P and K: Problems but not Showstoppers

A couple of articles intended to turn down the alarms on phosphorus and potassium supplies, without necessarily squelching them altogether.

Vaclvac Smil (the second link above) makes some interesting points:

the International Fertilizer Industry Association, whose members include many of the world’s most prominent fertilizer producers, traders, and shippers… “does not believe that peak phosphorus is a pressing issue, or that phosphate rock depletion is imminent. Nevertheless, it believes that efforts to minimize phosphorus losses to the environment and optimize phosphorus use should be encouraged.”

And that is precisely as it should be, because wasteful use of all kinds of fertilizers is common and optimizing the applications brings substantial monetary and environmental rewards (phosphates are a major cause of aquatic eutrophication, their worst effects are persistent dead zones in many coastal areas around the world). Larger gains in reducing phosphate applications could be made by moderating typical per capita meat consumption, and a great amount of the element can be recovered from waste. In all Western countries, most fertilizers are now applied to feed not food crops, and hence moderating the current high rates of meat consumption (commonly in excess of 100 kg per capita) would reduce the amount of needed fertilizer. Such cuts would also have environmental and health benefits.

An even more important option – especially given the facts that much of modern meat, milk, and egg production is done in a concentrated manner, and that half of the world’s population lives in cities – is now available thanks to advances in phosphorus reuse from manures and municipal wastes.

h/t Roger Pielke Jr., via a tweet

Similarly, it is not the burning of fossil fuels, but their emission into the environment, that causes the greenhouse problem. This is the insight behind carbon sequestration.


  1. Whoa, not so fast!

    Smil says there's 400 years worth of Phosphorous supplies. 400 measly years. Wow, all's well for humanity for the next few billion years, then.

    "Similarly, it is not the burning of fossil fuels, but their emission into the environment, that causes the greenhouse problem. This is the insight behind carbon sequestration."

    Wrong, oh so wrong. The issue's both the emission of CO2 and our pre-emptive consumption of finite capital resources, depriving our descendents of any access to them.

    • There's a difference between proven reserves and supplies, first of all. Second, maybe in 400 years we'll be able to control the population. Anyway, we have to get past the climate crisis; we can worry about this later.

      And finally, growing animal feed is a bad idea. I think the amount of meat we should eat is the amount we can graze and feed scraps. Stop growing feed corn and the problem largely goes away.

      The issue of using up the carbon fuel as an instance of pre-emptive consumption is an interesting one. Bucky Fuller raised that one long before anyone had heard of a climate crisis.

      That is, we do not have enough coal to reboot civilization from a cold start. I do not think we will entirely forget how to use solar and wind, though. Anyway, we had better not. But if we come that close to extinction the near-surface coal and oil is already used up, so the remnant population will be out of luck on that score already.

      • ... we do not have enough coal to reboot civilization from a cold start. I do not think we will entirely forget how to use solar and wind, though

        Nor is there anything hard to obtain in a Magnox reactor.

      • Well, that's good news. What troubles me most is the vision of a long sequence of cold started global civilizations, just like our's at present, burning shit until they perish and the planet is wrecked, and a after just a few million years Mother Evolution starts it all over again. Pre-emptive consumption of fossil carbon fuel seems a good idea for the long-term health of our planet.

      • Magnox design is optimized for plutonium production, not electricity generation.

        If you want a natural uranium reactor, heavy water moderated design (like CANDU) is a better choice.

    • Right now the carbon emissions are a much more pressing concern than resource depletion. Exploiting a reasonable percentage of currently recoverable fossil fuels would be a climate disaster. Indeed this is the whole point of McKibben's recent tour: there are too many fossil fuels, not too few.

      I'm surprised that we don't see fossil fuel companies running an all out CCS R&D effort. If they figure out how to shove C underground for a reasonable price, they get to stay in business. Otherwise they all slowly fade away.

  2. Michael Tobis asks why Magnox was abandoned, despite its ability to work with natural uranium, natural carbon, and natural oxygen. The low volumetric heat capacity of carbon dioxide coolant is one likely reason. It made for a low net heat-to-electricity conversion efficiency because a large volume of it had to be pumped.

    Plus, the pipes had to be big. This wasn't too burdensome -- it went with the large minimum size of an unenriched U-and-C core that had to operate at a highish temperature -- but the smaller core that low-enriched uranium affords would have a hard time accommodating them. The same pressure as the CO2 was at, applied to keeping water from boiling, allowed smaller coolant channels to go with a smaller core.

    In a cold-start world, where all the uranium enrichment plants have been ruined one way or another, these considerations would not be persuasive, but once uranium enrichment has been worked out on a large scale for weapons purposes, putting it to this other use must have become so.

    Disagreeing with AA, I think the Windscale fire demonstrated a degree of optimization for weapon production greater than that of the Magnox plants, despite those plants' being descendants of the Windscale pile, because it used once-through air for cooling. That's why it could burn. And I guess it was smaller, because the lower operating temperature that would have been sought, to prevent this very ignition, would have allowed a smaller core still to attain criticality.

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