Phosphate Rock 101

Sep 28, 2016
By Marisabel Dolan

Phosphate rock is the only significant commercial source of the element phosphorus. It consists of the calcium phosphate mineral apatite together with quartz, calcite, dolomite, clay, and iron oxide as the so-called gangue constituents. 

Phosphate rock (or phosphorite) refers to phosphate ores that have been commercially mined. There is a particular phosphate rock quality requirement for each process. For example, phosphate rocks used for commercial production of phosphoric acid by the wet process contain about 65 to 87 percent bone phosphate of lime (BPL), depending upon the origin. BPL is defined as the phosphate content, expressed as Ca3(PO4)2, of phosphate materials. Commercial rocks contain varying amounts of other compounds, either physically mixed or substituted in the mineral itself.

Phosphate ores may be found in igneous or sedimentary rocks. Apatite is the name of phosphate based minerals in phosphate ore whether the ore is of an igneous or sedimentary origin. The majority of the phosphate rock resources are sedimentary, i.e. they originate from remains of marine life in regions that were once covered by seas, and got transformed into substantial phosphate deposits over the millennia. Other resources are igneous or volcanic in origin.

The impurities contained in the phosphate rock can have an effect (not always harmful) on downstream production processes and products. For example, impurities have the potential to influence the speed of corrosion-erosion, filtration rate, surface of filtration, as well as the density and viscosity of the phosphoric acid product. Impurities found in phosphate rock include carbon dioxide (increases foaming and therefore the use of antifoam reagents), magnesium oxide (high content decreases filterability), and aluminum and iron oxides (high content decreases the recovery of phosphorus pentoxide; but these oxides can reduce corrosion). 

World production of phosphate rock increased in 2015, with most of the increases taking place in the Middle East and South America, to more than 220 million tons, representing close to a 70 percent increase over the production level achieved in 2000. China was the dominant producer with 45 percent of the world’s production, followed by Morocco and Western Sahara then the United States. Phosphate rock production and consumption is estimated to increase with growing population and food production needs driving phosphate fertilizer applications in the future. Phosphate rock, through the production of phosphoric acid, is the main source of phosphorus in the production of phosphate fertilizers, as illustrated in Figure 1.3

Figure 1.3 Phosphate Fertilizer Value Chain

Phosphate rock is a non-renewable natural resource. As such, there are concerns that phosphate rock reserves are being depleted around the world. According to the U.S. Geological Survey, world phosphate rock reserves were estimated to be around 70 million tons in 2015, representing more than trifold increases from 2005 levels. During the 2005-2015 timeframe, main producers such as China, Morocco (and Western Sahara), and the United States have seen their reserves decline. However, during the same period, new phosphate rock mines have been developed in Algeria, Jordan, Brazil, and Peru. Fertilizantes Fosfatados S.A. (Fosfertil) is the largest producer of phosphorus and nitrogen fertilizers in Brazil, operating phosphate rock mines in Catalao, Tapira and Patos de Minas. In April 2016, Value Fertilizantes (owner of 79 percent of Fosfertil) announced that it is resuming the development of a phosphate ore mine in the town of Patricinio (in the state of Minas Gerais). Phosphate rock developments in Peru include the Bayovar mine in the Piura Province. The mine has the potential to produce close to four million of phosphate rock (29 percent  P2O5) annually during an estimate lifetime of 27 years. Thus, while some reserves are being depleted there are new deposits that are currently being exploited. However, the availability to develop new mines or expand existing ones depends on discovery of new resources, water resources, and capital. Nexant has the capability to advice on fundamental issue of the phosphate rock industry including the effect of the new upcoming supply in future regional trading patterns and phosphate rock prices.