Of the fossil fuels coal, as we have seen, retained a commanding position throughout the first half of 20^th century, though world output after the First World War remained fairly static. If we look at individual countries, however, the situation is rather different: there were considerable differences in the uses to which coal was put and in the economics of its production.

In some countries, such as Germany and Austria, the variety known as lignite was extensively mined. This is a brown coal, with a low calorific value, that is intermediate between peat and the hard black bituminous coals familiar in Britain. Again, not all coals are suitable for the manufacture of metallurgical coke, essential for steel-making. Thus a particular region may be rich in coal, but nevertheless have to import varieties to satisfy local requirements. As we shall see, a similar position pertains in the case of petroleum. Although the North Sea was to make Britain self-sufficient in oil, it did not make her independent of imports. For certain purposes Middle East crudes were necessary, though the cost of these could be offset by export-of North Sea oil to countries, such as the USA, where it was in demand.

Coal production during this period was influenced by various factors. Energy consumption is an important index of industrial activity. Inevitably, therefore, the demand for coal, as the dominant fuel, reflected the world economic situation. Up to the First World War, with industry expanding generally, the demand rose steadily, from about 750 million tons in 1990 to nearly twice as much in 1914. After the war, growth resumed, but at a very much lower rate - about 3/4 per cent annually. The business depression of the 1930s cut output by 40 per cent between 1929 and 1932 and it had not entirely recovered even at the outbreak of the Second World War in 1939. Nevertheless, some countries fared better than others. Whereas Britain and the United States lagged, Germany had fully recovered by 1939. These three countries, incidentally, produced 90 per cent of the world's coal in 1990, and in 1950 the figure was still 60 per cent. Russia, by contrast, was a very small producer in 1900 (15 million tons), and was scarcely affected by the depression that afflicted the western world, but by 1950 was the second largest coal producer in the world. At that time China entered the lists to create a new industrial economy based on coal: her annual production of 40 million tons had increased to 400 million tons in 1960.

Another factor influencing the demand for coal was the adoption of new kinds of power. Electricity and coal gas were not really rivals, because they both required coal for their generation. Petroleum was a different matter, however; while its main use was as a fuel for road transport, a development which was novel to the twentieth century and in which coal had never had a real foothold, oil became increasingly used at sea. In this connection we must distinguish between the use of oil as a substitute for coal to raise steam to drive either reciprocating engines or turbines and its use in internal combustion engines of the diesel type. The first important vessel to be fitted with diesel engines was the British Selandia (1912); by 1950 a third of the world's merchant vessels were propelled by diesel engines.

There were, in fact, two aspects to fuel and shipping. On the one hand, growing use of oil for propulsion correspondingly diminished the demand for coal. No less important was the fact that countries dependent on imported fuel turned increasingly to oil which, by the use of tankers, could be more cheaply transported than coal. Thus in the first half of 20^th century countries such as Norway and Argentina halved their coal imports. In Britain, traditionally an exporting country, coal exports fell from 73 million tons in 1913 to 13 million tons in 1950.

Although fuel economy inspired by exhaustion of resources was not to become a major international preoccupation until the 1970s, in the first half of 20^th century rising costs alone gave a strong incentive to economy, and the use of alternative fuels. In the United States, for example, an over-all increase of one-third in the efficiency of coal utilization was effected between 1909 and 1929. In the British steel industry 25 cwt of coke was required for every toil of pig-iron made in 1900: by 1950 this had been reduced to 13 cwt and in the 1970s the most efficient producers required only 10 cwt. . .