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Just for anyone who's not up on what modern chemistry/biochemistry is cooking up to solve the problem of excess CO2, it might not be completely unreasonable to say we could have a way to fix massive amounts of CO2 in the next 5-10 years, assuming the powers that be are willing to throw money at the development of what has already been discovered. On the chemistry end of the spectrum, this is what I believe to be the most promising development in CO2 fixation I have ever seen: http://www.sciencemag.org/content/327/5963/313.full They do have video of it in action that they showed at a conference, and the results are simply stunning. For those without institutional access, this is a very small molecule that binds copper and forms a bond between 2 CO2 molecules making the compound Oxalate (http://en.wikipedia.org/wiki/Oxalate), which can then be turned into any of a number of useful compounds. Only uses electrons, acid, and a very easy to synthesize organic molecule. Performs millions of turnovers with 95+% efficiency, and is stable in air. There are pictures in the supplemental of the oxalate crystals formed. It's pretty amazing, and they stumbled on it completely by accident, and performed no engineering whatsoever to optimize their setup (which would help a lot with efficiency). On the biochemistry side, you have carbonic anhydrases (http://en.wikipedia.org/wiki/Carbonic_anhydrase), which will catalyze the conversion of CO2 to HCO3 using only water and a metal cofactor. They are already incredibly efficient (they are among the most efficient enzymes around, and will happily truck along at the rate of diffusion until the protein degrades - which takes a very, very long time). All that needs to be done to make them effective for carbon fixation is to optimize the pH and temperature at which they will function, which many powerplants/power companies are already contracting out to biochemistry labs to do. Since you can isolate HCO3 as a solid (baking soda!), you can simply complex it with a counterion that will prevent its re-dissolution or prevent it from coming into contact with water again (bury it underground in a lined container? Preferably both methods). Better yet would be to chemically convert it into something useful (another protein could do this, or we could use it in some sort of chemical reaction). These are things that are happening right now, and will be effective ways to fix CO2. The problem isn't so much the way as the will at this point - once there is actual urgency about climate change that reaches across political lines, there will be enough funding to solve the problem of excess CO2. You could imagine a dedicated CO2 fixation site being mated up to a power-plant (nuke, solar, wind, etc.), as well as perhaps a chemical production facility of some sort. Oxalate is tremendously useful, as is bicarbonate, in the lifecycle of microorganisms, and many will happily use these molecules as carbon sources. With a little metabolic engineering, we could convert oxalate/bicarbonate to any of a number of biofuels (not saying that organic combustibles should be our goal, but they are what get grant money...) BobTheFerret fucked around with this message at 04:55 on Dec 7, 2011 |
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Dec 7, 2011 04:45
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Pellisworth posted:
Ahh yep, my bad, that's what I was thinking when I was referring to pH optimization was bringing things into the range where you can use calcium or other ions to bring down solubility. Removing bicarbonate would be as simple as having an immobilized enzyme with a mobile reaction phase bringing in water that is not saturated with bicarbonate, while drying the saturated water product in a separate chamber (you could use seawater as you suggested, since it seems to be a great source of counterions). Recapture the water and you can have a self-contained system that only requires the addition of counterions. I'm not sure where you're thinking we're losing efficiency at if we're only going to bicarbonate (other than the issue of heat for evaporation...) - CO2(g) -> HCO3(aq) is just enzymatically accelerated, and pairing with a counterion isn't an energetically demanding process. The biggest issue with bicarbonate is having to dry it to take it out of the system, but if you use something like a nuclear powerplant (where excess heat is always an issue), it seems a bit more feasible. As well, most other plant designs (coal and natural gas) use turbines, which have plenty of waste heat that could be used. CO2 fixation using enzymes is a big DOE project right now, and grant proposals have been written that would use carbonic anhydrase (example: http://www.netl.doe.gov/publications/proceedings/01/carbon_seq/5a5.pdf - first one that came up in google). The lab I work in currently (not the one in the pdf) is a potential recipient of the money, so it's a project close to my own heart. I know that resources are limited in ocean water, but zinc is pretty easy to come by terestrially (and we're definitely interested in exotic metals to do this, as they may be faster than Zn). What we'd ideally like to do generate bicarbonate with one enzyme, and then deprotonate bicarb in another and bind it to calcium or another ion to make a poorly soluble product like lime (or ideally do CO2 -> HCO3 -> CO3 -> CaCO3 all in one protein, which might be possible). Or, of course, we could take HCO3 generated in the CA and perform some other C-C bond-forming reaction, which would be ideal (but a bit harder). There are candidates for this, since bicarbonate is the product of lactate decomposition for example, and anabolic pathways in other organisms can take us in the opposite direction and incorporate HCO3 into energetic molecules. BobTheFerret fucked around with this message at 05:37 on Dec 7, 2011 |
