Risks of coal gasification, Fischer-Tropsch, and other synfuel processes

My reading on the topic of using coal as a starting material to produce synfuels is sadly negligent, but I have also seen that there are very few of us on this forum who understand the process at all. So instead of just running to Google and Wikipedia and keeping the results to myself, I'd like to open up the topic to discussion:

What are the environmental risks involved in making synfuels from coal? Why are laboratory processes like Fischer-Tropsch so dangerous to the environment? Can't the heavy-duty pollutants -- including materials that are dangerously radioactive when released through combustion -- be filtered out and properly contained? Since it's a hydrocarbon, can't coal be subject to thermal depolymerization? Would subjecting it to combustion in a superheating furnace (sorry, I do not know the technical term for this process) release more energy and leave only the radioactive pollutants, which occur in much smaller amounts?

Keep in mind that I'm posing my questions for didactic, not argumentative, purposes. I have only the most basic understanding of these issues at present, and am better-informed about biosynthetic energy sources (diesel and alcohols) than those from entirely lab-synthetic processes. Many of us in this forum haven't so much as thought of synfuels, yet it is possible that some improvement on current technology could make synfuels a significant source of energy in the near-term.

(Actually, I fibbed a bit. I've done some online reading on F-T, but none of the sources I've read have given the evironmental risks more than a brief nod -- the biggest problem seems to be the lack of aromatic compounds in F-T synfuels, which have undesirable effects on some engine parts. There's a lack of introductory technical information on non-F-T synfuels, and, the info sources tend to be slanted in one way or another -- the best reasons I know to consult fellow DUers.)

--p!

1) No matter what process is used, the ultimate pathway looks like this:

fossil carbon -> blah blah blah -> CO2. So, we are continuing to burn non-carbon-neutral fuels, and therefore continuing to make climate change worse, not better. Which (wait for it) will kill us all.

2) Mining coal is an environmental disaster. Continuing to use coal will turn the Appalachians into a wasteland.

Bonus 3rd reason: coal will run out, just like oil and natural gas. And it will run out all that much faster, if we start mining it for syn-fuels.

So what prize would you like today? </Circus fair voices>

I frequently rail against FT, on exactly the grounds you offer. I should be clear that I am really railing against coal.
I would add yet another reason to fear and oppose FT chemistry. FT processes require heat. If the heat is provided by burning coal, the release of CO₂ is much faster than it would be if we simply burned the coal.

I do need to note however that many papers published on FT chemistry involve the use of biomass. This is less offensive, but only slightly less offensive. FT chemistry can in theory be used with atmospheric carbon dioxide and nuclear or solar (all forms of solar including wind) hydrogen.

A big strike against FT chemistry however is that it is synthetic petroleum analogues. Petroleum is a very dirty fuel. It basically makes a mess. We ignore this mess only because we are used to it.

In general, I would like to see aircraft replaced by high speed rail, ideally electrified rail. However for international travel, we still may wish to have aircraft in the future, if there is a future.

This would be the only application for FT chemistry (from biomass or atmospheric carbon dioxide) of which I might approve, to make jet fuel. Otherwise I don't really regard petroleum, synthetic or fossil, as an acceptable fuel. It is way too dangerous.

laws vary across the world.

the majority of the world's countries are
exempt from Kyoto limits

I confess to being a complete nuggins at chemistry, but I think a couple of E/E regulars have a fairly good background...

If it's anything like coking leftovers, it'll involve a plethora or cyantes, ammonia compounds, heavy metals and other shit I can't even pronounce: To what extent these can be catalysed/degraded, and what would end up in a big pit of unpleasantness, would certainly be didatic...

Why is it that you regard only the radioactive components of coal as the most dangerous?

It happens that coal burning releases large amounts of radioactivity, but this is by no means the most serious toxicity problem with coal.

Coal contains a plethora of contaminants, of which only a few are radioactive, uranium, thorium and their decay products. The amount of elements like lead, cadmium, and mercury are far more toxic. In addition there are vast amounts of sulfur. Most means of disposing of this sulfur will ultimately (in our oxidizing atmosphere) end up as sulfuric acid. This is not a good thing.

In answer to your question about potential removal of these contaminants I would note some very important issues that you are missing. First, the contaminants are dilute. When coal plants release metric ton quantities of mercury, or for that matter, uranium, they are fine aerosols contained in far greater metric ton quantities of ash. The concentration of these poisons takes place by leaching from water flows and, ultimately, uptake by living material in the food chain.

The "clean coal" marketing campaign talks about things like scrubbers and the like, and electrostatic ash traps, but what they don't tell you is that there is no way that these processes are 100% effective and even if they were you still have to dispose of whatever you may trap somewhere. Suppose you captured all of the mercury contained in coal. Where do you put it?

Removal of these contaminants from vast quantities of waste requires energy, lots of it. Because the energy density (the amount of energy released per unit mass) is relatively low, you are talking about the processing (and ultimate disposal) of billions of tons of material, every year.

That's the biggest "oops!" I've made in some time.

I'm so accustomed to thinking of "hydrocarbons" that it completely slipped my mind that radioisotopes are not the only dangerous non-hydrocarbon components of coal, oil, etc. -- and not as a product of the machine age, but the Carboniferous. If you didn't occasionally point out that there were trace amounts of radioisotopes in coal, I'd probably have filed that piece of information away deep in the back of my mind, as well.

I've certainly heard of mercury, cadmium, lead, and other metals as poisons (among other things), but mainly involved with water pollution, such as the Minamata disaster and Itai-Itai syndrome. And I've read before that coal contains such "natural" pollutants.

It brings up another problem -- the problems that we're unaware of just from inattention. I'm a random wise-ass who reads a lot of stuff on-line; not the sharpest knife in the drawer, but occasionally well-informed. How much have our leaders overlooked the same way I did? Even if the answer is "much, much less", the possibility still exists that there's enough left to fill a large economy sized can of whoop-ass.

--p!