The aim of this experiment was to establish the effect of the ProBio Origi-nalTM preparation (hereinafter "preparation") on the composting process of bio-logically degradable waste in garden composters. The first stage of research was focused on the effect of different concentrations of the preparation onto the com-posting process in garden composters. Monitored parameters were the effect of the preparation on the course of temperatures during the composting process, material volume decrease and effect on the quality of the composted material. The input raw material was freshly cut grass provided by Centrální kompostárna (Central Composting Plant) Brno, a.s. The experiment was carried out in five garden composters (290 L) for a pe-riod of 13 weeks. Three composters were enriched with the preparation at different concentrations, two of them were reference composters. During the experiment, the course of the composting process was monitored (temperature, loss in material volume) as well as the compost quality (C/N ratio, nutrients, heavy metals).During the experiment, a positive influence was observed of the preparation on the course of temperature in the composters. The enriched composters reached in the mineralization phase the thermophilic temperature ranges for a period of two weeks. The rate of composted material volume reduction in the composters with the preparation was higher than that in the reference composters.
Moreover, a positive effect of the preparation was observed on the compost quality. As compared with composts from the reference composters, Ca and Mg concentrations in the resulting compost from the enriched composters were higher. The effect of the preparation on the concentration of other nutrients was not demonstrated.