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Dec 7, 2011 05:35
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Pellisworth posted:
The mechanism is pretty cool - it's literally direct bond formation between two bound CO2 molecules by formation of a CO2- radical. Uses only 4 electrons. HCl is not hard to get, but is actually not needed (they also use LiClO4, Li+ as a counterion), and in their system, the reduction potential for the bond-forming step is -0.03V vs. NHE (hydrogen electrode), which is damned good. Their mechanism using Li+ counterion actually allows them to recover all counterion, meaning that they only end up using electrons in the reaction. Here's a picture of the reaction mechanism for any interested parties. It's amazingly simple:  I'm not handwaving away the energy requirement at all in my original post - that's what I see as being the main issue. We could take out tons of CO2 as it stands right now, but there has to be a willingness to spend the money on generating energy to do it (in terms of dedicated or paired fixation systems).
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Dec 7, 2011 05:50
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Fried Chicken posted:How cost effective and scalable are these methods? My understanding is that the proposed solutions either didn't pan out (iron fertilization) BobTheFerret fucked around with this message at 06:11 on Dec 7, 2011 |
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Dec 7, 2011 06:01
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Pellisworth posted:Especially if you found a CA from a thermophilic organism. Do you mean high pH (low proton concentration maybe is what you were thinking)? I wasn't sure about that in your last post. pH stability is important, but actually, the internal pH in a protein can be way different from external, so as long as we perform all steps within the protein (from CO2 to CaCO3). Hypothetically we can just use amino acid residues in the active site to deprotonate HCO3 and have a calcium ion bound nearby as well as saturating Ca2+ in solution.
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Dec 7, 2011 06:09
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I don't usually think much about practical applications of these things :P
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Office Thug posted:Just wanted to chime in to say these are impressive technologies for CO2 fixation. I especially like the electrochemical one, I've been looking for a good way to capture CO2 from the atmosphere for synthetic fuel production through fission-breeder nuclear reactors. Could this system also work in oceanic environments, like capturing CO2 from sea water solutions? I'd talked about it in a later post, but having a source of waste heat for use from nuclear or other power sources is perfect for CO2 fixation, since that heat can go towards chemistry (like what you mentioned using H2 as a source). I firmly believe that enzymatic chemistry will be the future of simple fuel production (people will always need hydrocarbons and alcohols). If you want CO2 in a usable format, Carbonic Anhydrases are the perfect candidate - there are no small-molecule or bulk catalyst systems produced by chemists that can compete with them in terms of stability and rate. You can isolate lime or baking soda to get HCO3-/CO3 2- without any electron expenditure, though understandably you'd be interested in the electrochemical system (since you have plenty of electrons to use). Since you have a simple hydrogen source from waste heat, you could just process things directly from oxalate to ethane, ethanol, or some other hydrocarbon or alcohol depending on the catalyst you use. Efficient hydrogen production can also be done enyzmatically - there are some pretty amazing proteins that will form hydrogen from protons (hydrogenases) that a few groups are trying to couple with solar cells (a nuclear reactor would work just as well though!), and some small molecule mimics from the world of inorganic chemistry that are struggling to compete. And of course you have the new cobalt-phosphate based oxygen-evolving catalyst that was recently re-discovered by Dan Nocera at MIT. Incredibly simple, it already works, and costs very little due to the high abundance of the compounds involved in its construction. Might be useful for what you do. Here's a link: http://www.ncbi.nlm.nih.gov.proxy2.library.illinois.edu/pubmed/19088970
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Dec 9, 2011 22:08
