Where does the phosphate rock come from?
In the United States, main deposits of phosphate rock are in Florida, Tennessee, and North Carolina. There are also deposits that can be mined in Idaho. The phosphate rock, which eventually yields the phosphogypsum by-product, is recovered by open pit mining. The rock is transported to a washing facility, where it is separated from accompanying soil, stones, etc. and processed. The desired phosphorus content of the phosphate rock is in a form (calcium phosphate) that will not dissolve in water and so cannot be taken up by crops. As a result, phosphate processors must solve the problem of getting it into a water-soluble form. The most common solution to the problem is converting the calcium phosphate to phosphoric acid. There are wet and dry processes for doing the conversion. U.S. production facilities utilize a wet process in which the prepared rock is treated with sulfuric acid to produce the phosphoric acid. Phosphoric acid is water soluble so it can be taken up by crops. It can als
