## Carbon Emissions from Coal-Fired Power Plants

The 50 dirtiest electric power plants in the United States—all coal-fired—emit as much carbon dioxide as half of America’s 240 million cars.

The dirtiest 1% spew out a third of the carbon produced by US power plants.

And the 100 dirtiest plants—still a tiny fraction of the country’s 6,000 power plants—account for a fifth of all US carbon emissions.

According to this report, curbing the emissions of these worst offenders would be one of the best ways to cut US carbon emissions, reducing the risk that emissions will trigger dangerous climate change:

• Environment America Research and Policy Center, America’s dirtiest power plants: their oversized contribution to global warming and what we can do about it, 2013.

Some states in the US already limit carbon pollution from power plants. At the start of this year, California imposed a cap on carbon dioxide emissions, and in 2014 it will link with Quebec’s carbon market. Nine states from Maine to Maryland participate in the Regional Greenhouse Gas Initiative (RGGI), which caps emissions from power plants in the Northeast.

At the federal level, a big step forward was the 2007 Supreme Court decision saying the Environmental Protection Agency should develop plans to regulate carbon emissions. The EPA is now getting ready to impose carbon emission limits for all new power plants in the US. But some of the largest sources of carbon dioxide are existing power plants, so getting them to shape up or shut down could have big benefits.

### What to do?

Here’s what the report suggests:

• The Obama Administration should set strong limits on carbon dioxide pollution from new power plants to prevent the construction of a new generation of dirty power plants, and force existing power plants to clean up by setting strong limits on carbon dioxide emissions from all existing power plants.

• New plants – The Environmental Protection Agency (EPA) should work to meet its September 2013 deadline for re-proposing a stringent emissions standard for new power plants. It should also set a deadline for finalizing these standards no later than June 2015.

• Existing plants – The EPA should work to meet the timeline put forth by President Obama for proposing and finalizing emissions standards for existing power plants. This timeline calls for limits on existing plants to be proposed by June 2014 and finalized by June 2015. The standards should be based on the most recent climate science and designed to achieve the emissions reduction targets that are necessary to avoid the worst impacts of global warming.

In addition to cutting pollution from power plants, the United States should adopt a suite of clean energy policies at the local, state, and federal levels to curb emissions of carbon dioxide from energy use in other sectors.

In particular, the United States should prioritize establishing a comprehensive, national plan to reduce carbon pollution from all sources – including transportation, industrial activities, and the commercial and residential sectors.

Other policies to curb emissions include:

• Retrofitting three-quarters of America’s homes and businesses for improved energy efficiency, and implementing strong building energy codes to dramatically reduce fossil fuel consumption in new homes and businesses.

• Adopting a federal renewable electricity standard that calls for 25 percent of America’s electricity to come from clean, renewable sources by 2025.

• Strengthening and implementing state energy efficiency resource standards that require utilities to deliver energy efficiency improvements in homes, businesses and industries.

• Installing more than 200 gigawatts of solar panels and other forms of distributed renewable energy at residential, commercial and industrial buildings over the next two decades.

• Encouraging the use of energy-saving combined heat-and-power systems in industry.

• Facilitating the deployment of millions of plug-in vehicles that operate partly or solely on electricity, and adopting clean fuel standards that require a reduction in the carbon intensity of transportation fuels.

• Ensuring that the majority of new residential and commercial development in metropolitan areas takes place in compact, walkable communities with access to a range of transportation options.

• Expanding public transportation service to double ridership by 2030, encouraging further ridership increases through better transit service, and reducing per-mile global warming pollution from transit vehicles. The U.S. should also build high-speed rail lines in 11 high-priority corridors by 2030.

• Strengthening and expanding the Regional Greenhouse Gas Initiative, which limits carbon dioxide pollution from power plants in nine northeastern state, and implementing California’s Global Warming Solutions Act (AB32), which places an economy-wide cap on the state’s greenhouse gas emissions.

### Carbon emitted per power produced

An appendix to this report list the power plants that emit the most carbon dioxide by name, along with estimates of their emissions. That’s great! But annoyingly, they do not seem to list the amounts of energy per year produced by these plants.

