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Upward emission Trends

The sector of transportation consists of the movement of goods and people by different vehicles, consisting of subsectors, such as road transportation, railways, navigation, aviation and others[1]. 2011 data prove that a fifth of the greenhouse gas (GHG) emissions generated in the European Union (EU) of 28 were due to transportation activity. Transport emissions not only haven’t decreased, as emissions from other sectors such as the energy industry and manufacturing, but they have been presenting a continuous increase during the period from 1990 to 2007[2]. A slight downward trend has been observed after 2007, reaching minus 6% in 2011, mainly assigned to the economic recession[3].

Figure 1-GHG emission trends of various transport modes in EU-27

Figure 1: GHG emission trends of various transport modes in EU-27, 1990 – 2009

(*) Excluding indirect emissions from electricity consumption

Source: EC, 2012[4]

CO2 emissions differ by means of transport, mainly depending on the type of vehicle, as well as on the load factor. Road transport seems to be responsible for the majority of sectoral emissions, representing 19% of EU-28 emissions or 94% of transportation.

Figure 2-EU-28 GHG transport emissions by mode of

Figure 2: EU-28 GHG transport emissions by mode of transport, 2011

Source: EC, 2013 [5].

Transport’s Environmental Impact: CO2 Intensity

As it is already known, GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), as well as F-gases (hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride (SF6)). The uniform unit of CO2 equivalents is used to aggregate these into GHG emissions[6].

Transportation emissions mainly consist of CO2 that is caused by the process of fuel combustion in the vehicles’ internal combustion engines. Such fuels are petroleum-based, such as diesel, gasoline and Liquefied Petroleum Gas (LPG) that contribute to a different extent to CO2 emissions, according to their carbon content. Although the main gas product of fuel combustion is CO2, the process also results in the emission of other GHGs, such as methane (CH4), and Nitrous Oxide (N2O). Apart from fuel combustion, mobile air conditioners are responsible for hydrofluorocarbons (HFC) emitted at relatively low levels and accounted within the sector. Globally, more than 20% of CO2 emissions caused by human activity are due to transport[7].

Multidimensional Policy Response

European Union has played a significant role in the global efforts to reduce GHGs in all polluting sectors. Within the EU policy measures have been planned and implemented during the last 15 years, ranging from emission mitigation options for manufacturing standards and market mechanisms, to improving fuel quality and including aviation in the EU Emissions Trading System (EU ETS).

Manufacturing Standards

Manufacturing standards changes started in 1998, with the EU and the European Automobile Manufacturers agreeing in an upper limit of CO2 emissions per km at the level of 140 grams CO2/km. In 2008 the EU found that the 2012 target would not be met[8] and published another regulation, 443/2009, in order to set lower limits of CO2 emissions. Regulation 333 of 2014 is the last one that is active and according to that car manufacturers are obliged to ensure that their new car fleet emits less than 95 grams CO2/km by 2021, which means in terms of fuel an average consumption of 4.1 lt/100 km for petrol and 3.6 lt/100 km for diesel cars respectively. As far as vans are concerned, the latest regulation is 253/2014, amending the 510/2011 and setting the target as low as 147 grams CO2/km and the average fuel consumption limits to 6.3 lt/100 km petrol and 5.5 lt/100 km by 2020.[9] In May 2014 a strategy for Heavy Duty Vehicles (HDVs) was intended to be planned, with a timeframe of legislation proposals in 2015[10].

Apart from the car fuel consumptions and emissions, the EU has also set targets and regulations in order to control emissions from F-gases, which are: the “Mac Directive”, concerning the air conditioning systems of small cars, and the “F-gas Regulation”, which includes all applications where F-gases are used. Regulation 661/2009 introduced in 2009, which was updated by Regulation 458/2011, covers tyre rolling resistance and tyre pressure monitors that have been made mandatory on new vehicles, in order to achieve increased fuel economy[11].

Market Mechanisms

In parallel with the manufacturing standards, the EU has created market mechanisms to promote clean and energy efficient road transport, starting with Directive 2009/33/EC aiming at a broad market introduction of environmentally-friendly vehicles, and extending, also, to public procurement of all transport vehicles, according to the Public Procurement Directives (2004/17/EC and 2004/18/EC)[12]. Technical specifications for energy and environmental performance, along with environmental impacts are included as award criteria in the purchase procedures. Furthermore, the Directive on the Promotion of Clean and Energy Efficient Road Transport Vehicles (2009/33/EC) defines financial impacts so as to facilitate their inclusion in the purchasing decision[13].

