Results of the study of the chemical composition of the sludge of a biogas plant during the processing of cattle manure mixed with poultry manure and expired food products

The chemical composition of the sludge obtained from processing cattle manure mixed with poultry manure and expired food products was studied using the methane fermentation method. The studied load with cattle manure contains 1,4 times more proteins, 1,6 times more fats and 2,4 times less carbohydrates compared to the load with cattle manure and poultry manure. It was found that fermentation of the load with cattle manure increased the content of nitrate nitrogen by 1,4 times compared to the load with cattle manure and poultry manure. Fermentation of the load with cattle manure increased the content of total nitrogen in the sludge by 7,2, total phosphorus by 6,9, nitrate nitrogen by 4,5, organic matter by 13,2 times, and decreased total potassium by 2,8 times. The content of organic matter, total nitrogen and total phosphorus in the sludge increased during processing. When using sludge as an organic fertilizer, it is necessary to balance its composition. The resulting sludge meets the requirements of GOST 33380-2015 for heavy metal content. Paired linear regression equations were calculated for use in forming the composition of the loads.