Digested residue as a fertilizer after the mesophilic process of anaerobic digestion

Abstract

The aim of this paper is to determine the difference in quality of the digested residue after the process of anaerobic digestion by using different input raw materials. The research was conducted in the Republic of Austria on four facilities for biogas production. The raw materials used for biogas production were chicken manure, pig manure, Sudan grass and organic household waste. The research included chemical analysis and bacteriological tests of the samples taken. It was found that the digested residue in all of the samples, all of which are mildly alkaline, contains a low level of dry matter, 70% of which is organic matter. Biogenic elements were present in moderate concentration; the values of heavy metals were within approved limits. This analysis leads to the conclusion that the digested residues of all input materials can be used in agricultural production, especially so in plant production and grassland cultivation. Mesophilic and thermophilic microorganisms were found in the digested residue samples, but there were no cryophilic microorganisms and no pathogenic bacteria.