Nitrogen transformation during co-composting of spent pig manure, sawdust litter and sludge under forced-aerated system

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

18 Scopus Citations
View graph of relations


  • N. F. Y. TAM
  • S. M. Tiquia


Original languageEnglish
Pages (from-to)259-267
Journal / PublicationEnvironmental Technology
Issue number3
Publication statusPublished - 1999


Forced-aerated piles were built to investigate the transformation of nitrogen during co-composting of spent pig litter and sludge at 2:1 wet volume ratio. The total N concentration of spent litter-sludge increased during the early stage of composting due to the concentration effect as a consequence of strong degradation of carbon compounds in the spent litter-sludge piles. After day 21, the total N concentration decreased but there was no significant loss in nitrogen. The total mass of N was maintained at around 30 kg during the composting process. The ammonium- and nitrite-oxidizing bacteria increased in numbers during the active decomposition process (from day 0 to day 21), then dropped gradually as composting proceeded. At this early stage, the NH4+-N concentration declined and the (NO3-+NO2-)-N increased. However, the rapid decrease in NH4+-N concentration during the first 14 days of composting did not correspond to a rapid increase in (NO3-+NO2-)-N, indicating that some inorganic N was immobilized to organic N, some NH4+-N was volatilized, and some (NO3-+NO2-)-N was lost via denitrification. Denitrification only occurred during the early stage of composting and decreased significantly once the air was blown into the pile. Spatial variations in several physico-chemical and microbial parameters were found among four different locations of the forced-aerated piles, especially during the first 7 weeks of composting. The surface location had significantly lower temperature and population size of denitrifying bacteria than the top, middle and bottom locations, but higher concentration of total C and higher counts of ammonium-oxidizing bacteria were recorded in the surface location. © Selper Ltd., 1999

Research Area(s)

  • Animal waste, Denitrification, Heterotrophs, Nitrification, Nitrogen bacteria