Biomass is the conversion of energy from plants into energy we can use. Through photosynthesis, plants convert sunshine into stored energy. Burning those plants, including wood for fires, releases heat.

Archaeologists in this video found evidence of charcoal from fires in an excavation of prehistoric villages near Meyersdale, Pennsylvania. The Monongahela who lived there burned wood for warmth and cooking.

Wood remained a primary source of energy in Pennsylvania from colonial times until the late 1800s. Farmers harnessed the energy of draft animals and tapped into the energy of the wind and water. In the 1840s tycoon James Perkins realized the value of trapping logs for sawmills at a bend in the Susquehanna River. As a result of his floating fence, Williamsport, Pennsylvania, became the center of the lumber industry for three decades.

During the Industrial Revolution Pennsylvanians played a major role in unlocking the energy potential of fossil fuels -- coal, oil and gas. In the span of a few generations these deposits of solar energy transformed the nation into an industrial society. In 1859 Colonel Edwin Drake financed one of the first wells drilled for the purpose of finding oil in Titusville, Pennsylvania. The success of Drake's Oil Well changed the quiet farming area in northeast Pennsylvania into one of the nation's most important oil regions in the world until the discovery of Texas oil around 1900.

Coal was king from 1885 until the early 1950s when it was surpassed by petroleum as a major fuel source in the U.S. and then by natural gas a few years later.

Nuclear power gained importance as scientists discovered nuclear fission and fusion in the first half of the 20th century. The energy released by splitting or combining atoms released millions of times more energy than released by burning coal. In 1979 a series of mechanical failures and human error at Pennsylvania's Three Mile Island plant caused the nation's most serious nuclear accident. Despite a partial meltdown of the plant's nuclear core and the escape of radioactive gases, there was little threat to the public's health. However, the accident strengthened opposition to nuclear power and stopped the construction of more nuclear plants.

Attention shifted to renewable energy sources in the late 20th century for several reasons. Fossil fuels became scarce due to the Middle East oil crisis in the 1970s. The public voiced concern over the effects of fuel emissions on humans and the environment. New technologies that extracted energy from solar, wind, and hydroelectric power, grew more reliable and affordable. More recently, scientists have converted the energy stored in plants, or biomass, into biofuels that we can use.

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