Research undertaken by the International Fertilizer Development Centre (IFDC) has assessed the concentrations of cadmium and other trace elements across different phosphate deposits around the globe.
The highest concentrations of cadmium have been found in sedimentary and guano rock deposits, located in North and West Africa, parts of the Americas and on Pacific and Indian Ocean islands. Phosphate rock concentrates (and fertilizers) in these areas can reach concentrations close to 300 mg Cd/Kg P2O5, which is in excess of what is considered to be safe by the European Commission.
The highest concentrations of lead within phosphate rock concentrates were recorded in Brazil, Australia and Morocco. Arsenic concentrations, meanwhile, were highest in Egypt, China, Jordan and Peru. Unlike cadmium, even the highest among these are thought to be within the limits proposed by the European Commission.
Although the research undertaken by the IFDC shows most safer phosphate rock concentrates to be of an igneous nature, various sedimentary rocks meet even the strictest heavy metals standard proposed. When the results of IFDC’s research into cadmium is overlaid against current rock production volumes, around half is thought to contain less than 20 mg Cd/Kg P2O5 (presuming that they are eventually fed through a phosphoric acid unit). This includes product from Russia, Brazil and South Africa (currently all of an igneous origin), as well as that from Jordan, Saudi Arabia, Australia, Kazakhstan and some Egyptian material (all of a sedimentary background).
There are numerous projects currently being developed across North America (Canada), Africa (South Africa) and Oceania (Australia) which are similarly low in heavy metal contents. Many of these could be brought into production, providing a market and funding can be found.