Study On The Phosphorus During The Aerobic Composting Process

With adjustment of the agriculture structure and the development of its industrialization, large-scale and intensive livestock farm has rapidly developed. The dimension is from small to large, and the area is from point to surface, which makes the country economy improve. Because of the poor management of the livestock farm and its disjointing with agriculture, a large amount of the livestock wastes are disposed at random, which pollutes the water, soil and air, effects the health of people, destroys the biological environment, and disturbs the further development of the livestock industry.Composting is one of ways to handle the wastes, which is a fermentation process under the conditions with appropriate moisture, C/N ratio, and oxygen. During the process the organic materials will be turned to the stable humus, which can be used as fertilizer and amend for the plant soil. Thus the pig manure changing into the organic fertilizer is important way to protect biological environment and promote the sustainable development of the agriculture.74% plant soil lacks available phosphorus in our country, but there has abundant total phosphorus. The P fertilizer can be easily rooted by the acidic or alkalescent soil. The inorganic P hardly moves in soil and the utilization rate of inorganic P is about 10% to 25%, so the P fertilizer is a limited factor to the plant output. During the composting the organic material can produce organic acid, which has active action for the insoluble P and can partly change inorganic P into organic P. The composting can improve the validity and utilization rate, and provide a new way to solve the contraction of P supple-demand. According to the study of the rule of the changingof P during the composting, this paper has some parts as follows:The first chapter narrates the pollution of the pig manure, the principle of the composting and its development in the country and overseas, the pollution to the environment of the P and its necessary of recycle utilization on detail. At the end the task based on the current study is put forward.In the second chapter, the experiment equipment is designed which includes physic structure and aeration system. According to the thermal balance, the minimum volume was confirmed and the equipment' s volume was set up. Meanwhile ventilation rate was calculated in theory, and the fan type was set in order to study the static aerobic composting that can offer the theory of controlling the microbe environment.In the third chapter, the variety of the organic matter, temperature, pH, and C/N ratio during the composting are studied. Results indicate that the temperature goes through four stages, such as temperature rising, heat preservation, temperature decreasing and stable stage. The highest temperature reaches 67. 9°C, and there are fourteen days that the temperature keeps above 55°C, which satisfy the demand for no harm to plant. During the initial of the composting, the pH is about 6. 5, with the temperature rising, organic acid being decomposed and transferred, the pH is rising to about 8. 5. At the end of the composting the humus is produced and the pH comes down to neutral salt range. The moisture is decreased during the whole process and keeps stable about 48%. The organic matter and C/N ratio are also reduced with the days of composting.In the fourth chapter , aerobic and thermophilic composting of pig manure, which is added 0%, 5%, 7. 5%, 10% superphosphate based on the wet quantity of the composting respectively are studied. Results indicate that available P increased to 45%, 59%, and 62% respectively and a quite part of the superphosphate was changed into organic phosphorus. The rate of solubilization P is correlated with C/P of...