Effects Of Different Factors On Dry Anaerobic Fermentation Of Agricultural Wastes

With the development of agriculture industrialization and intensive livestock farming industry, agricultural waste s which mainly comprised of crops straw and livestock manure are increased year by year. The effluent of agricultural wastes causes serious waste of resources and ecological environment pollutioaResource utilization of agricultural wastes is a fundamental way to solve the problems of agricultural wastes. Dry fermentation technology is based on traditional anaerobic fermentation. For increasing the percent of solid holdup of raw materials, the advantages of dry fermentation are as follows: the fermented material need not be diluted at the beginning of fermentation; the outcome is got without dehydratbn at the end of fermentatbn and no secondary pollution of biogas slurry. Thus the dry fermentation technology has good application prospect, which can not only solving the problems of agriculture wastes pollution but also relieve rural energy crisis.Under laboratory conditions, this paper studies the effect of different factors on agricultural waste dry fermentation, and thus providing basis for the manufacturing technique of agricultural waste dry fermentation. Based on fully analyzing the mechanism of anaerobic fermentation, this paper researches on dry fermentation, and obtains the following conclusions.(1) There are serious test groups of dry fermentation made by choosing cow muck, pig manure and corn straw as raw materials respectively. The results show that the total biogas production rate of cow muck is 22.3L/kg, which is highest in the three raw materia ls. So it chooses cow muck as mean raw material at subsequent researches in this paper, and chooses corn straw as the other raw material in order to adjust the solid hold up of dry fermentation.(2) To reduce the lignin content in corn straw, the pretreatments of acid solution, alkaline solution (NaOH solution) and microorganism method are studied. The results indicate that, when the concentration of NaOH solution is 4%, the removal rate of lignin is 62.1%, which is highest in the three pretreatments. However, if the corn straw is pretreated by acid solution or alkaline solution, the pH value in it is not good for methane bacteria growth, and at the same time the pretreatment process produced many harmful substances. Therefore, the microorganism method is chosen for pretreating corn straw.(3) With the solid holdup of 10%, 20%, 30% and 40% respectively, the biogas production rate of anaerobic fermentation is studied when the C/N is 20, the temperature is 37±1℃and the total solid (TS) content of inoculation amount is 10%. The results indicate that the total and daily peak value of biogas production rate is increased with the decrease of solid hold up.(4) With the solid holdup of 10%, 20%, 30% and 40% respectively, the biogas production rate of anaerobic fermentation is studied when the C/N is 25, the temperature is 37±1℃and the total solid (TS) content of inoculation amount is 10%. The results indicate that the total biogas production rate of dry fermentation (solid holdup 20%, 30% and 40%) is higher than traditional wet fermentation (solid holdup 10%). The total biogas production rate is highest when the solid holdup is 30%, and the daily peak value of biogas production rate is increased with the decrease of solid holdup.(5) With the solid holdup of 10%, 20%, 30% and 40% respectively, the biogas production rate of anaerobic fermentation is studied when the C/N is 25, the temperature is 52±1℃and the total solid (TS) content of inoculation amount is 10%. The results indicate that the total and daily peak value of biogas production rate is increased with the decrease of solid hold up too.(6) The methane concentration in biogas which made under different solid holdup are researched. The results indicate that the methane concentration in biogas is increased with the increase of solid holdup.