Application of the Thermophilic Fermentation Method to Obtain Environmentally Friendly Organic Fertilizer

In this study, the authors obtained samples of biological fertilizer by thermophilic fermentation of substrates of different compositions. Two types of effluent were studied in the experiment: food plant waste with the addition of cattle manure and liquid pig manure with litter cattle manure. To activate the process of obtaining fertilizer, the Agrarka biological preparation was added containing a complex of microorganisms and bacteria that accelerate the decomposition process. A detailed chemical analysis of the liquid and solid fractions of the raw materials and the obtained products was carried out for the content of total phosphorus (P), carbon (C), potassium (K), nitrogen (N), ammonium nitrogen (NH4+), organic matter, dry matter, cadmium (Cd), cobalt (Co), manganese (Mn), copper (Cu), nickel (Ni), mercury (Hg), lead (Pb), chromium (Cr), zinc (Zn), and arsenic (Ar). The indicators of acidity and ash content were determined and microbiological analysis was carried out. The obtained results showed that the thermophilic temperature regime of fermentation accelerated the decomposition process, positively affected the total content of the main nutrients in the studied substrates, and negatively affected the vital activity of microorganisms. In two types of effluents, there was a significant increase in the level of ammonium nitrogen by up to 60%, a decrease in the total carbon content by 15–30%, and dry and organic matter by 10–12% in both liquid and solid phases. However, in the effluent from food plant waste with the addition of cattle manure, the indicators increased by 13% in total carbon and by 8.2% in dry matter, and the ash content was 3 times lower than in the second effluent. Thus, thermophilic fermentation obtained two types of effluents with high-quality indicators corresponding to environmental and sanitary standards, since the content of microorganisms and heavy metals did not exceed the permissible limits.