industry
If the environmental record of a proliferation of diesel
cars in Europe is as unsatisfactory as portrayed, the
question then arises about how this paradigm switch ori-
ginally came to be and has remained in force for more
than 15 years.
Europe was confronted with shrinking fuel oil markets
from 1970 onwards and more dramatically, after 1979,
clearly reflected by oil company BP [88] sales data 1965
to 2011 which specifies the quantities of the crude oil
distillation products, light distillates (gasoline, petrol),
middle distillates (diesel) and fuel oil (which can be
converted to diesel) sold for Europe. The reasons for the
lack of demand for middle distillates were at the least
twofold. First, natural gas had increasingly pushed out
fuel oil as a heating fuel at the continental European
market since the mid 1960s [89]. In Germany, 18.6 mil-
lion (48%) households were connected to natural gas
networks by 2009 (http://www.statistica.com, 2012).
Then, in the 1960s in France, General de Gaulle's thrust
to make nuclear the key to energy independence meant
closing old power plants fuelled with middle distillates
[90]. Some experts believe that just the need of the
European oil refinery industry to place the excess fuel oil
on domestic markets made the powertrain paradigm
shift to diesel cars happen (for Germany [91]; for France
J. Lemaire, 2012, personal communication). Deputy
mayor of Paris Denis Baupin argues [92] that Peugeot
was encouraged to massively produce diesel cars in
order to get rid of diesel oil overproduction.
We believe the European oil industry co-initiated the
shift to diesel cars in the 1980s and 1990s in order to
find outlets for middle distillates. Even though the out-
standing diesel car boom has nowadays resulted in diesel
fuel demand above the natural capprovided by the
average composition of raw oil, the oil company ARAL
expresses the need of diesel fuel outlet clearly: Com-
bined production requires the sale of certain amounts of
gasoline and middle distillates. Since fuel oil sales are de-
clining, this share has to be marketed as diesel after ap-
propriate conversion(translated from German, [93]).
Not coincidentally, the oil industry, automobile industry
and European Commission have been the main players in
predetermining the development of European automobile
market through the Auto-Oil I and II programs (con-
cluded in 1996 and finalized by October 2000, [94]).
The voluntary agreement between ACEA and the European
Commission at the origin of the European diesel car boom
The first steps of rule-making in climate policy at a
European scale have been made in the 1990s. After a
slow progress in tightening the regulatory framework of
greenhouse gas emissions, the agreement reached at
Kyoto in December 1997 finally triggered of a voluntary
fuel economy agreement between the European automo-
bile manufacturers and the European Commission [95].
We believe that this agreement and preceding negotiations
initiated the European diesel car boom, as reflected in the
continuous increase in diesel car sales since the mid 1990
years (Figure 1). The voluntary character of the agreement
was based on a new let's work together approach,implying
areinforcement of the dialogue with industry and the en-
couragement, in appropriate circumstances, of voluntary
agreements and other forms of self-regulation[96].
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It has been argued that the agreement diluted and
postponed environmentally effective climate regulation
[97]. It was an inappropriate policy instrument to use
for regulating CO
2
particularly as the European Union's
commitment to the UNFCC Kyoto Protocol was binding
[98]. The reasons why voluntary instead of binding mea-
sures were chosen are manifold. First of all, the volun-
tary agreement was able to break the deadlock after
many years of difficult negotiations in EU climate policy
negotiations. As a lowest common denominator out-
come, industry favoured such an approach as it prom-
ised to be less demanding than conventional policy
measures. The Commission took advantage of the vol-
untary attribute, since binding environmental policies
stipulated co-decision of the European Parliament and
the Council according to the Maastricht Treaties [97].
The resort to a voluntary agreement has been in line
with the neo-liberal paradigm change where governance
has been increasingly characterized by flexible, market-
based and non-regulatory policy instruments [38]. This
multi-level governance approach becoming prominent in
the 1990s further weakened the EU Commission based
on multi-national governance contained by subsidiarity
rules and being more often than not merely a policy ad-
visor than a policy maker. Voluntary arrangements also
mirror a particular European-style governance. High
level of communication and lobbying activities between
the car industry and political decision makers succeeded
in shaping European and national policy design that
served to replace effective climate regulation [97]. The
agreement was negotiated largely without public partici-
pation. The cooperative procedure between limited
stakeholders with high willingness to compromise largely
precludes the possibility of technology leaps and results
in remaining in a business-as-usual trajectory, the largest
shortcoming of the European model of regulation [99].
