Fossil fuel

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The Keeling Curve Wp→ of atmospheric CO2 concentrations measured at the Mauna Loa Observatory Wp→.
Fossil fuels are stores of energy containing material, usually hydrocarbons, which were formed over geological time usually from plant life, including algae. Beginning in the industrial revolution, and at an accelerating pace since, these materials, beginning with coal, have been used as fuel. During the 20th Century petroleum and natural gas have been used extensively. As of 2013 these fuels are the underlying basis of global production.

However, using fossil fuels to power global civilization releases CO2 at a rate much higher than the natural processes which remove it from the atmosphere. As of 2013, the concentration of CO2 in the atmosphere had increased gradually over the previous century to nearly 400 parts per million and, if the present rate of consumption of fossil fuel continued, would rise much higher.

The rise of CO2 to levels of 500 parts per million or beyond, and other factors such as release of methane Wp→ and black carbon Wp→, will result in substantial global warming and significant climate change, much of it unpredictable, but much obvious, including rising sea levels, increased precipitation, and more vigorous weather events. Rising sea levels from melting of stored ice in the polar regions will result in flooding of coastal areas populated by a billion people or more.

The levels of CO2 reached by 2013 will, even if no more were added, result in some global warming, which there is no known or accepted way to prevent.

Fossil fuels vary in the amount of CO2 they release when produced and burned with natural gas releasing much less CO2 and oil obtained from the oil sands of Alberta resulting in substantially more. This is due to natural gas exhaust being partly water, and the great deal of energy necessary to produce fuel from the oil sands. This is the basis of the protests against the Keystone Pipeline; to prevent global warming a substantial portion of the available fossil fuels would have to remain in the ground, particularly the most polluting. (It has been acknowledged by Christina Figueres, executive director of the UN Framework Convention on Climate Change, that a significant portion of the world's fossil fuel reserves are "unburnable" if dangerous climate change is to be avoided.[1])


Measure

The following measurement equivalents are helpful in understanding fossil fuel data.

  • 1 gram calorie = 4.184 joules
  • 1 British thermal unit (Btu) = 1054 joules
  • 1 kilowatt-hour = 3.6 x 106 joules

A calorie or gram calorie (g cal) is the amount of energy needed to raise the temperature of one gram of water one degree Celcius. There is also a kilogram calorie (kg cal) equal to 1000 g cal.

If a fuel is completely combusted, all of the carbon in the fuel goes into the atmosphere in carbon dioxide (CO2). The mass of the carbon dioxide is 11/3 times the mass of the carbon that was in the fuel (because it contains two oxygen atoms which each have an atomic weight of 16, as well as the carbon atom which has an atomic weight of 12).

Oil and natural gas quantities are usually expressed at a standard temperature and pressure of 60 F (15.6 C) and 1 atmosphere.

Crude oil

  • 1 m³ weighs about 870 kg. (A typical value; different oils have different densities.)
  • Heating value = 43 kilojoules per gram (typical).
  • A typical crude oil is about 83% carbon by weight.
  • 42 US gal. = barrel (abbreviated bbl.); 6.29 barrels = 1 m³
  • 1 barrel weighs 138 kg.

Natural gas

Natural gas is a mixture: predominantly methane (CH4), but also containing heavier hydrocarbons, mostly other members of the alkane series such as ethane (C2H6), propane (C3H8), etc. It is called dry natural gas if the liquid component is less than 0.1 gal. per cubic foot of gas. A typical dry natural gas may be taken to be 90% methane by volume and have a molecular weight of 18. It would have the following properties:

  • Density = 765 grams/m³
  • Heating value = 54.7 kj/g
  • 76% carbon by weight

 

  • 35.32 cubic feet (cf) = 1 m³

Note that some of the abbreviations used with cubic feet are irregular:

  • Mcf = thousand cubic feet (not mega (million) cubic feet)
  • MMcf = million (106) cubic feet
  • tcf = trillion cubic feet

Coal

  • The heating value of coals varies from 26 kj/g for low-quality lignites to 37 kj/g for anthracite. Bituminous coals are intermediate. 29 kj/g can be taken as typical for coal in general.
  • A typical coal is 73% carbon by weight. Lignites are the least carbonaceos, anthracites the most.
  • Coal contains 0.2 to 7 percent sulphur

Notes

  1. She stated this in an interview in October 2013. She bases her opinion on studires by the International Energy Agency, the Intergovernmental Panel on Climate Change (IPCC), and others. ('UN climate chief rules out carbon budget', Guardian Weekly, Manchester, UK, 1-7 November 2013, p. 8.)