Composting of the solid fraction of pig slurry amended with natural zeolite (clinoptilolite)

A small-scale (50-55 kg), 12-week experiment was carried out to observe the effect of amendment of pig slurry solids with two different doses of natural zeolite-clinoptilolite: 1% (substrates 2 and 5) and 2% (substrates 3 and 6) by weight, in comparison with the control (unamended solids, substrates 1 and 4) on decomposition processes when stored under anaerobic conditions or with turning after three and six weeks of storage at 18-23 degreesC. Temperature in the core of the substrates was recorded in one hour intervals. Zeolite had no positive effect on temperature during the first half of the experiment. The temperatures reached were not sufficient to ensure sanitation of the stored substrates. Significant differences in dry matter (DM) content (P<0.05) were observed between substrates 1 and 3, 2 and 3, and 4 and 6. The differences in the ash content were significant especially between substrates 1 and 3 (P<0.05). Considerable increase in total phosphorus (% DM) in the second half of the experiment was observed in substrate 3 (6.8 times higher in comparison with the control). The pH, total nitrogen and water-extractable forms of nitrogen were affected too. A dose-dependent effect of zeolite on the loss of nutrients in liquid released during the first 48 h of storage was observed.