Upgrading Struvite Recovered from Dairy Waste into Marketable Fertilizer and Feed Products

This project develops a commercial process for modifying phosphorus recovered from dairy manure and other waste streams into marketable feed and fertilizer products. Phosphorus release from dairies and other concentrated feeding operations is a growing environmental problem. Meanwhile, domestic supplies of mined phosphorus are rapidly depleting, confronting U.S. agriculture with serious cost impacts in the near future. Successful modification of a die pelletizer enabling the crystalline struvite recovered from waste organic matter to be converted into a phosphorus-rich pellet will be a low-cost means of "recycling" this nutrient. It will then be possible to transport phosphorus from where it is a problem - animal feeding operations -- to where it is needed - produce farms and greenhouses. The employment of commonly available infrastructure to process a new, bio-based phosphorus fertilizer and nutritional supplement will be particularly attractive to feed and fertilizer dealers already positioned to process and retail these items. A market for struvite will also encourage wider adoption of anaerobic digesters at animal feeding operations, since the struvite can be most efficiently extracted from manure management systems. Modified in the way this project envisions, struvite will be easily transportable, provide a slow-release source of phosphorus and nitrogen when incorporated into soil, and be digested by animals as a nutritional supplement. This research will also explore opportunities for incorporating struvite into multi-nutrient products, enabling fertilizer distributors to customize "bio-based" fertilizers as they currently do with synthetic nutrient formulas. Unmodified struvite, as it emerges from manure waste streams, is unfortunately too fine to be efficiently handled by fertilizer distributors or be incorporated with other substances. The struvite therefore requires an "upgrade" to its compaction to make its texture consistent with other substances typically handled by agricultural supply facilities. Multiform estimates such an upgrade will more than triple the value of struvite. If this project can arrive at a commercially viable process for compacting struvite that avoids the cost of a specialized processing facility, it will reduce the time required to deliver struvite to market by several years, and avoid capitalization costs of half a million dollars or more. Furthermore, a standardized method for utilizing commonly available die pelletizers to render granulized struvite will make the product available across a very wide market.