Can Coal Be Clean?

Clean coal is kind of a pipe dream. It's pretty much a rock that can be burned, and since it can be burned without any kind of purification process (in fact, I'm not sure if you can do anything to purify a solid like that) it is bound to have all sorts of nasty things, like heavy metals, mercury, arsenic, sulfur dioxide (which is one of the worst ingredients for acid rain) and the like. That's not even mentioning the significant quantity of CO2 that is released from burning coal. Most so-called "clean coal" tech has focused on removing the toxic compounds and dangerous particulate from emissions, and to a lesser degree reducing CO2 in emissions. In the past, coal burning plants used to respond to complaints in the local communities about their smoke and dust by making their smokestacks taller, thus making it so that the smoke and gasses would be blown further away from the local populace... thus spreading the problem into a larger area, and affecting more sensitive habitats. Nowadays, they try to improve filters and carbon capturing systems, which is only mitigating the larger problem. And while it is just about impossible to burn something that doesn't produce CO2, the sheer quantity that coal is able to produce gives it unique status as an especially dirty pollutant.

Something that may have an impact on how coal can be used is a method known as the Fischer-Tropsch process. It is a process that can be used to make liquid hydrocarbons from pretty much any combustible carbon-containing compound, such as biomass, natural gas, and coal. It does so by first generating carbon monoxide, then combining it with hydrogen. The process was first discovered by German scientists during the 1920's, and was subsequently used to convert coal to liquid fuel during WWII to power German war machines. While CO2 is still produced during the production and combustion of Fischer-Tropsch fuels, it can be captured more easily in the lab, and the other pollutants can be stripped from the gas stream during the production process as well, thus making a cleaner burning fuel. The process has been considered for mass use several times throughout US history, though economic aspects usually brought any advancement to a halt. In fact, some of these events may have been engineered to some degree: "The last time investors started lining up money for Fischer-Tropsch plants, in the 1970s, the OPEC oil cartel opened up its spigots and pushed the price of crude down to $10 a barrel, and that was that". Meanwhile, South Africa has based the majority of their fuel consumption on Fishcer-Tropsch fuels produced from local coal deposits. While it isn't the best alternative to petrol based fuels in terms of CO2 emissions, synthetic fuels are comparable in power, have fewer side products, and in some ways are easier to obtain than oil. After all, we would be able to make it from local sources, instead of having to import most of the ingredients.

While there wouldn't be a need to import most of the materials for Fischer-Tropsch fuels, and they can arguably be made cleaner than many current petrol based fuels, I would be remiss to overlook the aspect of how coal is obtained (though the making of such fuels from biomass would be a nice way to take care of garbage disposal at the same time). One of the greatest impacts coal has on the environment, while it has a more localized effect than the spreading of emissions, can be the mining of the coal from the ground. Whether it's shaft mining, strip mining, or the charmingly named "mountain top removal," there is usually some sort of impact on the surrounding area. Shaft mining, while there seems to be a relatively minimal effect on the ecosystem, can be dangerous work. And while one may think that the shaft is usually left behind after the work, most modern projects fill in the shaft after they leave to prevent some sort of collapse on the surface when the tunnel supports give. Strip mining leaves a massive gouge in the earth, which nature will be slow to reclaim due to the solid rock surfaces left behind with development, and often the rock that they can't use just gets dumped into nearby areas, managing to kill off another area, or perhaps blocking a source of water for a region and spreading the devastation further indirectly. Perhaps the one way this could be made productive is if someone found a way to make a city in the walls, kind of like the ancient city of Mesa Verde. But then, mountain top removal is just destructive, and unfortunately cheap enough that companies will use it anyway. So, even if we found a way to make synthetic fuels with coal feedstock, there would be the issue of how we would obtain it without causing more direct destruction than the insidious elements from the burning of fossil fuels could hope to match. In fact, it may compound the issue, as there would be less living plant biomass to take up the CO2 being produced.

Whatever the case, the one thing that is easiest to take from what I've learned is this: If there's a trick to clean coal, it is to not burn it as coal.

Extra links:
http://www.afdc.energy.gov/pdfs/epa_fischer.pdf 
http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process
http://www.economist.com/node/13235041?story_id=13235041