Cleaner coal energy ads.. how clean is coal energy?

I’ve seen those clean coal energy ads on CNN a couple of times now. They show people doing day to day cleaning around the house with quotes such as ‘Cleaning the curtains 2c’. At the end of the ad they say that coal energy is efficient, clean and abundant (I’m working from memory here but it boiled down to that). So it made me wonder:

How clean has coal energy become?
It seems to me that no matter how advanced technology gets, extracting energy from coal would still involve burning it which is far dirtier then pretty much everything else (oil, hydro, nuclear, solar, wind, etc).

And also, if its true that coal energy is significantly dirtier than other sources would there be a case against the advertisers for false advertisement or something like that?

Come on… no one is interested in coal anymore?

There are a variety of “clean coal” approaches. You have to look at what makes coal “dirty”. In the classic sense there are elements other than carbon and hydrogen such as sulpher, organic material, even Uranium. Modern coal plants can be equipped with “baghouses” to filter and collect particulates, “FGD” (Flue Gas Desulpherization) systems to eliminate sulpher compounds, “SOX/NOX Reduction” systems to eliminate most oxides of sulpher and nitrogen, etc. which will reduce these emissions to perhaps 1% or less of the emissions of an old uncontrolled power plant. There will be some net emissions, however.

There are other technologies which pre-process the coal and can almost completely remove sulpher and other materials before the coal is actually burned. The cost effectiveness is still in question however.

If you do burn the coal, of course you do have CO2 emissions and, since coal is more carbon intensive than other options like natural gas, you get more CO2. You can process the coal to create a gas similar to natural gas and a carbon rich by product to reduce the CO2 emissions, but again at considerable cost.

My take would be that a state of the art coal plant is not appreciably dirtier than a gas, oil, biomass etc plant except for the amount of CO2 emissions. Whether CO2 is “dirty” or not kind of depends on where you are on the global warming argument. It isn’t dirty from the standpoint of clouding the air or causing respiratory problems.

I used to work in a coal fired power plant (doing some control systems work, not directly related to the generators). There are a lot of EPA regulations involved. It’s not like they just burn the coal and let everything just whiz on out the smoke stacks. A large amount of real estate is devoted to the scrubbers and such. I happened to work at one of the largest coal fired plants in the ohio valley, and standing outside of it you couldn’t tell much was going on. It certainly wasn’t pouring soot into the atmosphere or anything like you might imagine.

The main thing that coal plants generate (besides heat) is fly ash. In the olden days this probably would have just gone out the stacks as soot, but these days it’s collected and shoved into large silos, which are emptied constantly by trucks. People make concrete and all sorts of stuff out of fly ash.

Even with all of the scrubbers and such, there was still a large issue about sulfur content in the coal. The plant I was in mixed high sulfur coal (the local stuff, which was much cheaper) with lower sulfur coal (much more expensive, shipped in from far distances). It was my understanding that there was a tradeoff between the cost of the coal and the environmental costs to clean up the output. If they used too much of the cheap stuff it actually cost them more in the end because of the additional work required by the scrubbers. The plant I was in did not do any pre-treatment of the coal. They simply shoved it in with an appropriate mix of high and low sulfur coal, crushed it, and sent it in to the boilers.

Hydro and wind power are obviously going to be cleaner. Wind isn’t going to effect much, but hydro dams up the river and has a sometimes drastic effect on wildlife downstream. Nuclear is a funny thing. There’s no air pollution from nuclear plants, but the nuclear waste is really, really nasty stuff and there really isn’t an effective way to deal with it.

Hydro and wind plants simply can’t produce enough power to keep up with the demands. For the company I worked for, coal produced over half of the energy. Nuclear energy accounted for the next largest chunk, and IIRC that all came from a single plant. Hydro and other stuff like a pilot plant burning old tires accounted for probably less than 1 percent. These ratios will vary quite a bit depending on what area you are in, but mostly the largest plants will be nuclear, and the second largest will be coal. Even though the largest plants are nuclear, there aren’t many of them, so most of the energy from most places will be from coal.