The European style of policymaking fundamentally di-
verges from the US model which shows a preference for
command-and-control measures with technology-for-
cingfeatures. The latter unfolds in a competitive and
politically more conflicting environment. It merits to have
initiated remarkable technology leaps, i.e. the three-way
catalyst or the electric car (cf. [6]). Technology-forcing
type of regulation is considered to be non-transferable to
a European Union setting due to multi-level decision-
making processes with institutions having comparatively
low bargaining power and a long-standing governance
mode inclined to concertation and search for consensus.
While the Commission believed that the voluntary ap-
proach offered greater flexibility to manufacturers and
performance-based standards avoided dictating technol-
ogy, the contrary has happened. As Keay-Bright [98] ar-
gues, the voluntary agreement was a good example of
regulatory capture. The fuel economy target was solely
to be achieved by technology-based standards without
targeting any technology beyond business-as-usual. As
such, it did little to support alternative powertrains and
relied heavily on direct injection diesel and gasoline
technology [98]. The ACEA commitment was thus
straightforward: European car manufacturers have high
expectations for () direct injected gasoline and diesel
engines, which are two of the most promising routes to
achieve the central commitment of 140 g CO
2
km
1
in
2008[95]. Even that the terms of the commitment were
designed to assist both the maintenance of petrol and
diesel internal combustion engine technology, ACEA
raised uncertainties associated with the introduction of
gasoline direct injection technology. This technology
was supposed to break the strong trend towards diesel-
powered passenger cars[100]. Accordingly, series produc-
tion of passenger cars with common rail direct injection
started earlier (e.g. by Daimler in 1997) than competing
petrol cars with direct injection technology which entered
the market much later (e.g. VW in 2005, Ford in 2012).
The Commission had granted the automobile industry
major concessions through the terms of the agreement.
It may also be ascribed to a Commission which lacked
expertise and which had not conducted any technical
studies of its own about CO
2
abatement strategies and
its costs for industry. European automobile manufac-
turers could thus make profitable their investments in
diesel direct injection technology. They in fact dictated
the technological development of the automobile indus-
try through the establishment of certain terms for the
agreement[98].
Moreover, the European Union also agreed to intro-
duce legislation on emission standards which deviated
from the principle of fuel-type neutrality. Indeed, while
in 1992/1993 NO
x
+ HC thresholds were at the same
level for any of both major fuels (Euro 1), 4 years later
when Euro 2 legislation entered into force, the European
Union granted more lenient emission standards for
diesel than for petrol. From then on, diesel vehicles
could emit 40% more NO
x
+ HC than petrol ones. The
deliberate compliance of higher threshold values of
pollution to one fuel type must be interpreted as a pol-
itically motivated measure to promote growing dieseli-
zation. In all the following stages of standardization,
higher emission standards were granted to diesel fuel.
This leniency for diesel vehicles contrasts with legislation
in the United States, which is fuel-neutral(quoted in
[101]). European Commission vice-president Günter
Verheugen, responsible for enterprise and industry policy,
however stressed when the more lenient Euro 5 regulation
was going to be introduced: It will not hamper the com-
petitiveness of the EU's car industry(quoted in [101]).
Whereas the profitability of the car industry declined
during the 1990s resulting in over-capacity of production
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[38], the advent of common-rail injection systems be-
came a great opportunity for European automakers at
the end of the decade. Diesel car performance improved
significantly and its demand was boosted in Europe. Car
suppliers and manufacturers, especially those with a
market leadership in diesel like VW and PSA could reap
major benefits while most car manufacturers' petrol-
engine capacity sat idle [102]. The real challenge consisted
in conquering overseas markets. The US market with its
more stringent environmental legislation was at stake.
European automakers had to make sure to comply with
future US exhaust regulations. If they were not able to
meet them, gasoline hybrid technology led by the Japanese
was to become the dominant alternative powertrain in the
USA [103].
The European-Japanese powertrain debate
The European diesel versus Japanese hybrid technology
debate produced strange effects. In 2003, Toyota was ex-
cluded from talks between ACEA and the European Com-
mission over Euro 5 emission laws due in 2010 [104]. The
stance of Japanese carmakers was not appreciated with
their European counterparts since they considered diesels
to be a dead-end technology environmentally: When
equipped with all future after-treatment equipment, diesel
cars will become as expensive as hybrid cars,says
Katsuhiko Hirose, hybrid project general manager for To-
yota [103]. European Union emission legislation however
remained more lenient and did not require or simply post-
poned the need for after-treatment equipment. Dated
technology could therefore be artificially kept alive. We
believe that this conduct contradicted the self-imposed
best available technologylegislation laid down by the EU
stating that emission limit values, parameters or equiva-
lent technical measures should be based on the best avail-
able techniques[105].
