Thin stillage (TS), a byproduct from the fermentation of corn in the production of fuel ethanol, is used as a component of animal feed. As a consequence of the loss of carbohydrate during fermentation, element concentration of TS is high. TS phosphorus (PS) is problematic because animal feed prepared with TS results in animal wastes high in PS. The PS may contaminate nearby water bodies leading to eutrophication with subsequent algal bloom and hypoxia. One possible remedy would be to remove a portion of PS from TS, thereby lowering the PS levels in animal waste. The removed PS could be recycled, decreasing the demand for mined PS which is in finite supply and will become exhausted in the future. Thin stillage was treated with two biobased flocculants, hemoglobin (HEM) or porcine blood (PB), which caused the solid phase of TS to rapidly sediment, leaving an aqueous supernatant. The optimal concentrations of the flocculants were determined two ways: concentration(s) giving the fastest decrease in turbidity and concentrations giving the highest percent pellet mass. The aqueous supernatant contained about one-half of PS and about one-third of the total Kjeldahl nitrogen (TKN). Optimal removal of PS with FeCl3 occurred at pH 4.0. About 85% and 87% of supernatant PS was removed by treatment with FeCl3 after flocculation of TS with HEM or PB. FeCl3 also removed a portion of the TKN, but the TKN levels of PS-depleted supernatant were partially restored by TKN from HEM and PB. In conclusion, flocculation of TS allows separation of the aqueous and solid phases of TS. The aqueous phase can be used as a component of a fertilizer, or alternatively, aqueous phase PS can be removed by treatment of FeCl3. The PS-depleted aqueous phase can be mixed with flocculated TS solids to produce a lower PS animal feed.

Concentration and removal of phosphate from corn thin stillage using biobased flocculants and ferric chloride

255th National Meeting (2018)

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