Reducing Phosphorus Concentration in Animal Feed Coproducts from the Corn Distilling Industry
2010
Alkan-Ozkaynak, A. | Karthikeyan, K.G. | Roa-Espinosa, A.
High phosphorus (P) content of animal feed coproducts of dry grind corn ethanol plants can lead to dietary P levels that are incompatible with P-based nutrient management plans. Therefore, treatment of thin stillage, the dominant P contributor of coproducts, was investigated using centrifugation followed by chemical treatment with coagulants (lime, alum, ACH) and flocculants (anionic and cationic polymers). The majority of the P and solids in thin stillage are in the dissolved form (<0.45 µm). Centrifugation resulted in a solids fraction with high crude protein and low P content, which could be appropriate for use in animal feed rations. Removal of both inorganic (dissolved reactive P) and organic (phytase hydrolyzable P) P was achieved with chemical treatment. Lime treatment resulted in significantly (p < 0.05) higher P removal (up to 85%) than Al-based coagulants (up to 70%). Anionic polymers resulted in better flocculation and produced bigger and more stable flocs compared to those obtained with cationic polymers. The low total solids removal achieved could be attributed to the inability of chemicals used to separate the dissolved solids component. Our results suggest that while both Ca-based and Al-based coagulants are effective in reducing the P content of thin stillage, extremely low alkalinity of thin stillage limits the effectiveness of acidic coagulants.
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