Non-renewable energy resources

1. Non-renewable energy resources

2. Formation of Coal. Coal is predominately Carboniferous in age, 299.8 – 361.7 Ma. During the upper Carboniferous, areas with a latitude between 5°S and 20°N, experienced a relatively stable period tectonically. Deltas deposited upward coarsening sequences. Abundant vegetation thrived in the hot, moist conditions. During a flood, old deltas would often be abandoned as rivers cut new routes to the sea. With no fresh sediment, they would compact down under their own weight and subside below sea level. Ultimately the river might return to deposit a new upward fining sequence on top. In addition to these isostatic changes, a number of eustatic rises of sea level caused flooding, allowing new sequences to develop on top of old. This resulted in a rhythmically repeated sequence of deposited sediment. Where dead vegetation accumulated on a slowly subsiding delta, the waterlogged (anoxic) conditions prevented decay. The resulting peat was eventually buried and compressed. Over time, the amount of pressure and heat acting on the peat increases. This causes longer hydrocarbon molecules to break into smaller molecules. Whilst the hydrocarbons are being broken down, methane is being released. Turning Peat into Lignite, which has a lower percentage of methane but a higher percentage of carbon. This process continues turning Lignite into Sub-bituminous coal, then Bituminous and then finally Anthracite coal. Anthracite coal has the highest purity, containing 95% carbon.

3. Formation of Oil. Again oil was predominately formed during the Carboniferous. The same processes for the formation of coal, are used for the formation of oil. The difference is, oil is formed in tropical marine environments. Dead marine organisms, such as plankton, would sink and accumulate on the sea bed of deep basins. At the bottom of a basin, the environment is anoxic preventing decay.The constant accumulation of new sediment would compact the older sediment, creating dark muds. As the layers of sediment increases, the heat and pressure exerted on these remains begin to rise. The degree of heat and the amount of pressure, along with the type of biomass, directly influence whether oil or natural gas is formed. As heat increases, a lighter gas is formed. If the temperature rises to an even higher heat, or if the biomass is predominantly plant material, natural gas is formed. The temperature to create oil is between 60 - 120°C, ‘Wet’ gas is between 120 - 140°C and ‘Dry’ Natural gas is above 140°C. As well as heat the age of the crude oil is important. The older the oil, the lower its viscosity will be, meaning it is easier to extract.

4. Extraction • Coal is extracted by deep mining and open cast mining. Deep mining is labour intensive and cannot remove huge quantities of coal so it is relatively expensive. Open cast mining is more mechanised but all the rock above the coal must be removed so it is only economically viable where coal is quite near the surface. • Crude oil is found in geological structures where the liquid oil can flow through permeable rock and collect in the pores between the particles of a porous rock. The natural pressure of the gas above the oil, or water beneath the oil, will force the oil to the surface when a pipe is drilled down to the oil reservoir.

5. Extraction

6. Nuclear Power • Key Terms: • Fissile Fuels: a fuel where the nuclei of the atoms can be split by neutron bombardment, releasing large amounts of energy. • Isotope: A variety of an element where the number of neutrons is different. • Large amounts of energy are released when small amounts of matter from the nuclei of atoms are destroyed. • Nuclear fission involves the splitting of the nuclei of fissile fuels that have large atoms, such as the isotopes uranium 235 and plutonium 239. • Nuclear fusion involves the joining of the nuclei of small atoms, such as the isotopes hydrogen 2 and hydrogen 3. • Only nuclear fission is commercially viable at the moment; fusion being a research project.

7. Nuclear Power • Limiting Factors: • A number of factors have limited the growth of nuclear power. • The technology is very complex so it is difficult to use in less technologically advanced societies, • The complex technology makes it more expensive, • There is strong public opposition to nuclear power in some countries because of the possible link with nuclear weapons and concerns over safety, especially after the reactor accidents at Three Mile Island (1979, USA) and Chernobyl (1989, Ukraine), • Uncertainty over the long-term disposal of radioactive waste, • Uncertainty over the total costs of nuclear power since no commercial reactor has been fully decommissioned.

8. Energy density • The high energy density of fossil and nuclear fuels makes them very useful. • The high temperatures that are reached when coal is burned allow the smelting of metal ores, • Burning fossil fuels and nuclear fission give temperatures that are high enough to produce high pressure steam, which can spin turbines and generators in power stations, • The high energy density of fossil fuels allows a small mass of fuel to do a lot of work, so 5kg of petrol can carry 1000kg of car for 50 miles, • 85 tonnes of aviation fuel can carry a 400 tonnes Boeing 747, including 400 passengers, for 3500 miles from London to New York. If the fuel had a low energy density then the weight of the fuel carried would make the flight impossible, • The high energy density of nuclear fuel means that reactors require very little fuel. This means that power stations can be located where the transport of fuels with a lower energy density would be a problem. A reactor only needs to have a few tens of tonnes of fuel replaced each year, compared with the 10000 tonnes of coal that would be burned by a similar sized coal fired power station every day.

