adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane
- Provides 25% of world energy
- The world has 1 trillion tons of reserve
- U.S. has about 300 billion tons
- If all energy was to be supplied by coal, U.S. would have enough for
at least 200 years
- Australia also has hundreds of years of resrerves
Formation of Coal
- Dominantly from plants buried in swamp environment
- On burial the coal changes character in the following stages:
The character of coal changes as pressure and temperature increases. We
notice a general trend towards higher carbon content as volatiles and
moisture are lost. In the crust, at higher temperatures and pressures,
metamorphism turns coal into graphite.
Disadvantages of Coal
- Sulfur as sulfide oxides to form sulfuric acid in mines or on
burning causes acid rain.
- Strip mining while cheapest, needs reclamation.
- Underground mining- subsidence.
- Ash left is 5- 20% of original volume.
- Transporting coal is difficult.
- Trains - Primary method of transportation.
- Conversion to electricity on site - The problem with this method
is that you then need to transfer the power to remote locations that
can use it. Transporting electricity loses a great deal of
- Coal slurry in pipelines - Mixing coal with water to produce a
semi-liquid material that can be piped. This is not done very much.
- Conversion to synthetic oil or gas - used to be done quite often
to produce gas, before actual natural gas sources were utilized. One
problem with this method is that the natural gas produced by this
method happens to contain quite a lot of carbon monoxide mixed in
with the methane.
Coal itself can be found near the surface and deep below ground. Due to
this there are several different ways in which it is mined, depending on
the location. Surface, or Strip Mining
- As the name implies, this form of mining simply takes coal from near
the surface. First, the vegetation and soil overlying the coal must be
removed. Then any rocks or overburden must be removed, generally by
blasting with explosives and by using heavy land moving equipment.
This waste rock is then set aside in spoil piles while the coal
underneath is mined, and is replaced after the mining process is
completed. This method of mining generally recovers almost 100% of the
coal present in the deposit.
- There are two major forms of mines that are created using this
method of mining. The first is a strip mine:
The other form of surface mining is that of a contour mine used in
Surface spoils from haphazard coal mining pose severe acid drainage and
Another method employed to mine for coal is to dig underground, removing
coal, in the more traditional image of mining. This method creates tunnels
and caverns. These can either be dug into the side of a mountain where a
known coal deposit outcrops, or into more flat topography, digging
straight down. A map view of this style of mine looks like the following:
Dark areas are coal that is left behind to hold the overlying rock.
Lighter areas are mined.
- This method of mining recovers only fraction of the available
- Sinkholes and troughs can be caused by this form of coal mining
after the mines have been abandoned and the overburden collapses
into the tunnels..
The amount of carbon now believed to exist in gas hydrates exceeds that in
all known fossil fuels and other organic-carbon reservoirs combined.
Methane hydrate, the most common form, is found on the sea floor and in
areas of permafrost. This may become a potential source of fuel, but the
technology for recovering methane hydrate is still in its infancy.
Links of Interest
For those of you who are further interested in the subjects covered in
this lecture, the following are links to other web sites covering these