How Much Energy Is Enough? - The Renaissance of Renewable Energy - page 61

Figure 3.6. Share of energy consumption by sector in different parts of the world.
Non-energy use indicates the use of fuels as raw materials, for example, oil to produce
plastics or fertilizers. Source: IEA website.

Industrial Energy Use
We are used to thinking of cars as machines that consume energy, but it is worth
considering the amount of energy that is already 'embodied' in a car when it rolls off the
production line. About 80 per cent of a car consists of metal - steel, aluminium and copper.
The rest is plastics, glass and rubber. Starting with the mining of iron ore, and continuing
throughtothelabourrequiredforitsmanufacture,transportandsale,ittakesabout100,000
megajoules of energy just to put an average car into a showroom. This is equivalent to
roughly two years of driving. In other words, the process of making a car requires about
one-fifth of the energy the car will consume in its lifetime. With computers the embodied
energy is even greater, compared with the energy requirements of the device, as it takes
four times more energy to produce a personal computer than to operate it throughout its
lifetime (Williams 2004 ).

Most industrial processes require huge investments of heat and mechanical power, and
almost every manufactured product undergoes several stages of energy input, starting with
the raw materials (see Table 3.10 ) . It takes about 200 megajoules of energy to manufacture
one kilogram of aluminium from bauxite ore. Paper, a product so cheap and ubiquitous in
wealthy countries that it is often given away for free, is also an energy glutton. Just imagine
the energy required to chip, grind and boil the wood into pulp, and then to roll and dry
the pulp into paper. No industrial product better illustrates the profligate use of energy in
modern industrialised societies.

Table 3.10. The amount of energy required to manufacture industrial materials
from a raw natural source

Material Source Embodied energy MJ/kg

Aluminium Bauxite 190-230

Aluminium Recycled metal 10-40