Aviation Addressing

Taking into account that aviation transport constantly rises in popularity, while it is projected to present a 70% increase in emissions by 2020 compared to 2005 levels, even if fuel efficiency improves 2% per year, the EU has decided to include the aviation sector in the EU ETS[14]. Since early 2012, all flights’ emissions from, to and within the EU-28 Member States plus Iceland, Lichtenstein and Norway are included in the EU ETS, with plans for the following years being made to include all aviation transport going to and from the EU to non-European destinations.

Fuel Quality

Since fuel quality plays an important role in GHG emissions from transport, the EU has taken further policy action by publishing the Directive on Fuel Quality Standards (FQD) (2009/30/EC) in 2009. This directive comes along with the 2009/28/EC Directive for Renewable Energy, which includes a target of 10% renewable energy in EU transport sector by 2020. The FQD sets a target of 6% reduction of the climate harmful emissions for the fuel suppliers and their products full life cycle, by blending biofuel in petrol or diesel, of by improving fuel production processes in refineries. Member states may need an additional reduction of 4% from fuel companies, which can be achieved through energy supply for electric vehicles or through carbon credits from third countries, with implementations of clean development mechanisms. Finally, according to the European Commission’s White Paper on Transport (2011) a long term goal is set, supporting a 50% reduction in the use of “conventionally-fuelled” cars in urban transport by 2030[15].

A Shift towards Natural Gas

Natural Gas (NG) is a clean burning fuel which primarily consists of methane (CH4). It can be used in vehicles in two forms, liquefied natural gas (LNG) and compressed natural gas (CNG), which can serve in both road transport vehicles and heavy duty vehicles. The majority of natural gas vehicles (NGVs) have spark ignition engines[16]. As energy efficiency of spark-ignited gas engines is lower than that of diesel engines, CNG have higher energy consumption compared to diesel vehicles, although it still remains lower than that of gasoline fuelled cars[17],[18].

From an environmental point of view, however, carbon intensity of methane is lower because of the higher hydrogen-carbon ratio of methane in contrast to diesel or gasoline. Depending on the size of engines, this low intensity mainly leads to CNG vehicles having lower tailpipe CO2 emissions than those from diesel and gasoline engines. Moreover, NG engines, using any combustion system, cause low Particulate Matter (PM) emissions, that are usually comparable to those of PM filtered diesel engines 17.

The usage of NG vehicles is not spread worldwide, with almost 79% being concentrated in just 7 countries (Table 1). Iran is the world leader in the use of NG vehicles, while the only EU country in the list is Italy, with about 5% of the world’s NG fleet. Italy has a long history in CNG cars usage and many promotion incentives for the use of NG in the transportation sector being applied. The penetration of CNG in the EU transport sector is limited, with only 0,4% of cars using NG. The NGV industries in the EU have, already, invested around € 2 billion to create a gas refueling network with stations all over Europe, with Italy and Germany having the most CNG refueling stations[19].

Table 1: Natural Gas Vehicles (NGVs) worldwide and in main EU countries

  Total NGV population (road transport only) No. of filling stations
Country Total NGVs % of total vehicles in country % of total NGVs worldwide CNG stations L-CNG stations LNG stations
Iran 3,300,000 27,09% 18,61% 1,992 0 0
Pakistan 2,790,000 79,67% 15,74% 2,997 0 0
Argentina 2,244,346 17,53% 12,66% 1,916 0 0
Brazil 1,743,992 4,97% 9,84% 1,793 0 0
India 1,500,000 3,53% 8,46% 724 0 0
Italy 846,523 2,07% 4,77% 959 7 0
USA 250,000 0,10% 1,41% 1,438 0 46
Germany 96,349 0,20% 0,54% 915 0 0
Bulgaria 61,270 1,83% 0,35% 106 0 0
TOTAL EU 1,098,902 0,40% 6,20% 2,969 34 43
TOTAL World 17,730,433 1,64%   22,162 441 1433

Source: ACER, 201420

In the US, there have been made efforts of reducing emissions in the transport sector with legislative actions and federal programs and incentives. As far as taxation is concerned, there has been a Tax Increase Prevention Act in 2014, which blocks the tax increases in the NG market and offers several bonuses to businesses that use and promote NG vehicles. Furthermore, the Federal Transit Authority (FTA) offers grants to help the funding of local and regional transit systems, in order to purchase vehicles and construct facilities that are environmentally friendly. There has been also a Voluntary Airport Low Emission (VALE) vehicle program by the Federal Aviation Administration (FAA) that funds NG vehicles and infrastructure at the US airports. Finally, the US Environmental Protection Agency (EPA) started the “Clean School Bus” program in 2003 to assist schools to replace the school buses with new, low-emission buses to improve the air quality and the health of children[20].

