Application of thermophilic aerobic digestion in protein enrichment of high strength agricultural waste slurry for animal feed supplementation

B. McNeil, L.M. Harvey, J.O. Ugwuanyi

Research output: Contribution to journalArticle

8 Citations (Scopus)

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.
Original languageEnglish
Pages (from-to)1641-1651
Number of pages10
JournalJournal of Chemical Technology and Biotechnology
Volume81
Issue number10
DOIs
Publication statusPublished - Jan 2006

Keywords

  • thermophilic aerobic digestion
  • protein enrichment
  • amino acid content
  • agricultural waste slurry
  • animal feed
  • protein quality
  • pharmacology

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