Coal is the second energy used in the world with 24 % total consumption.
Coal is a generic term which designates a set of solid combustibles having various compositions and caloric powers. These combustibles have in common a vegetal origin and four compounds in a variable rate : a carbon matter, water, gas and a rock phase.
Coal was almost the unique combustible dating from the industrial revolution of XIX century with the development of steam engine and the increase of requirements in the steel industry. Since, oil, then nuclear and gas come to complete the energy range available and today coal only represents 25 % supply in primary energy of the planet.
The world coal production reaches 3.5 billion tons to which we add 900 million tons lignite. 50 % coal produced is used for electricity production, 16 % for steel industry, 5 % for cement works. The left 29 % are used for heating and other industries, including organic chemistry.
Reserve are huge, i.e. 1 000 billion tons, that means 250 years consumption at this rhythm, but their future exploitation might be strongly competed with the existence of other energy sources, which necessitate less manpower and then, may be, cheaper in the long run, as well as with limits imposed to greenhouse gas emissions.
Coal is irreplaceable for some of its applications, for ore reduction in blast furnaces or organic chemistry for example. Coal remains the first electricity producer in spite of the disability constituted by a 4 % hydrogen content, which is lower than that of oil products, having as a consequence a more important CO2 emission for a same caloric power. Solutions exist and are progressively implemented, to reduce significantly polluting releases.
Coal is issued from the accumulation of variable vegetal substance : tree fern from coal forest, spores, mangroves, algae, deposited on spot (autochthonous fields) or after transport (allochthonous fields). These fields are either marsh zones (present peats), or lakes, or deltaic zones which sank regularly, enabling the forest to carry on prospering over long periods of time.
Sediments were buried until variable depths reaching some 100 m for lignite, until several kilometers for anthracite. When buried, the organic carbon transformed itself into mineral carbon by an action of micro-organisms (carbonation), the water was expulsed in a great proportion and the rock became indurate.
The term “coal” designates products issued from the carbonation of organic matters:
- Charcoal or vegetal coal is issued from wood carbonation. It is prepared by craftsmen and industrially, to be used as a combustible.
- Bone coal or animal black is issued from bone carbonation. It is used as an absorbing filter, pigment black (ivory black) and fertilizer.
- Activated carbon (or activated charcoal) appears as a black, light powder, constituted essentially of porous structure carbon matter. It is prepared from charcoal or bone coal.
It has several applications in chemistry, filtration, industry, medicine, food-processing.
Hard coal is carbon rock. It is a solid fossil combustible rock issued from the decomposition of organisms dated from the Carboniferous (-360 to -300 million years).
Bestougeff (1978) considers that 20 % deposits formed in the Carboniferous, 35 % in the Permian; 17 % in the Jurassic, 13 % in the Cretaceous and 13 % in the Tertiary.
Although the quasi-totality of countries is equipped with coal resources, the repartition as per continents is not equal : 11 % in North America, 42 % in Asia, 37 % in USSR, 5 % in Europe, 3 % in Australia-Oceania, 2 % in Africa and 1 % in South America. The Northern Hemisphere (93 %) is better equipped than Southern Hemisphere (7 %).
Greatest fields are the following by importance in decreasing order:
- Russia permo-carboniferous field, from Dombass and Kazakhstan
- Siberia cretaceous Jurassic platform
- Western America and Canada field (Jurassic and Tertiary)
- Chinese and outside Mongolia platform (Permo-Carboniferous and Jurassic)
- Carboniferous from Appalachians
- Variscan North European field
- Coal from Gondwana, Permo-Triassic from Australia, from South India, Africa and Brazil
- Cretaceous and Tertiary field from Colombia – Venezuela and Chile
IEA counts each year coal reserves. These reserves correspond to raw coal quantities that mining (or also national organizations) considers to be able to extract under local technical and financial conditions conceivable in a short run.
Concerning a field, the reserves of which reach 100 in situ, the reserves registered are frequently equal to 50 after deducting droppages in safety pillars or outside quarry profiles, and taking into account the extraction rate.
To calculate the medium caloric power of coals, we define “tce” ton of coal equivalent, NCV (net caloric value) of which reaches 7000 kcal/kg, i.e. conventionally 0.7 toe : ton oil equivalent (although one ton oil has 9500 kcal/kg in an average, in realty.
An estimate was carried out country by country of tce number for each gross ton produced.
In an average, we obtain 0.78 tce/t for coals and 0.3 tce/t for lignites.
In order of magnitude, knowing that cost at the mine of the coal ton varies from 10 $/t for most competitive mines to 200 $/t for most onerous mines, we can estimate that 50 to 65 % reserves may be produced at less than 100 $/t, price which is the equivalent of an oil at 25 $/bl. (1.83 tons of raw coal / ton of oil and 7.35 bl./t of oil). The world should then dispose of 375 billion tons oil equivalent, a part of which, probably from half to two thirds would have a cost price lower than that of oil.
Coal is the second electricity source (in Germany, 50 % electricity is produced by coal).
Asia (essentially Russia and China) has huge coal reserves.
It is possible to transform coal chemically in the future to make a synthetic motor-fuel with it.
As you can note, China is from far the greatest coal producer, but its domestic demand is almost equivalent. So, this raw material is sufficient for this country. The United States also have little excess of production compared to their domestic demand. It is sufficient for them too. Then, India and Russia have enough as well. On the contrary, the European Union imports more than the double of what it produces, however, its energy demand in this raw material is not excessive. Africa has some excess, not much, as Latin America (in marginal rates). Oceania exports far more than it uses.
China: driving power, coal
The electricity production is ensured at over 70 % by coal.
In spite of that, the energy production fails and several provinces suffer current breakings (26 out of 31 provinces and regions of the country had current breakings in the first quarter of the year 2005).
To offset this lack, the government made the coal production increase. The production increased from 2.1 billion tons in 2004 to 2.4 billion in 2010.
An eventual future: clean coal:
Clean coal is not a new type of coal but a concept : to use coal to produce more energy with low pollution.
This concept emerged from saving requirements, to dispose of a less onerous energy and with more important stocks than oil, while satisfying companies wishing less local pollutions (smog, acid rains) and less global pollutions (greenhouse).
Clean carbon principle:
It is an aggregate of techniques and technologies aiming at improving energy outputs of coal power stations and at reducing pollutant emissions (NOx, SO2, and so on) and greenhouse gas (CO2).
The implementation of a clean carbon sector lies on:
- A modernization of energy power stations
- Generalization of filtering and recycling systems of atmospheric pollutants
- The adoption of new technologies such as co-combustion of biomass or the integrated coal-gasification combined cycle
- CO2 capture and sequestration techniques.