Volkswagen, Renault, PSA/Peugeot-Citroen and
DaimlerChrysler alleged not to believe in hybrids. We
think that the very successful marketing of diesel cars
by European automakers made them blind for more
progressive and challenging technological develop-
ments. Hybrid technology necessitates the command
and integration of both electric and combustion engine
involving high investments. European automakers were
able to defer these costs in the long term by holding
on to the profitable diesel path.
While Japanese automakers offered series produced
hybrid models as of 1997, the first European-produced
hybrid was a double-priced Mercedes in 2009 as com-
pared to Toyota Prius. European carmakers however ad-
mitted slowly but surely that diesel technology was not
to be a long-term solution. While diesel technology was
expected to lower CO
2
-emission levels, it could not
meet future nitrogen oxide emission rules. Volkswagen
Group CEO Bernd Pischetsrieder put it this way: Diesel
cars will not be abolished. They will however only sur-
vive in large cars.The high cost of tailpipe emission
treatment could only be internalized in more expensive
segments of the car market [106].
Fiscal measures to reduce car CO
2
In the boom years of the European diesel car proliferation
following the voluntary agreement's coming into effect in
1998, European legislation did not only refrain from giving
adequate attention to toxic emissions but was literally
constrained by the agreement to do so. If Member States
were to introduce fiscal measures to address, for example,
noise or adverse health effects, such measures could be
regarded as discriminatory against the technologies which
ACEA had chosen to promote [98].
The strategy of the voluntary agreement was three-
pillared. Next to the main supply-side measures to reduce
car CO
2
emissions, an additional 10% emission reduction
was to be achieved through a labelling scheme and car-
related fiscal measures to influence consumer demand
[107]. When the voluntary agreement was verbalized,
ACEA President Pischetsrieder initially called for no
negative measures against diesel-fuelled cars(interview,
in [98]). The Commission finally agreed to include in the
text a vague reference to unhampered diffusionof CO
2
-
efficient technologies in order to cater for ACEA's con-
cerns regarding fiscal measures. As Kågeson [108] asserts,
this wording served to replace ACEA's condition in an
earlier outline proposal that no negative measures against
diesel-fuelled carsshould be taken. Moreover, the Com-
mission bowed to ACEA pressure and agreed to review
the commitment under certain circumstancesshould fis-
cal measures interfere with the particular fuel-efficient
technologies which the manufacturers were trying to pro-
mote ([95] in [98]). Just a couple months after the volun-
tary agreement was signed, Pischetsrieder referred to this
matter and made clear that although we do not question
the right of the Community and its Member States to ex-
ercise their prerogatives in the field of fiscal policy,chan-
ging the structure of vehicle taxation could have serious
consequences for the competitiveness of the industry and
the employment in the sector[109].
Member States were initially slow to adopt CO
2
-based
fiscal measures. In 2002, only the UK and the
Netherlands had adopted measures to align car taxes
along CO
2
emissions. By then, the share of diesel cars
had increased incessantly not alone due to persistently
lower taxation of diesel fuel granted by most Member
States but by European consumers appreciating diesel
driving style and torque [110]. A further increase of die-
selization beyond the natural capprovided by the aver-
age composition of raw oil (about 40%) could however
fuel anti-diesel initiatives and become problematic for
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the automobile industry [98]. ACEA's negative stance to-
wards Member States' adoption of CO
2
-based car taxation
was thus tempered. In 2008, ACEA solely expressed con-
cerns regarding the lack of fiscal harmonization which
would have distorting effects on the internal market. Four-
teen Member States had adopted CO
2
-based taxes on pas-
senger cars by then [38].
