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Post by eclipse on Nov 15, 2012 12:29:16 GMT 9.5
Anyone come across solutions for peak phosphorus? I wonder what percentage of the phosphorus we eat is actually retained by the body, and not just passed through? I'm wondering how much Phosphorus we could actually recycle from sewerage, and how much we might need to top up from the oceans. (And how we might do that?) The first job is obviously to redirect all sewerage back to land and stop the (mostly) one way journey of those NPK nutrients out to sea. But what if that is not enough? Can we can 'top up' the Phosphorus in the soil by sustainable fishing which would pass extra nutrients back through our bodies, through our sewerage, back towards the land? Then of course the next problem is the whole world trying to eat more seafood, instead of less! How are we going to solve peak phosphorus? Really?
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Post by anonposter on Nov 15, 2012 18:32:02 GMT 9.5
Checking Webelements it seems the abundance of P in the crust is only an order of magnitude lower than in Humans and at the level of parts per thousand so that would indicate that there is no such thing as peak P possible any time soon. Of course the low abundance in water means that we should be doing what we can to prevent it getting there (i.e. recycling from sewage, which I suspect could meet most of our needs) but we very well could mine it if we needed to from ordinary rocks (though that'd be more expensive than high grade deposits). |
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Post by eclipse on Nov 15, 2012 20:30:20 GMT 9.5
Yes but the peak occurs when we move from mining higher concentrations of 'conventional' phosphorus rocks. I don't know how economically viable it is mining the other stuff you're talking about, or how viable it is full stop. In other words, if we can ramp it up fast enough to meet demand. Check the wiki: "Peak phosphorus is the point in time at which the maximum global phosphorus production rate is reached. Phosphorus is a scarce finite resource on earth and due to its non-gaseous environmental cycle has resulted in alternative means of production other than mining being unavailable.[1] According to some researchers, Earth's phosphorus reserves are expected to be completely depleted in 50–100 years and peak phosphorus to be reached in approximately 2030.[2][3] Whereas in stark contrast the International Fertilizer Development Center in a 2010 report estimates that global phosphate rock resources will last for several hundred years.[4] The predominant source of phosphorus comes in the form of phosphate rock and in the past guano." en.wikipedia.org/wiki/Peak_phosphorus |
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Post by eclipse on Nov 16, 2012 7:23:13 GMT 9.5
It gets worse. From The Conversation (below) we learn a few statistics. One statistic is comforting, in that 98% of the phosphorus we consume is passed through our bodies and can be recycled. The next statistic is very worrying: only 1/3 of the P we apply to our farmlands is actually taken up by the plants we grow! That means we'd be running at a 2/3rd's loss each year if we relied solely on waste recycling. theconversation.edu.au/backing-biochar-the-australian-governments-role-10513MODERATOR
I fixed your link. Don't forget to click on the hyperlink button and insert your link between the brackets. Thanks. |
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Post by edireland on Nov 16, 2012 9:54:59 GMT 9.5
This is the only resource that I have no yet worked out an effectively infinite source yet.
(As some of you have seen I have already proposed methods to allow meat production, and thus food production, to be scaled up enormously while reducing the amount of land required to grow feed, and also allowing forage fish harvesting to stop).
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Post by anonposter on Nov 16, 2012 16:14:25 GMT 9.5
The next statistic is very worrying: only 1/3 of the P we apply to our farmlands is actually taken up by the plants we grow! That means we'd be running at a 2/3rd's loss each year if we relied solely on waste recycling. Hydroponics could probably do better than that, sure it's more expensive but it'd still be within the realm of possibility. No-till farming according to the wiki article can also help (though you need GMOs to really be able to do that well, there might even be scope for reducing P requirements there as well). |
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Post by Nick P. on Nov 21, 2012 19:32:03 GMT 9.5
A thought occurs to me that's never been answered to my satisfaction. When phosphorus runs off of the field, where does it 'end up'? Logically I'd imagine it ends up in the ocean eventually. So if that's the case then when we're off recycling what we can what to stop us from going and extracting what we need to 'top off' the cycle from the ocean? Hell, if you're extracting uranium from the oceans already to fuel breeder reactors you could probably even co-locate the process. ----- Also as an aside people tend to use aquaculture and hydroponics as helpful techniques which is all fine and good and I don't disagree with the notion, but just to add a little grist to the mill I suggest that aquaponics might be Even Better(TM). It combines aspects of both aquaculture and hydroponics to try and get the best of both. en.wikipedia.org/wiki/AquaponicsDescribed briefly a typical setup has a tank for fish and a grow bed of soil-less media for plants. Periodically the fish waste is pumped into the grow beds which both waters the plants and the fish waste feeds the plants, this in turn also keeps the water clean for the fish. Very productive, provides vegetable matter along with animal protein as well. I notice in a different thread on this site the notion of crop production shifting northward is considered a no-go in Canada at least because of the Canadian shield formation where it's not so much dirt as nothing but rock. It seems as though this ceases to be an issue with alternative growing techniques such as this. After all, tanks and simple greenhouses don't care if they're on top of a giant granite plate. |
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Post by eclipse on Nov 21, 2012 20:16:36 GMT 9.5
