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Phosphate Recovery

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Some basics

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Phosphorus and phosphates

Phosphorus is one of the most common elements on earth and is essential to all living organisms. In nature it always occurs combined with other elements, forming phosphates.
Phosphate resources are located in the earths crust in the form of phosphate rock. The main commercial deposits are located in Morocco, the USA, the Former Soviet Union, China and South Africa. Western Europes only commercial deposit is situated in Finland.
The known reserves of currently exploitable phosphate rock are estimated at about 40 billion tons. At the peak rate of consumption (150 million tons per year) these reserves will last more than 250 years.
In addition there are bast phosphate resources present in the earth crust which, with todays technology, are not yet commercially exploitable.

Extending resources

Historically, the main plant nutrients, nitrogen and phosphorus, were recycled in agricultural communities. Food was consumed close to its place of production and the resulting animal and human manures were applied to the same land.
The growth of cities and the intensification of agriculture has led to the depletion of soil nutrients. Translocated away from the land, this resulted in the break-up of the recycling loop. Simultaneously the requirement for high crop yield has increased the need for the application of inorganic fertilisers.
One of todays challenges consists of responding to the increasing demand for food and the growing nutrient requirement from agriculture without exhausting phosphate mineral resources.


Main uses of phosphate


One of the keys to expanding the expected lifetime of these resources lies in restoring the nutrient recycling loop. In its simplest form, this would involve the transportation and application of sewage sludge from urban areas to agricultural land. New technologies are now becoming available to remove and recycle phosphate from wastewater, for use in both agricultural and industrial applications.

A multipurpose product

There are four main applications for phosphates.

Agriculture
Agriculture is by far the largest user of phosphate, accounting for 80 to 85% of total consumption. It is one of the three main plant nutrients, along with nitrogen and potassium, occurring in inorganic fertilisers. In addition, an increasing number of countries are using phosphate contained in municipal wastewater sludge for agricultural purposes.

Food and animal feed supplements
Food grade phosphates are used in many foods including dairy, meat, bakery products and soft drinks. Also, because of its high value as a nutrient, phosphate is widely used in the manufacturing of animal feed supplements. These applications are discussed in the Phosphate and Nutrition section.

Detergents
Until the middle of this century, most domestic laundry was washed with soap-based products. In 1947, the first synthetic detergents for household use were introduced. The appearance of these new products on the market marked a major step forward in the efficiency of domestic laundry products, both in terms of hygiene and cleaning performance.
At the heart of these new formulations was sodium tripolyphosphate (STPP), used s a "builder", a component whose basic role is to soften water and to optimise the washing conditions for the other active ingredients. The qualities which make STPP the builder of choice are presented in the Phosphates and Laundry Detergents section.

Other industrial applications

Apart from their role in laundry detergents, phosphates play a key role in dishwash detergent formulations and are also used in such diverse applications as metal surface treatment, corrosion inhibition, flame retardant, water treatment and ceramic production Despite such widespread use, these applications represent only about 3% of total consumption.


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