Forming of environmentally friendly technologies of pig manure utilisation

Abstract

Research on BAT for intensive pig rearing showed that manure utilisation is the most sensitive and important element of any relevant technology. Formation of the manure utilisation technology includes the following steps: to identify the most applied practices by the decomposition method and block-hierarchical scheme; to create a mathematical model of pig manure utilisation, which includes characteristics of pig manure, utilisation techniques, machines and equipment for manure handling, and characteristics of produced organic fertilizer; to determine the most effective technology; to make a list of optional combinations of machines and equipment; to compare the obtained values in all combinations by the sound indicators using the Pareto method. The described procedure was tested on a pig complex with the complete pig rearing cycle with the average stock of 16,500 heads and manure humidity of 93 %. The most effective technology for this pig complex was found to be separation of manure into fractions with the subsequent processing of the solid fraction by passive composting and the biological treatment of the liquid fraction in an aeration tank and batch-type settling tanks. This technology features the following values of the main indicators: utilisation costs of one ton of pig manure with due account for nitrogen loss 1.99 thousand roubles per t, ecological and economic effect of the technology use and organic fertilizer application is 10463.6 thousand roubles per t and economic efficiency of BAT introduction 3495.7 thousand roubles per t. The technology indicators may be slightly improved if composting is replaced by bio-fermentation in closed installations and if the hose injection systems are used for clarified liquid application. In this case the costs are lower by 5-7 % and the effectiveness of BAT introduction is lower by 2-3 %.