If carbon emissions were strictly proportional to the amount of energy produced, that would tend to undercut the the notion that the biggest carbon emitters are especially naughty. But in fact there’s a lot of variability in the amount of carbon emitted per energy generated. You can see that in this chart of theirs:

So, it would be good to see a list of the worst power plants in terms of CO2 emitted per energy generated.

The people who prepared this report could probably create such a list without much extra work, since they write:

We obtained fuel consumption and electricity generation data for power plants operating in the United States from the U.S. Department of Energy’s Energy Information Administration (EIA) 2011 December EIA-923 Monthly Time Series.

### 26 Responses to Carbon Emissions from Coal-Fired Power Plants

1. Frederik De Roo says:

Interesting! Wouldn’t the third paragraph (dirtiest 1%, ca 60 plants) perhaps fit better between the first and the second paragraph? (50 resp 100 plants)

2. William T says:

The variability in your graph might be because some states have larger non FF generation capacity than others, not because some coal plants are much less efficient.

• John Baez says:

Right. That already implies that coal-fired power plants are more ‘naughty’ than non-fossil-fuel plants, but that’s not news. It would be a lot better to see carbon emissions per kilowatt-hour for lots of plants, together with information about what kinds of plant these are.

3. domenico says:

I am thinking that it is easier to increase the thermodynamic efficiency of some plants (and possibly reduce the emission of carbon dioxide), than that of 120 million cars.
That is, the search for improvements on huge power centrals, it is convenient for both states (less carbon dioxide, more technology, more health in the affected areas), and producers (savings on materials purchased and best prices).
It is possible the replacement of obsolete plants, but it is easier to fight for a pollution abatement (it is possible obtain faster results).
It is interesting the idea of slowly increasing the cost of polluting plants (so that the political lobbying does not win: it is good to spend money on research, rather than policy, if the legislation does not involve radical changes), in order to obtain a adaptation of the industry to a policy of reducing emissions of carbon dioxide.

• domenico says:

I am thinking an utopia: if each industry in a country must use a little part of the revenue (for example the five for thousand each year) to reduce the energy consumption for single product (at least a five per thousand reduction for single product), then there is a virtuous circle.
Today the cost of raw material is the same in all the world, so that the transformation of the raw material in product with energy is the different cost for country: with the robot, and machine, the workforce cost for single product is low.
Each product is used for other production, so that the reduction cost using the energy saving can be a great cumulative effect (if the final product is made in N factories, and each factory reduce the consumption of a same amount).
It think that is an advantage for a country, and its industries, to make energy saving.

4. Berényi Péter says:

Why water vapor emission is not called “hydrogen pollution”?

• John Baez says:

Because a phenomenon known as ‘rain’ quickly intervenes when the humidity rises above a certain point, while carbon dioxide stays in the atmosphere for hundreds of years.

• Berényi Péter says:

I can see atmospheric carbon dioxide concentration is conjectured not to converge exponentially to preindustrial levels even if fossil fuel burning is stopped, but I don’t see why. However, if it would postpone the next continental glaciation of the Northern Hemisphere, perhaps indefinitely, that can’t be worse than 2 miles of ice over North America, Europe and parts of Asia with a hundred times more airborne dust than we currently have, can it?

Okay, let’s suppose we abhor a future with inhabitable land above 40N and we strive for dust. It is still not clear why “carbon pollution” is mentioned instead of “carbon dioxide pollution”, when there is a vast difference between them. Carbon pollution (black carbon, soot) is something which actually exists, it is pollution indeed in the sense it is harmful to human health (which carbon dioxide is not, at least not until its concentration is increased twentyfold or more) and it is also a powerful forcing on climate, with twice the efficacy of GHGs. But its atmospheric lifetime is short, comparable to that of water vapor and it is relatively easy to eliminate it by doing things properly.

