EM SC 240N
Energy and Sustainability in Contemporary Culture



Learning Objectives Self-Check

Read through the following statements/questions. You should be able to answer all of these after reading through the content on this page. I suggest writing or typing out your answers, but if nothing else, say them out loud to yourself.

 Are industry organizations reliable sources of data and/or other information?
 LIst the following from smallest to largest: short ton, long ton, metric ton (tonne).
 How much coal do the U.S. and world have left: a few years, around 50 years, around 100 years, or well over 100 years?
 When burned, how much more carbon dioxide does coal emit than natural gas: 10% more, 50% more, or about twice as much?
 Does "clean coal" have any emissions or other environmental problems?
 Identify 2 sustainability benefits and 2 sustainability drawbacks of using coal as an energy source.

We'll start with the most straightforward aspect: how much do we have, and how long will it last? That is an obvious question to ask, because if we are going to run out anytime soon, it is clearly not sustainable.


To Read Now

Most energy sources have an "industry organization" or "industry association" associated with it. These organizations are funded by companies in the industry (e.g., the World Coal Association is funded mostly by coal producers, energy companies that rely on coal, and others) and promote policies that will increase the use of the energy source. They often fund and perform research, devise ad campaigns, lobby various levels of government, write press releases, and more. You should not view them as impartial - they exist solely to promote the energy source. However, they are generally a reliable source of data, e.g. how much coal was used in a year, the portion of GDP from coal, etc. They are also good sources of information regarding industry technology and trends.

But please keep this in mind when looking for energy data: if at all possible, you should use information (including data) from the EIA (Energy Information Administration), IEA (International Energy Agency), World Energy Council (WEC), or some other reliable, impartial source. Note that these industry organizations will usually use data from one of these impartial sources, but it's always best to go to the original source.

  • "How Much Coal is Left?" U.S. EIA.
  • (Optional) "Coal Facts 2015" World Coal Association. Go to the World Coal Association website (feel free to look around), then click on "Resources" in the top menu bar. In the "category" drop-down box, click on "Statistics" then click "Filter." Then open up and browse through the "Coal Facts 2015" document. (As you can see, this is the most recent statistical document they have.)

First and foremost, note all of the various caveats issued in these reports. As the EIA notes: "The amount of much coal that exists in the United States is difficult to estimate because it is buried underground." (Probably not what you want to hear from the authority on the topic, but bear with me.) The same goes for the rest of the world, and it is more difficult in a lot of other countries because even less is known about the underground resources. Also, there is a difference in the basic assumptions regarding the statistics.

Terminology is important to keep in mind.

  • Demonstrated reserve base is the amount of coal that is estimated to be in place and could conceivably be mined commercially. Some of this is difficult to get to because of access issues (technical, political, etc.).
  • 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"). Estimated recoverable reserves are a subset of the demonstrated reserve base, and thus are always smaller.
  • Recoverable reserves at active mines "represent the quantity of coal that can be (mined) from existing coal reserves at producing mines" and they "essentially reflect the working inventory at producing mines."
  • You will also sometimes see total resources identified, which are a scientific estimate of all coal in the U.S., including coal that has yet to be discovered. It is not likely that all of this can be accessed, and further, we would not want to because it would require widespread destruction of the landscape.

All of these quantities use some estimation, with the bigger reserves requiring more estimation, so take all of them with at least a grain of salt. They should be considered a good estimate, with the estimated recoverable reserves probably being a reasonably good (but possibly conservative) estimate of what's left and can be realistically mined. You don't need to memorize all of these terms, by the way! It wouldn't hurt, mind you, but the goal here is for you to understand that coal resources are known to varying degrees, and for you to be conscious of which estimates companies/organizations/people cite.

Different estimates of coal reserves in the U.S. based on different categories
Figure 3.2: 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.)
Source: U.S. EIA

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.

Source: Encyclopaedia Britannica and U.S. EIA

"Very impressive" you might be thinking, but what does it all mean for sustainability of supply? Glad you asked! The EIA states that: "Based on U.S. coal production in 2017 of about 0.78 billion short tons, the recoverable coal reserves would last about 325 years, and recoverable reserves at producing mines would last about 26 years." (FYI, two years ago they said we had about 283 years, but this year's increase is because we are mining less coal than last year, as you will see below). How do they get this number (325 years)? Hint: it is based on the current production and the Estimated Recoverable Reserves (ERR).

Click here for calculation

  • The ERR is stated as 253 billion short tons in the most updated numbers (not the graphic above). If this number is correct, and current rates hold at 0.78 billion tons/yr, then there are 253 billion/(0.78 billion/yr) = 324.35 years, rounded up to 325 years. Pretty simple math, once you have the numbers!

