ENVIRONMENTAL SAFETY OF THE TECHNOLOGY OF HANDLING DIGESTATE OF DIFFERENT GENESIS

Abstract

In the modern world, biogas technology is gaining momentum as an ecological alternative to the production of biofertilizer after anaerobic fermentation of various types of waste. Due to the large amount of organic, nutrient and biologically active substances, biogas digestates are often applied directly to the soil as an organic fertilizer to improve soil quality and increase yield. The purpose of the article is to determine the ecological safety of the digestate obtained after anaerobic fermentation of chicken litter and sewage sludge, as part of a biocomposite for soil purification from heavy metals. The methodological basis of this study are experiments on the phytotoxicity of digestate samples based on the results of the germination of pepper seeds in Petri dishes using aqueous solutions of untreated digestate and digestate treated with phosphogypsum. The expediency of choosing a phosphogypsum treatment method was due not only to the possibility of reducing the presence of pathogens in digestates, but also to obtain a biocomposite capable of adsorbing harmful elements from the soil and feeding it with necessary substances. Using the germination index, the level of phytotoxicity of digestate based on various organic wastes was assessed, the effectiveness of the use of digestate as a biological fertilizer was substantiated. It was determined that digestate based on sewage sludge became an ecologically safe substrate for the germination of pepper seeds. Digestate from chicken litter treated with phosphogypsum on the 20th day of anaerobic fermentation showed a phytotoxic effect on pepper seeds. Indicators of the germination index increased on the 30th day of anaerobic fermentation, which indicates a decrease in the toxicity of the material after the end of the anaerobic fermentation process. In general, a germination index higher than 50% was observed in all samples of untreated digestate and a greater number of samples of treated digestate for both substrates. The article provides recommendations for evaluating the maturity of digestate using the seed germination index as a quick indicator for determining the phytotoxicity of substrates and, accordingly, the level of environmental safety of the material for soil and plants.