The Broken Phosphorus Cycle
The gardeners among us know about NPK. These three elements N (nitrogen), P (phosphorus) and K (potassium) are the main constituents of a complete fertiliser.
Nitrogen is considered the most important and luckily it’s not hard to get. After all it makes up 80% of the atmosphere so we have an almost inexhaustible tank around us.
Potassium is perhaps less easy but so far I have never heard of a possible potassium shortage. I am not too sure how big farms go about it but at a home compost bin level, banana peels and hardwood ashes seem to do the trick.
How about phosphorus? Again not a big deal on a small garden scale. Nothing wrong with a bit of horse poo, for example. But since the mid 19th century large crop farms have become increasingly dependent on super-phosphates. One of the problems with this stuff is that it is not renewable. It comes from big mines, most of which are located in five countries, and it takes huge amounts of energy to process. Not unlike oil, actually. Back in 2008, fertiliser prices went up by 600%, which influenced food prices. This resulted in violent riots in 40 developing countries.
The problem is that we have broken the phosphorus cycle. Solution? Recycle the phosphorus. Cattle manure is part of the solution, of course, but even human waste could be used. Research on sewage sludge processing has been carried out in Sweden and Germany around 2003. However, the method is not competitive yet.
References:
Phosphorus shortage:
https://theconversation.com/how-the-great-phosphorus-shortage-could-leave-us-all-hungry-54432
Peak phosphorus
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