Just brainstorming for fun: and I doubt any of this would be economically viable. But I'm wondering if the military or a huge industrial firm got involved, whether granite would be that much of an issue? I'm thinking about an almost apocalyptic global warming scenario where the military industrial complex just decides that rocky plain over there MUST grow food. How might they do it? I guess it depends on the shape of the granite. If it's smooth enough land, I'm wondering if there are big industrial strength grinders that can munch up a few top inches of granite? Something like this, but turned downwards so it can grind the top rocks into sandy loam.  Once the land is flattened into sandy dust, then they add a bunch of biochar, and maybe start growing meadows and grasslands for cattle to graze. Do the Polyface farm cow & chook rotation routine, and REALLY build up some soil! After a while, you'd never know there had been granite there. The next stage might be growing a crop that was pretty indestructible like hemp (for both food and fibre). Scientists say it doesn't need a lot of fertiliser or real quality soil, and at least it would be providing some protein in the hemp seeds and fibre for paper and clothing and cloth. Then swap it back for the Polyface farm cattle grazing to restore nitrogen to the soils and recharge it for other crops. But again, it depends on the expense and viability of the industrial-strength grinder I'm talking about. |
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Post by edireland on Nov 21, 2012 22:47:13 GMT 9.5
A better option might be just to cover the entire thing in huge amounts of greenhouses.
Dam off a bay that if fed by one of those supermassive glaciers that is going to be melting soon and tap off all the meltwater to irrigate teh entire thing.
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Post by Nick P. on Nov 22, 2012 11:49:20 GMT 9.5
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Post by anonposter on Nov 22, 2012 13:05:43 GMT 9.5
A thought occurs to me that's never been answered to my satisfaction. When phosphorus runs off of the field, where does it 'end up'? Rivers and Ocean as I understand it. Logically I'd imagine it ends up in the ocean eventually. So if that's the case then when we're off recycling what we can what to stop us from going and extracting what we need to 'top off' the cycle from the ocean? Concentration is lower than typical crustal rocks, though being a liquid could help things since you don't need to pulverise water. Hell, if you're extracting uranium from the oceans already to fuel breeder reactors you could probably even co-locate the process. You could probably get quite a bit of other stuff out of it as well. I notice in a different thread on this site the notion of crop production shifting northward is considered a no-go in Canada at least because of the Canadian shield formation where it's not so much dirt as nothing but rock. It seems as though this ceases to be an issue with alternative growing techniques such as this. After all, tanks and simple greenhouses don't care if they're on top of a giant granite plate. Hydroponics and related technologies could be used anywhere there is water, energy and nutrients. Though they aren't likely to be as cheap as conventional farming in soil so it'd be a last resort option. Dam off a bay that if fed by one of those supermassive glaciers that is going to be melting soon and tap off all the meltwater to irrigate teh entire thing. Or use nuclear desalination if that turns out to be insufficient. |
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Post by Nick P. on Nov 22, 2012 17:04:02 GMT 9.5
Concentration is lower than typical crustal rocks, though being a liquid could help things since you don't need to pulverise water. You could probably get quite a bit of other stuff out of it as well. If you'll indulge me in using a trite buzzword, this is feeling more and more like a perfect moment of synergy. Besides phosphorus there's much talk of fresh water resources becoming constrained in the future. So in rolls the prospect of nuclear driven desalination. Science saves the day again! Personally I'm fond of Multiple Effect Distillation driven by the plant waste heat. It's an almost purely thermal process so you get to use the waste energy you'd 'throw away' otherwise and you get to preserve almost all of the generated electricity to sell as it's the higher value product. Afterwards you end up with hyper-saline brine which is usually sent back into the ocean, where frequently this could have detrimental effects on the local ecology. So, in at least some cases, why don't we not dump the brine out? Instead, put it to use. First, when we talk about extracting uranium from seawater it's usually in the context of baskets of wadded up adsorbent cloth out in currents. This is because the cost of pumping the water or trying to perform any sort of concentrating would rapidly make the entire process uneconomical. Well in this case we're pumping and desalinating the water anyway so the concentrated brine is essentially 'free'. Why not place your adsorbent material in the brine stream? This way you'd need that much less of it to get the same amount of uranium. Then there's magnesium which is already commonly extracted from seawater anyway. Oh look, 'free' concentrated brine. Phosphorus as well, mentioned previously. South Korea is working on commercially extracting lithium from seawater, so there's that as well. So on and so forth, until you get to the salt which can be disposed of by leaving the brine to evaporate in ponds and scooping it up for use later. Which I guess is a round about way of saying: Yes, I agree. You probably get quite a bit of other stuff out of it as well. |
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Post by Saul Wilson on Dec 18, 2012 16:57:52 GMT 9.5
Asteroids are rich in phosphorus but if we want to use sea water and nuclear power there are some better methods than boiling off the water such as filtering off the salt with nano filters and electric fields leaving water with virtually no salt and all the trace minerals and metals there. You could then use the water as both irrigation and fertilizer or just leave it out to evaporate the water off slowly. Which the physical technology of nanotechnology and the advancements in chemistry (with and without electrical fields) you could probably get a fair amount of phosphorus and potassium and such. Fish and seaweed help bring these elements into our waste streams and there is some interesting work in turning sewage into safe fertilizer with slow release phosphorus. Improved efficiencies of application to crops using robots and sensors will help too. Any increase in phosphorous prices will encourage these developments.
