Assessment of products of anaerobic fermentation of organic raw material from poultry last by microbiological indicators
Authors: Podoba Yu. , Pinchuk V. , Tertychna O. , Beznosko I. 
Published: August 2024

The product of anaerobic microbiological transformation of bird droppings is a liquid suspended product (digestate), the composition of which is characterized by new chemical features acquired due to the activity of anaerobic microorganisms. This process takes place in biogas plants, and as a result of methane fermentation of bird droppings, biogas and residues of organic raw materials are formed, which are used as fertilizer. The international practice of using digestate as an organic fertilizer or soil improver for the farm’s own needs is similar to classic composts and does not require sanitary and microbiological certification, but there are voluntary certification standards, as well as various industry guidelines on the quality of organic fertilizers. The work analyzes international and national sanitary microbiological standards regarding digestates, products of processing by-products of animal husbandry and organic substances for application to the soil, in particular Regulation (EU) 2019/1009 of the European Parliament and the Council of June 5, 2019 «On establishing rules for placing fertilizers on the market EU», DSTU 7527:2014 «Poultry droppings. Technologies of biological processing. General requirements», DSTU 7938:2015 «Organic fertilizers. Agronomic requirements for the quality of fertilizers for use in organic production». Information from scientific articles, standards of individual countries and guidelines of international voluntary certification bodies regarding the assessment of digestate applied to the soil as an organic fertilizer or soil improver is summarized. It has been established that mandatory sanitary microbiological characteristics for such substances are Salmonella bacteria (Salmonellas spp.) and Escherichia spp. bacteria, as well as the standards of some countries and scientific literature recommend determining Coliform bacteria and Streptococ-cus faecalis bacteria, the presence of which indicates the possible presence of potentially dangerous strains of microorganisms. With the use of laboratory equipment, the granulation conditions of the solid fraction of the digestate were optimized to obtain granulated organic fertilizer from the sludge of the biogas plant. A microbiological analysis of granulated digestate from a biogas plant on bird droppings was carried out in order to establish its compliance with the sanitarybacteriological requirements for organic fertilizers. The presence of pathogens of infectious diseases in poultry droppings and the presence of phytopathogens in grain, which is used for the preparation of premixes, increases their probable migration into the composition of organic fertilizer in case of improper methane fermentation with violation of temperature and exposure conditions. Microbiological analysis of granulated digestate showed the absence of Salmonellas spp. and Escherichia spp. bacteria in the studied samples, but a high number of mold fungi 1.2·104±7.25·102 CFU/g was found, which may be a consequence of storage wet raw materials. In order to prevent microbiological contamination during the storage and transportation of raw materials and organic fertilizers, a necessary condition is compliance with sanitary requirements for all technological processes, starting from the conditions of keeping and feeding animals to the conditions of storage of finished products and application to the soil. The content of harmful microorganisms in the digestate of biogas plants operating on bird droppings or animal manure without litter or the addition of plant residues and chemicals depends mainly on the quality of the droppings and water. The quality of raw materials affects the quality of the digestate and is determined by the sanitary-epidemiological condition of animals and premises, microbiological contamination of feed, pre-treatment of raw materials for loading to the biogas plant. It was established that the granular digestate from bird droppings meets the requirements of Ukrainian standards DSTU 7527:2014 regarding organic fertilizers from poultry droppings and DSTU 7938:2015 regarding organic farming, which allows for further substantiation of optimal application technologies. To control the secondary bacterial contamination of organic raw materials during the storage process, the effectiveness of the use of commercial biological preparations was evaluated. The perspective of using commercial microbial preparations, in particular MycoHelp, to control mold fungi of the genus Penicillum spp. in the technologies of processing by-products of agriculture into organic fertilizers and preventing spoilage of finished products during storage.