David Scott's Thoughts
The following are topics not covered in David's responses to BLOG contributions.
One of my great pleasures comes from Smelling Land readers who take the time to contact me and, as becomes clear from what they say, have carefully read the book. For example, when a reader finds an error in a relatively obscure part of the book like an appendix. After my first, stop-breathing-for-a-moment of embarrassment, I realize that somewhere out there Smelling Land has found another careful editor.
After the Enhanced Edition was released, I received this kind of thoughtful input from several readers. So I spoke with my publisher, Vern Burkhardt, of QP Publications, suggesting we include an “addendum” with corrections that could be placed in each book from then on. But Vern—and others—thought an addendum would be off-putting to most readers, so I was persuaded to leave it.
I now realize I have the chance to bail out of these embarrassments via this website.
- Figure 36.3, p. 347 of the Enhanced Edition: This figure was to be a time-stretched repeat of Figure 36.2. But somehow the electronic conversion caused the curves of Slave Renewables and Liberated Renewables to go nutty. Please pay attention only to Figure 36.2.
- P.454, 1st paragraph of Appendix B: In the 1st line “increase” should be “decrease,” and in the 5th line “voltage” should read “current.”
The next printing of Smelling Land—to be released in late spring of 2009—will correct these annoying errors. I may also add another Appendix or two. And, because I can’t resist, with this next printing I’ll take another shot at getting the words right—and perhaps adding, or subtracting, or clarifying a sentence or two.
As your broker might say, “Please bear with me.”
On Carbon Capture and Sequestration
During the US election evening of November 4, “Clean coal”—the oxymoronic slogan of the coal lobby—ran across TV screens as the results tumbled in. The irony was palpable. Here was America entering a new era of political promise, while the coal lobby was clawing at its receding past.
“Cleaner coal,” maybe! “Clean coal,” a mission-impossible hoax!
Worldwide, the coal lobby and their fossil fuel siblings are foisting this kind of nonsense—implying we can move to an environmentally sustainable fossil-fuels-forever future by using carbon capture and sequestration (CC&S).
Fortunately, some have pointed out that CC&S will be much more difficult and expensive than many proponents claim. Still, because the resource industries and many governments are pushing CC&S, I’m afraid it will die a long, lingering, expensive death.
The motivation for CC&S is to continue using fossil sources without sending significant CO2 into the atmosphere. In the case of coal, the primary market target is electricity generation.
The following thoughts are intended to provide a context against which CC&S proposals can be tested—before they receive massive public funding.
- The most important observation: CC&S cannot eliminate CO2 emissions from free-range transportation vehicles like airplanes, ships, cars and trucks. How can we catch and sequester the CO2 from a Boeing 737 flying at 33,000 feet? How do we capture CO2 from our car’s tailpipe? CC&S technologies can only be used for stationary applications. For free-range transportation, the sole route is via hydrogen manufactured from water using sustainable, non-carbon sources.
- It’s not C we must sequester, it’s CO2: In his book, Consilience, E. O. Wilson cites a Chinese proverb, “The first step to wisdom is to get things by their right names.” For energy planning, neglecting this advice has repeatedly led to misadventure. So we must remember: It’s NOT carbon that must be captured, it’s carbon dioxide. And that makes a huge difference.
This distinction may seem obvious. Yet the choice of words like “carbon capture,” rather than “carbon dioxide capture” can mislead public understanding. If we were to sequester carbon only, we’d first need to rip the carbon out from the CO2. This would require more energy than was released when oxidizing the carbon to get useful energy in the first place. It’s CO2 that we must capture and sequester, not just C.
- If we want zero-CO2 emission electricity generation, why struggle with CC&S when nuclear power awaits? The coal lobby argues for continuing coal-fired electricity generation, using CC&S as a prophylactic against CO2 emissions. But if we want CO2-free electricity generation we have nuclear power plants—which are an excellent alternative to coal-fired stations. For environmental gentility, nuclear wins hands down. And beyond its environmental benefits, nuclear power has many advantages over coal-fired plants. These including cost, especially if we include the capital and the operating and maintenance costs of coal-fired CC&S.
After Smelling Land was released, I came to recognize how persistently the coal lobby was promoting the CC&S “solution”—and, remarkably, expecting taxpayers to pay development costs.
