The aim of this study was to investigate the ammonia uptake by natural zeolite when used as an ingredient during the composting process. The amounts of 5 a nd 10% of natu ral zeolite were applied to organic fraction of municipal solid waste as volume and compared with the s Vstem of nonadded. The results clearly, showed that the ammonia releases during the composting processes reached to higher levels in the nonadded composting system of the organic debris derived from municipal solid waste of Samsun. The natural zeolite readily trapped excess nitrogen during the processes and reduced ammonia odors. It was found that the ammonia concentration in the final compost decreases with increasing the amount of natural Zeolite used. Ammonia uptake efficiencies were 74.94 and 87.98% for end product containing 5 and 1096 natural zeolite, respectively. Significantly, the addition of natural zeolite to municipal solid waste compost was found to have a beneficial effect on the characteristics of the end product. (C) 2007 American Institute of Chemical Engineers Environ Prog, 26: 149-1567 2007.