Fossil Fuels
Fossil fuels are formed from organic material, both plant and animal remains. When the organic material is put under immense pressure, such as would occur when it is buried at the bottom of oceans, the pressure of the water changes this organic matter into liquid and gaseous hydrocarbons. It is estimated that a 10 foot thick layer of organic material would produce one a one foot thick layer of coal (although there are many factors that would affect this).
This process is known as catagenesis. Where the bulk of this organic material is mostly plant matter, the process tends to form coal. Where the organic material is mostly animal based, the process tends to form oil. Gas is released during this process and is trapped by non permeable rock layers.
Many of the oil and coal fields date to one specific period in history, which is the Carboniferous era.
According to figures released in 2008 by the Office for National Statistics, the UK oil reserves are estimated to be as much as 2.7 billion tonnes. However this estimate includes figures of oil reserves that have not yet been shown to exist. The amount of proven oil reserves is 0.4 billion tonnes.
The estimates for gas reserves is 1,950 billion cubic metres. However the reserves known to exist are approximately 300 billion cubic metres.
carbon emissions from burning fossil fuels
Burning fossil fuels is the UK's largest source of carbon dioxide (CO2) emissions into the atmosphere. Approximately 40% of the UK's emissions come from the power stations burning coal, oil and gas. 25% of these emissions come from the transport sector and 15% comes from homes. Burning natural gas emits less carbon dioxide than coal or oil. (FOE)
The UK carbon dioxide emissions decreased in the 90's when the switch to North sea gas took place.
References:
(FOE) Fossil fuel carbon dioxide emissions
One way to continue to allow fossil fuel power stations to be used in the future is to add carbon capture devices and to use carbon sequestration technologies. There are currently three types of capture technology:
- post-combustion
- pre-combustion
- oxyfuel
The Longannet power station on the Firth of Forth was fitted with the UK's first carbon capture unit on at trial basis. Three of the turbines had prototype flue gas desulphurisation (FGD) equipment fitted. The 'captured' carbon dioxide is turned into liquid form ready for storage (wherever that may be).
If this trial shows that similar capture mechanisms can be used on all the existing coal fired stations in the UK then that will go a long way to meeting the UK 2020 carbon reduction targets!
I am not aware that any UK coal fired power stations using CCS in a production environment at this time.