The debate around fuel-neutral taxation
By 2002, the Commission intended to harmonize excise
duties on diesel fuel for private cars. It proposed to un-
couple the tax arrangements for fuel used for commer-
cial purposes from those for fuels used for private
purposes in order for Member States wishing to do so to
increase the excise duty on diesel fuel used for private
purposes to bring it into line with the excise duty levied
on petrol [111]. It would reduce tax distortions by fuel
tourism and be environmentally consistent. The Com-
mission was increasingly concerned about internalizing
external costsstating that lower taxes on diesel fuel
were the main factor in the spread of diesel-engined
vehicles:
There is a lesser degree of environmental cost cover-
age for diesel than for petrol because the current re-
quirements for nitrogen oxide emissions per kilometre
for new diesel cars are significantly less stringent than
those for petrol cars. Diesel engines also emit signifi-
cantly higher amounts of particulates than petrol en-
gines. On the other hand, diesel cars emit significantly
less CO
2
km
1
because of their lower fuel consumption
than petrol cars. Therefore, according to criteria used to
assess the impact on the environment (gas and particu-
late emissions, noise), there would be no reason for tax-
ing differently diesel fuel and petrol consumed by
passenger vehicles. A reasonable balance would mean
both being taxed at broadly similar rates[111].
With the only exception of the UK, all other Member
States apply lower tax levels on diesel fuel. However, due
to the need for unanimous agreement in the Council of
Ministers, a fiscal alignment remained highly unlikely.
The European Commission can only encourage Member
States to align fuel taxes according to their CO
2
content.
Some countries however resisted such recommendations
and have kept tax rates low in order to attract fiscal rev-
enue by so-called fuel tourismof road hauliers [112]. In
addition, the European Parliament had rejected the pro-
posal on grounds that a higher taxation of Diesel fuel
would have significant repercussions on the automobile
industry which possessed a competitive advantage in this
technology (report from Piia-Noora Kauppi, A5-0383
/2003, German text). The Green Group in the European
Parliament [113] was the only group to support, in
principle, the Commission's proposal. We believe that
ACEA felt confident to continue counting on low diesel
fuel taxes even the association had less of a hold on
those non-car-related taxes.
Hence, the ill-advised unilateral focus of European
regulation on CO
2
with low emphasis on toxic emissions
as compared to US or Japanese legislation cannot be
blamed alone at stakeholders at the European level. The
European Commission launched another attempt to
align fuel taxes in 2011. With the revision of the Energy
Taxation Directive, the Commission's proposal again was
to tax fuels in a neutral way and to ensure a fair compe-
tition in the internal market. All fuels would compete on
the basis of their carbon content instead of tax advan-
tages. Even the proposal expressively did not seek to
penalize diesel but to tax fuels in a neutral way on the
basis of their merits instead of tax advantages(EU Tax-
ation Commissioner Algirdas Šemeta in [114]), it resulted
in shifting the litre price level of diesel above the petrol
price level according to the higher energy content of the
former. Very generous transitional periods until 2023 were
thus scheduled to make such a move acceptable. However,
still the proposal was going to meet strong resistance in
the European Parliament and in different Member States.
Fiscal measures encouraging diesel at the national level
As described above, the third pillar of the voluntary
agreement aimed at introducing car-related fiscal mea-
sures to influence consumer demand. Due to subsidiarity
rules, the European Commission could however only
stimulate Member States to follow its recommendations,
which consisted in taxing transport fuels equally
according their CO
2
content.
Numerous national tax systems in Europe positively
discriminated diesel fuel and, to a lesser degree, diesel-
driven vehicles long before EU rulemaking in climate
policy started off. At the end of the eighties, there was a
need not to jeopardize the economic and financial bal-
ance of the road haulage sector which accounted for
most of the diesel fuel consumed. At that time, a very
small proportion of private cars (15%) used diesel fuel.
The amount they consumed was therefore marginal
(about 10% of total sales of diesel fuel) CEC [111]. Trig-
gered off by subsidized taxation of diesel vehicles and
fuel, the European car industry could invest into this
type of powertrain with extraordinary commitment. As a
result, the rate of diesel cars on Europe's roads had in-
creased greatly by the end of the 1990s.
Mayeres and Proost [115] fail to see the rationale for a
more advantageous treatment of diesel carsin most
European countries. Burguillo-Cuesta et al. [116] wonder
that available literature on the transport sector's energy
demand has paid little attention to this issue considering
that the outcome of this preferential treatment amounts
to a socio-economic phenomenon that deserves to be
analyzed. As costs of driving have declined, the so-
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called rebound effectmakes people take advantage of
the saved moneyby driving diesel-powered cars more
and with larger and more powerful vehicles. This
phenomenon is meanwhile believed to make up a bigger
share of environmental consequences of dieselization
than the technical features of diesel cars [116].
