Processing of Manure in Biogas Plants

Abstract

Biogas obtained from agricultural waste is becoming increasingly important as a renewable resource. Biogas can be obtained by biological and thermochemical methods. The first is the decomposi­tion of organic substances without air access due to the fermentation process, which takes place at a temperature of 30-40 degrees Celsius for «clean» waste (for example, microbiological industry) or 55-60 degrees Celsius for animal waste and urban wastewater. As a result of decomposition, biogas and a number of valuable components (nitrogen, phosphorus, potassium oxide) are formed, from which a highly effective organo-biofertilizer is prepared. (Research purpose) The research purpose is increasing the uniformity of the temperature field over the volume of the bioreactor to intensify the thermophilic process of anaerobic processing, increasing the yield of biogas and improvement of the quality of the biofertilizer. (Materials and methods) For the purpose of laboratory experiments, droppings from the poultry house of the peasant farm “Khemzet” of the Kabardino-Balkarian Republic were used with the analysis performed in the laboratory of the agrochemical service “Kabardino-Balkarian”. The total daily heat consumption and the capacity of the heat exchanger-agitator were determined using mathematical modeling and the laws of thermodynamics. (Results and discussion) The contents of the methane tank were heated by a heat exchanger using a coolant, and mixing was carried out using a mechanical stirrer combined into one heat exchanger–stirrer unit powered by an electric motor. It was shown that during the thermophilic process, more intensive and deeper fermentation of precipitation occurs, which contributes to a decrease in the volume of the methane tank, more effective destruction of helminths and weed seeds. It was found that during thermophilic fermentation, a greater amount of heat is needed to heat the sediment in the methane tank, 12-15 days are enough to disinfect the mass. (Conclusions) It was found that the optimal values of the temperature of the substrate processing process are 56.6 degrees Celsius; the mixing time is 17 minutes, the number of revolutions of the heat exchanger-agitator is 7.5 revolutions per minute. Chemical analysis of the obtained organo-biofertilizers was carried out.