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Transport and Sustainability
Transport and Sustainability

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1 The transport energy challenge

Activity 1

Timing: 10 minutes

Before reading the rest of this section, make a list of what you consider to be the main issues and challenges concerning energy use in transport.

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Discussion

Energy use in transport reflects a mix of concerns that varies over time and between countries. The list that you have just made will contain a number of issues and may well be influenced by what is happening at the time you are studying.

Important topics include:

  • the health implications of local air pollution, particularly NOx from diesel vehicles
  • the urgent need to reduce global carbon dioxide emissions
  • continuously changing world oil prices affecting domestic fuel prices
  • the possibility of armed conflicts (such as the war in Ukraine) interrupting oil supplies
  • the honesty (or otherwise) of vehicle manufacturers about the emission standards of their products.

Energy issues are rarely about energy alone. They may also be about:

  • financial costs (varying from the personal cost of travel, through to that of energy costs affecting industrial competitiveness)
  • the impacts of traffic congestion (from its effects on people to its economic cost)
  • energy security (i.e. not being dependant on energy supplies from politically unstable or unfriendly nations)
  • health (for example, the effects of local air pollution or obesity brought about by lack of physical exercise)
  • a whole range of environmental issues (such as the land take for new transport infrastructure, global warming etc.).

Appreciating the importance of energy use in transport requires a look at UK national energy statistics. These use two categories of energy:

  • Primary energy − this is essentially energy in its ‘raw’ form. Examples include crude oil before it is refined and the fuels used to generate electricity, such as natural gas and nuclear heat.
  • Delivered (or final) energy − this is the energy that the consumer actually receives (and pays for): refined petrol and diesel, mains electricity, piped natural gas.

The statistics also split energy use into different sectors: the domestic sector − people’s homes; the services sector – shops, offices, schools, etc.; transport and, finally, industry.

Box 1 Energy units

Perhaps the most familiar energy unit is the kilowatt-hour (kWh). Household gas and electricity bills are normally expressed in these. In electrical terms this is the amount of energy used by a 1 kilowatt (kW) appliance, such as a small electric fire, in one hour.

The prefix ‘kilo’ means 1000 and is shortened to ‘k’. 1 kW = 1000 watts.

Most of the energy calculations in this course are in watts, kilowatts and kilowatt-hours.

Energy statistics may use a ‘scientific’ unit of the ‘joule (J)’. This is the (tiny) amount of energy used by a 1 watt device in 1 second. 1 kilowatt-hour = 3.6 million joules.

Larger energy units use other prefixes. Those used in this course are:

  • mega – shortened to ‘M’. 1 MJ = 1 million joules and 1 kWh = 3.6 MJ
  • giga – shortened to ‘G’. 1 GJ = 1000 MJ
  • tera – shortened to ‘T’. 1 TJ = 1000 GJ
  • peta – shortened to ‘P’. 1 PJ = 1000 TJ

Figure 1 shows the breakdown of UK primary and delivered energy for 2018 in different ways. The top bar shows the actual primary fuels used. The three bars below show the delivered (or final) energy use expressed in three ways: by fuel, by energy sector and by end use.

In 2018 transport accounted for over 80% of the UK’s oil consumption and 40% of the UK’s final energy use. Liquid fuels produced from oil made up 97% of the final transport energy demand. Electricity made up less than 1%.

Described image
Figure 1: UK primary and final energy use, 2018
Show description|Hide description

This figure shows UK primary and final energy use in a stacked bar form. There are four horizontal bars, one above the other. The top bar is labelled at the left ‘Primary energy’. The lower three bars are labelled together as ‘Final energy’ and individually as being broken down ‘by fuel’, ‘by sector’ and ‘by end use’. There is an x-axis at the bottom which is marked in Petajoules with a scale running from zero to 9000.

The top bar, primary energy, contains the following items: coal, shown in black, about 360 petajoules; oil, shown in orange, about 2870 petajoules; gas, shown in blue-green, about 3140 petajoules; nuclear heat, shown in purple, about 660 petajoules; and renewables, shown in green, about 1000 petajoules. The total is just over 8010 petajoules.

The second bar, final energy broken down by fuel, contains the following items: solid fuel, shown in black, about 80 petajoules; liquid fuels, shown in orange, about 2660 petajoules; gas, shown in blue-green, about 1830 petajoules; electricity, shown in blue, about 1080 petajoules; bioenergy and heat, about 320 petajoules. This gives a total of nearly 6000 petajoules. There is a further section of the bar marked losses in conversion and delivery, shown in light grey of about 2040 petajoules which makes up a total of just over 8010 petajoules, equal to that in the top primary energy bar.

The third bar, final energy broken down by sector, contains the following items: domestic, shown in blue, 1730 petajoules; services, shown in blue-green, about 910 petajoules; transport, shown in orange, about 2390 petajoules; and industry, shown in pink, about 950 petajoules. The total is nearly 6000 petajoules, identical to that for the second bar.

The fourth bar, final energy broken down by end use, contains the following items: space and water heating drying, shown in yellow, about 2420 petajoules; high temperature heat, shown in dark red, about 150 petajoules; cooking, shown in light purple, about 140 petajoules; transport, shown in orange, about 2440 petajoules; lights and appliances, shown in light yellow, about 690 petajoules; and industrial machinery, shown in dark brown, about 150 petajoules. The total is nearly 6000 petajoules, identical to that for the second and third bars.

Figure 1: UK primary and final energy use, 2018

The UK produces oil but its oil reserves have been falling. Peak UK oil production was in 1999 and it has fallen since then. The UK both imports and exports oil and its products. It became a net oil importer in 2006 and in 2023 net imports were almost a half of the total UK consumption (DESNZ, 2024).

The cost of oil imports is a serious national concern. The world price of oil has varied enormously from year to year since the 1970s. The COVID-19 pandemic resulted in curbs on transport use across the globe and a fall in oil demand. The world oil price fell from US$70 a barrel in 2018 to only US$30 in spring 2019. However, the war in Ukraine and restrictions on the purchase of Russian oil forced the price back up to over US$100 a barrel.

As will be described in Section 7 of this course, there is an ongoing rapid switch from oil to electricity as the UK’s main transport fuel. This raises the question of how much extra (low carbon) electricity will be required. At present, the transport oil fuel is burned with a relatively low efficiency in internal combustion engines (see Section 4 of this course). As shown in Figure 1, the UK’s final electricity consumption in 2018 was nearly 1100 PJ or about 300 TWh. Of this only about 5 TWh (about 1.7%) was used for transport. Electrifying the UK’s car and van fleet could produce an extra electricity demand of 65 – 100 TWh by 2050 (DfT, 2021a). You might like to reflect on exactly how all this is going to be generated.