The carbon dioxide (CO2) concentration in the atmosphere, one of the main greenhouse gas (GHG) emissions, has drastically increased from 280 ppm
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05
Road Road
(electric traction)
Road > Rail 4–7 times (Megajoules per NTKM)
(diesel traction)Road Road (composite) 0
FIGURE 1.24
Energy consumption: inter-city freight road and rail. (Adapted from Asian Institute of Transport Development (AITD), Environmental and Social Sustainability of Transport: Comparative Study of Rail and Road, Asian Institute of Transport Development, New Delhi, 2002.)
12,000 10,000 8000 6000 4000 2000
0 Jan/74
Ktoe (kilo-tonne of oil equivalent)
Jan/81 Jan/88 Jan/95 Jan/02 0
2000 4000 6000 8000 10,000 12,000
FIGURE 1.23
Road sector petrol consumption. (Adapted from M. Karpoor, Vision 2020 Transport, prepared for the Planning Commission, 2002.)
at the start of the industrial revolution in the year 1800 to 380 ppm in 2011.
The threshold level of CO2 emission is predicted to be 550 ppm; if it exceeds this level, it may lead to severe problems such as melting of the polar ice caps, a sea level rise of up to 1 m by the year 2100, an increased frequency of extreme climate events, permanent flooding of coastal cities, disruption of the ecosystem and extinction of species [15]. To avoid these wide-ranging consequences, international experts believe that it is absolutely essential to limit the global temperature rise within 1.5–2.5°C. In this direction, the G-8 nation summit recently decided to take some initiatives to at least halve the global CO2 emissions by 2050. GHG’s affecting the climate change has gained great momentum due to the Kyoto protocol. The ultimate objective of the Kyoto protocol is to stabilise the atmospheric concentration of GHGs and it commits industrialised nations to reduce their emissions of baskets of GHGs by around 5% between 2008 and 2012 as compared to 1990 levels [15]. It may be noted that India is a signatory to the multilateral treaty of the Intergovernmental Panel on Climate Change (IPCC). A transport vehicle gets more attention as it contributes about 20–25% of the CO2 released to the atmosphere, and this share tends to increase [7].
Transportation is an important societal need for better human life and eco- nomic development. Considerable importance is being given for combating the regulated emissions such as CO, HC, NOx and particulate matter (PM) from transport vehicles. As the GHGs emission is not under the regulated criterion, much emphasis is not historically given to the GHG emissions from the vehicles.
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0
(Megajoules per PKM)
(car andRoad bus)
Road(bus only)
Road(car only)
(electricRail traction)
(dieselRail traction)
(composite)Rail
FIGURE 1.25
Energy consumption: inter-city passenger road and rail. (Adapted from Asian Institute of Transport Development (AITD), Environmental and Social Sustainability of Transport: Comparative Study of Rail and Road, Asian Institute of Transport Development, New Delhi, 2002.)
GHG emissions from transport vehicles are mainly CO2, N2O and CH4. The transportation GHG emission contribution made by different types of vehicles is given in Table 1.7. It is clearly seen from the table that automobiles contribute about 70% GHG emission in the total transportation sectors. The development of new technology is so far mainly targeted to reduce regulated emissions enforced by the country’s legislation, as the customer’s expecta- tion is primarily focussed on fuel economy, comfort and safety. There is an urgent need to reduce GHG emission from all sectors, including the trans- port sector, to avoid global warming consequences. In this direction, the European Union (EU) has taken a number of initiatives to control CO2 emis- sion from transport vehicles.
The GHG emission formation mechanism, control measures, issues and challenges from transport vehicles are reviewed and discussed in the fol- lowing sections.
1.9.1 Mechanism of GHG Pollutant Formation in Internal Combustion Engines
The main GHG pollutants from internal combustion engines are CO2, N2O and CH4, and the pollutant formation mechanism is briefly described below.
1.9.2 CO2 Emission
CO2 is not considered as an obnoxious pollutant from the combustion point of view as a complete combustion is expected to yield higher CO2 emissions.
