刚读完一篇文章，从全球食品安全和供求的角度讨论未来可能出现的磷危机磷稀缺。文章很长，但是视角有些意思，尤其是谈到动物尿和粪便是可贵的磷来源的时候。
先普及几个有关屎粪尿的单词
Excreta: waste matterdischarged from the body, esp. feces and urine. (google)
Feces:also known asexcrement, is waste product from an animal's digestive tract (Wikipedia)
Dung: animal feces(Wikipedia)
Guano (via Spanish, ultimately from the Quechua wanu) is the excrement of seabirds, cave-dwelling bats, pinnipeds, or (in English usage) birds more generally.(source: Wikipedia)
Urine: you know as IknowJ
文中谈到“冲水厕所的发明意味着‘肥水不再流人田’。当时就有文化人站出来反对说‘这无异于偷走了农民的天然肥’。大名鼎鼎的雨果就是其中一员，他把反对的声音写进了流芳百世的《悲惨世界》”。
At the same time, the introduction of flush toilets in townsmeant that human waste was discharged into water bodies instead of beingreturned to the soil. There were protests among intellectuals that farmers werebeing robbed of human manure. Among them was Victor Hugo who wrote in LesMiserables:
他是这样说的：
Science,after having long groped about, now knows that the most fecundating and themost efficacious of fertilizers is human manure. The Chinese, let us confess itto our shame, knew it before us. Not a Chinese peasant – it is Eckberg who saysthis – goes to town without bringing back with him, at the two extremities ofhis bamboo pole, two full buckets of what we designate as filth. Thanks tohuman dung, the earth in Chinais still as young as in the days of Abraham. Chinese wheat yields ahundredfold of the seed. There is no guano comparable in fertility with thedetritus of a capital. A great cityis the most mighty of dung-makers. Certain success would attend theexperiment of employing the city to manure the plain. If our gold is manure,our manure, on the other hand, is gold (Hugo, 1862).
这一段话里，雨果老人高度赞扬“中国人很早就懂得人类粪便是肥的事实”；甚至不无夸张地说，“一个伟大的城市应该是能输出粪便的巨无霸”。
文章在搜集全球范围磷储量、磷使用和磷流量分析后，又再次回到人类尿液和粪便的价值上，指出尿液和粪便回收利用是磷可持续的重要途径之一。中国和其他发展中国家还在使用的茅坑（pitor composting toilets）非常直接和高效地发挥着粪肥的作用；而马桶或冲厕的粪液很可能和其他工业废水混合在一起排入土壤，造成潜在的重金属和其他有机物的污染。马桶时代，如何安全回收利用粪尿成为一个亟待解决的问题。文章说，单纯的尿液是去菌的（sterile），可以为谷类作物提供50%以上所需的磷。瑞典就有两个城市明文规定“所有新建的厕所必须有尿粪分离（urine-diverting）的装置。”
(a) A urine-diverting dry squat toilet from India (photo: S.Vishwanath www.rainwaterclub.org);(b) a urine-diverting dry toilet from Sweden (photo: Dana Cordell).
其实提到粪肥的时候，我也是很有感情的。儿时在老家串完门吃饱饭，走着长长的山路，从来不用担心没地方解决。妈妈会说：就在那个田里吧，小苗长得快。其实在那时真是件畅快的事情～
补遗：文章中还比较了素食和肉食人群的屎尿磷含量，根据世卫组织2006年的调查，素食人群每年排泄物平均含0.3kg的磷，而肉食人群每年排泄物平均含磷为0.6kg。不知道蒋老师看了会不会又不由自主地举起素食主义的大旗呢？
文章：
Cordell D, Drangert JO, White S, 2009. The story ofphosphorus: Global food security and food for thought. Global EnvironmentalChange, 19(2): 292-305
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