Microbiology of composting pig waste: Comparison of vermicomposting and open heap techniques

Against the background of an effective waste management, microbiological studies of composting pig waste were investigated. Freshly deposited excreta from confined pigs in a private pig farm in Benin City, Edo State, Nigeria were composted by two aerobic methods – vermicomposting and open heap. Microbial (bacterial and fungal) counts and characterization were carried out periodically within the 40 weeks of composting, using standard techniques. The results showed that only duration of composting significantly (p < .0.05) affected microbial counts as the counts decreased from the initial value at week zero to much lower value at week 40. A total of 274 bacterial and fungal isolates were recovered from the composting waste and majority (60.58%) were isolated from the open heap. Bacillus subtilis, Pseudomonas aeruginosa and Aspergillus flavus were the predominant isolates recovered (9.49% each), and were the only isolates recovered throughout the period of composting irrespective of the composting technique. Staphylococcus aureus and Salmonella typhimurium were the least isolated (1.09% each). Vermicomposting technique was recommended on health and environmental grounds.