Naked Science Forum
Life Sciences => The Environment => Topic started by: John Chapman on 24/12/2008 16:01:00
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John Chapman asked the Naked Scientists:
Hello Chris
I listened to a fascinating article of yours on a podcast from Australia's RN Breakfast show on 14 Nov. It was about the use of Magnesium Silicate (Olivine) as a method of carbon sequestration. It is a subject so important I wonder if you would consider making a more in-depth report for The Naked Scientist. Your RN article left me with many questions unanswered and I would like to know how exploitable this reaction is domestically. For instance:
1) You said the carbon-grabbing reaction is exothermic. How much heat does it produce? Will I one day be buying bottles of CO2 for my Olivine heater in the same way that I might buy bottles of butane for my gas heater?
2) Could I fit a filter of crushed olivine to the flue of my gas boiler so that it absorbs all the CO2 and at the same time produces a second lot of heat? Could I then also vent the exhaust directly into my living room to receive a third lot of heat? After all, the the crushed olivine should have removed all the CO2 and any particulates. This would be an incredibly efficient and economical way to burn gas as well as being carbon neutral.
3) Some time ago I remember you talking to Dave about a material that when heated produced electricity. I think you suggested it would be a good way to exploit the wasted heat from car engines. Could this material be mixed with the magnesium silicate and used to convert CO2 directly into electricity?
Finally,
4) Why have I never heard of this before? Why are newspapers around the world not running headlines like 'Global Warming Cured' and 'Planet Saved'? Can I now turn my heating back up and leave the light on when I leave the room?
url=http://www.thenakedscientists.com/HTML/podcasts/]I think The Naked Scientists is a fantastic program[/url] and has changed my outlook on the world. Since listening to your podcast I have gained confidence, learned how to win friends and influence people; I can now look bullyboys boldly in the eye; I've grown an extra three inches and what's more I'm taller. And now I'm going to develop the Olivine heater and filter, make millions of pounds, save the planet and rule the world. I won't forget that you and the BBC helped me to get there. And I've not even paid my license fee!
All the best,
John Chapman
What do you think?
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Hello John
Where can one get olivine ? if its true then how are you getting on and I am very interested its probably too easy but it sounds good ,I would still like to try it
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Olivine is one of the most plentiful minerals on earth. Chemically, it is magnesium silicate and is what most of the mantle is made from.
I wasn't expecting this question to be posted as a blog and it is probably meaningless to anyone who hasn't heard the podcast I referred to. So I'll try to paraphrase the report as I (now a little vaguely) remember it.
Scientists have known for some time that in geological periods immediately following the creation of mountain ranges the level of CO2 in the atmosphere drops significantly. This is because plate tectonics (or continental drift) which creates these mountains does so by pushing hot magma through the crust and exposing it to the atmosphere. Magnesium Silicate has an incredible affinity with CO2. It requires heat to kick start the reaction but, after that, it is exothermic and fuels itself. It will keep going until either the Olivine or the CO2 runs out. To give you an idea of how powerful this affinity is, it is estimated that 1 cubic kilometer of olivine is capable of removing an amazing 4 billion tons of CO2. When you consider that gasious CO2 is around 1000 larger in volume than liquid (or solid) CO2 then the volume of gaseous CO2 capable of being held by 1 cubic km of Olivine is quite unbelievable.
Going back to the mountain ranges, what I think happens is that the surface of the mountain combines with the CO2 to produce magnesium carbonate and silicon dioxide. Silicon dioxide is a grainy quartz and is, to all intents and purposes, sand. This allows the newly reacted surface to be permeable to air (and therefore CO2) allowing the underlying rock to further react until the new sandy crust is so thick that air cannot permeate. Plants then colonize, adding organic material and the crust becomes soil. If this reacted crust was, say, 6 inches deep then the whole surface of an entire mountain would comprise many, many cubic kilometers of reacted olivine. Then consider an entire range of mountains and it is not hard to understand how the production of the mountains significantly affects atmospheric CO2 levels.
