## Bigger stuff

The largest stuff most people buy is a house.

In Chapter H, I estimate the energy cost of making a new house. Assuming we replace each house every 100 years, the estimated energy cost is 2.3 kWh/d. This is the energy cost of creating the shell of the house only - the foundation, bricks, tiles, and roof beams. If the average house occupancy is 2.3, the average energy expenditure on house building is thus estimated to be 1 kWh per day per person.

What about a car, and a road? Some of us own the former, but we usually share the latter. A new car's embodied energy is 76 000 kWh - so if you get one every 15 years, that's an average energy cost of 14 kWh per day. A life-cycle analysis by Treloar, Love, and Crawford estimates that building an Australian road costs 7600 kWh per metre (a continuously reinforced concrete road), and that, including maintenance costs, the total cost over 40 years was 35 000 kWh per metre. Let's turn this into a ballpark figure for the energy cost of British roads. There are 28 000 miles of trunk roads and class-1 roads in Britain (excluding motorways). Assuming 35 000 kWh per metre per 40 years, those roads cost us 2 kWh/d per person.

Newspapers, junk mail, magazines: 2 kWh/d

House-building: 1 kWh/d

Car-making: 14 kWh/d

Transporting the stuff

Up till now I've tried to make estimates of personal consumption. "If you chuck away five coke-cans, that's 3 kWh; if you buy The Independent, that's 2 kWh." From here on, however, things are going to get a bit less personal. As we estimate the energy required to transport stuff around the country and around the planet, I'm going to look at national totals and divide them by the population.

100 km

Figure 15.5. Food-miles - Pasties, hand-made in Helston, Cornwall, shipped 580 km for consumption in Cambridge.

Freight transport is measured in ton-kilometres (t-km). If one ton of Cornish pasties are transported 580 km (figure 15.5) then we say 580 t-km of freight transport have been achieved. The energy intensity of road transport in the UK is about 1 kWh per t-km.

When the container ship in figure 15.6 transports 50 000 tons of cargo a distance of 10000 km, it achieves 500 million t-km of freight transport. The energy intensity of freight transport by this container ship is 0.015 kWh per t-km. Notice how much more efficient transport by container-ship is than transport by road. These energy intensities are displayed in figure 15.8.