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Application of thermophilic aerobic digestion in protein enrichment of high strength agricultural waste slurry for animal feed supplementation
Author(s) -
Ugwuanyi J Obeta,
Harvey Linda M.,
McNeil Brian
Publication year - 2006
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.1574
Subject(s) - slurry , food waste , chemistry , anaerobic digestion , digestion (alchemy) , ammonia , aerobic digestion , raw material , thermophile , food science , protein quality , pulp and paper industry , aeration , chemical oxygen demand , waste treatment , volume (thermodynamics) , waste management , wastewater , environmental science , chromatography , biochemistry , environmental engineering , methane , enzyme , organic chemistry , engineering , physics , quantum mechanics
Abstract Thermophilic aerobic digestion (TAD) is a relatively novel waste processing technique with the potential to improve the safety and nutritional value of many agricultural and food industry wastes for use in animal feed supplementation. TAD of model agricultural waste slurry, at soluble chemical oxygen demand (COD) load of approximately 8.0 g L −1 , was implemented to study the effect of the process on crude protein accretion and waste quality. Digestions were carried out under batch conditions at 0.1, 0.25, 0.5 and 1.0 vvm (volume of air per volume of waste slurry per minute) aeration rates and pH 7.0, and at pH 6.0, 7.0, 8.0, 9.0, 9.5 and without pH regulation at 0.5 vvm, all at 55 °C. All reactions were carried out for 156 h using thermophilic populations indigenous to the waste. Digestion at 0.5 and 1.0 vvm led to the greatest degradation of total suspended solids (51.17% and 52.03% respectively) and the highest accretion of crude protein in treated waste (131.28% and 258.94% respectively). Protein content of the digest decreased as digestion pH increased beyond neutral. Slurry soluble protein content decreased with digestion progress, while the ammonium increased early in the process before decreasing progressively. The percentage content of most amino acids in the digest decreased slightly relative to raw waste. The quality of waste protein was comparable with the FAO standard for protein supplement for feed use. Overall, the digested waste was significantly improved relative to the raw waste. With appropriate process optimization TAD has clear potentials for use in the improvement of various wastes for recycling in animal feed. Copyright © 2006 Society of Chemical Industry