As for the long atmospheric lifetime of carbon dioxide, I would never venture further than a century in the future with any forecast, because we shall have molecular nanotechnology with software driven molecular assemblers sooner than that for sure. As soon as it happens, airborne carbon dioxide with free transport will become the most precious resource imaginable, providing the default building material for almost anything. With self replicating manufacturing facilities available, it can get depleted in no time if it is not replenished from less accessible carbon or hydrocarbon reserves. Or from limestone, but in this case the prodigious amount of lime milk as a byproduct would threaten with catastrophic ocean basification. Therefore it is wise to preload the atmosphere with this stuff as much as possible before that technological transition comes about.

With that kind of technology atmospheric concentration of carbon dioxide can be regulated at will. However, it would be a hard political decision to drop it back to preindustrial level, because that would involve reducing foliage cover over vast semi arid regions considerably. Who would dare take responsibility for such a large scale devastation?

• Frederik De Roo says:

…molecular nanotechnology with software driven molecular assemblers…airborne carbon dioxide with free transport will become the most precious resource imaginable, providing the default building material for almost anything… it is wise to preload the atmosphere with this stuff as much as possible before that technological transition comes about.

I admire the elaborated science fiction (“never venture further than a century in the future with any forecast”) but why don’t you try a similar yet more down-to-earth argument such as: “Plants capture carbon, and we are fertilizing them right now.”

• John Baez says:

Berényi wrote:

I can see atmospheric carbon dioxide concentration is conjectured not to converge exponentially to preindustrial levels even if fossil fuel burning is stopped, but I don’t see why.

I’ll assume you’re using ‘exponentially’ in the mathematical sense, rather than as a synonym for ‘fast’.

The atmospheric CO2 doesn’t converge exponentially because, even in a linear approximation, it doesn’t obey an equation like

$\displaystyle{ \frac{d x}{d t} = - a x }$

where $x$ is the difference between the concentration and some equilibrium concentration. If you imagine the simplest model where some CO2 is held in the atmosphere, some in the warm upper ocean layer, and some in the colder deep ocean, you’ll write down an equation like this:

$\displaystyle{\frac{d \vec{x}}{d t} = - A \vec{x}}$

where

$\vec{x} = (x_1, x_2, x_3)$

is a vector describing the concentrations in the air, upper ocean and lower ocean (minus some equilibrium values), and $A$ is a 3 &times 3 matrix.

This model is oversimplified—but already you see why we don’t usually get solutions where the excess CO2 concentration in the air decreases exponentially:

$x_1(t) = c e^{-at}$

Instead, the CO2 excess in the air will start by decreasing exponentially as CO2 goes into the upper ocean—but then the upper ocean becomes saturated, and stops absorbing so much CO2 from the air. At this point a slower process takes over, as the upper ocean more slowly transfers CO2 to the lower ocean.

In reality things are much more complicated! But I hope this answers your question why the atmospheric CO2 concentration doesn’t obey a simple exponential decay curve.

Here’s a quick explanation that sketches some of the relevant processes, from the article I already pointed you to:

Unlike other human-generated greenhouse gases, CO2 gets taken up by a variety of different processes, some fast and some slow. This is what makes it so hard to pin a single number, or even a range, on CO2’s lifetime. The majority of the CO2 we emit will be soaked up by the ocean over a few hundred years, first being absorbed into the surface waters, and eventually into deeper waters, according to a long-term climate model run by Archer. Though the ocean is vast, the surface waters can absorb only so much CO2, and currents have to bring up fresh water from the deep before the ocean can swallow more. Then, on a much longer timescale of several thousand years, most of the remaining CO2 gets taken up as the gas dissolves into the ocean and reacts with chalk in ocean sediments. But this process would never soak up enough CO2 to return atmospheric levels to what they were before industrialization, shows oceanographer Toby Tyrrell of the UK’s National Oceanography Centre, Southampton, in a recent paper.

Finally, the slowest process of all is rock weathering, during which atmospheric CO2 reacts with water to form a weak acid that dissolves rocks. It’s thought that this creates minerals such as magnesium carbonate that lock away the greenhouse gas. But according to simulations by Archer and others, it would take hundreds of thousands of years for these processes to bring CO2 levels back to pre-industrial values (Fig. 1).

