Method of designing of manure utilization technology
Institute for Engineering and Environmental Problems in Agricultural Production – IEEP, Filtrovskoje shosse, 3, RU196625 St. Petersburg-Pavlovsk, Russia
Specific feature of modern livestock farms is concentration of a large number of animals and subsequent significant environmental load. The biggest negative impacts are on the atmosphere through ammonia emissions and on water bodies through nitrogen and phosphorus compounds leakage, with manure being the major source of these pollutants. The proper choice of an effective low-cost manure handling technology with high nutrients retention ensures the environmentally sound operation of these farms. With this aim in view a designing method of manure utilization technologies is proposed. Relevant available technologies were reviewed, a mathematical model was created and technology assessment criterion was defined. Manure utilization technology is understood as a set of activities, including manure processing, manure storage (if necessary) and soil application of organic fertilizers. To create a mathematical model 12 manure utilization technologies were examined. These technologies are based on various methods of manure processing, such as long-term maturing, composting, biofermentation, separation into fractions, drying and biogas production. The created mathematical model takes into account the economic and environmental performance of each technology. The proposed approach makes it possible to calculate and compare the level of nitrogen preservation in manure and required inputs for different technologies depending on the farm animal stock. To assess and select the most suited technology the eco-efficiency criterion is suggested, which takes into account the yield increase, the cost of generated energy (for biogas production), and reduced negative impact on the environment. The paper presents example of using the method to make a choice of technologies for a dairy farm. Experience in the use of the method shows that the average values of nitrogen preservation in the manure, which may be achieved without involving excessive costs, are 72% for cattle manure, 70% for pig manure and 78% for poultry manure.