An introduction to energy resources
An introduction to energy resources

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

An introduction to energy resources

4.6 The fossil fuel 'bank'

During the period of accumulation of most coal and petroleum, the past few hundred million years, the equivalent of around 1023 J of chemical energy have been 'banked' by Earth processes. As you have seen in Sections 4.3 and 4.4 carbon is added to these reservoirs continually, at a rate today that is equivalent to about 5 × 1017 J yr−1. That rate of growth represents roughly a mere thousandth of present world energy demand.

Question 13

If the consumption of energy from all primary sources in 2002 were 451 EJ, how long would the fossil fuel energy 'bank' last at that rate of consumption?


The fossil fuel energy 'bank' would last (1023 J)/ (4.51 × 1020 J yr−1), or about 220 years, at this rate of consumption.

In fact, the 'bank' contains only about 0.04% of the amount of organic carbon preserved in sedimentary rocks. However, that total store of buried organic carbon is finely dispersed, at an average concentration of about 0.4% in sedimentary rocks. At that level, it can never be exploited, either economically or with an efficiency that yields more energy than it consumes.

Although buried organic carbon is widely distributed, concentrations sufficient to constitute resources are rare and very restricted in space and geological time relative to small amounts of organic carbon that are present in many sediments.


Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371