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Also try some of the papers linked to here, which explain these pictures:

• John Baez says:

Berényi wrote:

As for the long atmospheric lifetime of carbon dioxide, I would never venture further than a century in the future with any forecast, because we shall…

Whoops, I liked what you were saying there, but then you violated your quite reasonable policy not to make forecasts further than a century into the future!

I agree that we should focus on what’s happening in the next century. People who go further than that tend to make predictions based on scenarios they happen to find plausible—but these scenarios vary wildly from person to person, from apocalyptic disasters to utopias like the one you sketched.

My original point was a simple one: the reason we talk about ‘carbon pollution’ but not ‘hydrogen pollution’ is that rain rapidly takes H2O out of the atmosphere, while no comparably quick natural process exists for CO2.

• Berényi Péter says:

John, I see your point. However, should high atmospheric carbon dioxide concentration become a problem indeed (which it is not for the time being), it does not look too difficult to keep its level low in the upper ocean, speeding up absorption tremendously. Neither it is prohibitively expensive, at least compared to alternatives.

• R. D. Schuiling and P. L. de Boer, Rolling stones; fast weathering of olivine in shallow seas for cost-eﬀective CO2 capture and mitigation of global warming and ocean acidiﬁcation, Earth Syst. Dynam. Discuss. 2 (2011), 551–568.

• Frederik De Roo says:

Please notice that this paper was not accepted for publication in ESD because the second reviewer had serious comments (which are also available online together with the authors’ response).

• Berényi Péter says:

It is quite irrelevant if it was accepted or not, the point is “rate of olivine weathering is not hampered by reaction-inhibiting silica at the surface of olivine grains” if “continuous mutual impacts remove such reaction-inhibiting surface layers” in “high-energy shallow marine environments as a giant marine ball mill”. The rest is engineering, not science, even if Anonymous Referee #2 can’t see that.

5. grlcowan says:

Forsterite spontaneously picks CO2 out of air, even though CO2 there is only 0.0004 mole and volume fraction there. The idea of enhanced weathering is to harness this tendency. It gives hope that we can get the mole fraction back to its natural value of 0.00028.

I think there is also a proposal by R.D. Schuiling to inject coal furnace flue gas deep down in a huge pile of olivine* chips, taking advantage of the much higher than 0.0004 mole fraction in the gas to get a quicker reaction, and a useful increment to the coal’s energy yield (which might be harvested by running high-pressure water lines through the pile).

I don’t have a URL at the moment for this, maybe someone has it at their fingertips.

For a coal that was pure carbon, the energies would go thus:

C + O2 —> CO2, delta ‘H’ -393.52 kJ/mol

CO2 + ½ Mg2SiO4 —> MgCO3 + ½ SiO2, delta ‘H’ -85.14 kJ/mol

———————————————————————————–

C + O2 + ½ Mg2SiO4 —> MgCO3 + ½ SiO2, delta ‘H’ -478.66 kJ/mol

The bad news for this 20 percent increase in carbon combustion’s energy field is, you need 70.34655 tonnes olivine per 12.011 tonnes carbon, 5.857 tonnes per tonne.

The good news is, the amount of olivine within easy shovel range exceeds, by a factor a lot more than 5.857, the amount of similarly accessible coal. Schuiling and Tickell show a satellite photo of a many-square-mile patch of laterite—hydrous ferric oxide—in Africa, and remark that this is the corrosion layer, a few tens of metres thick, that grows over geological time on an olivine surface.

*Olivine is a mixture of the above-mentioned forsterite with fayalite, Fe2SiO4, ferrous orthosilicate. When atmospheric CO2 turns the forsterite into magnesium carbonate, aka magnesite, and the magnesite dissolves and runs into the sea, the fayalite rusts and stays.

6. Speed says:

This is all very interesting and useful information but what is the financial cost? What will the proposed actions do to the price of electricity to individuals and industry?

• John Baez says:

It’s easier to get information about a similar question: the effects of the forthcoming EPA regulations on future power plants. Try this:

• Michael Wines, E.P.A. Is Expected to Set Limits on Greenhouse Gas Emissions by New Power Plants, New York Times, 13 September 2013.

and for more details:

• Berényi Péter says:

Those EPA regulations are designed to kill coal fired power plants selectively while giving a competitive edge to natural gas fired ones. It is clearly a plot designed by Big Oil to grab the entire market, nothing else.

