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DoE Considers Artificial Trees To Remove CO2
eldavojohn writes "CNN is running an article on a new angle of attack to reducing greenhouse gases. After meeting with the US Department of Energy on the concept, the researchers revealed the details that each 'tree' (really a small building structure in the concept design) would cost about as much as a Toyota and remove 1 ton of CO2 from the air per day. Don't worry, they're accounting for the energy the 'tree' uses to operate: 'By the time we make liquid C02 we have spent approximately 50 kilojoules [of electricity] per mole of C02. Compare that to the average power plant in the US, which produces one mole of C02 with every 230 kilojoules of electricity. In other words, if we simply plugged our device in to the power grid to satisfy its energy needs, for every roughly 1,000 kilograms [of carbon dioxide] we collected we would re-emit 200, so 800 we can chalk up as having been successful.' Each unit would remove 20 automobiles' worth of CO2 from the air and cost about as much as a Toyota... so the plan might be a five percent surcharge on automobiles to fund these synthetic tree farms."
Yeah, it's realy, really, really, really, old technology.
My ism, it's full of beliefs.
If CO2 COULD be a solid in the ocean, it WOULD be a solid in the ocean and there would be huge piles of the stuff down there.
A few hundred feet down, the pressure is still less than 10 atmospheres and temp is obviously above 0ÂC (273K). CO2 under those conditions is still very much a gas. It won't stay solid at 0ÂC unless you're above about 5,000 atmospheres. Even at the bottom of Challenger Deep, you're barely 1100 atm.
http://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-temperature_phase_diagram.svg
As an experienced scientist, placing any form or CO2 in water is a very bad idea. Eventually it will change states from solid to gas or from solid to dissolved in water, which then is known as carbonic acid. This is exactly how your body deals with CO2, it is dissolved in your salty blood, where it is expelled as a gas from the lungs. Only hemoglobin transports oxygen to the tissues, it does not transport CO2 in any way shape or form. CO2 will influence the affinity oxygen has for hemoglobin, and in the presence of higher concentrations of carbonic acid, hemoglobin more readily releases oxygen to the surrounding tissues. Hemoglobin will also transport CO, carbon monoxide, but the binding is through carbon-metal (iron) back bonding, not through the oxygen. I didn't even mention the unknown effects this would have on marine life.
The only way to curb CO2 in the atmosphere is to stop burning fuel and let natural vegetation grow. This also means letting forests GROW and not clear cutting for land development, wood, and paper.
It would make a lot more sense to use real trees. They don't "cost as much as a Toyota," they grow by themselves from seeds, and are self-replicating. They don't extract carbon dioxide in the form of stuff that has to be liquified and then sequestered somehow; they extract CO2 and solidify it in the form of cellulose, a material that is naturally solid at room temperature and pressure.
Obviously, if the trees are then allowed to rot, the CO2 returns to the atmosphere, but that is an easy problem compared to the problem of sequestering CO2 for a few centuries. Just pile it up in the desert, where it won't rot. Or, heck, bury it and let geological forces compress it for a while, and you make new coal that our successors a few million years later can deal with. Wood is a heck of a lot easier to sequester than carbon dioxide!
In short, I can't think of anything more idiotic than designing "artificial" trees, when nature has been evolving real trees optimized to do exactly this task (removing carbon dioxide from the atmosphere)-- and has had a few hundred million year head start.
http://www.geoffreylandis.com
Finally, my M.S. on the deep-ocean sequestration of carbon dioxide becomes relevant!
CO2 is a supercritical liquid at depth, denser than water. Here's the stuff at 3300 meters (courtesy of MBARI)
Here's your phase diagram.
Here's some pictures that show CO2 at depth.
Once at depth, the CO2 will slowly dissolve into the seawater, lowering the pH. Of course, we're doing this at the ocean surface as-is, so one can make the argument that it's less bad to acidify the deep ocean slowly vs. surface waters quickly.
If you drop dry ice overboard, a goodly amount of it will dissolve before reaching bottom. There's research on this; I leave finding the reference as an exercise.
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