We're always asked
What in the world is clean coal?
The energy and electric utility industries are full of overly complicated issues, jargon, and misconceptions, partly because the industries often find themselves at the intersection of physics and politics. Questions that we are constantly asked in our classes include “what is clean coal?” and “is coal coming back?” Given similar phrases used by the President during the 2018 State of the Union address, let’s examine these topical questions.
First let’s look at the word “clean.” How is it defined? In this context our environment consists of air, water, and ground. All energy sources have a life cycle, from discovery and extraction through use and then disposal or recycling. So, words like “clean energy” would be defined as an energy source that has no detrimental impact to the earth’s air, water, and ground during its life cycle. Simple enough? That may be a high standard as most energy sources do have some negative impact to the environment, but that is the definition of “clean.”
So how about “clean coal?” There is no such thing. Putting these two words together is like saying “beef chicken” or “good evil.” It doesn’t even rise to the level of an oxymoron (i.e. “jumbo shrimp”). Let’s explain.
The life cycle of coal includes mining (not clean in regards to emissions, water impact, or impact to the ground); coal transportation (not clean in regards to emissions, which then negatively impact water and ground—unless there is no transportation because the coal power plant is sited at the mine); burning the coal to generate electricity (not clean, but we’ll come back to that); and then disposal of the coal ash after the coal has been burned (not clean, and a growing environmental hazard to deal with after the coal plant has retired). So, no part of coal’s life cycle being used as electricity generation is clean. In fact, coal is the most environmentally dirty way to generate electricity today. Use of coal for energy makes our air, our water, and our ground dirty.
When proponents of coal use the words “clean coal” they are referring to technology that could potentially remove the carbon dioxide from the emissions for one part of the life cycle: when coal is burned to create steam to turn a turbine to generate electricity. This is called carbon capture. Then the captured carbon is collected and something is done with it, called carbon capture and sequestration (CCS). This has been a promising set of technologies for some time. Perfecting it would be a good thing as it could be applied to other fuels that are burned to create electricity, such as natural gas or biomass. There is a successful CCS plant in Texas, called Petra Nova (see https://www.utilitydive.com/news/nrg-completes-texas-carbon-capture-plant-retrofit/433799/), but also many failures and cost over runs in the US (https://www.utilitydive.com/news/southern-suspends-work-on-kemper-coal-gasification-units/446091/). Today’s sad reality is that this technology is difficult to make work and expensive (many level-ized cost of energy analyses add an additional 50% premium for CCS on top of coal’s cost per megawatt-hour). Much more time and money is needed to determine if this will be a fruitful path forward for coal. In the meantime, a wide variety of cleaner electricity generation options are much more financially compelling than coal.
Before we close and to be fair let’s apply the same standard of clean to another electricity generation energy source: solar. Wait, solar is clean, isn’t it? Again let’s examine the full life cycle. When electricity is generated from solar energy it is done through the use of solar panels. Within the solar panels a silicon chemistry reacts to sunshine (solar energy) with electric charge which then travels through thin conductors eventually gathered at the end of each panel. The silicon in solar panels starts off as quartz which needs to be mined (with the associated environmental impacts of a mining operation), refined in hot furnaces (which take a lot of energy), and then further refined with a variety of toxic chemicals and acids (some of which are recycled, but all of which needs to be handled and disposed of carefully). There have been studies of the carbon footprint involved in manufacturing solar panels and there is growing focus and transparency in this part of solar generation’s life cycle. One study published in 2014 from the Argonne National Labs measures the carbon footprint of solar panel manufacturing at 140 pounds (.07 tons) per megawatt-hour. That’s not zero, but consider for a moment that the US Energy Information Adminstration estimates that one diesel truck puts out 224 pounds of carbon dioxide an hour and imagine the equivalent carbon footprint from coal mining. Even taking the mining and refining parts of the life cycle into account solar is a lot closer to “clean” compared to coal.
Once a solar panel is producing electricity, it is clean—no emissions, no impacts to water, and no impacts to the earth. Compare that to coal’s 2000 pounds of carbon dioxide per megawatt hour to understand what the opposite of clean is. Finally, it should be noted that studies have to be performed on the environmental impact of recycling or decommissioning solar panels, but do you think it will measurable compared to the trillions of gallons held in coal ash ponds across the country?
It would be a little easier for everyone to understand the industry by using terms like “carbon capture” instead of “clean coal.” How about “when is coal coming back?” We invite anyone in the Administration, Department of Energy, the Environmental Protection Agency, or anyone else to join us when Utility Classroom comes to Washington, DC, on March 21 to describe what happens when “Clean Energy Meets the Electric Utility Industry.” We’ll save you a seat!
Spoiler alert: coal isn’t coming back.