The more the aggregate tax level of driving is lower
for a diesel car than for a petrol one, the higher diesel
penetration would be and so would be the rebound ef-
fect, yet our thrust here is not this apparent correlation
but a question of political economy, i.e. to track the rea-
sons why aggregate diesel taxation not only varies greatly
among developed world regions such as the EU, USA
and Japan but also varies strongly within Europe. Among
aggregate taxation, we understand the sum of car-related
taxation, such as registration and circulation tax plus the
fuel tax and so do tax incentives vary greatly, based on a
multitude of threshold values and performance criteria.
The EU CARS 21 High Level Group on the Competi-
tiveness and Sustainable Growth of the Automotive In-
dustry objects that this multitude would lead to a
fragmentation of the internal market and would there-
fore require greater coordination of the incentives [117].
We wish to analyze the varying degree of dieselization
within several European states along four assumptions.
We consider the dieselization level directly related to ag-
gregate diesel taxation rates, which has been acknowl-
edged by the European Commission [111]. Firstly, diesel
cars are treated more advantageously in those countries
which have an automobile or supplier industry with a
strong stake in diesel technology. We believe that
safeguarding employment in the automobile sector has
been an important momentum to open up market
shares for diesel cars. Secondly, a strong bias towards
ecological modernization curbs the tendency to treat
diesel cars more advantageously than petrol cars. We as-
sume that advanced ecological modernization checked
by a participative civil society will have a positive effect
on environmental policy formulation, thus restraining
dieselization. Thirdly, diesel cars are treated more ad-
vantageously in countries with a corporatisttype of gov-
ernance, i.e. where the state has preferential relations
with industry. We use here a wider definition of corpor-
atism including corporatist without labourto include
the French model of state-led capitalism). Lastly, small
states with a lot of potential transit traffic tend to tax
diesel fuel at low levels. The reason here is to maximize
aggregate fuel tax collection (the so-called fuel tourism
effect).
As for the first assumption, we have plotted in Figure 5
the share of newly registered diesel cars in 2007 to direct
automotive employment in 13 EU countries. The year
2007 was chosen because it was prior to the worldwide
recession in 2008/2009 largely influencing car sales.
Excluding two outliers, we find a surprisingly high cor-
relation between dieselization and employment in the
automobile industry. Both Swedish and particularly
German dieselization rates are delinked from relative
automotive employment. We find high to very high
automotive employment and export-led production in
both Germany and Sweden. Dieselization can therefore
only be marginally attributed to safeguarding employ-
ment in these countries.
The second assumption takes ecological modernization
into account. We assume that strong performance in
comparative ecological modernization has positive effects
on environmental policy formulation and consequently
curbs the tendency to tax diesel cars and fuel more advan-
tageously than petrol cars. European countries scoring
best on the index of Scruggs [122] are Germany,
Switzerland, Austria and the Netherlands while for the
remaining field, there is a sloping tendency from North to
South, apart from the UK which scores rather low.
Germany
It is worth mentioning that Germany takes a leading role
in ecological modernization (see also [123]) while at the
same time, automobile production is outstanding and
the comparative employment in this sector is very high.
Germany hosts several lead developers of diesel technol-
ogy (BMW, Volkswagen, Daimler), yet unlike in other
manufacturing countries which peak in Diesel technol-
ogy, aggregate tax incentives for diesel have only been
moderate with a resulting dieselization below the Euro-
pean mean (Figure 2, cf. also [13]). Lower diesel fuel
prices are balanced by a moderate car tax penalty for
diesel cars. The penalty was however lowered when in
2009 automobile tax was modified to become contingent
Figure 5 Dieselization rate versus automotive employment.
Share of diesel car registration [13], automotive employment [118].
The numbers of employees [118] were recalculated to the share of
direct automotive employment by country with data from Eurostat
[119] and from Nomisweb [120] regarding the United Kingdom as
well as from Anell [121] regarding Sweden, respectively. IE, Ireland;
EL, Greece. The coefficient of determination R
2
and regression line
have been calculated excluding Sweden and Germany.
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on CO
2
emissions. Promptly, diesel car sales were
fuelled reaching a record high of 48.1% in 2012. Howso-
ever, civil society has an eye on air pollution control
more than in most other countries. Public discourse on
issues of urban particulate matters pollution has been
particularly animated in the early 2000s before the par-
ticulate filter was introduced. The critical debate on
diesel ceased however after almost all new diesel cars
were equipped with filters. Excess NO
x
emissions of
diesel cars have not been a major issue of debate in the
general public, not even after NO
x
levels in many
German cities exceeded EU threshold levels.