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WAFFLEHOUND posted:I read that entire paper and it doesn't conclude the way you think it does. It basically says "If any man-made fracturing is responsible for methane leakages, it has more to do with a century of unregulated extraction activites in the area" and concludes by saying fracking has bad PR but none of the evidence really supports the notion that fracking is responsible for increased concentrations. First off, I agree with you that fracking by itself should not be generalized as evil (there's a lot more dangerous ground water contamination coming from heavy metals and halogenated aromatics from manufacturing and electronics). Oil recovery over the last 100 years has probably been far worse for ground water, and contamination from that could certainly arise from the naturally occurring deadly junk good old mother earth has produced. That said, when you say something like quote:There's no groundwater contamination from fracking at all You're opening yourself up to criticism for making a conclusion which is absolutely not true. Yes, the contaminants may be pre-existing, but changes in their concentration could certainly be due to fracking. I would also agree with you that the fracking procedure is harmless if the formulations used in fracturing were readily available for public scrutiny - but I don't think we can conclude that to be the case with formulations kept a secret as they are now. Leaving the formulation unknown also makes it difficult to know what to look for when you're trying to investigate possible groundwater contamination. In my opinion, the absolute best thing a natural gas company could do under these circumstances is to add in detectable non-harmful compounds that diffuse at the same rate as possible harmful compounds they inject or recover, in order to demonstrate whether they actually are contributing in any way to ground water contamination. A radiolabeled compound would be very simple. Or a fluorophore. Go out of your way to prove your innocence - it's nothing compared to paying for studies or lawyers. But, because that is not currently done, we're reduced to arguing from a position of ignorance; I don't know if you're completely honest (I give the benefit of the doubt and say that you're informed on this topic) or shilling (the unfortunate possibility that you're informed but could possibly happen to have a vested interest in the subject...). You have no way of knowing the contents of the fracking media unless you personally work in the industry (and even then, it's not likely unless you're high up or were involved in its formulation). I really don't think you can honestly say you know for certain that there is no ground water contamination due to the media. Moreover, I wonder how much of a contribution the process of natural gas recovery accelerates the process of ground water contamination by existing formations of naturally occurring organics. If the whole idea is to increase permeability and porosity of the rock to release the natural gas contents, it certainly wouldn't be outside the realm of imagination to think that you could increase groundwater contamination by fracturing natural barriers between the organic reservoir and groundwater. What may have been only a small leak into groundwater could be turned into a flood. If folks are making the argument that fracking is harmless because the detected contaminants were already there prior to fracking, we need to focus on seeing what the process does to contaminant concentration. If you can say for certain that that stays constant throughout the process, in every case, then I would happily agree with you that fracking is harmless. But the odds of that being the case are vanishingly small... quote:Particularly with that region, I encourage you to go look at methane being reported in wells a century ago. Century(ies) old anecdotal evidence of methane in wells doesn't really provide any good evidence for your point. Yes, people have noticed the gas was there, but that doesn't tell us at all whether or not fracking has had an impact on its concentration, or even what the gas was (god knows chemistry was far from an exact science prior to 50 or 60 years ago). You definitely can't go and say that the contaminants were all there previously and that we should completely ignore the materials used in fracturing or liberated by it as a possible groundwater contamination source. Lastly, that PNAS paper definitely does not support your assertion that fracking has just had some bad PR. It suggests (as you said) that a lack of regulation in previous gas recovery resulted in contamination. The whole process is currently very poorly regulated. It is consequently very unlikely that fracking is not contributing to groundwater contamination. The authors would not suggest extensive studies of methane contamination if their work was evidence of only non-anthropogenic contamination. Here's the conclusion for those without institutional access. quote:Based on our groundwater results and the litigious nature of shale-gas extraction, we believe that long-term, coordinated sampling and monitoring of industry and private homeowners is needed. Compared to other forms of fossil-fuel extraction, hydraulic fracturing is relatively poorly regulated at the federal level. Fracturing wastes are not regulated as a hazardous waste under the Resource Conservation and Recovery Act, fracturing