Phosphorus Sustainability Trevor Ghylin, P.E. CEE 320

Learning Objectives/Exam Questions Understand the global phosphorus cycle Why is phosphorus important to our society? Where does it come from? Where does it end up? Is the current phosphorus system sustainable? How long will supplies last? What are the problems with the current system? What impact does phosphorus mining produce? How does phosphorus affect lakes, rivers and oceans? What are the two major losses of phosphorus? Understand phosphorus recovery from wastewater How is phosphorus recovered?

Outline About me Background on phosphorus Why is phosphorus important? Where does it come from? Where does it go? Is it sustainable? What are the problems with the current system? Nutrient Recovery from Wastewater Questions

Bio

Question for You Why is phosphorus important to our society?

Why is Phosphorus Important? Biological Need DNA and RNA ATP Phosphorylation Membranes Bones Agricultural Need Limited resource There is no replacement Essential ingredient for food production

Question for You Where does Phosphorus come from?

Where does Phosphorus Come From?

Where does Phosphorus Come From? Cont’d Phosphorus Mining Acid Pond/Phosphoric Acid Gypsum Phosphate Rock

Where does Phosphorus Come From?Cont’d

Five countries control 92% of the world’s remaining phosphate rock reserves. Morocco occupies Western Sahara and controls 77% of world reserves. The United States has been the source of about one-third of the world’s production in the last century (Vacari, 2011) 80% from a region of central Florida east of Tampa known as Bone Valley. U.S. economic reserves are sufficient at current rates of exploitation for about 40 years. Production rates have been declining for 30 years. In the future, the U.S. will rely on imported phosphorus. Since 2004, U.S. no longer exports phosphorus. Now imports 10% of total consumption.

Sustainability of Phosphorus – Pre-2010 Projections Peak phosphorus was projected for Alarming projections Global reserves of 15,000 Mt (million metric tonnes) of phosphate rock Population projected to grow from 7B to 10.5B by year Phosphate demand growing at 2% per year in the near term. 90 years of global supply at then current rates of extraction.

Sustainability of Phosphorus – Updated Projections >400 year phosphate supply Peak phosphorus may occur around 2145 or earlier depending on actual population growth and increased per capita consumption of phosphorus. Morocco estimates increased from about 5,000 metric tonnes to 50,000 metric tonnes Global reserve estimates increased from 15,000 metric tonnes to 65,000 metric tonnes

Sustainability of Phosphorus Radioactive waste Raw phosphate rock contains cadmium and uranium Phosphorus mining creates large stockpiles of radioactive gypsum (CaSO4)

Question for You Where does Phosphorus end up?

Eutrophication Fish Kills Toxic Algae blooms Dangerous to pets and humans Nuisance Odors

Problems Phosphorus Mining Phosphate rock is a non-renewable resource There is no alternative or replacement for phosphate rock Many countries are at the mercy of the five that control the world’s phosphate reserves Phosphate mining creates local environmental problems Phosphorus Pollution Phosphate fertilization creates regional environmental problems due to eutrophication of surface waters and dead zones

Radioactive Gypsum Stockpiles Florida's Rich Phosphorus Fields The stadium-size gypstacks are especially abundant on the Bone Valley Formation in west central Florida, one of the world's richest sources of phosphorus.

Where does Phosphorus end up?

Radioactive Mining Waste Aerial photograph of the waste produced by intensive phosphorus mining.

