Coal
Coal deposits formed about 300 million years ago (Carboniferous era) from plant matter. Under pressure and temperature, the plant matter becomes carbon-rich. This process is very similar to pyrolysis.
The energy in these deposits was originally from photosynthesis, using carbon dioxide and water to create hydrocarbons.
This energy is released by combustion.
Coal Use
Steam Electricity Generation
Coal, a primary energy source is converted to the secondary energy source of electricity.
This thermal to mechanical conversion based on steam is called the Rankine cycle. Similar conversions are found in nuclear, natural gas, geothermal, and solar thermal electricity generation
Quadrilemma Priorities
How does coal align with energy system priorities?
Stakeholders
- Mine laborers
- Mine owners
- Coal electricity plant owners
- Electric Utilities
Techno-economic Perspectives
Coal-fired electricity diagram
Environmental Perspectives
Coal has several environmental effects
- GHG emissions from combustion
- Toxic releases from sulfur, mercury, and other chemicals
- Surface mines create debris issues
- Ash storage has spilled
Sulfur Deposition Progress EPA
Nitrogen Deposition Progress EPA
Total Mercury Emissions over time, Streets et al.
Socio-Technical
The workforce associated with coal has dropped from 178 thousand persons in the late 1980s to about 41 thousands persons in 2025.
U.S. Bureau of Labor Statistics data
“Clean Coal”
Clean coal is a term used to describe various technologies to mitigate the environmental impact of burning coal.
This DOE Article desribes clean coal and how it supports quadrilemma priorities.
Coal Carbon Emissions
If you burn one kilogram of coal, how much carbon dioxide is emitted?
We can either use a published emissions factor, or estimate from our knowledge of molecular weights.
If we assume our coal is 100% carbon, then each atom of coal will oxidize and become a molecule of carbon dioxide. From the atomic weights on the periodic table, we know that the ratio of masses for carbon dioxide and carbon is 44/12.
1\ kg\ coal = 1\ kg\ C \frac{44\ kg CO2}{12\ kg\ C} = 3.67\ kg\ CO2