The following is a slightly modified version of an essay that I posted to The Oil Drum .
I have stated on several occasions that I believe global warming is a greater immediate threat than Peak Oil. As long as the demand is there, energy companies will strive to supply fuel to the marketplace. To meet the demand, we will develop tar sands, while consuming enormous quantities of natural gas. We will turn natural gas (or even coal) indirectly (and inefficiently) into ethanol. Finally, we will turn vast quantities of carbon into fuel via what I term “XTL” technologies. XTL technologies consist of a partial oxidation (POX) reaction followed by the Fischer-Tropsch (FT) reaction. When the POX feedstock is natural gas, this is referred to as a gas-to-liquids (GTL) process. If the feedstock is coal or biomass, this is referred to as CTL, or BTL respectively.
I won’t go into a detailed explanation of the POX and FT reactions. What I will give is a quick, layman’s overview. When a hydrocarbon material is burned (e.g. natural gas, coal, biomass, etc.), it can be completely oxidized (combusted) to carbon dioxide and water, or it can be partially oxidized to carbon monoxide and hydrogen. The latter POX reaction is accomplished by restricting the amount of oxygen during the combustion, and it is a potentially deadly reaction should it inadvertently occur inside your home. The resulting mixture of carbon monoxide and hydrogen is called synthesis gas (syngas) and can be used in the manufacture of an abundance of organic compounds.
The FT reaction is a bit more complex than the POX reaction. You can find in-depth information on the FT reaction here. In short, the FT reaction converts syngas generated via the POX reaction into a distribution of long-chain hydrocarbons. Hydrocarbons in the diesel fuel range are very common, making this reaction an ideal way to extend the fossil fuel economy.
At present, the economics for GTL are far more favorable than for CTL or BTL. There are enormous reserves of natural gas throughout the world. Worldwide reserves of natural gas are estimated to be 6,200 trillion cubic feet, of which 3,000 trillion cubic feet are estimated to be stranded. (Reserves are considered to be stranded if it is uneconomical or impractical to get them to market.) This is enough stranded natural gas to produce 300 billion barrels of fuel, according to Syntroleum (Warning: It’s a 3.4 meg PDF).
GTL is not a pipe dream. The process is technically viable, having been demonstrated on numerous occasions. It is economically viable depending on the price spread between natural gas and oil. Despite the fact that the capital costs for GTL plants are approximately twice those of conventional oil refineries, a number of projects have been announced in Qatar. Plants are being built, and the fuel produced will help supply some of the shortfall that Peak Oil will generate.
Of course there is a catch. GTL is not all that efficient. There are efficiency losses during both the POX and the FT processes. It would be far more efficient to run automobiles directly on the natural gas. Due to the fact that the gas is stranded, this is obviously not an option. But the efficiency losses are significant. According to the Syntroleum link, it takes 10,000 cubic feet of gas to make 1 barrel of fuel. 10,000 cubic feet of natural gas contain roughly 10 million BTUs, but a barrel of fuel contains only around 5.5-6 million BTUs. Forty percent of the BTUs are either lost as radiant heat, or turned to steam and consumed in the GTL plant. Unless carbon sequestration is in place (unlikely), all of those BTUs ended up as carbon dioxide in the atmosphere. On top of that, the BTUs from the barrel of fuel are going to end up as carbon dioxide in the atmosphere once the fuel is burned in an engine.
The reason I find this more worrisome than Peak Oil is that I believe this path is inevitable, yet the consequences are unpredictable. We will make and use GTL fuel, as inefficient as it may be. Our carbon dioxide emissions are likely to accelerate in our quest to maintain affordable energy. As stranded gas supplies are consumed and GTL production peaks, there is CTL, with the same efficiency problems, waiting in the wings. From my view, the fossil fuel economy will be with us for a long time to come.
Look at the figure below, and think of the experiment we are conducting. Atmospheric carbon dioxide levels are at their highest levels in human history. The trend in the graph shows a linear increase in atmospheric levels. The trend didn’t deviate at all during the oil shocks of the 70’s.
Source: National Oceanic & Atmospheric Administration
I believe I can see the foresee the consequences of Peak Oil. It certainly won’t be a picnic. But I think I can plan for it, and I believe that we will eventually adjust to a post-oil world. But I can’t foresee the consequences of warming the earth up by 5 or 10 degrees C. Humanity has never had to deal with this problem. The Sahara Desert was once lush with vegetation and teemed with wildlife. Consider the impact if this is the fate of the Corn Belt of the Midwest. Yet I see nothing to indicate that we are going to veer from the course we have set.
