Phosphates

Phosphorus is an element vital to all life on Earth. In the body it is key to cell reproduction, growth, and metabolism. Likewise in plants it is necessary for cellular growth, reproduction, and photosynthesis. Without this element neither animals nor plants could survive. 

Phosphorus, like other vital nutrients has a cycle by which it is recycled. The difference in phosphorus to some other nutrient cycles is phosphorus does not cycle in the atmosphere. Organic phosphorus is deposited into the lithosphere through the excrement and decays of animals by means of microorganisms that breakdown the organic matter, releasing the stored phosphorus into the soil for uptake by plant roots. Animals eat these plants to obtain the phosphorus needed for growth. However not all phosphorus is taken up in the roots, some of this organic material undergoes a sedimentary process, where in the presence of water it becomes a negatively charged ion of phosphorus and oxygen known as phosphate, PO4-3. Phosphate in this form is unstable by itself and seeks to attract to other elements in the sediment with opposite charges to bond to. Therefore phosphates bond to iron and calcium to form phosphate rocks.

 

In the natural environment geologic uplift moves the rock back up to the surface. These rocks are weathered and will eventually release the phosphorus back into the ground; however this process takes place over geologic time. This process is too long to support the large amount of agriculture grown all over the world. Therefore, phosphate rocks are mined and processed to produce phosphoric acid that is used in fertilizers to maximize growth and yield from crops.

There are several locations in the World that have large deposits of these phosphate rocks that we are currently mining. The United States is the largest producer of phosphate rock in the World with 75% of the phosphate mined in the U.S. coming out of mines in central Florida. The majority of this phosphate rock is then exported, mainly to China. Many worry that at the rate we are mining and exporting our own supply of phosphate rock, we will soon no longer have an available supply for our own agricultural support. Scientists once estimated the rate of depletion of the U.S. supply at over 300years, however in recent years this estimate has dropped as low as 30years!!

This extreme and unsustainable depletion of this vital nutrient is only one cause for alarm in this process. The phosphate rock is mined through a process of strip mining. Strip mining removes 20 to 40 feet of the surface area to get to the rock. The rock, under the surface naturally contains some levels of uranium and radium. The toxic elements are not harmful when contained in the rock under the surface. However, once the rocks are mined they undergo a “wet processing” to remove the phosphorus. One of the by-products of this wet process is waste clay slurry that contains high levels of this now exposed uranium and radium. This waste cannot be disposed of so it is stored in huge settling ponds at the site of the mine. These settling ponds pose great risk to the environment as they collect rain water that initially would have recharged the local water table, along with the occasional spill or leak that has happened, and directly contaminated the local water supply. Waste clay settling ponds are only one of the toxic results of this process. Phosphogypsum, or gypsum, is another toxic result of the phosphate wet process.

 

 

The phosphate rock, once removed, is sent further to a processing plant where the rock is mixed with sulfuric acid. The product of this chemical reaction is phosphoric acid that is easily assumable by plants. The by-product of this stage of the process is phosphogypsum. Phosphogypsum is a radioactive material that also cannot be disposed of; therefore it is stored in a mound system that results in huge mounds, 200 meters high, of radioactive material. These mounds are referred to as “gyp stacks”. In Florida there are currently 20 of these gyp stacks, over a 600 acre plot of land and more are being built. Both the gyp stacks and the settling ponds have failed in containing the toxic matter and have contaminated the surrounding ecosystems. This vital nutrient that is needed to support strong growth of plants is damaging and toxic in the process of removal, and in the application process to the very agriculture it is mined to benefit.

Once the phosphate rock is processed into phosphoric acid it is used in fertilizers. These fertilizers however are being applied in a manner in which the plants are receiving the needed nutrients in excess. The result of this process is excessive run off of phosphorus into our water ways. What does phosphorus do? It promotes plant growth. In our water ways in such high levels phosphorus causes rapid growth of aquatic plants such as algae. The overgrowth of plant life in water ways causes multiple problems in the ecosystem of the water. This process of obtaining phosphorus faster than nature intended is one that has toxic and damaging repercussions from start to finish; however it is also needed to maintain maximum growth of our agriculture.

This vital nutrient is both necessary, and scarce in its natural process. There is no doubt that this process of retrieval is not sustainable, but a solution that is sustainable, I feel is going to take a global effort, and patience.