Fossil fuel


Fossil fuels are hydrocarbon fuels or hydrocarbon containing fuels such as
petroleum (including natural gas) and coal. The utilization of fossil fuels
has fueled industrial development and largely supplanted water driven mills
and wood or peat burning for heat.

With nuclear power, it compounds the nuclear-fossil energy.

When generating electricity, energy from the combustion of fossil fuels is
often used to power a turbine. Older generators used steam generated by the
burning of the fuel to turn the turbine, but in newer power plants the gases
produced by burning of the fuel turn a gas turbine directly. The burning of
fossil fuels is the major source of emissions of carbon dioxide which is one
of the greenhouse gases.

Origin

There are two theories on the origin of fossil fuels: the biogenic theory
and the abiogenic theory. The two theories have been intensely debated since
the 1860s, shortly after the discovery of widespread petroleum. According to
the biogenic theory, fossil fuels are the altered remnants of ancient plant
and animal life deposited in sedimentary rocks. The organic molecules
associated with these organisms forms a group of chemicals known as kerogens
which are then transformed into hydrocarbons by the process of catagenesis.
According to the abiogenic theory, fossil fuels are primordial, being part
of the Earth as it formed.

The abiogenic theory was favored early because in the late 19th century it
was believed that the Earth was extremely hot (possibly molten rock) during
its formation. This would have precluded the accretion of hydrocarbons,
which would have been oxidized into water and carbon dioxide. When it was
later discovered that all fossil fuels contain traces of biological debris,
the biogenic theory gained strength because no one believed that life (even
microbial life) could exist at the depths at which petroleum had been found.

Subsequently, it has become clear that the Earth formed by accretion of cold
matter. Microbial life has also been discovered 4.2 kilometers deep in
Alaska and 5.2 kilometers deep in Sweden. Further, at least ten bodies in
our solar system are thought to contain traces of hydrocarbons. These
discoveries led to a revival of the abiogenic theory, popularized by Thomas Gold.

In the middle of the 20th century it was possible to divide supporters of
the two theories along geographic lines. Petroleum geologists in the United
States and many in Europe favored the biogenic theory whilst those in Russia
and also many microbiologists favored the abiogenic theory. Nowadays,
however, the biogenic theory is widely regarded as correct based on
significant advances in the understanding of chemical processes and organic
reactions and improved knowledge about the effects of heating and pressure
during burial and diagenesis of organic sediments.

A limited resource

Fossil fuels are a finite resource, but the alarmist reports from the early
1970s (the 1973 energy crisis) that oil supplies would run out in the 1990s
have proven wrong. Significant usage of hydroelectricity and nuclear power
and scientific advances have reduced the dependancy on fossil fuels, of
which household usage has increased nonetheless.

Sooner or later we will have to find alternatives (in the form of some kind
of renewable energy source), however many people share a viewpoint that the
time at which we would run out of fossil fuels is far in the future. As
hydrocarbon supplies diminish, prices will rise (the principle of supply and
demand). It has therefore been pointed out that higher prices will lead to
increased supplies as previously uneconomic sources, such as tar sands or
artificial gasolines (which require more expensive production and processing
technologies than conventional petroleum reserves) become economically viable.