More thoughts on the P crisis. Each one of us excretes about a gram of P per day in our urine (according to The Main Features of Ecological Sanitation, Ecosanres Factsheet #2, 2005), so roughly 365 g P per person per year. There are some 2.6 billion people without sanitation and about half of these live in rural areas. If all these 1.3 billion rural people used EcoSan toilets, then they would urinate a total of 1.3 billion × 365 g P per year which they'd use as fertilizer. That’s around 475,000 tonnes P per year and, with DAP [chemical formula (NH4)2HPO4] costing, say, USD 1000 per tonne − which is equivalent to P costing USD 4260 per tonne, the phosphorus in all this urine is worth just over USD 2 billion per year. And then there’s the value of the nitrogen and potassium in it as well …
So, is this a lot of money? Well, the estimated spending required in developing countries on new coverage to meet the MDG sanitation target (see Global costs of attaining the Millennium Development Goal for water supply and sanitation by Guy Hutton and Jamie Bartram, Bulletin of the World Health Organization, January 2008) is USD 142 billions or some USD 14 billions per year during 2005−2014, so the value of the P in the urine of 1.3 billion people is approx. 14% of this.
So is it all worth it? Very probably − but this is not a reason to be fanatical about sanitation and the impending P crisis. As I keep saying, if poor rural farmers want to use the nutrients in their excreta to increase their incomes, then fine − and we should help them to do so at low cost and at minimal risk to their health and the health of those who eat their crops (and this is where Dr Peter Morgan’s book Toilets That Make Compost is so very useful). And if this nutrient use helps in any way at all to postpone the P crisis by a few years, even a decade or two, then that's all to the good.
About Me
- Duncan Mara
- University of Leeds, United Kingdom
- I'm an emeritus professor of civil engineering at the University of Leeds in England. I've been working on low-cost sanitation in developing countries since the mid-1970s, and also on low-cost wastewater treatment and reuse. I was a lecturer at the University of Nairobi, Kenya, 1970-73 and then a senior lecturer at the University of Dundee, Scotland, 1974-79 before moving to Leeds in late 1979. I was a visiting professor of sanitary engineering at the Universidade Federal da Paraiba in Campina Grande, northeast Brazil, during 1976-95, and since 1996 I have been a visiting professor of environmental engineering at the Instituto Cinara, Universidad del Valle in Cali, Colombia.