Energy and carbon dioxide savings in transport

Transport is responsible for nearly one-quarter of greenhouse gas emissions worldwide. It is also the sector where emissions are growing most rapidly (Figure 11.9). Road transport accounts for the largest proportion of this, over 70%, shipping around 20% and air transport about 10%.23 The world population

Figure 11.9 Historical and projected carbon dioxide emissions from transport by modes, 1970-2050. Projected data by the World Business Council on Sustainable Development (WBCSD) under a business-as-usual scenario; historical data from the International Energy Agency.

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Estimated data (WBCSD) -

Estimated data (WBCSD) -

Figure 11.9 Historical and projected carbon dioxide emissions from transport by modes, 1970-2050. Projected data by the World Business Council on Sustainable Development (WBCSD) under a business-as-usual scenario; historical data from the International Energy Agency.

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of light motor vehicles, currently around 750 million, is projected to rise by a factor of 2 by 2030 and a factor of 3 by 2050, most of the growth occurring in developing countries.24 This trend seems inevitable when account is taken of the very large differences today in car ownership in different countries - in terms of persons per car, about 1.5 in the USA, 30 in China and 60 in India. Under similar assumptions, by 2050 a growth in aviation is projected by a factor of 5, again much of it in the developing world. Increased prosperity brings increased demand for personal mobility and also increased movement of freight. In the transport sector the achievement of reductions in carbon dioxide emissions will be particularly challenging.

There are three types of action that can be taken to curb the rapidly growing carbon dioxide emissions from motor transport (Figures 11.9 and 11.10). The first is to increase the efficiency of energy and fuel use and to move to non-fossil-fuel sources of energy. We cannot expect the average car to compete with the vehicle which, in 1992, set a record by covering over 12 000 km on 1 gallon of petrol - a journey which serves to illustrate how inefficiently we use energy for transport! However, it is estimated that the average fuel consumption of the current fleet of motor cars could be halved through the use of existing technology - more efficient engines, lightweight construction and low-air-resistance design (see box on p. 346) - while maintaining an adequate performance. Further, possibilities exist for the use of electric propulsion driven from larger and more efficient batteries or from fuel cells powered by hydrogen fuel supplied from non-fossil-fuel sources. The second action is to plan cities and other developments so as to lessen the need for transport and to make personalised transport less necessary - work, leisure and shopping should all

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Figure 11.10 Projected transport energy consumption by region and by mode projected by the World Business Council on Sustainable Development (WBCSD) under a business-as-usual scenario.

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be easily accessible by public transport, or by walking or cycling. Such planning needs also to be linked with a recognition of the importance of ensuring that public transport is reliable, convenient, affordable and safe. The third action is to increase the energy efficiency of freight transport by making maximum use of the most energy-efficient forms of freight transport, e.g. rail or water, rather than road or air and by eliminating unnecessary journeys.

Air transport is growing even faster than motor transport. Global passenger air travel, as measured in passenger-km, is projected to grow at about 5% per year over the next decade or more and total aviation fuel use - including passenger, freight and military - is projected to increase by about 3% per year, the difference being due largely to increased fuel efficiency.26 Further increases in fuel efficiency are expected but they are unlikely to keep up with the increase in the volume of air transport. Biofuels as an alternative to kerosene are also being studied and are assumed, for instance in the IEA BLUE Map scenario, to have replaced 30% of conventional aviation fuel by 2050. Hydrogen has also been proposed as a long-term possibility but the effect on the dry upper troposphere of injection of the resulting water vapour has yet to be evaluated - it would probably lead to an unacceptable increase in cloud cover unless flight altitudes were substantially lowered.

A further problem with air transport, mentioned in Chapter 3 page 63, is that its carbon dioxide emissions are not the only contributor to global warming; increased high cloudiness due to other emissions produce an effect of similar or even greater magnitude. Operational changes to minimise this effect have

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