The proposed regulation sets an upper limit of 1000 lbs CO₂ emission per MWh. Equivalent emission while burning pure carbon is 887.5 lbs, for methane it is 392 lbs.

It is impossible to operate a plant at ~90% thermal efficiency, not to mention over 100%, which would be required for actual coal. Therefore no coal fired power plant is viable.

On the other hand, a Combined Cycle Gas Turbine (CCGT) plant can achieve a thermal efficiency around 60% (653 lbs CO₂ / MWh) or up to 42% (933 lbs CO₂ / MWh) with a single cycle gas fired steam power plant.

In the wake of the recent widespread use of an old technology (hydraulic fracking) there is an overproduction of natural gas on the US market, that’s the woe EPA is trying to fix.

Once it is done, there is no limit to rising electricity (and gas) prices, a yummy prospect, is it not?

• Speed says:

The EPA document includes the following …
“As explained in detail in this document, energy market data and projections support the conclusion that, even in the absence of this rule, existing and anticipated economic conditions in the marketplace will lead electricity generators to choose technologies that meet the proposed standards. Therefore, based on the analysis presented in Chapter 5, EPA anticipates that the proposed EGU GHG NSPS will result in negligible CO2 emission changes, energy impacts, quantified benefits, costs, and economic impacts by 2020. Accordingly, EPA also does not anticipate this rule will have any impacts on the price of electricity, employment or labor markets, or the US economy. Nonetheless, this rule may have several important beneficial effects described below.”

The NYT piece says in part …
“In some ways, the debate seems moot. In an era of cheap natural gas, hardly anyone in the United States is building coal-fired power plants.”

So new rules aren’t needed. One could say that the rule making process here is a make-work undertaking just in case. Or one could say that where the EPA document calls for “government support” of technology development it is a ripe cherry ready to be picked by some set of rent-seekers. Perhaps the development of the new rules should become a just victim of sequestration.

• Berényi Péter says:

If “even in the absence of this rule, existing and anticipated economic conditions in the marketplace will lead electricity generators to choose technologies that meet the proposed standards”, then the absence of rules is clearly preferable. NYT may be right, “in an era of cheap natural gas, hardly anyone in the United States is building coal-fired power plants”.

But natural gas is only guaranteed to remain cheap if its market share is threatened by coal. With a rule effectively banning coal, it would no longer be the case. It would let producers restrict supply and drive prices up substantially.

• John Baez says:

Berényi Péter wrote:

Those EPA regulations are designed to kill coal fired power plants selectively while giving a competitive edge to natural gas fired ones.

Don’t worry: the American Public Power Association is trying to get the EPA to raise the limits for coal-fired power plants from the proposed limit of 1,400 pounds per megawatt-hour (which is already above the proposed 1,000-pound limit for gas) to 1,900 pounds. They will probably file a lawsuit to do this.

With a really good carbon market, we could avoid some of these fights: people could put more carbon dioxide into the air if they paid for the damage it caused.

7. arch1 says:

“If carbon emissions were strictly proportional to the amount of energy produced, that would tend to undercut the the notion that the biggest carbon emitters are especially naughty.”

The chart is tantalizing. If I’m thinking about it correctly, one can’t use it to conclude much about the naughtiness of the biggest emitters, but one *can* conclude that, in each state listed, the biggest 5 *producers* are as a group substantially *less* naughty than average (sometimes, radically so).

• arch1 says:

Oops, I mentally reversed the color key. So I *should* have said:

“…one can’t use it to conclude much about the naughtiness of the biggest *producers*, but one *can* conclude that, in each state listed, the biggest 5 *emitters* are as a group substantially *more* naughty than average (sometimes, radically so).

8. […] 2013/09/13: JCBaez: Carbon Emissions from [US] Coal-Fired Power Plants […]

9. prkralex says:

Six of the ten biggest power stations in the US are fossil-fuelled, while the other four, including the two biggest Grand Coulee and Palo Verde, are hydro -and nuclear-powered.