I poked around a little on the net and came up with the following, for the year 2000:

coal: 43 percent
gas: 19 percent
nuclear: 14 percent
renewable energy sources: 12 percent
petroleum: 7 percent
hydroelectric: 3 percent

So, as far as your ad is concerned, “efficient, clean, and abundant” seems to be basically true, if only because they go to great lengths to make it clean.

Well, my name for the first 7000 posts here was “Anthracite”, after all…

OK. I don’t even know where to begin. I don’t like to brag, but I am a bit of a specialist on this subject.

First off, there are a few basic pollutants from a coal power plant. Let me list the most significant ones:

  1. Particulates (primarily coal ash, but at some plants fractions of unburned coal).

1b) Bottom ash, which can contain significant amounts of unburned carbon, depending on the plant.

  1. Sulfur dioxide (produced from combustion of sulfur in the coal)

  2. NOx, or nitrogen oxides (typically assumed to be 98% NO, 2% NO2), which is caused by fuel-bound nitrogen and reaction of nitrogen in the combustion air with oxygen at the highest temperatures of the flame front.

  3. Carbon monoxide due to incomplete combustion. This is typically very small.

  4. Carbon dioxide due to complete combustion.

  5. Mercury, arsenic, cadmium, antimony, and other heavy metals, including some radionucleides. Typically this is fairly small, but mercury is of late a concern.

A modern coal power plant with the best available control technology (BACT, as the EPA calls it) can have remarkably low emissions. They can achieve sulfur dioxide removal efficiencies of 95% or greater, can have NOx emissions as low as 0.1 lbm/MBtu or less, and can achieve 99.99% particulate removal efficiency (on a mass basis). With the addition of a mercury scrubber and by use of a baghouse, they have the potential to remove 90% or more of the mercury, although this is a new and emerging technology which has not been installed on any large coal plants in the US.

A coal plant and an oil plant (where they still operate) with the same technologies have about the same potential for emissions. A gas plant is much “cleaner” in that it typically has practically no particulate or sulfur emissions, but does produce NOx emissions which can require an SCR system to remove.

I do not know of a single coal plant in North America over 25MW that does not have either an electrostatic precipitator or a baghouse. I would say an average removal efficiency is about 99.25%. An average continuous removal efficiency of SO2 would be about 90% (where scrubbers are installed, of course), with some rare plants being greater than 95%. An average continuous removal efficiency of NOx (where SCR systems are installed) would be about 70% while they operate during NOx season. Maybe 80% or more if they also have low-NOx burners and second or third-generation overfire air.

Another very, VERY important thing to note is that coal is a very different fuel than most others, and the quality of the coal and the impurities within it has a huge and profound impact on the performance, efficiency, emissions, and cost of operation. Sulfur content of coal can range from a low of 0.2% for some Wyoming PRB coals to as high as 6% or more for Canadian coals. Fuel-bound nitrogen can range from 0.5% to nearly 2%. Ash content can range from 1% (for a good Indonesian coal) to as much as 50% or more for a lignite coal. This is stuff I have to deal with every single day on the job.

engineer_comp_geek, the EIA figures you have listed show unit capacities, but not net generations. If you compare the actual net generation figures, I think you will find that the balances shift somewhat - dramatically, in fact, for some sources. Coal makes up between 50-55% of the net generation per year, depending on the year, whereas petroleum and renewables make up lesser percentages on a generation basis. Petroleum being, depending on the year, about 2-3%.

And I imagine you’ll find that the cost of the low-sulfur coal itself was pretty cheap (with 8400 Btu PRB coal being about $5 a ton FOB, and 8800 Btu PRB coal being about $7 a ton FOB, depending on the contract and year), it was likely the transportation cost that was high. I’ve seen it cost as much as $30 a ton to ship $4 a ton coal.

