Many people think with some trepidation about the day when the last drop of oil is brought to the surface. But perhaps another raw material has reached that point even faster, a raw material that is more important than oil and for which there are no alternatives: phosphorus. Phosphorus is a mineral that plants cannot do without. And phosphorus also plays an important role in the energy supply of the human body. In about 50 to 75 years, the mineral phosphorus could be depleted. It is true that such forecasts are always accompanied by some uncertainty. After all, new sites could shift the fatal moment into the future. But still, it ends somewhere. And because phosphorus is irreplaceable, it got scientists thinking about how we can obtain the material in the future. Well, there is such a location: in human urine.
- The supply of phosphorus in the soil is finite
- Phosphorus can be extracted from human urine
- How is phosphorus recovered from urine?
- Urine too valuable to simply flush away
- Waterless urinals in Heineken Music Hall
- Phosphorus or phosphate
The supply of phosphorus in the soil is finite
For use as fertilizer, phosphorus is mainly obtained by mining phosphorus-containing minerals. China, Morocco and the United States currently control the majority of the world’s available reserves. Some research suggests that peak extraction will occur around 2030. This is the time when the amount mined is the highest and then gradually decreases. In any case, the easily degradable phosphorus reserves will be exhausted in 50 to 75 years.
Phosphorus can be extracted from human urine
A person excretes 1.6 to 1.7 grams of phosphorus per day, 60 percent of which in the urine. That doesn’t seem like much. But according to a study by Dana Cordell of Linköping University in Sweden, that has been extrapolated to the entire world population, already 3 million tons of phosphorus per year. Urine can provide more than half of the phosphorus needed to fertilize crops.
How is phosphorus recovered from urine?
But how do we remove the phosphorus from the urine and bring it into a form that can also be used as a fertilizer? Well, to facilitate recovery, urine should preferably be collected separately from feces. Only then is it possible to use urine in a concentrated form as a possible supplier of phosphorus. In laboratories it has been possible to chemically stabilize fresh urine using bacteria. And through evaporation one manages to produce a powder in which almost all important minerals are retained. Ultimately, phosphorus precipitates from the urine as a solid in the form of struvite and can be easily filtered out.
Struvite as fertilizer
Struvite is very suitable as a fertilizer. And in powder form, better said in the form of granules or granules, the fertilizers are easier to transport and apply. The smell has now disappeared from the urine.
Urine too valuable to simply flush away
At the same time, the burden on rivers and seas due to waste water can be significantly reduced and the costs of water treatment can be reduced. Such systems represent a new way of thinking. In our Western world, centralized treatment plants are increasingly reaching the limits of their capacity. Yet the recovery of phosphorus from urine is still in its infancy. And recovery is not always a profitable activity. But urine is simply too valuable to simply wash it away. In addition to phosphorus, human urine also contains other important minerals that can be used as fertilizer in agriculture: nitrogen, sulfur and potassium.
Waterless urinals in Heineken Music Hall
A remarkable initiative in this regard in Amsterdam. Since 2016, Waternet has been collecting the urine of concertgoers in the Heineken Music Hall. Struvite (also called urine stone) is extracted from this, which serves as a basis for phosphate-containing fertilizers. Waterless urinals have the advantage that the urine can be collected undiluted. It is true that the urine contains drink residues and possibly the remains of stimulants and medicines, but that is not a problem. Waternet is concerned about the phosphates in the lake. A test also took place in 2011 during the Pinkpop festival where the urine of festival goers was collected.
Phosphorus or phosphate
The names phosphorus and phosphate are often (wrongly) used interchangeably for convenience. After all, phosphorus is a mineral and phosphates are compounds with phosphorus. When we talk about phosphate, this means that the mineral is linked to other substances. We can easily absorb phosphates through our diet, both plant and animal food.