On the other hand, CO2 is an important pollutant from the environmental point of view. The fuel containing carbon and hydrogen during combus- tion with oxygen is converted into CO2 and water vapour as products. The carbon content of some fuels by weight are 84–87% in gasoline, 85–88% in TABLE 1.7
Transportation GHG Emissions by Mode, 2000 (US EPA)
S. No. Mode of Transportation GHG Emission Contribution (2000) (%)
1 Passenger cars 36
2 Light trucks 19
3 Heavy trucks 16
4 Buses 1
5 Aircraft 10
6 Marine 5
7 Rail 2
8 Other (two- and three-wheelers) 11
Source: Adapted from K. A. Subramanian et al., Control of GHG emissions from transport vehi- cles: Issues and challenges, SAE Paper No. 2008-28-0056, 2008.
diesel, 75% in CNG, 82% in propane, 37.5% in methanol, 52.2% in ethanol and 0% in hydrogen [2]. The development of new technologies are mainly targeted for reducing regulated emissions such as CO, HC and particulate emissions resulting in higher CO2 emission. In general, conventional fuels are mostly carbon-based fuels that would generally lead to carbon-based emissions such as CO2, CO, HC and PM.
Figure 1.26 provides the transport sector CO2 emissions across modes for 2005. This shows that road transport is the largest contributor to emis- sions, and within this the key contributors are on-road vehicles such as cars and LDVs, that is, four-wheeled vehicles (including sports utility vehicles, small passenger vans with up to eight seats), and trucks. Between 1990 and 2005, CO2 emission from the world transport sector rose by 37%. During the same period, road transport emissions increased by 29% in the industri- alised countries and 61% in other countries, which includes primarily the developing countries [17]. The Intergovernmental Panel on Climate Change (IPCC) in its fourth assessment report (AR4) advises that to avoid the worst impact of climate change, global CO2 emissions must be cut by at least 50% (Figure 1.27). Transport has a very significant role to play in realising that goal.
Medium and light trucks
19%
Buses 3%
2- and 3- wheelers
1%
Rail 1%
Domestic aviation 6%
International aviation
6% Domestic
navigation 1%
International marine bunkers
8%
Other transport 1%
Cars and light duty vehicles
54%
FIGURE 1.26
Modal shares of transport CO2 emissions (2005). (Adapted from International Energy Agency (IEA), CO2 Emissions from Fuel Combustion: 1971–2005, IEA, Paris, 2007c.)
• It is desirable to continue tightening the policies to address climate change. Implementation of carbon abatement policies in the OECD would help in reducing emission in 2030. However, it would only be about 10% as compared to 2010.
• Non-OECD countries do make significant progress in reducing the carbon intensity of their economies, but this is outweighed by car- bon increases due to rapid economic growth. The net result is a pro- jected increase in global emissions of 28% by 2030.
• This leaves the world well above the required emission path to sta- bilise the concentration of GHGs at the level recommended by scien- tists (around 450 ppm).
• Our ‘policy case’ assumes a step change in the political commitment to action on carbon emissions. Even in this case, the path to reach 450 ppm remains elusive. However, a declining emissions path by 2030 is achievable, given the political will to shoulder the cost [4].
1.9.3 N2O Emission
N2O emission occurs during combustion at low (<950°C) temperatures and it is affected by fuel type, operating conditions and excess air level, oxygen in fuel, and catalytic activity. Exhaust gas recirculation (EGR) is one of the promising technologies to enhance the control of NOx emission by means of reducing the combustion gas temperature, which results in a high N2O emission. Most of the research in the world is focussing on reducing NOx
40
Billion tonnes CO2
30
20
10
0
40
Billion tonnes CO2
Non-OECD
OECD
Basecase Policy case
IEA ‘450 scenario’
30
20
10
0
1990 2010 2030 2000 2010 2020 2030
FIGURE 1.27
Global CO2 emissions from energy use. (Adapted from Asian Institute of Transport Development (AITD), Environmental and Social Sustainability of Transport: Comparative Study of Rail and Road, Asian Institute of Transport Development, New Delhi, 2002.)
emission by reducing the gas temperature, but it may negatively result in high N2O emission. The global warming potential (GWP) of N2O is about 320 times higher than the CO2 equivalent.
1.9.4 CH4 Emission
CH4 is typically formed due to incomplete combustion. This emission may be due to partial combustion, quenching and unburned hydrocarbon. This level may be higher in case of a CNG-fuelled vehicle.