Click here for last year's calculation

  • The ERR is stated as 254 billion short tons in the most updated numbers (not the graphic above). If this number is correct, and current rates hold at 0.73 billion tons/yr, then there are 254 billion/(0.73 billion/yr) = 347.95 years, rounded up to 348 years.

Calculation from two years ago:

  • The ERR is stated as 255.8 billion short tons. If this number is correct, and current rates hold at 0.9 billion tons/yr, then there are 255.8 billion/(0.9 billion/yr) = 284.2 years. Since they state that it is 283 years, I assume that the 0.9 billion tons/yr number is rounded down a bit

2015's calculation was a little more complicated, and I think is worth it to walk through:

  • The ERR is stated as 256.7 billion short tons. There are 1,000 million tons in a billion tons, so this is: 256.7 billion x 1,000 million/1 billion = 256,700 million short tons.
  • If this number is correct, and current mining rates hold steady at 984.8 million short tons per year, then there are 256,700 million/(984.8 million/yr) = 260.66 years, which is rounded to 261 years.

Note that this assumes that coal production rates will remain the same and that technology will not change. And this, of course, assumes that this it is reasonable to mine all remaining U.S. resources, given environmental and social impacts, but it is a good starting point for the U.S. The same set of assumptions (with different numbers) are used to estimate how long the world will have coal - the recoverable reserves and current levels of coal production. According to the World Coal Association, there are between 110 years and 121 years of reserves available worldwide.


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. It is energy-dense, and we know how to use it. (I think there's a ZZ Top song about that.) It turns out that it is also pretty cheap to use (ignoring externalities, of course!).

A chart showing the cost of fossil fuel-based electricity generation from 2004 to 2014. Coal is the cheapest, followed by natural gas, then petroleum.
Figure 3.3: As you can see from the chart, coal is the cheapest fossil fuel for generating electricity on a dollar per million Btu basis. This, of course, does not include external costs.
Source: Data downloaded August 2018 from U.S. EIA. Click here to view the raw data.

Despite the relatively low cost of fuel, 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 economics. Energy 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.

It is no exaggeration to say that coal has played a starring role in delivering the energy that was used for the development of the U.S. and many other countries (especially Western countries) in the past 200+ years. It also currently provides over 40% of global electricity (according to the World Coal Association), and is the primary source of electricity for many "developing" countries like China and India and industrialized countries like the U.S. Coal is relatively cheap (again, as long as you don't include external costs), abundant, and relatively easy to use. There is a reason we've been using it at such a high rate for so long! So far, so good. So what's the catch?

Sustainability Impacts

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

To Read Now

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.
Source: Borvan53, CC BY-SA 3.0
Figure 3.5: This interactive chart provides an alternative way to view sources of global carbon dioxide emissions. It was created by Our World in Data using Carbon Dioxide Information Analysis Center data as well.

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.

Pie chart showing the global greenhouse gas emissions by source. CO2 constitutes 76% of all emissions, methane 16%, nitrous oxide 6%, and F-gases 2%.
Figure 3.6: 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.

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.

One interesting irony is that carbon dioxide can be injected into oil wells to increase output, and has been since 1972. In addition to this, as pointed out in the EIA article above, about 10% of the methane emissions in the U.S. are due to venting of methane gas from underground coal mines. Recall that methane is about 30 times as powerful as carbon dioxide with regards to climate change.

While relatively inexpensive in simple terms (not including externalities), the external costs are likely quite high due in particular to negative health impacts (as you read in Lesson 1). But as you saw from the EIA, there other environmental concerns, such as mercury pollution, acid rain (which has mostly been mitigated through technology/policy), and remnants of power generation like fly ash. Coal mining can be a risky business, as you probably remember from the Upper Big Branch Mine disaster that killed 29 miners in West Virginia in 2010. There have been many other accidents in the U.S. as well, as indicated above. China is the world leader in coal mining fatalities, according to the Wall Street Journal, including over 1,000 killed in 2013 and 2012, with more than 33,000 deaths in the past decade. There is also environmental damage that often results from mining and mining waste.

In short, coal is a reliable energy source, and is generally a relatively cheap source of energy as long as externalities are not included. 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.

Check Your Understanding

A metric ton - which is the same thing is a tonne - is bigger than a short ton.

(a) true
(b) false

Click for answer.
ANSWER: (b) True. As indicated above, 1 tonne = 2204.6 lbs, which is about 1.1 short tons. (Less important to understand is that along ton is 2240 lbs, so is bigger than a metric ton. You will rarely encounter long tons, though.)

Optional (But Strongly Suggested)

Now that you have completed the content, I suggest going through the Learning Objectives Self-Check list at the top of the page.