The Netherlands
The Netherlands is a case in point for efficient policy
making. Whereas we find here one of the largest differ-
entials between (high) petrol and (low) diesel taxation
[112], the ratio of Diesel to petrol cars is surprisingly
low. Several reasons may serve to explain this low diesel-
ization. In this very densely populated country, inhabi-
tants are comparatively receptive to environmental
issues. This concern about air quality may be a crucial
reason why Dutch chose to keep dieselization low. How-
ever, a long-standing reliance on national gas for heating
and transportation purposes and a domestic refinery sec-
tor with higher output of light distillates than middle
distillates may also elucidate why high deterrence taxes
for diesel cars are prominent in the Netherlands.
A Dutch policy paper on traffic and transport emis-
sions [124] stated that it is not desirable for the diesel
share in new passenger car sales to increase for air pol-
lution concerns. The third national environmental policy
plan (1998) targeted to reduce the diesel share of new
passenger car sales from 11% in 1998 to only 5% in 2010
(G Geilenkirchen, personal communication). Dutch
registration and circulation taxes for Diesel cars are
close to prohibitive unless cars are driven a high mileage.
Whereas the annual circulation tax for a gasoline car is
approximately 600 ,itisdoubleforadieselcar.More-
over, registration taxes have been 1868 higher for diesel
cars than for petrol cars. This tax is currently being
transformed to a CO
2
-dependent tax, but a compensatory
diesel penalty will persist. As a result of the fiscal policies,
the share of diesel cars in the Netherlands has been much
lower than the EU-average, varying between 20% and 30%
(G Geilenkirchen, personal communication).
Belgium
The situation in neighbouring Belgium is very different.
The share of Diesel cars in Belgium has been high for
many years [125] and is still growing. Between 2000 and
2010 it increased from 40% to about 61% [115] (Figure 3).
Important distortions of the Belgian fiscal system are re-
lated to the taxation of diesel cars which make diesel cars
pay some 50% less fuel taxes per km than gasoline cars
[115,126]. As such, diesel cars have been dubbed as cash
cows- cars which generate cash and are milkedcontinu-
ously with as little investment as possible [126]. The Bel-
gian case is also revealing for the different approaches the
regional Flemish, Brussels-capital and Walloon govern-
ments are taking. As of January 2011, car tax collection
has become subject to the regions of Belgium. In 2012,
the densely populated Flemish region has introduced a
new vehicle taxation system based on the environmental
performance of vehicles. Apart from CO
2
emissions, it
takes the type of powertrain and the EURO car emission
standard into account. Prior to the reformulation, research
efforts have been focused on setting up a rating tool, the
so-called Ecoscore, a well-to-wheel life cycle analysis
which calculates for every individual car the impact of
several damage categories such as climate change,
health-impairing effects, effects on ecosystems and
noise pollution [126]. Concerns about diesel air pollu-
tion and the loss of lifetime due to the exposure to air
particulate matters have been much more noticeable in
Flanders and Brussels than in the rural Walloon re-
gion. In the latter region, a CO
2
-dependent bonus-
malus registration tax encourages the purchase of low
CO
2
-emission cars, whatever their fuel type. The
higher air pollution impact of diesel cars is not taken
into account. It may be argued that the different per-
ception is due to the strong urban-rural bias between
the Flemish and the Walloon communities; however,
we would not repudiate a stronger ecological con-
sciousness of Dutch-speaking Flanders to be linked to
the ecologically more modernized Netherlands. On the
contrary, it is striking how the indifference of the Wal-
loon region's legislation on air pollution mirrors the le-
gislative landscape in France.