wells are not covered under the Safe Drinking Water Act, and only recently has the Environmental Protection Agency asked fracturing firms to voluntarily report a list of the constituents in the fracturing fluids based on the Emergency Planning and Community Right-to-Know Act. More research is also needed on the mechanism of methane contamination, the potential health consequences of methane, and establishment of baseline methane data in other locations. We believe that systematic and independent data on groundwater quality, including dissolved-gas concentrations and isotopic compositions, should be collected before drilling operations begin in a region, as is already done in some states. Ideally, these data should be made available for public analysis, recognizing the privacy concerns that accompany this issue. Such baseline data would improve environmental safety, scientific knowledge, and public confidence. Similarly, long-term monitoring of groundwater and surface methane emissions during and after extraction would clarify the extent of problems and help identify the mechanisms behind them. Greater stewardship, knowledge, and—possibly—regulation are needed to ensure the sustainable future of shale-gas extraction. BobTheFerret fucked around with this message at 04:42 on Dec 12, 2011 |
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Dec 12, 2011 04:38
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WAFFLEHOUND posted:They're not some huge industry secret, several studies talked about/linked on this page discuss exactly what they are. What do you think the PR would be like if they started putting radiotags in fracking fluid? Organics (such a fuels) pick up radiation really easily and you know someone would run with a sensationalist headline. Also, no, fracking can't be responsible because a twenty meter fracture radius is well within the area where there isn't any increased permiability to aquifers which are often hundreds of meters away. Why the concern with PR over radiolabels? Also, "Organics...pick up radiation really easily"? What kind of blanket statement is that? Do you mean that high energy electrons in beta emission can reduce or cause the oxidation of aromatics? Or are you thinking of UV light absorption in delocalized systems? Also, a radiolabeled system does not have to be heavily emissive to be effective. You can use long half-life, naturally occurring isotopes with harmless decay mechanisms to do the exact same job. Hell, you don't even need to measure using decay, you can just use isotopic fractionation or mass spec with labeled organics that already occur to see if you're causing any issues. People will happily request or consent to PET scans, which involve intravenous injection of F19-labeled glucose molecules that are many, many orders of magnitude more hot than anything you would use for detecting groundwater contamination (not to mention that F19 does not occur naturally on earth...). My response to your assertion that fracking can't be responsible for groundwater contamination because a "20 meter fracture radius" won't possibly cause problems in aquifers "a few hundred meters away" (where do you get these numbers?) is to ask: is there any standardization in method in fracking? Does everybody drill the same size and use the same technique? As no regulation exists, my guess is no. You're making a lot of assumptions about the fracturing and gas extraction process and what happens during it. A major concern I can think of is the scenario you give where organics are preexisting. Since there is already interaction between organic deposits and groundwater, would the pressure of fracking and gas/petroleum product recovery possibly cause a change in equilibrium between the aquifer and organics? Because natural gas and other petroleum products are compressible and will potentially conduct that fracking pressure. You're so concerned with PR and conduct your defense of fracking with industry research, it makes me wonder if you might not have some sort of undisclosed financial interest.
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Dec 13, 2011 04:35
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WAFFLEHOUND posted:But seriously, you're the second person to imply that I'm an industry shill so I'm out because that's just dumb as poo poo. My apologies, but industry ties have been a huge problem in academic research, particularly in this field. There have been quite a few stories on Pennsylvania institutions (Penn State comes to mind), whose research faculty have been doing some very sketchy treatment of data in order to maintain large grants their geology departments (and other departments associated with the gas industry) receive. There's a 30 minute investigatorial segment on This American Life on the subject. http://www.thisamericanlife.org/radio-archives/episode/440/game-changer Hopefully that might help explain why people could misconstrue your unusual degree of persistence and willingness to argue from authority (you don't often feel the need to explain your positions) for support of the industry. BobTheFerret fucked around with this message at 06:42 on Dec 13, 2011 |
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Dec 13, 2011 06:39
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