Clean Coal: An Unsustainable Political Myth
"The laws of physics stop at the doors of Congress." Does this old chestnut, attributed to the late Representative Tom Moorehead, sound as fresh today as when it was first uttered in defense of attempts to legislate the impossible? Have you become so battered by partisan apologists who present imbecility as wisdom that you don't notice when an attempt is made to justify a policy proscription that is thermodynamically futile?
If so, then you must be a fan of Clean Coal.
It is an inescapable fact that our species is dependent on fossil fuels, those solar energy generated, stored-in-the-ground biofuels that allowed us to lift ourselves up from poverty and build modern civilization. When it comes to electricity generation - you know, the stuff that powers the Chevy Volt - this largely means coal. Unless we are willing to retreat to a standard of living that would produce violent revolution if politically imposed, everyone better get used to the idea that coal is going to be around for a long time.
Hence, the attempt to imagineer a vision of coal that satisfies the imperative to pump less carbon dioxide into the atmosphere. You remember carbon dioxide, that greenhouse gas that every living thing exhales because it is thermodynamically downhill from food?
When it comes to eliminating actual pollutants such as mercury, particulate matter, and sulfur dioxide, coal burning power plants have done a truly remarkable job cleaning up their act. Thanks to rational EPA regulations and narrowly focused cap-and-trade solutions, Pittsburgh is no longer covered in soot and acid rain isn't killing trees in New England. Through it all, regulators paid attention to physics so the utility industry hasn't gone bankrupt.
But none of these pollutants are desired end products of coal combustion. This means they can be eliminated without destroying the fundamental energy releasing activity of burning coal. The same is not true for carbon dioxide. Building a coal burning power plant that spits out electricity without producing carbon dioxide is like asking water to flow uphill.
But what about carbon sequestration? Let's just capture all that carbon dioxide and lock it up rather than spew it into the atmosphere. And if we hope to arrest global warming, let's make sure we lock it up not just until the next election but for geologic time.
Wow. Geologic time. Think how hard it's been to find a place to store spent nuclear fuel, the total mass of which is an infinitesimal blip compared to all the carbon dioxide our power plants spit out. Not only that, but spent fuel rods are conveniently solid. Not so carbon dioxide. Where is all that gas supposed to go?
Turn it into a liquid, you say? You know, the stuff that dry ice melts into? Uh. Hmmm. OK, you can turn carbon dioxide into a liquid as long as you keep it very cold and under tremendous pressure. Care to try that for geologic time?
Well then, let's turn those greenhouse gasses back into rocks. Lo and behold, there is a way to do that. It's called mineral carbonation, which you get when you react carbon dioxide with metal-oxide bearing materials, for example Mg3Si2O5(OH)4, collectively known as serpentines. Serpentines are abundant and easily mined. All you have to do is dig them up, refine them to get rid of nasties like chromium, and cobalt, ship the stuff to coal burning power plants, react it with the carbon dioxide that would otherwise head up the smokestack, then ship the resulting stable solid somewhere appropriate and bury it. Sounds simple, huh?
The material tonnage that would have to be transported back and forth to make this work is more than twice the tonnage of the coal that now gets shipped to power plants. While that may create a lot of "green" jobs, an awful lot of heavy stuff would have to be schlepped around, all of which consumes energy. And while mineral carbonation is exothermic, which means it naturally runs downhill, the reaction kinetics are so slow that it takes a lot of energy to make it move fast enough to keep pace with the volume of carbon dioxide produced by commercial power plants. In fact, the energy required is estimated to be between 60% to 180% of the total usable energy being produced by the power plant.
Clean coal is a myth. Congress can and will pass many bills dishing out grants, subsidies, and mandates trying to turn this illusion into a reality. While they certainly have the power to bankrupt us chasing this chimera, they cannot suspend the laws of physics.
Yet the charade goes on because we cannot live without coal and, by the Gospel according to Gore, we can't live with it. As a result, Congress gets what it craves even more than solutions - an unsolvable high profile squabble that will garner lobbyist attention and campaign contributions for geologic time.