France
In France, the only car taxation in force over the last
decade has been an ecologicalbonus-malus registration
tax. It has largely succeeded to improve fuel economy of
newly registered cars yet at a high fiscal cost and without
taking PM and NO
x
pollution into account. France was
the first European country in which diesel cars became
more popular than petrol cars and has been regarded as
an interesting case study of the overall impacts of diesel-
ization with rapidly expanding sales already after 1982
[127]. Concerns about air pollution by diesel fumes have
largely been absent due to a relatively low level of envir-
onmental awareness in France and a weak role played
by environmental groups[128]. On the other side, we
find a rather strong automotive manufacturing sector
with one of the lead developers for diesel engines
(PSA). Our third assumption is embedded in the active
and dirigiste role of the French state. A cooperative
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and non-adversarial atmosphere of policymaking be-
tween government and business taking place behind
closed doors and the belief that market forces do not
necessarily produce a socially optimal outcome with-
out the close supervision of the state[128] has left
much leeway for politics to steer broader issues of the
political economy. In the context of private transport,
the car manufacturer Peugeot obtained in 1985 gov-
ernmental assurance of lower taxes on diesel before
going ahead with a long-term strategy of substituting
petrol with diesel engines (Zmirou, Denis in [129]). By
the mid-1990s, Peugeot was the world's biggest produ-
cer of diesel cars. The French government tried to slow
increasing dieselization twice. In 1989, the Ministry of
Industry was preparing a reform of the energy pricing
policy that called for hiking taxes on diesel fuel. The
ministry argued that the tax gap between petrol and
diesel was encouraging, excessive developmentof
diesel-powered cars in France, reaching 23.9% of new
car sales in 1990. The hidden agenda behind was that
demand for diesel fuel was outrunning the production
capacity of French refineries, thereby obliging France
to import diesel fuel [130]. But the proposal was leaked
to the press and the haulage sector erupted in protest.
The government quickly repealed the plan [130]. By the
end of the 1990s, Dominique Voynet, France's Green en-
vironment minister, tried to pass substantial tax increases
on diesel. However, her success has been minimal, al-
though diesel taxes were raised slightly while taxes on
gasoline stayed stable for the first time [131].
Let us now have a brief look at Europe's geographical
extremes in the North-West and South-East revealing
some peculiar phenomena of dieselization growth.
Norway
Norway used to have a ratio of new diesel car registra-
tions of less than 10% until the turn of the millennium.
By 2005, figures began to rise very fast and reached a
peak in 2007 with 74.4% diesel share [13]. In 2007, the
Norwegian government had restructured vehicle tax-
ation by introducing CO
2
emissions as one of the main
components of the tax [132]. In conjunction with low
diesel fuel taxation, this policy measure was the key trig-
ger for the strong surge in the purchase ratio of diesel
cars. Consequently, emissions of NO
2
in major Norwe-
gian cities have increased largely [72]. The Norwegian
Institute of Transport Economics recently deemed ap-
propriate to possibly limit the use of diesel vehicles in
cities when NO
2
concentrations are highest [72]. New
fiscal policies have already been adopted, adding a NO
x
component to the tax to address both global and local
pollution[133]. The question arises why just 5 years
ago, when regulators zealously encouraged diesel tech-
nology no other alternatives were envisaged to reduce
CO
2
. Dryzek et al. [123] uphold Norway to be an ecologic-
ally modernized state, however weak and of comparatively
top-down the design. Even that environmentalists have
been secured participation in crucial policy-making com-
mittees in core zones of the state, they are small in num-
bers, lack autonomy and activism, and greatly rely on the
state for funding.
Greece
Greece used to embody the absence of Diesel in Europe
with the lowest EU-wide dieselization. A ban of vehicles
with diesel engines in Athens and Thessaloniki imposed
in 1991 has prevented a dieselization of Greece's car
fleets. The measure was taken to reduce notorious
Athens' air pollution and to limit the damage to ancient
limestone buildings caused by acid deposition at the
time of much higher NO
x
emissions of diesel cars.
Greece has been the only Member State of the European
Union to enforce such legislative measure knowing that
some other cities particularly in Central and Eastern
Europe suffer chronically from air pollution. Then in
2011, the Greek Ministry of Environment, Energy and
Climate Change passed a new bill in Parliament
concerning the lift of the circulation ban for diesel
Table 2 Dieselization in several European countries
Country Assumption 1 Assumption 2 Assumption 3 Assumption 4 Diesel
cars
attractive?
Car/supplier industry? Ecologically backward? Fuel tourism? Corporatist?
France ** * ** 5
Germany *** * 4
Belgium ** * ** 5
Netherlands ** 2
Spain ** ** * ** 7
Austria * ** ** 5
Norway * ** 3
Luxembourg * * *** ** 7
Rating: 0 minimum, *** maximum.
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engine vehicles in the city of Athens and Thessaloniki.
Combined with lower cost to run diesel vehicles, the re-
peal of the ban is expected to soundly stir the car market
[134]. Hesitations about an increase of NO
x
pollution
levels have not gained prominence in public discourse. It
has been pointed to nowadays apparently clean diesel
technology. We draw the uncritical approach to weak
ecological modernization which southern European
countries are supposed to suffer from, usually attributed
to the reactive character of environmental policy formu-
lation and fragmented administrative structures [135].
