The economy which we operate today is largely based on a one-way journey of natural resources – from source to sink:

Sources and Sinks drive the economy

Figure 1: Our economy depends both on the availability of natural resources and on the ability of the environment to deal with the wastes that we produce.

However, oil, like other fossil fuels, is a non-renewable resource, in other words it is not replenished by nature – it can only be used once. The source of oil is finite. Furthermore the use of oil leads to emissions of CO2 whose natural sinks are already saturated. Given the importance of oil to the economy it is not surprising that there has been a lot of debate about whether the Source or the Sink would ever limit our use of this resource, and when those limits would arrive.Amongst all the resources that we use oil is particularly important. It has been the availability of huge quantities of very cheap oil that has powered the unprecedented economic growth of the last century, just as coal was the energy source that underpinned the Industrial Revolution in the years before. Oil has wondrously been described as “fossilised sunlight” because it is derived from the sun that fell on plants over thousands of years. Oil is an incredible material –it is very portable, its derivatives – gasoline/petrol, diesel etc. – are volatile and so can drive combustion engines and as chemical feedstock oil underpins a huge range of industries. Oil also has around one and half times the energy density of coal and over four times that of wood – one litre of gasoline/petrol contains 32 MJ or 8.5 kWh – which is equivalent to about 8.5 days of human labour[1]!