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_11_Energy - GEL 1 Lecture 11 Energy Resources Living in...

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1 GEL 1: Lecture 11: Energy Resources: Living in the Oil Age (Ch. 14 – read selectively) Energy from Fossil Fuels Fossil fuels like coal, oil, and natural gas are non-renewable resources - they cannot be replaced within a useful time frame for humans (fossil fuels take millions of years to form) - nuclear energy is also considered non-renewable because of its dependence on exhaustible uranium ore (although reserves will last a very long time) - the engine of civilization runs mainly on fossil fuels Alternative forms of energy like solar, moving water, wind, biomass and geothermal are considered renewable resources - they are continually replaced as long as the sun shines and the earth maintains its hot interior. - prior to the Industrial Revolution (~1850), most energy needs were met by burning wood About 86% of the U.S. energy supply comes from fossil fuels - petroleum supplies about 40%, natural gas ~25%, and coal ~23% - remainder comes from nuclear power, hydropower, geothermal, wind, biomass and solar - the U.S. is utterly dependent on fossil fuels, with most of the oil going to transportation and much of the coal and natural gas going to generate electricity in power plants Our growth as a western civilization over the last century or so was fueled by the easy availability of cheap fossil fuels. W orld energy consumption is growing exponentially and is expected to be dependent on fossil fuels well into the 21 st century. Fossil fuels are rich in chemical energy that is converted to a useful form by adding oxygen (burning) - they are called fossil fuels because they are the residues of ancient plants that lived millions of years ago. The ultimate source of this stored chemical energy is the sun , the driver of photosynthesis. Fossil fuels are literally "fossilized sunshine". Coal : the rock that burns . . . Coal (a sedimentary rock) forms layered beds by the preservation, burial and compaction of ancient plant material. - plants live, die and accumulate rapidly in swamps and tropical river deltas (requires low- oxygen conditions to inhibit oxidation and bacterial decay)
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2 - the plant debris is rapidly buried by other plant debris and muck in a swamp - with continual burial by other plants or by overlying sediments, the temperatures and pressures increase to the point where the plant tissues become tightly compacted - CO 2 and CH 4 are released, accompanied by an increase in carbon - when carbon content is around 50-60%, the material is called peat (very low-grade, smoky fuel) - with deeper burial, if carbon content reaches 60-70%, material called lignite (soft, low- grade) - with even deeper burial, when carbon content reaches 70-90% it is called bituminous coal (most desired and most used coal - used to generate electricity and in steelmaking) - above 90% carbon, it is called anthracite coal (hard coal that burns without smoke) - bituminous coal is far more common and easier to mine than anthracite - a thick accumulation of organic remains may develop into a broad sheet-like layer as the swamp environment migrates along with sea level and shifting shorelines
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