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The
environmental movement and the debate about global
warming would be better served if people always
gave the sources for their "facts" — we might have more
light and less heat so to speak. So here's how I
derived the two basic facts implicit in the content
displayed on the CoalCube™, i.e. that it takes a
pound of coal to generate one kilowatt-hour (kWh) of
electricity and that each pound of coal burned creates 2
plus pounds of CO2. So here goes:
The primary source for the
pounds of coal per kilowatt number is the US Department
of Energy Table ES1 at the following URL:
http://www.eia.doe.gov/cneaf/electricity/epa/epates.html
The
following key data elements for the US for the year 2007
are taken from the indicated cells in the spreadsheet:
| Cell |
Description |
Value |
|
B5 |
Net Generation
(Thousands of megawatt-hours) by Coal
|
2,016,456 |
|
B42 |
Consumption of
Fossil Fuels for Electricity Consumption -- Coal
(thousand tons) |
1,046,795 |
|
B106 |
Average Price of
Residential Electrical Power per kilowatt |
$.1065 |
Calculations of Pounds of Coal per Kilowatt-hour (kWh)
based on the above data:
|
(B5) Net Generation Thousands of megawatt-hours
from coal |
2,016,465 |
megawatthours |
|
Times Kilowatts per megawatt |
1,000 |
kWh/ megawatthour |
|
Equals Net Generation of Kilowatt-hours from
coal |
2,016,456,000,000 |
kilowatt-hours |
|
(B42) Thousands Tons Coal to generate
electricity |
1,046,795 |
Thousand tons |
|
Times 1,000 Equals |
1,046,795,000 |
Tons |
|
Times pounds per ton |
2,000 |
Pounds per ton |
|
Equals Pounds coal to generate electricity |
2,093,590,000,000 |
Pounds |
|
Dividing Pounds by Kilowatt-hours Equals |
1.04 |
Pounds of Coal
per kWh |
Next comes
the calculations of CO2 per Pound of Coal burned to make
electricity. The US Energy Information Administration
publishes an Emissions of Greenhouse Gases Report,
and the Carbon Dioxide portion of the report can be
found at:
http://www.eia.doe.gov/oiaf/1605/ggrpt/carbon.html
Table
11 of the Carbon Dioxide report indicates that in
2007 the burning of coal in the US to generate
electricity caused an estimated 1,979.7 million metric
tons of CO2.
Here are the calculations:
|
CO2 from burning coal for electricity (Table 11) |
1,979.7 |
Million metric tons CO2 |
|
Times 1 million |
1,979,700,000 |
Metric tons CO2 |
|
Times |
2,204.6 |
Pounds per metric ton |
|
Equals pounds of CO2 |
4,364,446,620,000 |
Pounds CO2 |
|
Pounds of Coal to Generate electricity in US
(from above table) |
2,093,590,000,000 |
Pounds coal |
|
Pounds CO2 per Pound of Coal (Pounds CO2 divided
by Pounds Coal) |
2.08 |
Pounds CO2 per
pound Coal |
|
Times Pounds of Coal per kilowatt (from table
above) |
1.04 |
Pounds of coal per kWh |
|
Equals Pounds of CO2 per kilowatt-hour |
2.16 |
Pounds CO2 per kWh |
Note:
The 2007 numbers from Table 11 were projected, and the
total CO2 for 2007 for electricity generation (2,433.4
million metric tons) in Table 11 did not match the total
CO2 from power generated in the ES1 table (2,516 million
metric tons), so the the above calculations might be
somewhat different if final numbers were available for
Table 11. Whatever the exact number is, the
point is that burning coal to generate a kilowatt of
electricity will create, on average, over two pounds of
CO2.
Other
references:
eGridWeb, EPA
online tool to estimate emissions savings. Shows that
for 2005 the average CO2 per kWh was 2.135 pounds.
However, the tool can also provide specific detail by
region, and there are significant differences between
regions.
http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html
Pounds of
CO2 per pound of coal:
http://www.eia.doe.gov/cneaf/coal/quarterly/co2_article/co2.html
(1994 article notes 2.86 pounds CO2 per pound of certain
grade of coal assuming complete combustion).
Estimate of 2.3 pounds CO2
per kWh:
http://cdiac.ornl.gov/pns/faq.html
Good overview on Coal in
Wikipedia:
http://en.wikipedia.org/wiki/Coal |
