EM SC 470
Applied Sustainability in Contemporary Culture




Different estimates of coal reserves in the U.S. based on different categories
Figure 3.3: Levels of estimated coal reserves in the U.S. as of 2015 (this is the most recent figure available as of August 2018). (Link to download Excel file of figure data.)
Credit: U.S. EIA

As you can see in the chart above from the EIA, there is a range of estimates of how much coal is available, each having a varying level of accuracy. Feel free to review the coal page in EM SC 240N for an explanation of these, but the quantity that is most commonly used to indicate "how much is left" is estimated recoverable reserves. The estimated recoverable reserves are the portion of the demonstrated reserve base that can be realistically recovered, taking into consideration restrictions (e.g., "property rights, land use conflicts, and physical and environmental restrictions"). Consider it a very good scientific estimate of how much we can mine in the foreseeable future. The demonstrated reserve base also includes coal that could conceivably be mined commercially, but other issues (e.g., technological and political) make it unrealistic.

So how much coal is left?

  • The EIA states that: "Based on U.S. coal production in 2016 of about 0.73 billion short tons, the recoverable coal reserves would last about 348 years, and recoverable reserves at producing mines would last about 23 years." This number is derived by dividing the estimated recoverable reserves (254 billion according to the most updated numbers) by the annual use (0.73 billion): 254 billion/0.73 billion = 347.9 years, rounded to 348 years.
  • According to the World Coal Association, there are between 110 years and 121 years of reserves available worldwide. This is also based on estimated recoverable reserves.

Tons of Tons and Tonnes

There are many benefits to living in the United States, but having easy to understand energy units is not one of them. We use a mixture of Imperial and English units, with the system usually referred to as U.S. Customary units. Most of the rest of the world uses metric units, which are also considered SI units (Systéme international d'unités). Got all that? Good. (Here is an explanation of how convoluted the non-metric units are if you are so inclined.)

Coal in the U.S. is usually measured in tons, which is a unit I'm sure you have heard of, and likely used, before. A U.S. ton is equivalent to 2,000 pounds. However, to prevent confusion with an Imperial ton, the U.S. ton should be referred to as a short ton. A long ton, on the other hand, weighs 2,240 pounds. Finally, the metric ton, which is also known as the tonne, is equivalent to 1,000 kg, or about 2204.6 lbs. To summarize:

  • 1 short ton (U.S. Customary Unit) = 2,000 lbs.
  • 1 metric ton (1 tonne) (metric unit)= 2,204.6 lbs.
  • 1 long ton (Imperial unit) = 2240 lbs.

Credit: Encyclopaedia Britannica and U.S. EIA


The following are some facts about the feasibility of continued coal use:

  • Coal has been used en masse as an energy source since near the beginning of the Industrial Revolution in the late 1700s. The infrastructure for coal mining, transportation, and use (mostly in power plants) is well-established and if it were not for the environmental and social impacts, coal would be a good source of energy.
  • Coal is relatively inexpensive per ton, but coal is rapidly being replaced by natural gas and to a lesser extent, renewable energy. This is partially due to the lower emissions of natural gas, but mostly due to basic economicsEnergy generators want to make a profit like everyone else, and right now, natural gas and some renewables are simply less expensive, particularly in the U.S.
  • Over 40% of global electricity is generated with coal, according to the World Energy Council. and is the primary source of electricity for many industrializing countries like China and India and industrialized countries like the U.S. It is also used for steel production, which is an essential component of modern industrial production (buildings, bridges, etc.).

Sustainability Impacts

Now the bad news: coal has a lot of negative environmental and social impacts.

Optional Reading

Chart showing the total carbon emissions by source from 1800 through 2007. Coal is the largest single source.
Figure 3.4: This chart, which was created using Carbon Dioxide Information Analysis Center (part of Oak Ridge National Lab) data, shows the global anthropogenic emissions of carbon. As you can see, coal is the largest single source of carbon globally, overtaking oil in the early 2000s.
Credit: Borvan53, CC BY-SA 3.0

Probably the most important sustainability issue with coal is that it is so carbon-intensive. It emits about twice the carbon dioxide per Btu as natural gas and is responsible for more carbon dioxide emissions than any other energy source, and the energy sector is the largest source of carbon dioxide emissions worldwide. There are other concerns, according to the EIA, including mercury pollution and acid rain. While coal companies are generally very careful to replant any vegetation destroyed by mining, it can irrevocably compromise the landscape.

One possible solution to this is carbon capture and sequestration (CCS), which is a process that can capture CO2 and bury it (i.e., sequester it) in underground rock formations. Under ideal circumstances, up to 90% of the carbon dioxide will turn into solid rock and thus not pose a leakage threat. (This is usually what is referred to as "clean coal" technology, though it is notable that only the carbon emissions are reduced in "clean coal" plants. Mining waste and particulates and other emissions still make this a relatively "dirty" source of energy.) While promising, there is some indication that CCS might not be as effective as once hoped. It is only beginning to be demonstrated on a commercial scale, and some plants have had major issues, so the jury's still out. 

Pie chart showing the global greenhouse gas emissions by source. CO2 constitutes 76% of all emissions (11% from forestry and other land use and 64% is from fossil fuel and industrial processes, methane 16%, nitrous oxide 6%, and F-gases 2%.
Figure 3.5: This chart shows the global anthropogenic greenhouse gas emissions by percent. Some simple math shows you that about 76% of the impact on the climate that humans have is from CO2. This is a major reason why CO2 emissions are such a major focus.

In short, coal is a reliable energy source and is generally a relatively cheap source of energy as long as externalities are not included. Coal does provide good-paying blue collar jobs, and the loss of coal industries can be devastating to local towns. If externalities were to be included, the price would undoubtedly increase, especially if the social cost of carbon were included. CCS provides some hope for reducing the carbon dioxide emissions of coal use, but other significant sustainability problems will persist.