The “Europe 2020” strategy introduced by the EU in 2010, the EU Transport White Paper in 2011 and the European Commissions’ 2050 Roadmap are strategies that included cost-effective ways to reduce GHG emissions and “CO2 emissions per km” upper limits, set in order to push car manufacturers to support the use of more efficient fuel or fuel that produce less CO2 emissions, such as NG16.

However, the policies that have been planned in Europe in the past years have not quite achieved the results they pursued. Apart from Italy, all the other countries have a low adoption of NGVs, as Table 1 shows. There are, however, big prospects for NG usage in the EU transport sector. According to a study of the Oxford Institute for Energy Studies, there are some issues that the EU has to face and solve in order to achieve better penetration of the NG in the transport sector. Different vehicle taxation levels play a crucial role in the fuel usage and efforts should therefore be made to be smoothened. Furthermore, the benefits of NGVs are less promoted, because of the fast improvements that are made in the hybrid, the electric and the conventional cars. In addition, there are problems that the drivers of NGVs have to face every day, which are more practical issues, as the insufficient number of refueling stations. Finally, the status-quo liquid fuels can offer a higher fuel range, with a smaller fuel volume, which means that the NG users have to compromise with bigger vehicles that are able to hold sufficient amounts of NG for their needs.

Policy changes can foster solutions to the aforementioned problems. Pricing policies to maintain the difference between the NG and the other fuels’ excise duties or efforts for the expansion of the NG infrastructure grid, for both vehicle refueling and maintenance, could form steps towards the direction of NG higher adoption in the EU. Initiatives to offer grants or reduce taxation in CNG or LNG fuel stations should be supported by the Member States, in combination with awareness campaigns for the promotion of the usage of CNG as a clean fuel, the environmental benefits and the pricing differentials that NG offers[21].

By Charikleia Karakosta & Phaedra Dede


Charikleia Karakosta

is a Chemical Engineer and works as a Research Associate at the University of Piraeus Research Centre (UPRC), as well as at the Management & Decision Support Systems Laboratory of the National Technical University of Athens (NTUA). She has participated in several research and consultancy projects in the fields of energyenvironmental and climate policy, energy planning and management, technology transfer and decision support. She holds a PhD in Decision Support Systems for the Promotion of the Effective Technology Transfer within the frame of Climate Change from the School of Electrical and Computer Engineering and MSc in Energy Production and Management by NTUA. She has more than 110 scientific publications in international journals with reviewers, announcements in international conferences and chapters in books. For her work, she has received awards by the Alexander S. Onassis Public Benefit Foundation, the State Scholarship Foundation (IKY) and the NTUA. Contact:


Phaedra Dede

is an Electrical and Computer Engineer and works as a Research Associate at the
Management & Decision Support Systems Laboratory of the National Technical University of Athens (NTUA). She is a PhD candidate in Energy Management at the School of Electrical and Computer Engineering in NTUA and holds an MBA on Engineering- Economic Systems by NTUA. Her research interests focus on Energy Management, Climate and Energy Policy, Smart Cities and Municipal Authorities’ Decision Support, while she is involved in FP7 projects regarding climate policy implications as well as optimization of energy use in cities. Contact:

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[13]    EC- European Commission (2009). “Commission welcomes today's decision of the Council to adopt a new Directive on clean vehicles used by public authorities”, Press Release IP/09/503.
[14]    EC- European Commission (2007). Directive of the European Parliament and of The Council on the promotion of clean and energy efficient road transport vehicles, COM(2007) 817 final.
[15]    White Paper Roadmap to a Single European Transport Area – Towards a competitive and resource efficient transport system, European Commission, 2011.
[16]    European Gas Forum (2012). “Reducing CO2 emissions in the EU Transportation Sector to 2050”, available at:
[17]    Advanced Motor Fuels Implementing Agreement (AMF), International Energy Agency (IEA) website, “Methane (natural gas, biomethane)”, available at:
[18]    Karlsson, H., Gåsste, J. and Åsman, P. (2008). “Regulated and non-regulated emissions form Euro 4 alternative fuel vehicles”. Society of Automotive Engineers, SAE Technical Paper 2008-01-1770.
[19]    Agency for the Cooperation of Energy Regulators (ACER) (2014). “Regulatory implications of new developments in the gas supply chain”, Final Study Report, available at:
[20]    NGV America website, available at:
[21]    The Oxford Institute for Energy Studies (2014).”The prospects for Natural Gas as a Transport Fuel in Europe”, available at: