by Pixie » Thu 17 Jan 2008, 15:39:58
$this->bbcode_second_pass_quote('Tyler_JC', 'C')oal has peaked in terms of energy content...
How do you calculate that?
(I'm moving this into open discussion based on the lack of environmental discussion)
If you look at the percentage of lignite coming out of North American mines, it is going up. Lignite contains only about 52% of the heat, on average, of anthracite or bituminous coal. Lignite is sometimes called "brown coal" and my understanding is that it is younger. It's sort of like half way between peat and anthracite. When I find some time, I will do a spreadsheet calculation showing the heat content from year to year. I was alerted to this issue from an article that was posted here at PeakOil.com. The EIA data backed up the conclusion that coal energy has peaked in North America, even if we are dragging up a higher volume of crappy brown coal.
From Wikipedia:
ANTHRACITE: heat content of anthracite ranges from 22 to 28 million Btu per short ton (26 to 33 MJ/kg) on a moist, mineral-matter-free basis. The heat content of anthracite coal consumed in the United States averages 25 million Btu/ton (29 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter.
BITUMINOUS COAL: The heat content of bituminous coal ranges from 21 million to 30 million Btu/ton[vague] (24 to 35 MJ/kg) on a moist, mineral-matter-free basis.
LIGNITE: The heat content of lignite ranges from 10 to 20 MJ/kg (9 to 17 million Btu per short ton) on a moist, mineral-matter-free basis. The heat content of lignite consumed in the United States averages 13 million Btu/ton (15 MJ/kg), on the as-received basis (i.e., containing both inherent moisture and mineral matter).
Because of its low energy density, brown coal is inefficient to transport and is not traded extensively on the world market compared with higher coal grades. It is often burned in power stations constructed very close to any mines, such as in Australia's Latrobe Valley and Luminant's Monticello plant in Texas. Carbon dioxide emissions from brown coal fired plants are generally much higher than for comparable black coal plants. The continued operation of brown coal plants, particularly in combination with strip mining and in the absence of emissions-avoiding technology like carbon sequestration, is politically contentious.[