Coal replaced wood as the principal source of energy in the United States by the 1890s. The first coal-fired power plant was built in 1882, generating steam that turned a generator to make electricity. In 1884, Charles Parsons developed the more efficient high-speed steam turbine. By the 1920s, pulverized coal increased efficiency and reduced the air need for combustion.
The 1940 cyclone furnace used poorer-grade coals to produce less ash. Recently chemical technology has developed the combustion of culm (waste material from coal mining) to produce power and to decrease environmental load.