Anaerobic Digestion Of Different Substrates In Municipal Solid Waste

Anaerobic digestion is an important way of disposing the organic solid waste, that has been received more and more attention because it can recover energy. Carbohydrate,protein and lipid are the primary substrates that can be utilized by bacteria in the anaerobic digestion system.The solid waste comprise of different substrates that will present disparate property. So it is necessary to investigate the characteristic of a single substrate in the anaerobic digestion system.The author select rice,soybean,celery and fat as the representative material of carbohydrate,protein and lipid. Through the anaerobic digestion experiment, the speciality of every single substrate has been analynased. Experiments were designed and carried out on the mesophilic and thermophilic anaerobic digestion of every single substrate and the mixed substrate under controlling or uncontrolling pH. The experimental results were discussed , and the characteristic difference of the four substrates was primarily concluded.The results of mesophilic anaerobic digestion of the substrates show that the rate of hydrolysis/acidification of rice was rapid, and the pH value must be controlled otherwise the digestion will be failure. Both of two digestion bottles of soybean cann't get in the phases of producing methane, and both of the concentration of ammonia and that of VFA were the highest during the digestion of the four materials. The celery can be completely degraded, both of two digestion bottles had been in the phase of producing methane, and the rate of the degrading will be accelerated if only the pH was controlled. The fat has showed the most effective ability of producing gas and methane, and its cumulative methane production is up to 13758ml, which is 93.59% of the gas's output.The results of thermophilic anaerobic digestion are differ from that of mesophilic digestion. The rate of hydrolysis/acidification of rice was slower as them mesophilic hydrolysis, and both of two digestion bottles cann't get in the phases of producing methane. But the soybean was degraded more complete during thermophilic anaerobic digestion process. The digestion of cellulose would be failure if the pH of the system was not controlled. Fat meat cannot be degraded completely, which indicate the digestion activity of fat meat was different between the mesophilic and thermophilic temperature conditions, and the cumulative gas in the condition of uncontrolling the pH was higher than that of controlling the pH.The co-digestion experiments were carried out on both of the mesophilic and thermophilic conditions. The mixed substrate was composed of the four materials and every dry material hold a quarter of the total solid. The results showed that the cumulative gas production of the mesophilic anaerobic digestion was 3379ml and that of the thermophilic anaerobic digestion was 4373ml, but the substrates of both of the two experiments were not degraded mostly, which indicate that the proportion of the four materials was not the best.