To put it further into context, the whole of mankind produces around 30 billion tons of CO2 each year. So if 1 kilometer of olivine could be encouraged to fully combine with CO2 every 6 or 7 weeks it would completely wipe out man's entire CO2 production!
The report largely comprised an interview with Peter Kelemen from the University of Columbia who was suggesting that heavy industry, such as new coal burning power stations could be built on olivine fields. Their CO2 could be pumped down directly into the bedrock, never to see the light of day.
Since hearing this report, I have heard another similar one on Naked Scientist's 'Breaking Science News'. Listen to the show at http://www.open2.net/breakingscience/clones_bacteria_dalmations.html (http://www.open2.net/breakingscience/clones_bacteria_dalmations.html). In this report Peter Keleman suggested that once kick started the reaction would produce temperatures of around 185 degrees C. But neither report suggested that this reaction might be exploitable as a source of heat or for either carbon sequestration or heat production domestically. Hence the question above.
By the way, I have now emailed Peter Keleman to pester him and will post his reply if it is forthcoming.
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I wonder if we really want to tie up a lot of CO2 like that. Plants need CO2, and the plankton convert CO2 to oxygen. Maybe if we bind up the CO2 we might be creating something we can't reverse.
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Hi Vern
I'm not sure I understand your reply. I take it you're not suggesting that the present level of CO2 is a good thing? (Apart from agricultural monocultures I'm don't think there's an awful lot of flora left on the planet to enjoy the increased levels, ha ha). Anyway, it's the subject for a different discussion and I could be wrong but my belief is that it is largely a fallacy that plants always 'breath in' oxygen and 'breath out' CO2.
I think most people would agree that we have already created a situation we can't reverse. Any action now is purely damage limitations.
Are you concerned that my grand plan to save the world might work too well and leave us short of CO2? Or are you just trying to put the cat among the pigeons in an attempt to encourage debate?
I've no idea what the consequences would be if we actually had too little CO2. What do you think? I certainly agree that tinkering with the environment is very dangerous, even if it is an attempt to put right our mistakes form previous tinkerings. My old Nan always used to say ' if you've dug yourself into a hole, stop digging'. Mind you she also thought she was an alien at one point, so who knows!
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Are you concerned that my grand plan to save the world might work too well and leave us short of CO2? Or are you just trying to put the cat among the pigeons in an attempt to encourage debate?
Yes; I would be concerned; no I am not Trolling[:)]
All of the carbon that's in the ground was once in the air and plants came along. The plants created an oxygen rich atmosphere that could then support animals. The system never was really stable; I think the animals have been gaining all along.
I'm not convinced that all climate change is necessarily bad. And if the past is a measure, we tend to over estimate the effect by about an order of magnitude.
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I have just received a reply from Prof Peter Keleman from the University of Columbia. He is the guy interviewed by Chris Smith who's paper started this discussion. I asked him sililar questions to thoses in the first post of this thread. Here are his answers:
Hello John,
Thanks for your interest in our work. Here are some quick answers to your questions:
1) You said the carbon-grabbing reaction is exothermic. How much heat does it produce?
for Mg2SiO4 + 2CO2 = 2MgCO3 + SiO2, 760 kJ/kg olivine carbonated
Might I one day be buying bottles of CO2 for my Olivine heater in the same way that I might buy bottles of butane for my gas heater?
not until you run out of gas, and wood, and coal, and a few other more efficient fuels, some "renewable", some not
2) Could I fit a filter of crushed olivine to the flue of my gas boiler so that it absorbs all the CO2 and at the same time produces a second lot of heat?
anything like this needs to produce more Joules/s than you lose via diffusion of heat and any advection (gas flow, ...); there are engineering approaches to this problem, they are cited in our paper in the context of "ex situ" mineral carbonation, and carbonation "at the smokestack"
3) Could a similar filter be incorporated into the air conditioning systems of tall office blocks to both remove CO2 and add heat to the air?
as for (2)
4) Why have I never heard of this before? Why are newspapers around the world not running headlines like 'Global Warming Cured' and 'Planet Saved'? Can I now turn my heating back up and leave the lights on when I leave the room?