The collapse in production of phosphorus in the 80s/90s was due to reduced demand from the Soviet Union which used it inefficiently until they collapsed. There is no long-term problem, just some regular supply and demand spikes and falls in the near-term future.
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Post by anonposter on Dec 18, 2012 17:05:21 GMT 9.5
Asteroids are rich in phosphorus Not really, meteorite P concentration is about the same order of magnitude as earth crustal rock composition. but if we want to use sea water and nuclear power there are some better methods than boiling off the water Boiling the water would work and if done using waste heat would be effectively free. such as filtering off the salt with nano filters and electric fields leaving water with virtually no salt and all the trace minerals and metals there. Details? Because that's quite vague. |
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Post by eclipse on Dec 20, 2012 21:17:22 GMT 9.5
Hi Anon,
out of interest, what do you think the levels of uranium ore might be out in the asteroid belt? Would there be enough to run, say, nuclear powered mining ships that slowly munched their way through the goodies, occasionally popping out 'baby' mining ships as they reproduced out there?
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Post by anonposter on Dec 21, 2012 13:09:44 GMT 9.5
Hi Anon, out of interest, what do you think the levels of uranium ore might be out in the asteroid belt? Information on that is a bit hard to come by, certainly carbonaceous meteorites have worryingly low concentrations of Uranium and Thorium. U and Th are both lithophiles so differentiated bodies can be expected to have higher concentrations, I suspect we could find enough in space to be able to use nuclear technology where it makes sense without being dependant on Earth but I doubt U and Th will be exported to earth the way Pt might (actually there little is worth exporting to Earth, space mining would be mostly for building structures in space) and it may even be better to lob up U from earth than trying to mine it in space (I guess we'll know when we get into asteroid prospecting). Would there be enough to run, say, nuclear powered mining ships that slowly munched their way through the goodies, occasionally popping out 'baby' mining ships as they reproduced out there? Probably enough, but solar would probably play a bigger role in that scenario where it'd actually be reliable and can be easily concentrated with gigantic flimsy mirrors. I suspect that the main use of nuclear in space would be to quickly move around the solar system, power on objects which don't get ≈99.9% sunshine would be the other big use. |
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Post by David B. Benson on Dec 22, 2012 13:02:57 GMT 9.5
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Post by anonposter on Dec 22, 2012 17:18:07 GMT 9.5
OTOH Uranium does have a high energy density and if you're using it to run a rocket you may not care if it takes more energy to mine than you can get out of it.
Reading up on how Uranium ore is formed it does appear that planets with volcanoes similar to Earth's (even if none are active) should have some U deposits.
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Post by Greg Simpson on Dec 23, 2012 14:30:41 GMT 9.5
Metallic meteorites also contain the minerals troilite, graphite, cohenite and schriebersite, along with trace amounts of chromium, iridium, cobalt and rare earth elements like gallium and germanium.from www.armaghplanet.com/html/meteorites.html Gallium and germanium are not generally considered rare earth elements. This makes me not trust the source. |
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Post by anonposter on Dec 23, 2012 15:05:09 GMT 9.5
According to webelements Ge is a bit more than an order of magnitude more common in meteorites compared to crustal rocks while Ga is somewhat less common (though not an order of magnitude).
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Post by Roger Clifton on Dec 24, 2012 16:59:42 GMT 9.5
Arguments based on "peak" anything are referencing an obsolete paradigm, that the limits to growth are defined by finite resources.
Across the last thirty years it has become horrifyingly evident that the growth of industrial society is limited by its wastes.
Our waste CO2 has accumulated to a level of 1.5 kg/m2 worldwide: it is in the greenhouse above all farmland, forest, ocean, ice, desert and city. If we visualise the ten or so square metres at our feet as being covered with 15 kg of rubbish, with nowhere left to put it, then we are looking at the limits to our survival, let alone our growth.
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