9. Finite resources Non-renewable energy resources are finite resources, so as they are used the reserves are depleted. This is very important where industrial societies have grown up on local fuel supplies, such as in the heavy industrial regions that grew up on the coalfields of the North-eastern USA, the Midlands in the UK and the Ruhr region of Germany. When the local supplies are depleted the industries may only survive if foreign supplies can be imported easily.

10. Available Resources • The total amounts of fossil fuels and uranium that exist are very large. But much of this is not included within the estimates of reserves because the technology to exploit them has not been developed or it would be too expensive to do so. • A lot of oil and coal is inaccessible because it is too deep, found in small amounts or is in inaccessible places, • Oil shales are solid hydrocarbons that cannot flow to the surface like crude oil. To extract them they must be quarried or heated underground so they will melt and can flow to the surface. The amount that could be exploited is much greater than our total reserves of crude oil, but it is more expensive to extract than crude oil, so not much is currently used, • A huge amount of uranium exists but most is found in very low purity ores, which cannot be economically exploited. The energy cost of extracting uranium would be greater than would be released when the uranium underwent fission.

11. Level of technological development • The development of new technologies may allow us to exploit the resources we already use more effectively and make it possible for new resources to be used. • The use of natural pressure to force oil to the surface is called primary recovery. About 20% of the oil is usually extracted. Secondary recovery involves pumping down natural gas or water to maintain the pressure and increase the total recovery rate to about 40%. Tertiary recovery involves the use of solvents, steam or detergents to make the oil less viscous so it will flow more easily. This typically increases the total recovery to about 60%, • Coal that is too deep to be mined can be burned underground under controlled conditions to produce a mixture of fuel gases including Hydrogen, Carbon Monoxide and Methane, • Uranium 238 is over 100 times as abundant as uranium 235 but it cannot be used in normal reactors. Nuclear fast reactors can use uranium 238 and produce much more energy, but the technology is very complex and not fully developed because of the high costs involved, • The fusion of hydrogen nuclei releases the huge amounts of energy produced in the Sun. The controlled fusion of hydrogen has been achieved on Earth and research continues, but the technology is very complex and is many years away from commercial use.

12. Level of technological development • The development of new technologies may reduce the environmental impact of energy use. • Fuel and flue-gas desulphurisation have reduced the acid rain caused by burning coal, • A range of technologies has been suggested for carbon sequestration to store the carbon dioxide released when fossil fuels are burned. The carbon dioxide may be used during tertiary oil recovery, increasing the rate of oil extraction and leaving the carbon dioxide underground.

13. Environmental Impacts • The extraction, processing, use and waste disposal of fossil and nuclear fuels all have environmental impacts. • The mining of coal and uranium ores may cause: habitat loss, noise, dust and turbid drainage waste. • Oil extraction and transportation all release greenhouse gases and impact on climate change. • The burning of fossil fuels causes: acid rain, global climate change, increased levels of carbon monoxide, photochemical smogs, smoke and ash. • Nuclear power plants can lead to the loss of habitat for aquatic organisms, due to the large quantities of water needed to cool down nuclear waste. As well as the initial loss of water, the heated water and nuclear waste is then released which negatively affects water quality. Also, human health is at risk from ionising radiation.

14. Political and international trade problems • The desire for energy-hungry countries to satisfy their own energy needs may influence political decisions in an attempt to protect future supplies. • Crude oil provides most of the world’s energy but reserves are not evenly distributed. The MEDCs use over half the world’s oil production but only a small proportion of this is home-produced. Most of the world’s oil reserves are in the Middle East, which makes it the focus of trade and political interest, • The possible link between civil nuclear electricity and nuclear weapons has led to some countries to try to curtail the availability of technology to countries that are considered to be untrustworthy.

15. Economic problems • The world’s trade system encourages us to make decisions based on which of our options will be cheapest. This may not be the best long-term decision. • Cheap natural gas contributed to the closure of the deep coal mines in the UK when there was still a lot of coal that could have been extracted. North Sea gas will be exhausted within a few decades, but it will not be possible to reopen the coal mines because hey are flooded and unsafe. • Fossil fuel use causes economic costs that are not paid by the energy industry. Costs such as pollution damage are paid by other sectors of society such as agriculture, forestry or the health service. • The decision to use nuclear power did not include accurate estimates of the total cost of decommissioning, which are still unknown.