As we state in our paper, this is a hypothesis at the moment, not tested let alone implemented on an industrial scale. In particular, the chance of filling pore space with reaction products and lowering permeability to unacceptable levels, and or coating all fresh olivine surfaces with a carbonate reaction rim that limits total reaction rate via slow solid diffusion, are potential negative feedbacks. We anticipate that there may be solutions to these possible problems, but until we run field tests ... don't turn your heating up.
In addition, note that there are issues with transporting CO2 to the potential peridotite storage sites, and that involving a cubic km of rock to sequester billions of tons of CO2 per year involves a huge industrial infrastructure that would not be free. We hope that a carbon credit system will be developed, facilitating this and other projects, but all will have to compete with each other to see which is most efficient, verifiable, safe, ... and all will involve additional expenditure per kW/hr of fossil fuel energy you use, so you'll maybe want to keep the thermostat low on that basis.
Can I start thinking about the possibility of developing the use of olivine domestically or have I got the wrong end of the stick?
hard to judge, and we should all be pursuing options in parallel since the future is by no means clear, but you probably have the wrong end of the stick; again, see work on ex situ mineral carbonation, perhaps starting with IPCC report on this subject by Mazzotti et al.
So it seems like I may not save the world with this one. Although I'm not licked yet.
His paper was published in the PNAS (Proceedings of the National Academy of Sciences) (see http://www.pnas.org/content/105/45/17295.full.pdf+html?sid=b55ce52b-d559-4d81-bd6d-4d4e1f475d7b ) Do any of you academics here have access to a PNAS account or know how I can get to see this paper?
Peter also suggested reading the IPCC (Intergovernmental Panel on Climate Change) report by Mazzotti et al which I think is this one http://www.ipcc.ch/pdf/special-reports/srccs/srccs_chapter7.pdf and forms chapter seven of the larger report "Carbon Dioxide Capture and Storage". See http://www.ipcc.ch/ipccreports/srccs.htm
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Keep up the good work son!
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This is fascinating stuff. Does anyone know what 760kJ/kg equates to in everyday language?
Might I one day be buying bottles of CO2 for my Olivine heater in the same way that I might buy bottles of butane for my gas heater?
not until you run out of gas, and wood, and coal, and a few other more efficient fuels, some "renewable", some not
2) Could I fit a filter of crushed olivine to the flue of my gas boiler so that it absorbs all the CO2 and at the same time produces a second lot of heat?
anything like this needs to produce more Joules/s than you lose via diffusion of heat and any advection (gas flow, ...); there are engineering approaches to this problem, they are cited in our paper in the context of "ex situ" mineral carbonation, and carbonation "at the smokestack"
John you said before that the reaction will generate 180 degrees C. If so, why do you think Prof Keleman feels this is not exploitable as a domestic source of heat. Ground Source Heat Pumps will heat a house grabbing background heat from an ambient temperature difference of around 10 degrees. If a domestic unit was sat in your house then I don't understand why heat loss from diffusion through the unit would be relevent.
I would like to have a play around with some of this olivine. I have access to industrial CO2. I was thinking that the CO2 could be heated initially by passing it through a decorators hot air gun and forced through a column of olivine (crushed to increase surface area) until the reaction becomes self sustaining. If it is such a common mineral then it can't be that difficult to get hold of a few kilos. I wonder if it occurs anywhere naturally within travelling distance of London. Any geologists out there who know where I can get some?
I took a quick look at the IPCC report the Prof suggested and it will make interesting reading over the weekend. I would really like to read his paper, especially the part about "ex situ" mineral carbonation.
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Hi Geek on the Edge
Professor Keleman has kindly sent me a pdf copy of his paper called "In Situ Carbonation of Peridotite for CO2 Storage". (Peridotite is an igneous rock comprising mainly olivine).
If anyone would a copy email or pm me your email address and I'll forward it.