---

Abstract:The intensive livestock production is responsible for a number of environmental threats. The main source of animal waste is generated in the form of slurry. The inadequate fertilizing (against the BAT rules) can often lead to contamination of soil and water. In turn, the presence of heavy metals found in factory farms by the use of animal feed supplements, prevents its use as a fertilizer. Therefore, other possibilities to recycle the waste are being studied. The aim of the research was to analyze the effect of heavy metal ions on the methane fermentation process yield in contaminated slurry. The manure studied came from dairy cattle farm in Greater Poland region. The tested substrate has been contaminated by heavy metal salts. In the experiment, the following salts have been used ZnO4·7H₂0, CdCl₂·2,5H₂O, CuSO4·5H₂O, Pb(NO₃)₂. Anaerobic biodegradation of the fertilizer has been carried out in thermophilic conditions, which enables to indicate the effect of temperature on the efficiency of the occurring process. Furthermore, by comparing mesophilic and thermophilic fermentation, one can notice a higher methane yield from the contaminated slurry during the fermentation at lower temperatures.

---