Small European states with heavy transit traffic
As for our fourth and last assumption, we find a group
of small countries with low fuel taxation, particularly on
diesel. Their rationale is not to maintain a competitive
industry nor is ecological modernization at stake. The
collection of fiscal revenue is crucial. Due to a fast
internationalization of road freight transport and trucks
that cover thousands of kilometres on a single tank of
diesel, optimized refuelling strategies make road-haulier
companies choose to fill up in those countries where
diesel tax is lowest. Geographically, in between the above-
covered countries, we find tiny Luxembourg with a large
impact on dieselization beyond its borders. Its fuel taxes
on diesel have been consistently low, just above the mini-
mum EU level. According to the European NGO feder-
ation Transport and Environment, the loss of diesel sales
in neighbouring countries by fuel tourismmay not seem
to be disastrous, but it provides a political excuse for
their regulators not to raise diesel taxes. Apart from
Luxembourg, we find Austria and Slovenia keeping
diesel tax low for such incentive [112].
Table 2 summarizes the effect of the assumptions for
several countries. Each country is scrutinized along all
assumptions. The more any of the assumption holds
true, the more stars are attributed with a minimum of 0
and a maximum of 3 stars. The degree of dieselization in
each country can be read from the last column adding
up the stars.
Conclusion
This paper has dealt with the process of the techno-
logical petrol to diesel powertrain paradigm shift which
has taken place rather mutely in Europe for 2 decades.
We have attempted to show that while the shift away
from petrol-fuelled cars has become an absolute neces-
sity in a world of climate change, the path taken by
European stakeholders - both politics and industry - has
rather shifted Europe further away from the stated ob-
jective: the diesel path did not manage to reduce heating
up the planet when accounting not only for those emis-
sions laid down in the Kyoto protocol (CO
2
) but for
black carbon as well. On top of that, it has persistently
exacerbated local pollution with regard to noise, nitro-
gen oxide and particulate matter.
We investigated into how the unilateral positioning
of European politics and industry on the diesel para-
digm made this shift happen. A shift which prevents
the continent from exploring alternative and more sus-
tainable pathways such as hybridization and electrifica-
tion as yet [8].
The socio-economic consequences of current trans-
port policies are rarely called upon. Diesel motion has
reduced the cost of driving in Europe when considering
inflation-corrected and sales-weighted average fuel
prices and taxes over time [112]. Car drivers have be-
come accustomed to have an easy escape from high
travel expenditures with diesel fuel more economic than
petrol in a double way: one volumetric unit is both
cheaper and of higher energy content. The momentum
of long-standing preferential conduct by the state will
not easily be turned around as the recent European
Commission's proposal to harmonize fuel excise duties
has revealed, yet not only private customers' inertia is at
stake. Small Member States' budgets accustomed to reap
wind-fall profits from the so-called fuel tourismcould
not easily give up preferential diesel fuel policies. It will
have to be seen whether imbalances in the world's fuel
markets and more competitive powertrain strategies of
other global players might in the end show European
carmakers the way forward.
Competing interests
The authors declare that they have no competing interests.
Authorscontributions
MC and EH developed the study design, performed the research and drafted
the manuscript. Both authors read and approved the final manuscript.
Received: 21 December 2012 Accepted: 15 April 2013
Published: 22 June 2013
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doi:10.1186/2190-4715-25-15
Cite this article as: Cames and Helmers: Critical evaluation of the
European diesel car boom - global comparison, environmental effects
and various national strategies. Environmental Sciences Europe 2013 25:15.
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... The adoption of diesel engines ( Figure 1) has been extensively discussed, see for example (1), but in broad terms it was the result of concerns about CO 2 emissions, the potential for diesel to be more fuel efficient, and the availability of diesel fuel following a switch from oil to gas as a heating fuel. It was driven by favourable regulatory and tax environments that held the cost of diesel fuel below that of gasoline. ...
... For the compressor, it seems reasonable that the reduction in specific speed that fol lows from allowable increases in inertia may lead to 1-3 percentage points increase in efficiency. A reduced demand on range may enable as much as 4 points increase, div ided between the impeller inlet (1), diffuser (2), and volute (1). For the turbine, the trade-off is conceptually a simpler one between inertia and efficiency, and 5 percent age points appears to be a realistic goal. ...
... Historical share of diesel engine cars in major markets(1). ...