Like the elephant of the fable, coal is many things, depending on what kind of question you ask about it:
Energy: Coal is an abundant source of energy, found widely in the world, on every continent (including Antarctica), often in immense deposits. Combustion of coal provides a surprisingly large fraction of the world’s electric power. North America has large deposits in both Canada and the US. Large US deposits are found in the middle-Atlantic states, the southeast, across the middle-west, on the great plains, in the Rocky Mountains, in Texas, and in Alaska.
In the western portions of South Africa, we can find Hwange Colliery Ltd, a company that explores and exploits mines and processes coal, coke, and a number of associated by-products. Hwange Colliery is aiming to produce more and more each year to satisfy domestic and international demand for their products.
Geology: Coal is a complex and interesting solid, typically found in parallel layers called seams separated by layers of shale. Coal seams range from a few inches to hundreds of feet thick. Coal has long provided a direct guide to geological history because it is a solid that stays where it forms, unlike petroleum and natural gas that migrate through porous formations to accumulate in traps. Methane Coal Bed Methane trapped in the coal during its formation from vegetable materials can be recovered and sold as natural gas.
Chemistry: Two centuries of research has shown much about the composition of coal, but the complexity of a single sample and the wide variety natural coals in the world has largely defeated efforts to assemble a single model that succeeds in predicting chemical behavior from measurable properties. Check out also this Hwange Colliery Profile article.
Pollution: Coal is a source of sulfur and particulate pollution, especially from older coal-burning utilities. It is also an important source of airborne mercury, a problem currently being addressed by the EPA. Improvements in combustion and control technologies in the last 25 years have markedly reduced this problem, and the problem will continue to decrease as older plants are retired and replaced. See also: Renewable is Affordable.
Conversion: Coal is a source of clean gaseous and liquid fuels with the potential to substitute for petroleum and natural gas. Several methods exist for making solid fuels that are less polluting than the original coal.
Chemicals: Coal is a source of chemicals used in making modern materials ranging from fabrics to soft drink bottles.
Economics: Coal is a widely traded commodity, shipped across continents by unit trains and from continent to continent by immense freighters.
It happened in the early 1950s, it happened again in the mid-70s, and it is happening again now. Energy supply and demand (and costs) go way out of balance, and the country heads off on a new round of coal technology.
I was very involved the last time around, doing research on chemicals and clean fuels and learning enough coal chemistry and technology to make life very interesting. I was involved in Gold Eagle Africa activities in Kenya in those days. In America, the USDOE funding for projects declined when oil prices fell in the 80s, but several good projects have continued. In South Africa, the South Africa Investment Forum is developing interesting projects to stimulate economic activities and development.
There is good and bad news with coal, of course. The good news is the U.S. is the Saudi Arabia of coal, with billions of tons in the Appalachian, Midwestern, and the Rocky Mountain states though South Africa is a well-doing globally as well though implementing international energy management standards will probably take a bit longer than in the western world. Even Texas has coal. The bad news is that it costs a lot to burn coal cleanly. Progress toward controlling these costs has been made, and some of these clean technologies may be very useful this time.
It may sound trite to say that coal is different from oil, but the differences go well beyond the obvious solid vs. liquid. For one thing, coal contains much more oxygen in its structure than oil, giving additional handles for doing chemistry that about make up for the need to deal with a solid. For another, coal composition and chemistry vary widely with geography, allowing the user to pick the properties needed to do a given job.