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The over-enrichment of phosphorus in waste streams can lead to eutrophication and oxygen limitations for aquatic life. To understand the release of phosphorus from a soybean processing facility, it is imperative to track the flow of phosphorus in different streams during the processing of soybeans. The objective of the study is to develop process simulation models to study the flow of phosphorus in the soy-biodiesel process and evaluate strategies to mitigate phosphorus release by recovering phosphorous from soapstock and wastewater. Since most of the P is found in soybean meal, the processing of which releases phosphorus, a third case of lecithin recovery was also studied to reduce the amount of phosphorous in soybean meal. It was observed that phosphorus can be economically recovered from the soapstock, as well as the wastewater stream, with an estimated operating cost of USD 1.65 and 3.62 per kg of phosphorous recovered, respectively. The phosphorus recovered from both streams can be potentially applied as fertilizer to more than 13,000 acres of corn or 96,000 acres of soybean, respectively. The lecithin recovery case was found to have the highest revenue, and it led to a 54% reduction in phosphorous during soybean meal processing. 

Abstract Background and objectivesThe coproduct of ethanol industry, dried distiller's grains with solubles (DDGS), has phosphorus content in excess of the animal diet requirement, which leads to excess P in manure and causes environmental concerns. The objective of this study is to determine the technical and economic feasibility of recovering this excess P as a coproduct. FindingsThe amount of P was observed to reduce from 9.26 to 3.25 mg/g (db) of DDGS, which is consistent with the animal diet requirement of 3–4 mg P/g animal diet. For an existing dry grind plant of 40 million gallon ethanol capacity, an additional fixed cost of $5.7 million was estimated, with an operating cost increase of $1.29 million/year. ConclusionsThe total phosphorus recovered from the plant was estimated as 1,676 kg P/day, with an estimated operating cost of $2.33/kg P recovered. Significance and noveltyApproximately 37 million MT of DDGS is produced annually as animal food containing excess P, which is a serious concern for the environment. This study provides with an economically feasible solution to recover the excess P as a coproduct, which has a potential to be used as fertilizer on more than 56,000 acres of land annually, growing corn and soybean. 

Abstract Background and objectivesWet milling (WM) plants contribute to both point source and nonpoint source phosphorus (P) pollution by concentrating P in the coproduct corn gluten feed (CGF), the majority of which is undigested when consumed by ruminants, leading to manure management concerns. Phosphorus runoff from the manure consequently causes eutrophication in the water bodies downstream. This study investigates the economic feasibility of recovering the phosphorus at the front end from light steepwater to reduce P in CGF. FindingsThe amount of phosphorus in CGF was observed to reduce from 11.94 mg/g (db) to 2.44 mg/g (db), with phosphorus removal in the recovery unit calibrated with laboratory experiments. Direct fixed capital cost of $6.9 MM was estimated for the phosphorus recovery unit in an existing WM plant. ConclusionsWith a phosphorus recovery rate of 0.17 MT/hr, the operating cost of P recovery at the front end was estimated to be $1.23/kg‐P removed. Significance and noveltyRamifications of excess phosphorus in CGF on environment are an important understudied area. This study provided economic and technical feasibility of phosphorus recovery from CGF in WM industry, consequently producing a new coproduct and reducing the environmental burden.