So I decided to look at the mass of material we would need to sequester. By using atomic weights and some simple arithmetic, the mass of CO2 emitted compared with mass of fossil fuel burned is easily calculated. To do the analysis, I used the median of the H/C ratios set out in Smelling Land, chapter 34, “Tethers and Transition Tactics.” (Please note that expressions like CH1.85 are intended to give H/C ratios—and are not molecular formulae.)
To compare the mass of CO2 emissions with the mass of fossil fuels burned, we have:
- Carbon dioxide, CO2 = 12 + 16 + 16 = 44, for a “comparative mass” of 44.
- Typical crude oil ~ CH1.85 = 12 + 1.85 x 1, for a “comparative mass” of 13.85.
- Typical Athabasca bitumen ~ CH1.5 = 12 + 1.5 x 1, for a “comparative mass” of 13.5.
- Typical coal composition ~ CH0.8 = 12 + 0.8 x1, for a “comparative mass” of 12.08.
Observation 1: Whether we burn crude oil, bitumen or coal, the resulting CO2 produced is more than three times the mass of the fossil source itself.
Observation 2: CO2 is a gas while crude oil is a liquid and coal a solid. It's not possible to squeeze a gas having more than three times the mass of the original fuel into the volume the fuel originally occupied.
Observation 3: Some claim we can escape the huge volumes of gaseous CO2 by converting CO2 into rock. If this approach were followed, I suspect one of the promising “rocks” would be limestone (CaCO3). After all, this is how Nature has sequestered CO2 over the ages. Using the same “accounting” as we did for CO2 we have,
- Limestone CaCO3 = 40 + 12 + 16 + 16 + 16, for a “comparative mass” of 100.
This means the mass of rock will be between seven and eight times the mass of the original fossil sources.
Visualizing the amount of rock needed to sequester CO2
Can you imagine a world where every train delivering coal to a coal-fired generating station resulted in eight trains leaving the station to haul away the waste-product rock? (Because the density of rock is greater than coal, you might suggest we’d need somewhat fewer rock-loaded trains. But I doubt it, because the capacity of tonnage railcars is not limited by volume, but rather by tons per axle.)
Some have challenged my dismissal of CC&S saying, for instance, that CO2 is already being sequestered and used for such processes as tertiary oil recovery. Of course, this process has been used for decades. But the issue is not whether CO2 can be used for tertiary oil recovery. Rather, the issue is, compared with amounts released from burning fossil fuels, how much can be absorbed by this and other industrial CO2 processes. Moreover, where do we think the CO2 injected for tertiary recovery ends up? Eventually, the CO2-permeated crude will be pumped out of the ground.
Comparative masses are not the only issue
This bit of arithmetic shows comparative masses. Although these numbers alone should be damning to CC&S proposals, they are not the end of the story.
Before we can sequester, we must first capture the CO2. This requires extracting CO2 from flue gases that are overwhelmingly composed of nitrogen with some water vapor, bits of fly-ash and non-combustibles. Extracting the CO2 (gas separation) from these flue gases will be both energy- and capital-intensive.
And then we must find somewhere to store the stuff.
In spite of these realities, I expect many billions will be spent on CC&S demonstrations—mostly funded by taxpayers—until people reluctantly give up. The big spenders will still feel smug because they gave it their “best shot.” Yet a bit of simple arithmetic could save a lot of dollars from being wasted on doomed “best shots”—or the money could be applied to technologies with a chance of real payback, or to paying down national debts.
Too often exotic, technically-demanding strategies are undertaken without first asking the overarching, systemic questions. Sometimes simple numbers give the most revealing answers.
As Smelling Land observed, it’s almost always better to change the process and stop making a pollutant than to add collectors to catch the pollutant.
To evaluate the volume of limestone (CaCO3) produced from “sequestering” the CO2 effluent from burning coal, we need to know the mass densities of coal and limestone. CaCO3 density is about 2.71 gm/cm3. Coal (anthracite) is about 1.35 gm/cm3 while coal (bituminous) is about 1.25 gm/cm3. Then we must evaluate the void fraction of crushed rock and coal to get the total volumes. This goes far beyond what I’d intended in calculating the simple mass ratios.
Injecting CO2 increases the crude oil’s volume and decreases its viscosity.