Coal energy

The name ‘coal’ was derived from the anglo Saxon word ‘col’. Coal is a combustible sedimentary rock formed from accumulation of plant remains modified by chemical, biological and physical processes during and after burial. Coalification is the transformation of plant debris under reducing conditions into a continuous series of products having increasing percentages of carbon and diminishing percentage of oxygen and hydrogen. First stage product of coalification is peat and the last stage product is anthracite. Bituminous coal is the intermediate product. The origin of coal is from vegetable matter. In the first step, through a biological reaction, vegetable matter is converted into peat. Peat is then transformed to coal by some physic-chemical reactions. In geochemical terms, first process in coalification is the microbiological degradation of the cellulose of the vegetable matter. Then conversion of lignin into humic substances takes place. In the final stage, these substances condense to form large coal molecules. The various factors affecting coalification are climatic conditions, time, contact metamorphism, depth of burial and orogenic effects. Coal could form only in the places where climatic conditions favour production and conservation of plant residues. Older coals are superior to younger ones. In a vertical sequence at any one locality in a coal field, the rank of the coal seam rises with increasing depth. The quality of the coal increases with the increase of orogenic activity. Second and final stage of coalification is a result of metamorphism due to heat or pressure.