permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Phosphorite - Wikipedia, the free encyclopedia - Interesting reading for
farmers using rock phosphate
http://en.wikipedia.org/wiki/Phosphorite

Production and use

"Deposits which contain phosphate in quantity and concentration which are
economic to mine <http://en.wikipedia.org/wiki/Mining> as
ore<http://en.wikipedia.org/wiki/Ore>for their phosphate content are
not particularly common. The two main
sources for phosphate are guano <http://en.wikipedia.org/wiki/Guano>,
formed from bird <http://en.wikipedia.org/wiki/Bird> droppings, and rocks
containing concentrations of the calcium phosphate mineral,
apatite<http://en.wikipedia.org/wiki/Apatite>
.

Phosphate rock is mined, beneficiated, and either solubilized to produce
wet-process phosphoric acid <http://en.wikipedia.org/wiki/Phosphoric_acid>,
or smelted to produce elemental
phosphorus<http://en.wikipedia.org/wiki/Phosphorus>.
Phosphoric acid is reacted with phosphate rock to produce the fertilizer
triple superphosphate <http://en.wikipedia.org/wiki/Superphosphate> or
with anhydrous
ammonia <http://en.wikipedia.org/wiki/Anhydrous_ammonia> to produce
the ammonium
phosphate <http://en.wikipedia.org/wiki/Ammonium_phosphate> fertilizers.
Elemental phosphorus is the base for furnace-grade phosphoric acid,
phosphorus pentasulfide, phosphorus
pentoxide<http://en.wikipedia.org/wiki/Phosphorus_pentoxide>,
and phosphorus 
trichloride<http://en.wikipedia.org/wiki/Phosphorus_trichloride>.
Approximately 90% of phosphate rock production is used for
fertilizer<http://en.wikipedia.org/wiki/Fertilizer>and animal feed
supplements and the balance for industrial chemicals.

Froth flotation <http://en.wikipedia.org/wiki/Froth_flotation> is used to
concentrate the mined phosphorus to rock
phosphate<http://en.wikipedia.org/wiki/Rock_phosphate>.
The mined ore slurry is treated with fatty
acids<http://en.wikipedia.org/wiki/Fatty_acids>to cause calcium
phosphate to become
hydrophobic <http://en.wikipedia.org/wiki/Hydrophobic>.

For general use in the fertilizer
<http://en.wikipedia.org/wiki/Fertilizer>industry, phosphate rock or
its concentrates preferably have levels of 30%
phosphorus pentoxide (P2O5), reasonable amounts of calcium carbonate (5%),
and <4% combined iron <http://en.wikipedia.org/wiki/Iron> and
aluminium<http://en.wikipedia.org/wiki/Aluminium>oxides. Worldwide,
the resources of high-grade ore are declining, and the
beneficiation of lower grade ores by washing, flotation and calcining is
becoming more widespread.

In addition to phosphate fertilisers for
agriculture<http://en.wikipedia.org/wiki/Agriculture>,
phosphorus from rock phosphate is also used in animal feed supplements,
food preservatives, anti-corrosion agents, cosmetics, fungicides, ceramics,
water treatment and
metallurgy.[10]<http://en.wikipedia.org/wiki/Phosphorite#cite_note-Phosphate_AIMR_Report_2008-10>

The US is the world's leading producer and exporter of phosphate
fertilizers, accounting for about 37% of world P2O5
exports.[11]<http://en.wikipedia.org/wiki/Phosphorite#cite_note-11>The
world’s total economic demonstrated resource of rock phosphate is 18
Gt, which occurs principally as
sedimentary<http://en.wikipedia.org/wiki/Sedimentary>marine
phosphorites.
[10]<http://en.wikipedia.org/wiki/Phosphorite#cite_note-Phosphate_AIMR_Report_2008-10>

China <http://en.wikipedia.org/wiki/China>, the United
States<http://en.wikipedia.org/wiki/United_States>and Western
Sahara 
<http://en.wikipedia.org/wiki/Western_Sahara>[12]<http://en.wikipedia.org/wiki/Phosphorite#cite_note-12>are
the world's largest miners of phosphate rock, each producing about a
quarter of the total world production. Other countries with significant
production include Brazil <http://en.wikipedia.org/wiki/Brazil>,
Russia<http://en.wikipedia.org/wiki/Russia>,
Jordan <http://en.wikipedia.org/wiki/Jordan> and
Tunisia<http://en.wikipedia.org/wiki/Tunisia>.
Historically, large amounts of phosphates were obtained from deposits on
small islands such as Christmas
Island<http://en.wikipedia.org/wiki/Christmas_Island>and
Nauru <http://en.wikipedia.org/wiki/Nauru>, but these sources are now
largely depleted."