Phosphorus Sustainability The net effect of this cycle Mining of phosphorus in concentrated locations Broad distribution over agricultural lands Shipping as food to urban areas Discharge to landfills or water bodies (and eventually into the ocean) Along the way significant losses occur from erosion of agricultural lands and runoff from improper land application of animal wastes Natural ecosystems recycle phosphorus intensively, an estimated 46 times in terrestrial ecosystems, and 800 times in the oceans (Volk, 2003) Human systems pass much of the phosphorus through after a single use. If more phosphorus were recycled and conserved, less would need to be mined, and society would have more time to make any necessary adjustments

Sustainability of Phosphorus Only 17% of phosphorus fertilizer makes it into the human diet Improper land application of animal wastes Most technically and economically feasible potential for reuse is the loss of about half of the nutrient content of animal waste CAFOs produce large volumes of animal wastes. In the U.S., only about half of this material is properly returned to agricultural use Much of it is either accumulated in waste piles or applied to lands in amounts beyond what can be assimilated by crops, therefore resulting in excessive runoff

Sustainability of Phosphorus Agricultural erosion Difficult to control Phosphorus is strongly bound to soil particles Past practices of overfertilization increased this loss Agricultural practices known collectively as conservation agriculture (described below) can reduce this loss, but it is likely to remain significant even with intensive practices No-till agriculture Genetically modified crops resistant to herbicides Herbicides can be used to limit weed growth instead of tilling which increases erosion Improved field leveling or contour farming, or precision timing or placement of fertilizer

Sustainability of Phosphorus Food waste About 57% of the phosphorus that makes its way to the food supply is lost as food waste between “the harvest and the fork.” Food waste is an area of nutrient waste that has not yet garnered much attention. 3 Mt/yr flow of phosphorus as human wastes Only about ten percent is currently reused. About 40% winds up in landfills. The balance is discharged to surface waters, where it contributes to environmental problems. There has been a considerable amount of effort to remove phosphorus from this flow for environmental protection, as well as to recover it for recycling. Human usage is only about 17% of total phosphorus demand.

Solutions Phosphorus can be recycled Sweden has set a goal to recycle 60% of phosphorus from wastewater to productive soil by 2015 Germany also has goals for recycling phosphorus from sewage

More Mouths, More Mines This photograph shows an outlet pipe from a phosphate waste impoundment in Lakeland, Florida; the waste forms a stream that joins the water table. The phosphate mines in central Florida pose an environmental threat to the region.

The Role of Phosphorus This eerie photo shows liquid wastes mixing in an impoundment pond in one of Florida's phosphate mining areas.

A Vanishing Act Extensive mining and agriculture in west central Florida have lowered the water table enough to turn springs into sinkhole. On June 27, 1994, a gaping sinkhole developed in a 400-acre, 220-foot-high gypsum stack containing a liquid impoundment of acid and ammonium. About 4 million cubic feet of phosphogypsum and an undetermined amount of acidic water disappeared through that shaft into the ground.

Lingering Legacies This photo shows one area of a holding pond at a Louisiana fertilizer factory. The plant is one of many along an eighty-five-mile stretch of the Mississippi River known as the "chemical corridor."

Recovering Phosphorus from Wastewater Nutrient Extraction Crystallization processes that produce struvite (MgNH4PO4) or other precipitates Recover as much as 40% of plant influent phosphorus Produce sterile mineral slow release fertilizer The recovered phosphorus does not pay for the cost of the process but is a secondary benefit. The primary benefit is the prevention of struvite formation in equipment which causes maintenance problems and requires costly chemicals to prevent formation. Madison MSD is in the process of implementing a phosphorus recovery process provided by Ostara Inc.

Recovering Phosphorus from Wastewater Incinerator Ash Phosphorus can be recovered from biosolids incinerator ash using acids or thermal processing with chlorine compounds. Ash can be directly used as fertilizer if there are no heavy metals in the source biosolids (i.e. animal wastes). Source separation can be used to recover phosphorus Collect urine separately Urine contains the majority of phosphorus in human waste and is normally sterile Concern about excreted pharmaceuticals and other chemicals Urine can be used directly as a fertilizer if diluted 5-10 fold

Conclusions Understand the global phosphorus cycle Why is phosphorus important? Where does it come from? Where does it go? Is it sustainable? What are the problems with the current system? What impacts does phosphorus mining produce? How does phosphorus affect lakes, rivers and oceans? Understand phosphorus recovery from wastewater How is phosphorus recovered?

Questions? Consulting Graduate School Environmental Engineering