It’s not. If I were to sum up this whole post in two words, those are the ones, “it’s not.” The term clean coal is an exaggeration of a technique which reduces some of coal’s harmful effects, but there has never been, is not now, and will never be anything “clean” about coal.

Let’s start with dirty coal

Heat, pressure, and decaying organic matter lead to a carbon-rich sedimentary rock that we call coal. It is considered a fossil fuel because all of that carbon comes from organisms that lived and died millions of years ago and eventually became part of this layer of rock. This is not a renewable or sustainable source of energy unless we have the patience to wait another few million years for a fresh supply. By that point we ourselves will be part of that layer. Crazy thought.

Where does coal come from?

Given that coal is formed under intense pressure from layers of soil and rock above it, we can figure that it must be found buried deep in the Earth. Just like some of the large oil reserves that have been found in various parts of the world, the distribution of coal is not universal. In the US, current major reserves are located in the Appalachian Mountains and in some of the central and mid-western states. For quite a long time coal has been mined from, well, mines. Since this is dangerous work a new method was devised to make the process safer and faster, and also employ far fewer workers. But there are trade-offs.

Mountaintop Removal

Instead of digging deep underground to extract the coal, why not peel back the top of a mountain and just scoop it out? That is the idea behind mountaintop removal, an alternative to working in the hazardous coalmines of yesteryear. Unfortunately this involves removing any associated ecosystems from the top 500 feet or more of the mountain’s peak. And where does all of this material go? The convenient thing about mountains is that they are typically accompanied by valleys. The layers that are removed from the top of the mountain are dumped into theses valleys which leads to blocked waterways and even more destroyed land. When coal companies are in a hurry to take advantage of a good economic situation they will often dump all of the trees as well, instead of using them for commercial purposes like lumber. Also as a note, 500+ feet of mountain is not moved with a shovel, it’s moved with explosives, and lots of them.

But they put the ecosystems back!

Coal companies can take advantage of state waivers when it comes to the reclamation phase of the process. The company does not have to restore the ecosystem if they claim that the newly cleared land will likely attract development projects. They are essentially saying that they have done a favor to the state by paving the way for economic growth, at the expense of the environment of course. In reality, less than 3% of cleared mountaintops end up being used for this purpose and the rest may take over a hundred years for the forests and associated ecosystems to return. Even when companies do attempt to put things back how they found them, it is nearly impossible to truly rebuild a whole ecosystem with all of its complex pieces. Sprinkling grass seed and calling it a day does not count.

Once the coal has left the ground it is treated with certain chemicals before arriving at the power plant. The leftovers from this treatment are in the form of a slurry. This sludge contains heavy metals like lead, arsenic, and mercury which are toxic and the slurry is sometimes dumped into the rest of the removed mountain material, allowing it to leak into waterways and other areas.

Burning coal for energy

The process of burning coal for energy causes problems as well. Various toxic elements such as sulfur, arsenic, lead, and others are released when the coal is burned. As mentioned above, the chemical treatment that results in the slurry removes some of these elements, but this treatment is not always employed around the world. Particles in the exhaust also lead to air pollution and can cause acid rain and respiratory irritation. And then there’s the CO2. Carbon dioxide is a major greenhouse gas, and being that coal is mostly made up of carbon, it has a lot of carbon dioxide to release.

“Cleaning” it up

The technique employed to make coal “cleaner” is called CCS – carbon capture and sequestration (or storage). The carbon dioxide, which is the main greenhouse gas produced by burning coal, is trapped instead of being emitted. It is then transported for long-term storage. CCS is used in more than just coal plants and can be found in refineries, fertilizer plants, steel factories, etc.

There are three methods of capturing the carbon dioxide. First, CO2 can be captured before the coal is burned by mixing the fuel with a specific amount of oxygen to create carbon monoxide and hydrogen. This is then combined with steam which results in CO2. The CO2 is separated out, and the remaining gas is burned as fuel. A second technique opts to burn the coal in oxygen which releases water vapor and CO2. The gas is cooled and separated to capture the carbon. Third, the coal is burned in the ordinary fashion but the exhaust is sent through a liquid for filtration. The liquid can then be heated to release the captured CO2.

The second half of CCS is the “S,” sequestration/storage. It is not enough to capture all of this carbon, we have to put it somewhere. The preferred locations are emptied-out oil fields, salt mines, the ocean, etc. It can also be injected into active oil fields to help push the oil to a more reachable location. Which means we’re capturing all of this carbon just to use it to pump out more fossil fuels. Defeating the point. There is also the concern that the sequestered CO2 could escape from it’s burial grounds. Oil fields typically have lots of drilling locations and any one of them could be a route of escape for the contained gas. The process of injecting the CO2 into the ground has also been linked to some minor earthquakes across three US states.

(As a note, sometimes “clean coal” refers more to the treatment which removes toxic materials versus the removal of carbon dioxide emissions.)

The economics of it all

The developments in carbon capture seem promising, but unfortunately everything comes down to money. With the affordability of natural gas, it is not economically advantageous to build new coal plants, and especially not ones that use CCS. The systems needed to capture, compress, transport, and store the carbon emissions are prohibitively expensive. Even if a coal plant were to go through installing all of these systems, it would be losing about 20% of the electricity it generates because that amount would be used to run the CCS operations. Hopefully this will drive coal plants to be shut down and replaced with other forms of electricity generation.


Coal is the dirtiest fossil fuel and creates one third of the US’s carbon dioxide emissions. We need alternatives! Fortunately there are some good options among the renewables like wind and solar. Not-so-fortunately, at the moment the main competition is natural gas, which is a whole ‘nother can of worms.

I will tackle these other forms of energy in due time. Until then, back to coal. Back to coal!

Bring back the coal industry!

Without delving too far into politics, it is a current talking point to bring back the coal industry in order to create more jobs and revive the economy and yadda. I do feel for those who have lost their jobs due to changing economic trends. However, industries boom and bust for a reason, and for many reasons I think we can understand why the coal industry may need to be allowed to wither in favor of newer and, yes, “cleaner” alternatives. If we truly wish to help those who have lost their employment we should be offering training and skill development in current fields instead of reviving a dying industry. Adaptability is crucial in navigating today’s economy.

Final Thoughts

Knowing is half the battle, and now we know a little more about coal and how not-clean it is. I will admit that CCS appears to be a good method for reducing carbon dioxide emissions from coal combustion, but with all the other drawbacks of using coal and the economic hindrances, it can only mildly mitigate the damage that coal does to the environment. We as a society and planet need to invest more seriously in renewable energy instead of trying to make current methods slightly better.

[No worms were harmed in the writing of this post.]

*This post is part of HFTH’s Energy Week 2017! Stay tuned for more energy-related topics!*

3 replies on “How “Clean” is Coal?

  1. Nice thoughtful post 🙂
    I’m interested in fuel cell technology that can remove some of the pollutants from coal power plant off-gas and also concentrate the CO2 so that it can be stored. That’s at least an improvement to the status quo. But, as you say, no matter how you look at coal burning, there’s the unavoidable impact of coal mining.


    1. Thanks! Yes, I’m glad that technology is being developed/exists that can mitigate some of the byproducts of coal burning; at least the problem is being addressed. Hopefully we can continue to move away from coal though!

      Liked by 1 person

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