Hygienization assessment during heap co-composting of Turkey manure and olive mill pomace

Abstract

This study aimed to investigate the co-composting time effectiveness as well as the effect of the initial Carbon/Nitrogen ratio (C/N)i variation on the hygienization of olive pomace and turkey manure. Six different heaps, at 3 levels of (C/N)i ratios: 20, 22 and 28, were installed and monitored during 6 months and assessed at three steps: At the beginning, the end of thermophilicphase and the end of curing-phase. The microbial monitoring concerned 5 microbial pathogens contents, used as hygiene microbial indicators, namely: Sulphite-Reducing Anaerobes (SRA), Escherichia Coli (E. Coli), Total Aerobic Mesophilic Flora (TAMF), Staphylococci, and Salmonella spp. Initially, the mixtures showed high TAMF and Staphylococci loads. Meanwhile, SRA and E. coli populations were relatively low and Salmonella spp. was not detected. The microbial assessment showed a significant effect of composting time on the reduction of pathogens load, except for SRA where its population has increased significantly, while the (C/N)i had a non-significant effect on pathogen content of the end-product. The final values expressed as colony-forming unit per gram (CFU g-1), were as follow: Sulfite-reducing Anaerobes (≤3.1 x 103 CFU g-1), E. Coli germ used as an indicator of faecal contamination (<4 x 101 CFU g-1), Total aerobic mesophilic flora (≤1.4 x 106 CFU g-1), Staphylococci (<10 CFU g-1) and non-detection of Salmonella spp. Finally, the seed germination tests were carried out on three different seeds: lentils (Lens culinaris), barley (Hordeum vulgare) and durum wheat (Triticum turgidum) showed that the use of the compost extract is favourable for seed germination with germination index (GI%) values exceeding 85%. These results confirm the non-phytotoxicity and maturity of the composts.