COAL: RICH BENEFIT TO MANKIND

Press, Volume CVI, Issue 31349, 20 April 1967, Page 25

COAL: RICH BENEFIT TO MANKIND

The economic importance to New Zealand of making maximum use of the large deposits of coal in this country is being increasingly realised and has focused attention on the background to coal and its widespread use.

Geologists tell us that coal began forming in Britain 250 million years ago and in New Zealand about 65 million years ago. It was formed largely through the pressure of rock strata and sediment on vegetation that flourished on earth in the far-back carboniferous age.

The rocks of the outer crust of the earth were made in many ways, the ones associated with coal being from mud and sand brought down to the sea by great rivers. These are called sedimentary rocks because the sediment from which they were made settled on the ocean floor and developed into sand and mud banks. As time went on these banks became thicker and thicker and gradually hardened into sandstone and shale.

In the beginning the sediment came from a landscape devoid of life and vegetation, being created by the effect of the wind and rain on the granite formations. The process continued for millions of years, developing new stratified land masses over large under-sea areas. Later, great upheavals brought these sediment layers to the surface of the oceans and submerged other areas.

The newly-emerged land brought a new colour to the world—the green of plant life. Huge forests grew and died and the debris rotted

in swamps and lagoons where it was attacked by bacteria which played an important part in the quality of the resultant coal. As time went on, thick layers of sedimentary rocks were formed on top of the vegetable debris and the pressure and heat turned the debris into coal. Although the ingredients of coal vary, the raw materials of most seams do not differ greatly in elementary composition. A gradual concentration of carbons results from the elimination of hydogen and oxygen probably given off as water, carbon diokide and methane. The end products range from fresh water and vegetable matter to peat, lignite, brown and bituminous coal, anthracite and perhaps graphite. Coal mining is one of the oldest industries in New Zealand. It dates back to 1842, two years after New Zealand was declared a colony of England. The Rev. B. Y. Ashwell, who had established a mission on the banks of the Waikato river near Ngaruawahia, worked outcrops of coal on the river bank for the mission. New Zealand coals cover a wide selection in quality and properties, but our topquality coal is recognised as equal to the best in the world. The types range from the free-burning coals from the West Coast mines of the South Island to the slowburning fuels from Southland, Waikato and Taranaki. The coal fields are in the

Waikato, Taranaki, Nelson, Buller, Reefton, West Coast, Canterbury, North Otago, South Otago and Southland. All the North Island, Ohai, Canterbury and Taranaki fields produce sub-bitumin-ous non-coking coals. Except for lignite coal of a high sulphur content from Charleston, the Buller, Reefton and West Coast mines produce bituminous light to strong-coking coals. Coals from the main Canterbury and South Otago mines are sub-bituminous and noncoking and in Gore, Mataura, Invercargill and South Otago lignite is mined. During 1965 there were 127 mines operating in New Zealand, 85 underground and 42 open cast. Underground mines produced 60 per cent of the output of 2,659,043 tons of coal that year. Coal derivatives are so numerous that in a normal day contact is made with many of them. Farmers use coal-base fertilisers, lives are saved with drugs and anaesthetics derived from coal, and nylons and dyes to add glamour to women’s attire have their base products in coal.

The four main derivatives of coal are coal gas, ammonia liquor, coal tar and coke, but these in turn provide many other products. From coal gas, with derivatives in brackets, come purified gas, benzol (benzene, xylene, toluene and . pyridine), cyanogen (cyan- ' ide compounds and Prussian blue) and sulphur (sulphu. ric acid).

Ammonia liquor is the base for ammonia from which comes fertilisers, urea and nitric acid. Coal tar products include benzol (benzene, dyestuffs

and fine chemicals, pyridine, toluene, T.N.T. and explosives), phenol (picric acid, adipic acid, nylon, synthetic resins and explosives), cresols (wood preservatives), naphthalene oil (naphthalene, creosote, dyestuffs, phthalic anhydride, synthetic resins, plasticisers, phthalonitrile and phthalocyanines), anthracene oil (anthracene and anthraquinone dyestuffs), road tar and pitch.

Coke produces calcium carbide (acetylene, cyanamide, synthetic rubber, synthetic resins, acetic acid, acetone, isopropyl alcohol and acetate rayon), water gas (etmanol from aide) hyde, synthetic resins, ammonia, fertiliser, urea and nitric acid), carbon disulphide (viscose rayon), carborundum (abrasives) and iron (steel). Coal is obviously most valuable to any country favoured with large reserves of it and it is vital to the economy of New Zealand that maximum use is made of the large reserves of this indigenous and versatile product.