9 thoughts on “XTL: Promise and Peril”
Promised, over at TOD, to give my comments on your piece at Omninerd. To be sure your read it I post it here.
I think it’s a good piece, mainly because it is brief and clear, and shows at present there is not really an alternative. I doubt however if it is an entirely good introduction for the unaware, or laymen. This is because, IMO, there is not enough emphasis on the geological aspect. I’m afraid it will cause reactions to problem like my brothers’ when I explained PO:”Then w’ll just drill more”. And it is, like so many pieces on energy in general, focussing on transportation (though you do mention food production), where we depend on oil for so much more.
Sorry, RR. Forget to identify myself as TODer PaulusP.
I find this meme that gas-to-liquids will rescue stranded gas dubious. There’s all these limits pockets of gas located far from civilization that would be prohibitively expensive to build a pipeline to, check. But the next logical jump is a bridge too far.
Building a GTL refinery on-site and then, what, trucking oil back to civilization is going to be cheaper?
I think you’re right that GTL isn’t a pipe dream, it’s a pipeless dream.
There’s all these limits pockets of gas located far from civilization that would be prohibitively expensive to build a pipeline to, check. But the next logical jump is a bridge too far.
I dug up an old map yesterday using the Wayback Machine that shows the locations of the stranded reserves:
Stranded Gas Reserves
Each of those dots represents 25 trillion cubic feet of gas. Remember also that “stranded” may mean there is no market for the gas in the area, but there may be a market for the middle distillates that can be created from the gas. And companies are building GTL plants. They have determined that the economics support it, and there is enough gas to make a lot of fuel.
Remember also that “stranded” may mean there is no market for the gas in the area, but there may be a market for the middle distillates that can be created from the gas.
Well, if worse comes to worser, we can always build a fertilizer plant near one of those “stranded” pockets of gas, and then truck the fertilizer to Midwest corn farmers, who can use it to grow more corn to make more ethanol. 😉
Thank you for a excellent site and an excellent post. Reur comment, regarding ” the consequences of warming the earth up by 5 or 10 degrees C. …..I see nothing to indicate that we are going to veer from the course we have set.” I couldn’t agree more with your concern and your conclusion. Retired 10 years ago after 30+ years in the oil refining business. Peak oil, IMHO is a reality and a priceless opportunity for humanity to break the addiction to carbon based fuels…..however I am much, much more concerned about the consequences of global warming…..I think the effects will take place much sooner than is generally being predicted negatively impacting the inhabitability of large areas of the planet. The recent PBS piece on global dimming (google nova “global dimming”) convinced me of the immediacy of the problem. I strugggle to understand how our political institutions are going to even begin to address this in time.
Keep up your good work and commentary.
…however I am much, much more concerned about the consequences of global warming…..I think the effects will take place much sooner than is generally being predicted negatively impacting the inhabitability of large areas of the planet.
When thinking about global warming, you have to take the long view. The heating and cooling of the Earth and its atmosphere operates in long, natural cycles we can’t even begin to understand; and the time man has been on Earth represents only a very small bit of overall geologic time:
* There have been times in the past when it’s been both warmer and cooler than it is now.
* There will be times in the future when it will be warmer and cooler than it is now.
* And in five billion years or so, the Sun will expand to a diameter extending past the orbit of the Earth. And when that happens — it’s really going to be warm.
Knowing that the world is going to end in a few billion years does not mean that we should continue actions which will destroy much of what we enjoy in the next hundred.
Engineer Poet said, “Knowing that the world is going to end in a few billion years does not mean that we should continue actions which will destroy much of what we enjoy in the next hundred.”
Global warming is a fact. It’s also a fact that there was global warming and global cooling long before man walked on the Earth. There will also be global warming and global cooling long after we are gone.
Global warming and global cooling work in great, long, natural cycles that we can neither understand nor control.
We–as humans–are making global warming worse now, but we are also a necessary part of those natural cycles. In the span of all geological time, the span of human existence on the Earth and in the Solar System will be an infinitesimal fraction.
My main point is that global warming and cooling are all part of self-correcting phenomena and natural processes. If we screw it up and make it so warm that the Earth becomes uninhabitable, those natural cycles will exert their control as they’ve always done. We will die off and all the carbon dioxide we released will once more be captured by organic plants and turned into fossil fuels for the next cycle of human life in 75 or 100 million years.
Who knows, as that next cycle of human life starts, they will probably think it is too cold because all of the carbon dioxide will have been sequestered by the algae, plankton, giant ferns, and huge trees and there will be no green house gases in the atmosphere to hold the Sun’s heat in.
As I said, you have to take the long view. 😉
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