Pre-treatment of the coal is not done very often in the US, although some of the major mines do blend and do some gross separation of rock. Few coal plants have a wash plant on-site as well - the only two I’ve seen are Paradise (Kentucky) and Bonanza (Utah…well, OK, the wash plant is at the mine, but still, it’s a minemouth plant, same thing). BTW - if you ever wanted to look like the “swamp thing”, visit a coal wash plant some time. Pre-treatment simply has not been found to make economic sense (yet), otherwise it would be done. One of the many things I do on my job is studies of all sorts of pre-treatment schemes, and while they are neat, many of them are very questionable, have only worked on pilot scales (less than 1 ton/day), and are based on technology “not yet available” - never a safe bet.

In summary answer to the OP - yes, coal plants can be incredibly clean, but only if they are forced to do so by legislation, and at quite a bit of expense. A scrubber can cost between $50M to $200M depending on the plant, and an SCR system (for NOx removal) can cost more than $50M as well. And, of course, there is the operating and maintenance costs of these items, which can total as much as 1/3 the total cost of generation.

<irrelevant but light-hearted political-type jab>

Gee, I thought the free market would take care of that!

</irrelevant but light-hearted political-type jab>

<off topic informational retort>
The free market is taking care of it in that we now have emission credits and a market for trading those credits to lower emissions at the lowest possible net cost to the environment. Discussion continues on a “carbon tax” which would so a similar thing to reduce CO2 emissions in the most cost effective way. Implementation of these does get resistance from environmental groups which favor heavy handed regulation to allowing the market to find the most cost effective ways to limit emissions.
</off topic informational retort>

Oh, by the way, I found these numbers for 2002 net electrical generation by source:

Coal - 50.0%
Nuclear - 20.2%
Gas - 17.6%
Hydro - 6.9%
Oil - 2.5%
Other - 3.0% (Would include geothermal, solar, wind, biomass, etc.)


I spent about 40 minutes this evening writing a reply to this. I blipped to a dictionary site to check spelling (I was wrong,) and when I came back, the whole thing was gone, and the RedSox and Colts games were on. Now I’m back (the Colts won!), and Una Persson has dived in, as expected, to say half of what I had intended to say.

The coal-to-electricity business is cleaner than it was when I was a boy. Una Persson has explained most of that. The industry has done that to comply with government regulations.

The pre-powerplant part of the industry is also cleaner and safer than it was. Coal mining is a hazardous way to make a living, but it’s safer than it was. Due to more efficient methods and government regulations, fewer coal miners per ton of coal are dying from black lung and accidents than when I was young.

Every way of making electricity has its drawbacks. Mining nuclear fuel, for example, is hazardous, too. Hydro power eats up huge amounts of real estate, and the intitial cost is astounding. Wind power gets into a NIMBY thing over noise and spoilage-of-view. And nuclear? Hoo boy, step back and listen to the screaming. Solar is still quite expensive. Hamster cages are not bad, cost-wise, but the PETA folks are all over that.

The ads the OP saw are from the pro-coal folks, obviously. They have their own ax to grind, but maybe they’re right. Maybe. The president swore he was on their side before the election, and maybe he was. Maybe. It will be interesting.

“Busy, busy, busy.” --Bokonon (Kurt Vonnegut, jr.)

Actually, there are effective means to deal with nuclear waste - long term burial and reprocessing. That’s the great thing about nuclear - you always know where the waste is. You can’t say that about coal.

Dirt burners make up the majority of the power produced in the US and are much cleaner than they used to be. The problem is that the cleaner coal gets, the more expensive it is. Emissions regulations have understandably made coal more expensive and its costs are comparable to nuclear.

The important thing is that you can’t rely too much on a single source of power. It’s important to have a diverse supply of energy so that market forces don’t suddenly cause your fuel/component prices to skyrocket (like in the '70s - there’s a good reason you don’t see much electricity generated by burning oil any more). There’s room for coal, nuclear, gas, oil, diesel, hydro, and even solar and wind.