Typical values of CO2, CH4 and N2O emissions from vehicles using different fuels are given in Table 1.8. It can be seen from the table that a CNG-fuelled vehicle gives the lowest CO2 emission as compared to a petrol-, diesel- and LPG-fuelled vehicle. It may be attributed to the effect of CNG having the low- est carbon-to-hydrogen ratio among all fossil fuels. Further, it may be observed that the GWP of N2O and CH4 emission is about 320 and 63 times more than the CO2 equivalent, respectively. Some countries take measures to promote fuel-efficient vehicles around the world as given in Table 1.9. The countries are mainly aiming to reduce CO2 emission by improving the fuel economy.
1.9.5 Roadmap and Strategy for CO2 Emission Reduction by Other Countries
Some countries are setting the regulation for controlling CO2 emission from vehicles. The yearwise targeted CO2 emission of various countries and their strategies are given in Table 1.10.
Vehicle speed plays a vital role in fuel economy. Overspeed and a lower speed of vehicle would lead to fuel penalty. An internal combustion engine normally gives a higher fuel economy at medium speed. In Germany and the United States, the maximum speed will be normally up to 120 km/h.
However, in countries like India, the vehicle speed is generally limited to 20–30 km/h in urban areas, which may lead to heavy fuel penalty as most of the time the engine operates at a lower speed and idling conditions.
TABLE 1.8
Direct Greenhouse Gas Emissions from Passenger Cars on Petrol, Diesel, LPG and CNG under Real-World Driving Conditions
Fuel CO2 (g/km) CH4 (g/km) N2O (g/km)
GHG Emission (g of CO2 Equivalent/km)
Petrol 208.1 0.009 0.003 209.2
Diesel 180.5 0.004 0.007 182.7
LPG 189.3 0.007 0.003 190.4
CNG 168.6 0.0074 0.001 170.6
Source: Adapted from P. Hendriksen et al., Evaluation of the environmental performance of modern passenger cars running on petrol, diesel, automotive LPG and CNG, TNO- report 03.OR.VM.055.1/PHE, TNO Automotive, December 2003.
The Kyoto protocol objective is to reduce the CO2 emission by about 5–8%
in the target time frame of 2008–2012. For example, the EU has set a target of CO2 emission reduction to about 120 g/km by the year 2012. As most of the vehicles may be in a production stage, which will be sold by the year 2012, it may be a big challenge to meet the CO2 emission target. The industry could continue to cut CO2 from cars through improved vehicular technology, but specific legal requirements cannot come into force before 2015 [16]. The lead time for CO2 emission norms implementation needs to be formulated with the association of automobile manufacturers of the concerned country.
New vehicle models emitting CO2 emission of 120 g/km launched by the year 2000 were facing a lack of market acceptance. For examples, battery elec- tric-powered vehicle such as Audi Duo, Fiat Auto’s Seicento Elettra, Ford’s electric Think City vehicle, General Motor’s Astra and Corsa Eco, Mercedes A 160, PSA’s Electric Vehicles, Renault’s Electric Vehicles, Volkswagen’s Lupo and Golf CityStromer received poor acceptance from customers [16].
As the automotive industry is currently facing problems in meeting the stringent norms of regulated emissions, the additional burden of CO2 emis- sion reduction may lead to the slowdown of the overall economy.
The EU policy decision is focussed towards the goal of 120 g CO2/km by 2012 through improved vehicular technology. This may cost around Euro 3600 on average per vehicle. This is up to 10 times more expensive than sim- ilar or even more effective measures such as an increased use of biofuels and adopting an economic driving style. Reducing CO2 emissions through improved vehicular technology is up to 10 times more expensive than other traffic-related measures [16].
TABLE 1.9
Measures to Promote Fuel-Efficient Vehicles around the World
Country/Region
Fuel Efficiency
Approach Measures
United States, Japan, Canada, Australia, China, Taiwan, South Korea
Fuel economy standards Numeric standard in mpg, km/L or L/100 km European Union, California GHG emission standards G/km
European Union, Japan High fuel taxes Fuel taxes at least 50% greater than crude oil base price European Union, Japan Fiscal incentives Tax relief based on engine size,
efficiency and CO2 emission
California Technology mandates
and targets Sales requirement for ZEVs
United States Economic penalties Gas guzzler tax
Several U.S. states Traffic control measures Hybrid allowed in HOV lanes, ban on SUVs
India Fuel economy standards km/L
Source: Adapted from K. A. Subramanian et al., Control of GHG emissions from transport vehicles: Issues and challenges, SAE Paper No. 2008-28-0056, 2008.