Mitigation of ammonia emissions by natural zeolites during pig slurry composting

Abstract

The objective of this work was to evaluate the efficiency of the natural zeolites clinoptilolite and stilbite to mitigate ammonia (NH₃) losses during the initial phase of pig slurry (PS) composting. Three experiments were performed in pilot scale, each lasting 14 days. The zeolites were added to the PS in increasing rates, from 5 to 20% (w/v), on a substrate consisting of a mixture of sawdust (70%) and shavings (30%). Three applications of PS + zeolites were performed per experiment, followed by a turning. The substrate went through three additional turnings, between applications. The zeolites reduced NH₃ emissions and their efficiency was directly related to the applied rate. Clinoptilolite was more efficient than stilbite. In the average of the three experiments, clinoptilolite reduced in 24 to 76% NH₃ emissions. The results show the high potential of natural zeolites, mainly clinoptilolite, in mitigating NH3 volatilization during PS composting.