This might be headed off to great debates territory, but burial isn’t such a great thing IMHO. You’re talking about burying stuff and keeping it contained for a period of time longer than the span of recorded human history. Hundreds or thousands of future human beings could easily be killed trying to do an archeological dig to figure out just what the heck we buried there. It’s going to remain dangerous for much longer than we are likely to be around and know where it is. That’s hardly an effective way of dealing with it if you ask me.

Yeah, any time nuclear power comes up, it always comes down to the waste - a political question more than a practical one.

With coal, you end up dumping the exhaust into the atmosphere and who knows where it goes. With nuclear power, you package the waste and have a permanent trail so you will ALWAYS know where it is. You could even go back and retrieve spent fuel if someone thinks of a new thing to do with it.

Do you really think civilization is going to fall tomorrow? Anyway, there are plans to permanently mark radioactive waste disposal sites in such a way that future generations will know what’s there. I guess we better mark town dumps in the same way since there’s plenty of “toxic” substances that people throw away every day. I’m not going to say more because I don’t want to hijack this thread further.

Waw! thanks for the replies, I am VERY surprised to learn that almost half the energy produced in the states is coal…because here, in Quebec, something like 95% comes from hydro.

To be very honest, most people here think of coal plants as outdated 1950s things… but I guess I was too quick to judge…

What I get from Una Persson is that most of byproducts of coal bruning seem to be somewhat under control. For people that live close to or work at Coal plants, is there a noticeable difference on the air purity, smog and the such?

What is worse for air quality, living in a large city (say, Montreal or Toronto size city) or near a coal power plant?

And thanks again for the replies, I really learned a lot today…which is why read this board…

I happened to work in a very large coal fired plant. The area in and around the plant didn’t have the greatest air, due mostly to the large number of trucks constantly bringing coal in and fly ash out, and a couple of bulldozers running around shoveling the coal into various places. Once you got out of the plant though, the air wasn’t bad at all. The air in downtown Baltimore is definately worse.

One thing to keep in mind though is that power plants have very tall smoke stacks. What pollution they do produce tends to get shoved very high into the air, where the winds will disperse it over a very large area. It’s dispersed enough and there is little enough of it that you can’t really tell the pollution is even there just from walking around nearby, but they are shoving stuff into the atmosphere.

In a large city, most of the pollution comes from vehicles and the pollution enters the air at a very low level.

This is the plant where I worked (warning, PDF):

The picture is pretty close to the way it looks all the time. There are large smoke stacks, but it doesn’t look like there is much of anything coming out of them.

What’s a “baghouse”, if I may ask?


Dust collectors. Here’s an example:

I’ll just take the opportunity here to make a terminology correction that really screws up a lot of discussions on energy use. Almost half of the electricity produced in the states comes from coal, not half the energy. You might see the very low percentage of oil used in the electricity stats and wonder why oil is still important. That’s because it dominates the transportation sector and is important in the heat and industrial sectors.

Electricity is somewhat less than half of the total energy and this is often used in arguments to confuse things by saying “Nuclear accounts for only 5% of the world energy production” knowing many listeners will confuse this with electricity.

And this doesn’t even touch on the issue of the waste produced by mining coal, which can be just as problematic as the waste produced by burning it.

Thank you!

What is done with the dust? Can you burn it?


I think the reference given isn’t really a power plant “dust collector”. It’s more a general air cleaning system. The power plant baghouses are huge, sometimes consisting of thousands of fabric bags which act like vacuum cleaner bags. Plants use either these baghouses or electrostatic precipitators to collect “fly ash” and any other particulates. The precipitators collect the material on charged plates.

The ash is the non-combustible part of the coal. The heavier portions come out of the combustion region as bottom ash and the lighter parts are fly ash. The ash has a number of uses such as additives in concrete and various abrasives. You’ve heard of “cinder blocks”? This is where the term came from.

Here’s a nice overview of a modern coal plant:

(May take a bit to load - large pdf file)