Living without oil
Living without oil

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Living without oil

2 Oil for personal transport

Described image
Figure 2 Personal transport relies on crude oil.

Most obviously, oil products provide us with the energy to move us around (Figure 2) and a proportion of the 4 litres of crude oil each person consumes each day will be used to fuel personal transport. Several crude oil products are used to fuel transport. Petrol (called gasoline in some parts of the world) and diesel are the fuels primarily used for road transport, whilst kerosene is used to fuel jet aircraft.

You can start to estimate how much of the 4 litres each person consumes is used for personal road-based transport by roughly estimating how much fuel you use for personal transport each day. You could begin by trying to select a typical day and estimating how much fuel was consumed on that day; but transport needs vary so much from day to day, that it is more appropriate to look at a longer period, and take an average. One way to do this would be to look at the transport fuel consumed over a period of a week: Table 1 shows estimates of the amount of fuel (petrol) used for car transport in a relatively quiet week for the author.

Table 1 An estimate of the author's petrol usage for personal transport in a quiet week. All distances are approximate, and a fuel consumption of 17 km l1 is assumed. Note that, due to rounding errors, simply adding the figures in the final column would slightly overestimate the total volume of petrol used. A total of 225 km implies a consumption of 13.2 litres of petrol, not the 13.5 which would be obtained by adding the figures in the right-hand column.

Day Journey destination Length of return journey/km Estimated volume of petrol consumed/litres
Sunday cinema 30 1.8
Monday office 40 2.4
Tuesday train station 30 1.8
Wednesday office 40 2.4
Thursday office 40 2.4
Friday office 40 2.4
Saturday supermarket 5 0.3
TOTAL 225 13.2

In general, UK petrol engine cars have an average fuel consumption in the region of 17 kilometres per litre (km l1), which is the figure that has been used in the calculations in Table 1. Diesel engines tend to be more efficient and deliver an average of around 23 km l1.

Here scientific SI units, km l1, are used rather than miles per gallon which might be commonly used in the UK. Expressing kilometres per litre in the form km l1 is again a standard scientific way of expressing things.

Here is an example of the type of calculation used to generate the final column in Table 1.

Approximate distance to cinema and back = 30 km

Estimated fuel efficiency = 17 km l−1

Question 1

Try to estimate how many litres of petrol or diesel the main car user in your household has consumed in the last week. Make a list of the journeys made, estimating the total distance covered in kilometres. Don't worry about being exact - you are just trying to get a rough idea. If you have a small petrol engine car, you can assume that your fuel efficiency is 20 km l1; if you have an average-sized car, assume a fuel efficiency of 17 km l1; and for a larger car, assume 14 km l1. If you have a diesel engine car, assume a fuel efficiency of 23 km l1. If you have estimated your distances in miles (or read them in miles from the display in your car), then you will need to multiply by 1.6 to convert miles to kilometres.

If no one in your household uses a car, try to estimate how much petrol you would have used if you replaced your usual modes of transport with a small petrol engine car.

Answer

The answer for the author is in Table 1 and the associated text. Your answer will be personal to you.

Question 2

After processing, a typical litre of crude oil will yield around 0.46 litres of petrol, 0.23 litres of diesel and a variety of other products. Calculate how many litres of crude oil would have to be processed to supply your house-hold with fuel for the car for an average day. You should assume that the last week is a typical one. Once again, if no one in your household uses a car, estimate how much petrol you would have used if you replaced your usual modes of transport with a small petrol engine car.

Answer

The author's answer would be as follows:

Daily petrol consumption

= 1.9 litres approximately

A typical litre of crude oil will yield around 0.46 litres of petrol, so the number of litres of crude oil needed to generate 1.9 litres of petrol would be given by:

litres of crude oil processed = 1.9/0.46

= 4.1 litres

This answer is discussed in the text that follows.

Table 1 and the answer to Question 2 imply that the author's car is responsible for the consumption of 4.1 litres of crude oil a day. Three people live in the author's household and share the use of the car, so arguably the car's consumption can be divided between three, so the car alone accounts for about 1.4 litres of the 4 litres of crude oil each person in the author's one car household might be expected to consume each day. Coincidentally the author's calculations imply that in his household his car consumes the same amount of crude oil each day (4.1 litres) as the average UK citizen. Your calculations may give a quite different figure, depending on the car and the distance travelled.

The week shown in Table 1 is not a typical one for the author's family as the annual mileage recorded for his car is in the region of 10 000 miles or approximately 16 000 kilometres. This suggests that the car is responsible for not 1.4 but around 1.9 litres of the 4 litres of crude oil each of the three people in the household might be expected to consume each day. (You may like to check this calculation for yourself.) These are very approximate calculations, but they demonstrate that personal road transport is responsible for a very significant proportion of the crude oil consumed in the developed world. The calculation did not take into account trips made by public transport which also will be responsible for a small proportion of our daily consumption of crude oil.

  • Why is the consumption of crude oil in public transport likely to be much less significant in determining our individual consumption of crude oil?

  • Public transport carries many more passengers than cars can, so the consumption of crude oil by a bus or train will be spread across many more individual passengers.

Other forms of transport are important too - aviation is a huge consumer of fuel derived from crude oil (largely kerosene). A single return flight to New York from London could easily triple an individual's annual personal consumption of crude oil products.

However, as important as personal transport is in determining the amount of crude oil we consume, to gain a full appreciation of the centrality of oil in the modern world you also need to look at the role crude oil plays in transporting goods.

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