Heat Change And Wanter Reduction Of Cattle Manure In Aerobic Composting

It had been noticed by people for Agricultural solid waste utilization, and the aerobic composting of agricultural solid waste is one of the most important treatment method. much research on aerobic compossting has been done by many scholars, but the study of fermentation heat was usually done by dynamics simulations to estimate, it was unusual for reserch to the use of fermentation heat of composting. In this paper, the combustion heat of meterials was measured by oxygen bomb calorimetric during composting, and the heat yield was quantitatively determined.The microbial biodiversity and the development pattern of microbial group during composting were studied by culture microbial method. The results illustrated that bacterium was dominant position in the initial phase, the number of mesophilic and thermophilic bacterium, thermophilic fungi and thermophilic actinomycete were increased, but the number of thermophilic fungi and thermophilic actinomycetes were decreased. When the composting body got to the high temperature phase, the number of thermophilic bacterium and thermophilic actinomycete were increased, the number of mesophilic bacterium and mesophilic actinomycete were decreased,but it was difficult to find fungi, the bacterium was dominant position in this phase. When the body reached the manturation phase all the microorganism were increased, but the number of bacterium was the most of all. So the bacterium was dominant position in the composting phase.The aerobic composting process with material of different initial moisture was studied in laboratory experiments, and indicators such as temperature, total organic carbon(TOC), orgnic matter(OM) and combustion value were measured. The results indicated that the combustion heat changed regularly, and it had the similar law as organic matter during composting; The quantity of heat based on the losses of organic matter had the most value during initial phase, and the treatments had 20%(X1), 21.13%(X2),28.07%(X3),34.14%(X4) and 40.33%(X5) of that heat, respectively; the 65% initial moisture content was the best favorable for the activate aerobic composting and the total heat production was 2236 kJ·kg-1, If all of the energy was used to remove the water of the substance when the temperature of the water rose from 20℃to T℃(T≥55), the moisture content would decreased from 65% to 20%.The quantity of heat was measured by oxygen bomb calorimetric, and the loss of heat was the scope of 51.76～58.43% resulted from total bio-oxidation of organic compounds during composting. The number of greatest loss of heat was 3054.7～3673 kJ/kg-1 in initial phase. The number of heat based on the losses of organic matter was scope of 3555.2～4452.8 kJ/kg, and 1786.4～2252.80 kJ/kg of heat was released during initial coposting.Analysising the effect of heat production on moisture of substance by comparion of the changes of composting heat and moisture during composting. The results indicated that if all of the energy was used to remove the water of the substance, the 65% moisture content would decreased to the commercial requirement.The indicators such as temperature, total organic carbon (TOC), total nitrogen(TN), carbon to nitrogen ratio (C/N),volatile solids (VS) and germination index(GI) were measured. The results indicate that the combustion heat changes regularly, and has a good correlation with other indicators. It is concluded that the change of substance of composting could be considered a general indicator, that was, if the combustion value of the initial substance was about 12000 kJ/kg, the composting could be a good maturity mature when the combustion value of the final substance reduced to 6400 kJ/kg.