World food security depends on the use of fertilisers, and mainly on phosphate
fertilisers that are manufactured from phosphate ore, which is a limited
resource. The majority of remaining reserves are found in a limited number of
countries, which poses geopolitical risks. The report highlighted here describes
the various uses of phosphate and summarises ways in which dependence on mineral
reserves could be reduced.
What is the role of phosphate in food production?
Phosphorus is a chemical element that is a vital
nutrient for all living organisms and
cannot be substituted. In modern agriculture, it is essential for maintaining
the high production rate in agricultural systems. Since the 20th Century, the
flow of phosphorus into the environment has quadrupled, while its use provides
sufficient food to sustain high levels of population growth.
Producing the food consumed by someone who eats meat requires approximately
three times as much phosphate compared to producing food for someone with a
vegetarian diet. However, much of the phosphate consumed by the animals ends up
in manure, and so remains on the farm for further production.
Is phosphate a resilient resource?
The use of phosphate fertilisers intensified in the mid to late 19th century
with the use of guano (mined bird and bat droppings) from islands in the
Pacific. Before, bone meal was used for centuries as a source of phosphate.
Since the 20th Century, the primary source of phosphate for fertiliser and
animal feed supplements, is phosphorus extracted from phosphate-rich rocks.
Global sources of phosphorus fertilizer
Food Production - UNEP Yearbook 2011, p 37
The majority of the known remaining phosphate deposits are located in North
Africa (64%), the USA (15%) and China (6%). This concentration of production in
a limited number of countries, and the location of some of these deposits in
areas of geopolitical tension, has the potential to disrupt supply. Phosphate
rock was added onto the list of critical materials in may 2014.
Although reserves are expected to last for several centuries, at some point
there will be a decrease in production, and this decrease in availability needs
to be adressed. More effective methods of using fertilisers and ways to recover
the phosphorus that is lost into the environment at all points in the chain of
production need to be implemented. Recovery from
waste water is already in place in many
parts of the world where there are sewage
How is phosphate also an environmental pollutant?
Only 10-15% of applied fertiliser is taken up by crops; the majority remains
as a reserve in the soil. A large part of the phosphate extracted is lost into
the environment between extraction and use in the field. This phosphate finds
its way into rivers, lakes, and eventually the oceans.
In aquatic environments, this excess of
nutrients can cause
algal blooms and reduce
biodiversity, which is a process
known as eutrophication, that is caused by
phosphorus in rivers and lakes, but not in oceans, where it is usually caused by
How can phosphorus pollution be managed?
Efficient agricultural use of phosphate fertilisers and transfer from
agricultural land to surface waters can be
managed at three different stages:
- Managing sources: Applying the correct amount of fertilisers at the
right place and at the right time ;
- Controlling how it leaves farmland: Managing
surface water runoff over the
tracks used by machinery in fields and establishing cover crops in autumn ;
- Protecting aquatic environments : Building artificial wetlands,
silt traps and embankments,
managing riverbank zones with woodland and vegetated buffer
treatment plants contributes 60-80% of the
phosphorus in rivers, and there is a growing trend to recover it and to use it
again as fertiliser.
Phosphate compounds used also to be a core component of laundry and dishwasher
detergents, but use in laundry
detergents has been restricted in 2004 and 2013 by EU regulations, and further
restrictions will apply to dishwasher
detergent from January 2017. These
restrictions only apply to domestic cleaning products; they do not include
Although the soil reservoir is not sufficient to provide the required
phosphorus for maximum yields, taking this source into account when determining
the amount of fertiliser required can result in reduced application rates.