The recycling of carbon dioxide through Calcium Carbonation cycles studied.

[NNadir]

It's my time of the month: Reports on articles from Energy and Fuels.

Those who are familiar with my posts will recognize that I am no fan of coal energy - or any fossil fuels - but the focus of this paper, although it mentions coal, has long been of interest to me, since I am interested in any means that captures and concentrates carbon dioxide for possible use as a carbon source.

The abstract:

"The use of carbonation/calcination cycles of CaO/CaCO3 is emerging as a viable technique for the capture of CO2 generated in the combustion of coals for power generation. Specifically, the
choice of natural limestones as CO2 carriers is an attractive option because they are cheap and abundant materials, although previous studies indicate that the reactivity of the calcines toward
CO2 rapidly drops with cycling. This paper reports on the effects of the internal morphology of CaO particles on their capability of absorbing CO2. Calcines of a natural limestone with different
initial textures were repeatedly submitted to Carbonation/calcination conditions (up to 100 cycles).
The textural evolution, as well as the carbonation conversion, of the calcined and recarbonated samples was followed along the experiments. In addition to the known mechanisms of deactivation
due to grain growth and limited diffusion of CO2 through the product layer, we have found that pore closure is also taking place in our samples, together with an overall shrinkage of the particle.
All of these factors play a role in limiting the maximum carbonation conversions to around 10% after just 100 cycles."

This article reports on the nature of an important problem with using CaO to capture CO2, but such analysis helps illuminate the path to a means of solution.

From this coming month's Energy and Fuels.

[phantom power]

1. I assume there would be some way of "recharging" CaO?

[NNadir]

2. Yes, heating it. This drives off the CO2.

In this case, the carbon dioxide is not permanently sequestered; it simply becomes available for synthetic purposes. If the synthetic product is a polymer however, the carbon dioxide is sequestered. If however, the carbon dioxide is used to make a synthetic fuel, then a carbon cycle is established.

My view is that cyclic processes are the most environmentally benign. The model for such cyclic processes is nature itself.

That is the point of the paper. Continuous heating (decarbonation) and recarbonation changes the physical properties (pore size, surface area, etc) so that the mass efficiency of carbon dioxide recovery falls unacceptably low.

Note that like the so called "hydrogen economy" this is not a means of creating energy but is part of a means of storing it. This system requires an energy input, and a significant one at that.

[phantom power]

3. Any sustainable energy economy will require large new sources of

energy to drive the cycle (which ever cycle we end up using). I think that means we ought to start deploying new energy sources immediately. If not sooner.

I wonder if we will. I don't see a lot of urgency, outside of a few forward-thinking people such as yourself.

[NNadir]

4. I'd go nuts without "Energy and Fuels." Many of the scientists in this

journal are thinking seriously about the future. The reason I am subscribing to this journal, reading it and now, increasingly, reporting it here it to drive away the sense of hopelessness.

We in the United States live an increasingly rarefied and, frankly, hallucinatory world. Still even in this depressing insane asylum we call a nation, there are people who know what needs to be done. Almost all of the articles in Energy and Fuels that are not about the chemistry of coal and oil are written by such people. (Most of the people, however, who are not writing in Energy and Fuels about coal and oil live in remotely sane countries as opposed to the United States.)

Very little of what I write here is particularly original with the exception of some esoteric nuclear stuff.

Politically we in the United States will have to manage on the basis of catastrophe, and we are no means alone in the world in this regard, but there are countries that are carefully planning for the future, and the future will belong, justifiably, to them.

[AZCat]

5. Here's the link to the e-version and some subscription info

Since you think so highly of this journal, I am linking to the homepage of the journal and providing some subscription information (both web and hardcopy) for people who might also be interested in reading these articles.

The homepage is here: Energy and Fuels

According to their subscription page, Energy and Fuels 2005 (Vol 19, 6 issues) prices are:
Web Editions: $30
Web Archives: $30
North American Print Editions: $160
North American Print Editions (Student Rate): $120
Outside N.A. Print Editions: $199
Outside N.A. Print Editions (Student Rate): $159

Thirty bucks isn't bad, if you have any cash to spend. I won't until mid-January, but I think I might add this to my list of subscriptions. It's slightly out of my area, but aren't we all better off if we work to increase our knowledge of other areas?

[NNadir]

6. Thanx. I should have done that. The prices you posted are member rates.

It's a very good journal giving chemical perspectives on an important topic.

We are all indeed better off with broader knowledge, though the value of knowledge is eroding in the age of Bush. As it happens - though I'm not necessarily happy about it - I'm not in the energy business either.

[phantom power]

7. What if we did get into the energy business?

In the sense of trying to influence public energy policy? Is anybody out there trying to drum up support for one of these sustainable fuel cycle economies (besides H2)?

I don't see why we couldn't get the oil companies behind it. When I think of actually building industrial-scale fuel manufacturing plants, say DME, or what-have-you, it seems as though the refinery industry would be the people with the expertise and resources to do it.

Maybe the best way to start would be at the state level. Our current federal government seems like a lost cause, for the forseable future.

Could it even work like that? Or do we have to wait for these changes to emerge out of economic necessity (managing by catastrophe)?

[Squatch]

8. Two words: Iron Hypothesis

Reduced iron + HNLC areas = increased primary production = increased inorganic C uptake.

HNLC = High Nutrient Low Chlorophyll

[NickB79]

9. Is this the same as ocean seeding to stimulate plankton growth?

Last I read, that hypothesis was running into some problems when real-world data showed the expected carbon sequestering didn't occur like they thought it would, and that the plankton bloom died out to rapidly.

[Squatch]

10. Stimulate phytoplankton blooms

who are responsible for a large part of the inorganic C uptake.

As it turns out, the limiting factor, sometimes, in nutrient use is the amount of FE- available to phytoplankton. In HNLC areas, nutrients are abundantly available except for FE-.

It would be a logistic nightmare, though, to seed an ocean with enough Fe- to make an appreciable difference. You would probably put more C into the atmosphere from the ships necessary to carry the iron out there than the phytoplankton could use.

Still, it's worth investigating.