Phosphorus removal from ethanol thin stillage to produce a low phosphorus livestock feed and a valuable granular fertilizer.

Grain ethanol production byproducts or ?coproducts? are commonly used in modern beef finishing rations. The term distillers grains (DGS) is intended to include these and similar coproducts. The expansion of the ethanol industry has led to the wide spread availability and economic pricing of DGS, resulting in significant amounts of DGS being commonly included in beef finishing rations. The fermentation of the starch in corn during the production of ethanol results in a three-fold increase in the concentration of phosphorus in the DGS versus its concentration in corn grain. Excess phosphorus is considered a pollutant in surface waters. DGS typically replaces corn and protein supplements in the ration, and by doing so increases the phosphorus content in the feedlot manure by as much as 120% (Trenkle, 2006) at reasonable inclusion rates (20-40%). Thus, the amount of phosphorus present at the farm and the risk of polluting surface water can be increased. Reducing the concentration of phosphorus in DGS would reduce the amount of excess phosphorus being fed to livestock, thereby decreasing the risk of surface water pollution. In the past, efforts to address the challenge of excess phosphorus at livestock farms have considered feed management, in so far as eliminating unneeded phosphorus supplements, but most efforts have focused on manure treatment. Manure treatment can be effective. For example, Kansas Environmental Management Associates, LLC (KEMA) developed a wastewater phosphorus reduction system named Phred for use at livestock farms. However, this requires capital investment in a treatment system by each individual farm with a phosphorus imbalance, and results in decentralized production of removed phosphorus The ethanol industry has become the largest user of corn in the nation, which makes it one of the largest producers of livestock feed in the nation. Addressing the phosphorus surplus at the ethanol plant, is much more efficient than trying to address the problem at each feedlot?s location. Research from Iowa State University (Meyer, 2006) indicated that the amount of phosphorus excreted is directly related to the dietary phosphorus intake. So if the dietary phosphorus intake can be decreased by decreasing the phosphorus concentration in DGS, the excreted phosphorus should also be decreased. Based on available literature it is estimated that a reduction of phosphorus in the thin stillage by 50, 70, or 90 percent could reduce the phosphorus concentration in the final livestock feed (in this case ?wet distillers grain plus solubles?) by 31, 43, and 55% respectively. So, there is an excellent opportunity to significantly decrease surplus phosphorus being fed in feedlot rations. The Phred system developed by KEMA removes soluble phosphorus from livestock wastewater by converting it to an insoluble compound called struvite, or magnesium ammonium phosphate hexahydrate. Phred is a very simple system, utilizing a fluidized bed reactor to produce 1 ? 3mm diameter struvite granules.